Index

MRCOG Part 1: Comprehensive Anatomy Revision Guide

Author: Hermes Agent | Target: MRCOG Part 1 | Last Updated: May 2026

This document is an exhaustive, deep-dive study resource covering every anatomical concept tested in the MRCOG Part 1 examination. It incorporates clinical correlations, surgical significance, and high-yield exam facts throughout.

Table of Contents

1. Bony Pelvis
2. Female Reproductive Tract
3. Supports of the Uterus
4. Blood Supply of the Pelvis
5. Lymphatic Drainage of the Pelvis
6. Nerve Supply of the Pelvis
7. Anatomy of the Pelvic Ureter
8. Anterior Abdominal Wall
9. Perineum & Vulva
10. Male Reproductive Anatomy
11. The Breast
12. Embryological Anatomy

1. Bony Pelvis

1.1 Overview

The bony pelvis is a ring-like structure composed of the two innominate (hip) bones, the sacrum, and the coccyx. It serves to transfer weight from the vertebral column to the lower limbs, provides attachment for muscles of the trunk and lower limbs, and — critically in obstetrics and gynaecology — forms the bony passage through which the fetus must pass during childbirth.

The pelvis is divided into two anatomical regions by the pelvic brim (pelvic inlet): the false (greater) pelvis above and the true (lesser) pelvis below.

The False (Greater) Pelvis

• Boundaries: Posteriorly — lumbar vertebrae (L5); laterally — iliac fossae and iliac crests; anteriorly — anterior abdominal wall.
• Contents: Lower abdominal viscera (caecum, appendix, sigmoid colon), loops of small intestine.
• Obstetric significance: The false pelvis guides the presenting part into the true pelvis at engagement. A well-shaped false pelvis (wide iliac fossae) facilitates engagement.

The True (Lesser) Pelvis

• Boundaries: Posteriorly — sacrum and coccyx; laterally — ischial bones, obturator internus muscles, and pelvic ligaments; anteriorly — pubic bones and symphysis pubis.
• Contents: Pelvic viscera (bladder, ureters, uterus, ovaries, fallopian tubes, upper vagina, rectum, anal canal), pelvic blood vessels, lymphatics, nerves, and pelvic floor muscles.
• Obstetric significance: The true pelvis is the bony canal through which the fetus descends during labour.

1.2 Bones of the Pelvis

Sacrum

The sacrum is a triangular bone formed by the fusion of five sacral vertebrae (S1–S5). Key features:

• Sacral promontory: The anterior-superior margin of S1, a key landmark for pelvic measurements.
• Ala (wing) of sacrum: Lateral masses formed by fused transverse processes, articulating with the iliac bones at the sacroiliac joints.
• Anterior sacral foramina (four pairs): Transmit the ventral rami of S1–S4 nerves.
• Posterior sacral foramina (four pairs): Transmit the dorsal rami of S1–S4 nerves.
• Sacral canal: Continuation of the vertebral canal, containing the cauda equina and filum terminale. Terminates at the sacral hiatus (S5 level), covered by the sacrococcygeal ligament.
• Sacral cornua: Two bony projections flanking the sacral hiatus — important landmarks for caudal epidural anaesthesia.

Clinical pearl: The sacral promontory is palpated during clinical pelvimetry (diagonal conjugate measurement). A prominent promontory may indicate a flat (platypelloid) pelvis.

Coccyx

The coccyx is a small triangular bone formed by four fused rudimentary coccygeal vertebrae (Co1–Co4). It articulates superiorly with the sacrum at the sacrococcygeal symphysis (a secondary cartilaginous joint). The coccyx curves anteroinferiorly and can be fractured during a difficult instrumental delivery or by a fall. Coccydynia (pain in the coccyx) is a recognised complication of childbirth.

Innominate (Hip) Bones

Each innominate bone is formed by the fusion of three primary bones: the ilium, ischium, and pubis. These three bones meet at the acetabulum (the socket for the head of the femur).

Ilium

• The largest of the three bones.
• Iliac crest: Upper border, extends from the anterior superior iliac spine (ASIS) to the posterior superior iliac spine (PSIS).
• Iliac fossa: The concave inner surface of the ilium.
• Arcuate line: A ridge on the inner surface of the ilium that forms part of the pelvic brim.
• Iliopubic eminence: A prominence at the junction of the ilium and pubis.

Ischium

• Forms the posteroinferior part of the hip bone.
• Ischial tuberosity: Thick, roughened area bearing body weight when sitting. Site of attachment for the sacrotuberous ligament and hamstring muscles.
• Ischial spine: A sharp projection that is a key obstetric landmark (site of attachment of sacrospinous ligament). Used to measure the interspinous diameter (normally ~10.5 cm), the narrowest fixed pelvic diameter.
• Lesser sciatic notch: Below the ischial spine.
• Obturator foramen: A large opening between the ischium and pubis, mostly closed by the obturator membrane.

Pubis

• Forms the anterior part of the hip bone.
• Superior pubic ramus: Forms part of the pelvic brim. Contains the iliopectineal (iliopubic) eminence at its junction with the ilium.
• Inferior pubic ramus: Joins the ischial ramus.
• Pubic crest: Anterior border of the pubis.
• Pubic tubercle: A prominence at the lateral end of the pubic crest — important for inguinal canal anatomy.
• Symphyseal surface: The medial surface for articulation with the opposite pubic bone.
• Pubic arch: Formed by the inferior pubic rami meeting at the subpubic angle.

1.3 Pelvic Joints and Ligaments

Joints

Major Pelvic Ligaments

Sciatic Foramina

• Greater sciatic foramen: Formed by the greater sciatic notch, sacrotuberous ligament, and sacrospinous ligament. It transmits the piriformis muscle, superior and inferior gluteal vessels and nerves, sciatic nerve (L4–S3), posterior femoral cutaneous nerve, pudendal nerve (re-enters pelvis via lesser sciatic foramen), internal pudendal vessels, and nerve to obturator internus.
• Lesser sciatic foramen: Formed by the lesser sciatic notch, sacrotuberous ligament, and sacrospinous ligament. It transmits the internal pudendal vessels, pudendal nerve, nerve to obturator internus, and the tendon of obturator internus.

1.4 Pelvic Inlet (Pelvic Brim)

Boundaries

• Posterior: Sacral promontory and alae of sacrum.
• Lateral: Arcuate line of ilium, iliopubic eminence, and pecten pubis (pectineal line of pubis).
• Anterior: Pubic crest and upper border of symphysis pubis.

Diameters of the Pelvic Inlet

Clinical Pearl: The shortest pelvic inlet diameter is the anteroposterior (obstetric conjugate). In a platypelloid pelvis, the transverse diameter is wide but the AP is narrow (flat inlet) — the fetal head often engages transversely. The obstetric conjugate is the most important measurement in determining whether vaginal delivery is possible.

1.5 Pelvic Cavity

• Shape: A cylindrical space between the pelvic inlet and outlet.
• Anterior wall: Shallow (only ~4 cm) — formed by the bodies of the pubic bones and symphysis pubis.
• Posterior wall: Deep (~12 cm) — formed by the sacrum and coccyx.
• Lateral walls: Formed by obturator internus muscles and the ischial bones.
• Contents: Pelvic viscera, neurovascular structures, ureters, pelvic ureter, and pelvic floor muscles.
• Diameters: The pelvic cavity is widest in its transverse diameter (~12.0 cm). The AP diameter is relatively constant (~12.0–12.5 cm).

Mid-cavity: Level of the ischial spines. The interspinous diameter (between the ischial spines) is the narrowest fixed diameter of the pelvis (~10.5 cm). If this is <9.5 cm, it indicates mid-cavity contraction.

1.6 Pelvic Outlet

Boundaries

• Anterior: Inferior border of the symphysis pubis and pubic arch.
• Lateral: Ischial tuberosities, sacrotuberous ligaments.
• Posterior: Tip of the coccyx (sacrococcygeal joint).

Diameters of the Pelvic Outlet

Clinical Pearl: The subpubic angle (normally ~90–100° in females) determines the shape of the anterior pelvic outlet. A narrow subpubic angle (<80°) — as in android pelvis — results in a narrow anteroposterior outlet and may cause outlet dystocia. A wide angle (as in gynaecoid pelvis) facilitates delivery.

The intertuberous diameter is measured clinically. A measurement <8.0 cm suggests outlet contraction. The sum of the intertuberous + posterior sagittal diameters should be ≥15.0 cm for adequate outlet dimensions.

1.7 Pelvic Shapes (Caldwell-Moloy Classification)

In 1933, Caldwell and Moloy classified female pelves into four basic types based on the shape of the pelvic inlet. Most pelves (50–60%) are gynaecoid, while the rest are mixed or transitional forms.

Gynaecoid Pelvis (~50%)

• Inlet shape: Round to slightly oval (transverse diameter > AP by <2 cm).
• Sacrum: Curved, well-aligned.
• Side walls: Straight, parallel.
• Ischial spines: Blunt, non-prominent.
• Subpubic arch: Wide (~90–100°).
• Obstetric assessment: Most favourable for vaginal delivery. The fetal head typically engages in the occipito-transverse position.
• Interspinous diameter: ≥10.5 cm.

Android Pelvis (~20%)

• Inlet shape: Heart-shaped (wedge-like posterior segment).
• Sacrum: Straight, inclined forward (anterior sacral inclination).
• Side walls: Convergent (funnel-shaped).
• Ischial spines: Prominent, sharp.
• Subpubic arch: Narrow (<90°).
• Obstetric assessment: Unfavourable for vaginal delivery. Funnel-shaped pelvis with mid-cavity and outlet contraction. High risk of deep transverse arrest and outlet dystocia. The fetal head engages in the occipito-anterior or occipito-posterior position but fails to rotate.
• Interspinous diameter: Often <10.0 cm.

Anthropoid Pelvis (~25%)

• Inlet shape: Long, oval (AP > transverse diameter).
• Sacrum: Long, narrow.
• Side walls: Straight or slightly divergent.
• Ischial spines: Not prominent.
• Subpubic arch: Narrow to moderate.
• Obstetric assessment: Generally favourable. The fetal head often engages in the occipito-posterior position. Vaginal delivery is usually possible, though prolonged labour is more common due to persistent OP position.
• Interspinous diameter: Usually adequate.

Platypelloid Pelvis (~3–5%)

• Inlet shape: Flattened, oval (transverse >> AP diameter). Kidney-shaped.
• Sacrum: Straight, inclined posteriorly.
• Side walls: Divergent.
• Ischial spines: Blunt.
• Subpubic arch: Wide.
• Obstetric assessment: Least favourable for vaginal delivery. The AP diameter of the inlet is shortened. The fetal head engages transversely and may fail to descend through the inlet (inlet contraction). Caesarean section is often required if the obstetric conjugate is <10.0 cm.
• Interspinous diameter: Usually adequate.

Summary Table: Pelvic Shapes

Exam Fact: The android pelvis is the male-type pelvis. In females, it is associated with polycystic ovary syndrome (PCOS) and hyperandrogenism in some studies. The platypelloid pelvis is also known as the flat pelvis. Rickets historically caused platypelloid deformity (rachitic flat pelvis).

1.8 Clinical Pelvimetry

External Pelvimetry (Historical)

• Interspinous diameter: Between ASIS (normally ~24–26 cm).
• Intercristal diameter: Between iliac crests (normally ~26–28 cm).
• External conjugate (Baudelocque's diameter): From the depression below L5 spinous process to the upper border of the pubic symphysis (normally ~20 cm).
• Intertrochanteric diameter: Between greater trochanters (normally ~30–32 cm).
• Subpubic angle: Assessed by placing thumbs along the inferior pubic rami.

Note: External pelvimetry is largely obsolete in modern obstetrics, replaced by clinical examination (vaginal assessment of sacral promontory, ischial spines, sacrospinous ligaments, coccyx) and imaging (ultrasound, CT, MRI).

Internal (Clinical) Pelvimetry

Performed during vaginal examination. The following are systematically assessed:

1. Diagonal conjugate: The distance from the inferior border of the pubic symphysis to the sacral promontory (normally ≥11.5 cm). The obstetric conjugate is estimated by subtracting 1.5–2.0 cm. If the diagonal conjugate is >12.0 cm, the inlet is likely adequate.
2. Sacral promontory: Should not be easily reachable. If reachable, suspect inlet contraction.
3. Ischial spines: Are they prominent? (Grade 0 = not palpable; Grade 1 = palpable but not prominent; Grade 2 = prominent; Grade 3 = very prominent/overriding).
4. Sacrum: Curvature — a flat or straight sacrum suggests android features.
5. Sacrospinous ligament: Normally ~2 finger-breadths wide. A narrower ligament (<2 fingers) may indicate mid-cavity contraction.
6. Subpubic arch: Should admit 2–3 finger-breadths.
7. Bituberous (intertuberous) diameter: Knuckles of the examining hand (~4 knuckle-breadths = 8–9 cm).
8. Coccyx: Mobility (should move posteriorly ~2 cm).

1.9 Pelvic Dimensions Summary Table

1.10 Pelvic Floor Muscles

The pelvic floor (pelvic diaphragm) is a musculofascial sling that supports the pelvic viscera. It is divided into two layers:

Superior Layer: Pelvic Diaphragm (True Pelvic Floor)

The pelvic diaphragm is formed by the levator ani (the most important muscle) and the ischiococcygeus (coccygeus) muscles.

Levator Ani Muscle

The levator ani is the main muscle of the pelvic floor. It has three parts:

Pubococcygeus can be further subdivided: - Pubococcygeus proper → coccyx - Puboprostaticus (male) → prostate - Pubovaginalis (female) → vagina - Puboperinealis → perineal body - Puboanalis → intersphincteric groove between internal and external anal sphincters

Arcus tendineus levator ani (ATLA): A tendinous arch from the pubic bone to the ischial spine, providing origin for iliococcygeus and part of pubococcygeus. It is a key surgical landmark in pelvic reconstructive surgery.

Arcus tendineus fasciae pelvis (ATFP): Also called the "white line" of the pelvis. It is a thickening of the fascia of obturator internus, running from the pubic bone to the ischial spine. It is the attachment site for the pubocervical fascia (anterior vaginal support). Important in surgery for anterior compartment prolapse (paravaginal defect repair).

Ischiococcygeus (Coccygeus) Muscle

• Origin: Ischial spine.
• Insertion: Lateral border of sacrum and coccyx.
• Action: Pulls coccyx forward; supports pelvic organs posteriorly.
• Note: Lies on the pelvic surface of the sacrospinous ligament. Often considered part of the piriformis/levator ani complex.

Inferior Layer: Urogenital Diaphragm (Perineal Membrane)

The urogenital diaphragm is a triangular sheet of fascia between the inferior pubic rami, below the pelvic diaphragm. In current terminology, it is called the perineal membrane.

Components: - Deep transverse perineal muscle: From ischial ramus → midline raphe/perineal body. - Compressor urethrae (female): Compresses the urethra. - Sphincter urethrovaginalis (female): Encircles the urethra and vagina. - Superior and inferior layers of fascia: Enclosing the above muscles.

Contents of the Deep Perineal Pouch (between the two fascial layers): - Deep transverse perineal muscle - Compressor urethrae / sphincter urethrovaginalis - External urethral sphincter (rhabdosphincter) - Bulbourethral glands (male: Cowper's glands) - Dorsal nerve and vessels of clitoris/penis - Part of internal pudendal vessels

Pelvic Floor Openings

The pelvic floor has three major openings:

Innervation of the Pelvic Floor

• Levator ani: Branches from S2–S4 (direct branches from sacral plexus and pudendal nerve).
• Ischiococcygeus: Branches from S4–S5.
• External anal sphincter: Inferior rectal nerve (branch of pudendal nerve, S2–S4).
• External urethral sphincter: Perineal branch of pudendal nerve (S2–S4).

Functions of the Pelvic Floor

1. Support: Maintains position of pelvic organs (uterus, bladder, rectum, vagina).
2. Continence: Provides sphincteric action for urethra, vagina, and anal canal.
3. Childbirth: Must relax and distend during vaginal delivery.
4. Sexual function: Contributes to vaginal tone and orgasmic contractions.
5. Postural: Contributes to intra-abdominal pressure generation (with diaphragm and abdominal muscles).

Clinical Correlations: Pelvic Floor Dysfunction

1. Pelvic Organ Prolapse (POP): Weakening of the pelvic floor leads to cystocele (anterior), rectocele (posterior), uterine prolapse (apical), or enterocele (apical/posterior). The POP-Q system quantifies prolapse.
2. Stress Urinary Incontinence (SUI): Failure of urethral support mechanisms. The "hammock hypothesis" (DeLancey) describes the role of pubocervical fascia and endopelvic fascia. SUI is often treated with mid-urethral sling procedures (TVT, TOT).
3. Obstetric Anal Sphincter Injury (OASIS): Third- and fourth-degree perineal tears during childbirth, affecting the anal sphincter complex.
4. Episiotomy: A deliberate incision of the perineum to enlarge the vaginal outlet. Mediolateral is preferred over midline (higher risk of OASIS with midline).
5. Denervation injury: Vaginal delivery can cause stretching and denervation of the pelvic floor (especially pudendal nerve), contributing to postpartum prolapse and incontinence.

1.11 Perineal Body

The perineal body (central tendon of the perineum) is a fibromuscular mass located at the midpoint of the line between the ischial tuberosities, in the midline between the anus and the vaginal introitus.

Attachments to the Perineal Body

Clinical Significance

• The perineal body is a key support structure for the posterior vaginal wall and the pelvic floor.
• Obstetric trauma: The perineal body is often torn during childbirth (perineal tears). Its integrity is crucial for pelvic organ support.
• Repair: Repair of the perineal body after childbirth is essential to prevent long-term prolapse.
• Posterior colporrhaphy: Surgicalplication of the perineal body to correct rectocele.
• Perineotomy (episiotomy): Incision through the perineal body.

2. Female Reproductive Tract

2.1 The Uterus

The uterus is a hollow, thick-walled, muscular organ located in the pelvic cavity between the bladder (anterior) and the rectum (posterior). It is shaped like an inverted pear.

Dimensions

Anatomical Divisions

The uterus is divided into three main parts:

1. Fundus: The dome-shaped portion above the level of the fallopian tube insertions. It is the widest part.
2. Body (corpus): The central portion, between the fundus and the cervix.
3. Cervix: The narrow, cylindrical lower portion, opening into the vagina.

Angles and Position: - Anteversion: The long axis of the uterus is inclined forward relative to the long axis of the vagina (~90° angle). This is the normal position. - Anteflexion: The body of the uterus is flexed forward relative to the cervix (~120–130° angle between cervix and body). - Normal position: Anteverted and anteflexed (AV/AF). - Retroversion: Uterus tilted posteriorly. May be normal (congenital) or associated with pelvic pathology (endometriosis, adhesions). Retroverted gravid uterus usually becomes anterior by 12–14 weeks. - Retroflexion: Body of uterus flexed posteriorly relative to cervix.

Peritoneal Relations

• The peritoneum covers the uterus anteriorly (down to the level of the internal os, then reflects onto the bladder forming the vesicouterine pouch) and posteriorly (down to the posterior vaginal fornix, then reflects onto the rectum forming the rectouterine pouch (pouch of Douglas)).
• The broad ligament is a double layer of peritoneum draping over the uterus and extending to the lateral pelvic walls.
• Anterior: Vesicouterine pouch (between bladder and uterus).
• Posterior: Rectouterine pouch (pouch of Douglas) — the most dependent part of the peritoneal cavity in the female, and a common site for fluid collection, endometriosis, and tumour deposits (Blumer's shelf).

Layers of the Uterine Wall

1. Perimetrium (Serosa)

• The outermost layer — visceral peritoneum covering the uterus.
• Continuous with the broad ligament laterally.
• Anteriorly reflects onto the bladder; posteriorly reflects onto the rectum.

2. Myometrium

The myometrium is the thick, muscular middle layer, composed of smooth muscle bundles arranged in three ill-defined layers:

Myometrial Architecture: - The smooth muscle cells of the myometrium are arranged in a complex, interwoven pattern that allows for: - Massive stretch during pregnancy (from ~50–70 g to ~1 kg at term). - Powerful coordinated contractions during labour. - Haemostatic contraction after delivery (living ligature of the oblique fibres). - During pregnancy, the myometrium undergoes both hyperplasia (first half) and hypertrophy (second half). - The lower uterine segment forms in late pregnancy from the isthmus (see below). It is thinner and less muscular than the fundus, making it the preferred site for lower-segment caesarean section (LSCS).

3. Endometrium

The endometrium is the inner mucosal lining of the uterine cavity. It consists of a simple columnar epithelium with underlying lamina propria containing tubular glands.

Layers:

Arterial Supply: - Straight arterioles: Supply the basal layer. Not hormone-sensitive. Do not undergo cyclic changes. - Spiral arterioles: Supply the functional layer. Hormone-sensitive. Undergo vasoconstriction before menstruation, leading to ischaemic necrosis and shedding.

Cyclic Changes: - Proliferative phase (days 6–14): Oestrogen-driven. Endometrial thickness increases from ~2–3 mm to ~8–10 mm. Glands are straight and tubular. - Secretory phase (days 15–28): Progesterone-driven. Glands become tortuous and secretory (glycogen-rich). Stroma becomes oedematous and decidualised. Thickness reaches 10–14 mm. - Menstrual phase (days 1–5): Progesterone withdrawal leads to spiral arteriole vasospasm, ischaemia, and shedding of the functionalis.

Clinical Correlations: - Endometrial polyps: Focal hyperplasia of endometrial glands and stroma. - Endometrial hyperplasia: Thickening of the endometrium due to unopposed oestrogen — may be simple, complex, or atypical (the latter is premalignant). - Endometrial carcinoma: Most common gynaecological malignancy in developed countries. Presents with postmenopausal bleeding. Arises primarily from the endometrium. - Asherman's syndrome: Intrauterine adhesions, often due to postpartum curettage, leading to amenorrhoea and infertility. - Adenomyosis: Invasion of endometrial glands and stroma into the myometrium. Causes menorrhagia and dysmenorrhoea.

Uterine Isthmus

• The isthmus is a narrow region between the body of the uterus and the cervix, approximately 0.5–1.0 cm long.
• During pregnancy, the isthmus unfolds and elongates to form the lower uterine segment (LUS).
• The LUS is the preferred site for lower-segment caesarean section (LSCS) because:
• It is thinner and less vascular.
• It heals better.
• There is less risk of rupture in subsequent pregnancies compared to a classical (upper segment) scar.
• The upper boundary of the LUS is the vesicouterine fold of peritoneum (which is incised during LSCS).
• The lower boundary is the internal os of the cervix.

2.2 The Cervix

The cervix is the lower, narrow part of the uterus, approximately 2.5–3.0 cm in length. It connects the uterine cavity to the vagina.

Anatomical Divisions

Cervical Canal

• Internal os: Opening into the uterine cavity.
• External os: Opening into the vagina.
• Nulliparous: Small, circular or pinhole-shaped.
• Multiparous: Transverse slit (appears as an anterior and posterior lip).
• Endocervical canal: Between the internal and external os. Contains palmate folds (plicae palmatae) — longitudinal and oblique ridges of mucosa (also called arbor vitae uteri due to their tree-like appearance).

Cervical Stroma

The cervix is mostly composed of dense fibromuscular connective tissue (~85% fibrous, ~15% smooth muscle — markedly less smooth muscle than the corpus uteri). The stroma consists of:

• Type I collagen (predominant)
• Smooth muscle fibres (concentrated around the internal os)
• Extracellular matrix (proteoglycans, elastin)
• Blood vessels, lymphatics, nerves

Clinical Significance: - The fibromuscular nature of the cervix allows it to remain firm and closed during pregnancy (cervical cerclage can be placed if the cervix is incompetent). - During labour, the cervix undergoes effacement (shortening) and dilatation under the influence of prostaglandins and uterine contractions. - The cervical stroma contains prostaglandin receptors — hence prostaglandin preparations (dinoprostone, misoprostol) are used for cervical ripening.

Cervical Epithelium

Cervical Ectopy (Erosion): - Columnar epithelium of the endocervix extends onto the ectocervix. - Common in adolescents and pregnant women (hormonal influence). - Appears red on speculum examination (columnar epithelium is thin and translucent, showing underlying stroma). - Can be a normal finding (physiological ectopy) but may cause contact bleeding or increased discharge.

Clinical Correlations: - Cervical intraepithelial neoplasia (CIN): Premalignant changes in the transformation zone. HPV-related (especially types 16, 18). Graded CIN 1 (mild), CIN 2 (moderate), CIN 3 (severe/CIS). - Cervical carcinoma: One of the most common gynaecological cancers worldwide (especially squamous cell carcinoma ~80%, adenocarcinoma ~15%, other ~5%). Routinely screened with Pap smear/HPV testing. - Cervical incompetence: Painless dilatation of the cervix in the second trimester; treated with cervical cerclage (McDonald or Shirodkar suture). - Cervical polyps: Benign polypoid growths from the endocervical canal. - Nabothian cysts: Retention cysts of the endocervical glands; benign.

Cervical Ligaments (Supports)

The cervix is supported by several ligamentous structures (see Section 3 for details): - Cardinal (Mackenrodt's) ligaments: Main lateral support from cervix to lateral pelvic walls. - Uterosacral ligaments: From cervix/upper vagina to sacrum (S2–S3). - Pubocervical fascia: Anterior support from cervix to the pubic bone.

2.3 The Fallopian Tubes (Oviducts)

The fallopian tubes are paired muscular tubes (approximately 10–12 cm long) extending laterally from the uterine cornua to the ovaries. They provide the conduit for sperm transport, fertilisation, and early embryo transport.

Anatomical Segments

Exam fact: The ampulla is the most common site of ectopic pregnancy (accounting for ~70–75% of tubal ectopics). The isthmus accounts for ~10–12%, the fimbrial end for ~5%, and interstitial/cornual for ~2–3%.

Structure of the Tubal Wall

Epithelial Cell Types

Blood Supply

• Arterial: Tubal branches from uterine artery (medial 2/3) and ovarian artery (lateral 1/3). The anastomotic arcade runs in the mesosalpinx.
• Venous: Corresponding veins draining into uterine and ovarian veins.

Clinical Correlations

• Ectopic pregnancy: Implantation of the blastocyst outside the uterine cavity. The fallopian tube is the most common site. Risk factors include: previous tubal damage (PID, previous ectopic, tubal surgery), IUD use, smoking, and assisted reproductive technology.
• Salpingitis: Infection of the fallopian tubes, usually ascending from the lower genital tract. Can cause tubal factor infertility (blocked tubes) and hydrosalpinx (dilated, fluid-filled tube).
• Tubal ligation: Sterilisation procedure (modified Pomeroy, Filshie clip, bipolar diathermy). Usually performed isthmically.
• Salpingectomy: Removal of a fallopian tube (can be performed for ectopic pregnancy or as risk-reducing surgery in BRCA mutation carriers — bilateral salpingectomy with delayed oophorectomy).
• Cornual resection: Surgical removal of the interstitial portion of the tube (rarely performed, e.g., for interstitial ectopic).
• Sperm and ovum transport: Sperm reach the ampulla within minutes to hours after intercourse. The ovum is transported toward the ampulla within minutes of ovulation. The fertilised ovum remains in the tube for 3–4 days before entering the uterine cavity.

2.4 The Ovaries

The ovaries are paired almond-shaped gonads located on each side of the uterus, in the ovarian fossa (fossa of Waldeyer) — a depression on the lateral pelvic wall bounded by:

• Anterior: External iliac vessels and obturator vessels.
• Posterior: Internal iliac vessels and ureter.
• Superior: External iliac vessels.
• Inferior: Ureter and ovarian artery.
• Floor: Obturator internus muscle and its fascia.

Dimensions

Anatomical Structure

The ovary is divided into three zones:

1. Cortex (Outer Zone)

• Germinal epithelium: Surface epithelium (simple cuboidal to low columnar) covering the ovary.
• Tunica albuginea: Dense fibrous connective tissue beneath the germinal epithelium.
• Cortical stroma: Spindle-shaped stromal cells (similar to fibroblasts) in a collagen matrix. Contains follicles at various stages of development (primordial, primary, secondary, tertiary/Graafian).
• Ovarian follicles: Embedded within the cortical stroma. Each follicle contains an oocyte surrounded by granulosa and theca cells.
• At birth: ~1–2 million primordial follicles.
• At menarche: ~300,000–400,000 follicles.
• At menopause: Few (<1,000) to none.

2. Medulla (Inner Zone)

• Loose connective tissue: Rich in blood vessels, lymphatics, and nerves.
• Hilus: The medullary region adjacent to the mesovarium. Contains hilus cells (analogous to testicular Leydig cells) — can produce androgens and may give rise to hilus cell tumours (Leydig cell tumours of the ovary).
• Rete ovarii: Remnants of the mesonephric (Wolffian) system, located in the hilus. Analogous to the rete testis.

3. Hilum

• The point of attachment of the mesovarium (a peritoneal fold from the broad ligament).
• Entry/exit point for ovarian vessels, nerves, and lymphatics.
• Contains the hilus cells and rete ovarii remnants.

Ovarian Ligaments

Blood Supply

• Arterial: Ovarian artery — a direct branch of the abdominal aorta (below the renal artery, at the level of L2). It crosses the pelvic brim, runs in the suspensory ligament, and anastomoses with the ovarian branch of the uterine artery.
• Venous: Ovarian veins emerge from the hilum as a pampiniform plexus, then coalesce into a single vein.
• Right ovarian vein: Drains directly into the inferior vena cava (at L2 level).
• Left ovarian vein: Drains into the left renal vein (at L1–L2 level). This is a key embryological fact.

Lymphatic Drainage

The ovaries drain via lymphatics that follow the ovarian vessels: - Primary: To the para-aortic (lumbar) lymph nodes (at the level of the renal hilus, L1–L2). - Secondary (alternative pathway): To the external iliac and inguinal nodes (via lymphatics in the broad ligament).

Clinical Significance: The primary drainage to para-aortic nodes explains why ovarian malignancies often present with para-aortic nodal metastases before pelvic nodal involvement is apparent.

Nerve Supply

• Ovarian (sympathetic) plexus: Derived from the intermesenteric/aortic plexus, carrying fibres from T10–T11 spinal segments.
• Parasympathetic: Vagus nerve (vagal branches that travel with the ovarian artery).
• Afferent (pain) fibres: Follow the sympathetic pathway back to T10–T11 spinal segments — explaining why ovarian pain is referred to the T10–T11 dermatome (periumbilical region).

Clinical Correlations

• Ovarian cysts: Physiological (follicular, corpus luteal) or pathological (dermoid, endometrioma, cystadenoma, cystadenocarcinoma).
• Polycystic Ovary Syndrome (PCOS): Bilateral enlarged ovaries with multiple small peripheral follicles ("string of pearls" sign). Volume often >10 mL.
• Ovarian torsion: Twisting of the ovary (and often the tube) on its pedicle. Acute pelvic pain with nausea/vomiting. Ultrasound shows enlarged, oedematous ovary. Surgical emergency.
• Ovarian malignancy: Often presents late (vague symptoms). CA-125 tumour marker. Risk-reducing salpingo-oophorectomy (RRSO) in BRCA1/2 carriers reduces ovarian cancer risk by ~80–95%.
• Ovarian hyperstimulation syndrome (OHSS): Iatrogenic enlargement of ovaries due to gonadotrophin therapy for IVF. Can cause ascites, pleural effusion, and thromboembolism.
• Menopause: Ovarian volume decreases, follicles are depleted. Postmenopausal ovary should be ~2–3 cm or less. A palpable postmenopausal ovary (>3.5 cm) requires investigation (postmenopausal palpable ovary syndrome).

2.5 The Vagina

The vagina is a fibromuscular tube extending from the vaginal vestibule (external vaginal orifice) to the cervix. It is located between the bladder/urethra (anteriorly) and the rectum/anal canal (posteriorly).

Dimensions

Vaginal Fornices

The upper vagina surrounds the vaginal portion of the cervix, creating four fornices:

Clinical Significance of Vaginal Fornices: - Posterior fornix: Palpated during bimanual examination to assess the pouch of Douglas for tenderness (PID, endometriosis), nodules (endometriosis, malignancy), or fluid collections (abscess, haemorrhage). Culdocentesis is performed through the posterior fornix. - Culdoscopy: Direct visualisation of the pouch of Douglas via a culdoscope inserted through the posterior fornix (largely historical, now replaced by laparoscopy). - Anterior fornix: Approach for vaginal hysterectomy — the anterior peritoneal reflection (vesicouterine pouch) is opened here.

Layers of the Vaginal Wall

Note: The vagina has no submucosa — the lamina propria directly underlies the epithelium.

Vaginal Epithelium and Cyclic Changes

The vaginal epithelium undergoes cyclic changes in response to oestrogen and progesterone:

Maturation Index: A cytological assessment of the vaginal smear. Calculated as: - MI = Parabasal : Intermediate : Superficial cell percentages. - Normal reproductive age: 0 : 40 : 60. - Postmenopausal (no HRT): 60 : 35 : 5 (shift to left — atrophic). - Oestrogen effect: 0 : 10 : 90 (shift to right).

Clinical Pearl: The acidic vaginal pH (4.0–4.5) is maintained by Döderlein's lactobacilli, which metabolise vaginal glycogen to lactic acid. This acidic environment protects against ascending infections. Loss of lactobacilli (e.g., with antibiotics, douching) predisposes to bacterial vaginosis.

Blood Supply of the Vagina

The vagina has a rich anastomotic network of blood vessels:

Venous drainage: Via the vaginal venous plexus (which communicates with the uterine, vesical, and rectal venous plexuses) → internal iliac veins.

Clinical Significance: - The rich anastomotic blood supply explains why vaginal surgery can be associated with significant bleeding, but also allows good healing. - The vaginal venous plexus communicates with the rectal venous plexus → formation of rectovaginal fistulae can occur with malignancy, Crohn's disease, or radiation. - Varicosities of the vaginal venous plexus can occur in pregnancy.

Lymphatic Drainage of the Vagina

This is a high-yield topic for MRCOG Part 1:

Key point: The lower 1/3 of the vagina drains to superficial inguinal lymph nodes, while the upper 2/3 drains to pelvic lymph nodes (internal iliac). This is important for surgical management of vaginal cancer.

Nerve Supply of the Vagina

Clinical Significance: - The lower 1/3 of the vagina is sensitive to pain, touch, and temperature (somatic innervation via pudendal nerve). - The upper 2/3 of the vagina is relatively insensitive to pain (visceral innervation) — this is why vaginal surgery (e.g., hysterectomy) is often performed under regional anaesthesia (epidural/spinal) without discomfort. - Pudendal nerve block anaesthetises the lower vagina and perineum (used for operative vaginal delivery and perineal repair). - Vaginismus: Involuntary spasm of the vaginal muscles (pubococcygeus), often psychogenic in origin.

Bartholin's Glands (Greater Vestibular Glands)

• Located in the posterolateral aspect of the vaginal introitus, at 4 o'clock and 8 o'clock positions.
• Each gland is ~1 cm (pea-sized), deep to the bulbospongiosus muscle.
• Ducts open into the posterolateral vestibule (at the level of the hymenal ring).
• Secrete alkaline mucus during sexual arousal (lubrication).
• Bartholin's cyst: Duct obstruction (most common vulval cyst); may become infected (Bartholin's abscess).
• Bartholin's carcinoma: Rare (~1% of vulval cancers); occurs in older women; usually squamous cell or adenocarcinoma.

Skene's Glands (Paraurethral Glands)

• Located on the anterior wall of the vagina, near the urethral meatus.
• Homologous to the male prostate.
• Open into the urethral orifice or just within the urethra.
• Secrete mucus; thought to contribute to female ejaculation.
• Skene's duct cyst/abscess: Uncommon; may cause urethral obstruction.
• Skene's gland carcinoma: Extremely rare.

3. Supports of the Uterus

The uterus is supported by a complex system of ligaments, fasciae, and the pelvic floor. The traditional description of uterine supports includes three levels (DeLancey's levels) but the "ligaments" are actually fibromuscular condensations of endopelvic fascia.

3.1 DeLancey's Three Levels of Uterine Support

3.2 Detailed Ligamentous Supports

Cardinal Ligaments (Mackenrodt's Ligaments / Transverse Cervical Ligaments)

• Location: Base of the broad ligament, extending from the cervix and upper vagina to the lateral pelvic walls.
• Composition: Condensations of endopelvic fascia containing smooth muscle, connective tissue, blood vessels (uterine artery and vein), and nerves.
• Function: Primary support of the cervix and upper vagina. Prevents uterine prolapse.
• Surgical significance: The cardinal ligament is clamped and ligated during hysterectomy. The ureter passes through the cardinal ligament ~1.5–2.0 cm lateral to the cervix and runs under the uterine artery ("water under the bridge").
• Injury: Damage to the cardinal ligaments (during childbirth, or by traction/avulsion) contributes to pelvic organ prolapse.

Uterosacral Ligaments

• Location: From the cervix (at the level of the internal os) and upper vagina, passing posteriorly and superiorly to the sacrum (S2–S3).
• Composition: Smooth muscle and connective tissue, containing nerve fibres from the inferior hypogastric plexus (Frankenhäuser's plexus).
• Function: Pull the cervix posteriorly and superiorly, maintaining the uterus in anteversion.
• Surgical significance:
• The uterosacral ligaments are a key site of endometriosis (torch-light appearance on laparoscopy).
• Used as anchoring sutures in uterosacral ligament suspension (McCall's culdoplasty) during vaginal hysterectomy to prevent vault prolapse.
• Uterosacral nerve ablation (LUNA — laparoscopic uterosacral nerve ablation) was historically performed for dysmenorrhoea (now less common due to limited efficacy).
• Palpation: On rectovaginal examination, the uterosacral ligaments may be tender in endometriosis or PID.

Round Ligaments

• Origin: Uterine cornua (anterolateral aspect, below the tubal insertion).
• Course: Passes through the inguinal canal (via the deep inguinal ring) and terminates in the labia majora (blending with the subcutaneous tissue).
• Length: ~10–12 cm.
• Contents: Smooth muscle, connective tissue, blood vessels, lymphatics, and the genital branch of the genitofemoral nerve (L1–L2).
• Function: Maintains anteversion of the uterus (pulls fundus forward).
• In pregnancy: The round ligaments hypertrophy and elongate. They can cause round ligament pain — sharp, stabbing groin pain in the second trimester.
• Surgical significance: The round ligaments may be used for uterine suspension (in some pelvic reconstructive procedures). During laparoscopy, they are grasped to manipulate the uterus.

Broad Ligament

• Definition: A double-fold of peritoneum draping over the uterus and extending to the lateral pelvic walls.
• Shape: Coronally oriented, dividing the pelvic cavity into an anterior (vesicouterine) and posterior (rectouterine) compartment.

Subdivisions of the Broad Ligament

Components within the Broad Ligament: - Fallopian tube (uppermost margin). - Ovarian ligament (proper ligament of ovary). - Round ligament. - Uterine and ovarian vessels. - Ureter (at the base, just above the lateral fornix). - Epoophoron and paroophoron (Wolffian remnants). - Lymphatics and nerves.

Clinical Significance: - Broad ligament haematoma: Can occur after trauma or during difficult hysterectomy if the uterine artery retracts. This is a surgical emergency. - Broad ligament fibroids: Uterine fibroids that grow laterally, extending into the broad ligament. They can compress the ureter. - Broad ligament pregnancy: A rare form of ectopic pregnancy (secondary abdominal pregnancy). - Ovarian cancer: The broad ligament provides a peritoneal surface for tumour spread.

Pubocervical Fascia

• Location: A fibromuscular sheet extending from the cervix to the pubic bone, on the anterior aspect of the vagina.
• Function: Supports the anterior vaginal wall and bladder base (prevents cystocele).
• Attachments: Lateral attachments to the arcus tendineus fasciae pelvis (ATFP).
• Clinical significance: Defects in the pubocervical fascia (central, lateral, or transverse) cause cystocele and anterior vaginal wall prolapse. Paravaginal defect repair reattaches the pubocervical fascia to the ATFP.

Rectovaginal Fascia (Septum)

• Location: Between the posterior vaginal wall and the rectum.
• Function: Supports the posterior vaginal wall.
• Clinical significance: A defect leads to rectocele. Posterior colporrhaphy plicates this fascia.

Vesicouterine Ligament

• Connects the bladder to the anterior cervix.
• Forms the anterior sheath of the ureter (the ureter runs within a tunnel in this ligament before entering the bladder).
• Important during vaginal hysterectomy — avascular plane between cervix and bladder is developed, and the vesicouterine ligament must be clamped.

3.3 The Broad Ligament: Detailed Contents

3.4 Summary: Key Ligaments and Their Functions

4. Blood Supply of the Pelvis

A thorough understanding of pelvic blood supply is essential for MRCOG Part 1, as surgical procedures (hysterectomy, oophorectomy, myomectomy) and obstetric emergencies (PPH) require precise knowledge of the vascular anatomy.

4.1 Arterial Supply

Abdominal Aorta and its Branches

The abdominal aorta bifurcates at the level of L4 (the transpyloric plane) into the right and left common iliac arteries.

Common Iliac Artery

• Left common iliac: Crosses the left common iliac vein (which lies medial and slightly posterior).
• Right common iliac: Crosses the termination of the IVC.
• Relation: Both are crossed by the ureter at their bifurcation (L5–S1 level). This is the true pelvic brim — a critically important anatomical relationship: "the ureter crosses the pelvic brim at the bifurcation of the common iliac artery."

Internal Iliac Artery (Hypogastric Artery)

The internal iliac artery is the main arterial supply of the pelvic viscera and perineum. It divides into an anterior division and a posterior division at the upper border of the greater sciatic foramen.

Anterior Division of the Internal Iliac Artery

Posterior Division of the Internal Iliac Artery

Uterine Artery

The uterine artery is the most surgically significant vessel in gynaecology.

• Origin: Anterior division of the internal iliac artery (sometimes with the vaginal artery as a common trunk).
• Course:
• Descends on the lateral pelvic wall.
• Crosses the ureter anteriorly (the ureter runs below the uterine artery — "water under the bridge" — at ~1.5–2 cm lateral to the cervix).
• Reaches the lateral side of the cervix at the isthmus (level of internal os).
• Ascends along the lateral uterine wall (the ascending branch).
• Anastomoses with the ovarian artery at the tubo-ovarian junction.
• Branches:

Clinical Significance of the Uterine Artery: - Hysterectomy: The uterine artery is ligated during hysterectomy. At the isthmus level, it is ligated by clamping the cardinal ligament (which contains the artery). The ureter must be identified and protected. - Uterine artery ligation: Can be performed as a fertility-sparing procedure for postpartum haemorrhage (PPH) or for large fibroids. - Uterine artery embolisation (UAE): Interventional radiology procedure for symptomatic fibroids. Catheterisation of the uterine artery and embolisation with particles. - Internal iliac artery ligation: Life-saving procedure for uncontrollable PPH. Reduces pulse pressure in the uterine arteries by ~85%, allowing clot formation. - "Water under the bridge": The relationship of the ureter passing under the uterine artery is one of the most tested anatomical facts in MRCOG. During hysterectomy, the uterine artery is ligated above the ureter to avoid ureteric injury.

Ovarian Artery

• Origin: From the abdominal aorta at the level of L2 (below the renal artery origin).
• Course: Descends retroperitoneally, crosses the pelvic brim within the infundibulopelvic ligament, enters the mesovarium, and reaches the ovarian hilum.
• Anastomoses: With the ovarian branch of the uterine artery at the tubo-ovarian junction.
• Branches: Tubal branches to the lateral 1/3 of the tube.
• Clinical significance: Ligated during oophorectomy (part of the infundibulopelvic ligament division). The ureter runs medially and parallel to the ovarian vessels in the infundibulopelvic ligament — it must be identified before ligation.

Vaginal Artery

• Origin: Anterior division of internal iliac artery (sometimes arises from the uterine artery).
• Course: Descends on the lateral vagina.
• Anastomoses: With the descending (cervicovaginal) branch of the uterine artery and with branches from the middle rectal and internal pudendal arteries.
• Supply: Middle and lower vagina; adjacent bladder base.

Internal Pudendal Artery

• Origin: Anterior division of internal iliac artery.
• Course: Exits the pelvis via the greater sciatic foramen (below piriformis), crosses the ischial spine, and re-enters the pelvis via the lesser sciatic foramen to enter the pudendal canal (Alcock's canal) on the lateral wall of the ischiorectal fossa.
• Branches in the perineum:

Clinical Significance: - Pudendal nerve block: The internal pudendal vessels and pudendal nerve run together in Alcock's canal. Transvaginal pudendal nerve block targets this region. - Perineal trauma: Lacerations involving the perineal branches can cause significant bleeding.

Corona Mortis ("Crown of Death")

• An anastomotic network between the obturator artery (from internal iliac) and the pubic branch of the inferior epigastric artery (from external iliac).
• Located on the posterior surface of the pubic ramus.
• Clinical significance: Can be injured during inguinal hernia repair, placement of retropubic slings (TVT procedures), or pelvic fracture fixation — leading to significant (and potentially fatal) haemorrhage.

4.2 Venous Drainage

The pelvic venous system is characterised by extensive venous plexuses that communicate freely.

Ovarian Veins

• Right ovarian vein: Drains into the inferior vena cava (at L2 level, below the renal veins).
• Left ovarian vein: Drains into the left renal vein (at L1–L2 level).
• Pampiniform plexus: The venous network in the mesovarium that coalesces to form the ovarian vein.
• Clinical significance: The left ovarian vein's longer course and drainage into the left renal vein makes it more prone to pelvic congestion syndrome and pelvic varices (because of higher venous pressure). This is analogous to the left testicular vein draining into the left renal vein in males (left varicocele).

Uterine Veins

• The uterine venous plexus is a network of veins in the broad ligament (parametrium), surrounding the uterine artery and ureter.
• The uterine veins drain into the internal iliac vein.
• Clinical significance: The uterine venous plexus is a site of venous haemorrhage during hysterectomy. The close relationship with the ureter means that haematoma formation can compress or involve the ureter.

Vaginal Venous Plexus

• Surrounds the vagina, communicating with the uterine, vesical, and rectal venous plexuses.
• Drains into the internal iliac vein.
• Clinical significance: Varicosities of the vaginal plexus can occur in pregnancy and cause discomfort.

Rectal Venous Plexus

• Internal rectal plexus (submucosal) and external rectal plexus (perimuscular).
• Drains via the superior rectal vein (portal system → inferior mesenteric vein → portal vein) and the middle/inferior rectal veins (systemic → internal iliac vein).
• Portosystemic anastomosis: The superior rectal vein (portal) communicates with the middle and inferior rectal veins (systemic). This is one of the important porto-caval (porto-systemic) anastomoses in the body.

Portocaval (Porto-Systemic) Anastomoses in the Pelvis

The pelvis contains one of the four major porto-systemic anastomoses:

Key point: In portal hypertension, blood shunts from the portal system to the systemic system through these anastomoses. In the rectum, the superior rectal vein (portal) and middle/inferior rectal veins (systemic) communicate, leading to rectal varices (confused clinically with haemorrhoids).

Pelvic Venous Plexus Summary

Summary: Key Vessels by Region

5. Lymphatic Drainage of the Pelvis

Lymphatic drainage is extremely high yield for MRCOG Part 1. Understanding the lymphatic pathways is essential for understanding the spread of gynaecological malignancies and the rationale for lymphadenectomy.

5.1 Lymph Node Groups of the Pelvis

Anatomical Groups

Surgical Relevance

• Pelvic lymphadenectomy: Performed during surgical staging for cervical, endometrial, and ovarian cancer. External iliac, internal iliac, and obturator nodes are removed (above the obturator nerve).
• Para-aortic lymphadenectomy: Performed for ovarian cancer staging and for advanced cervical/endometrial cancer.
• Sentinel lymph node biopsy: Used in vulval cancer (inguinal nodes) and cervical/endometrial cancer (detection of SLNs with radiotracer/dye).

5.2 Lymphatic Drainage by Organ

Vulva

Key facts: - The vulva drains primarily to the superficial inguinal lymph nodes. - The clitoris can drain directly to the deep inguinal nodes (bypassing the superficial nodes) — this explains why clitoral carcinoma can present with deep nodal metastases. - Bilateral drainage: The vulvar lymphatics cross the midline at the mons pubis and perineum — tumours within 1 cm of the midline (including clitoral and perineal) can spread bilaterally. - Sentinel node: The sentinel node for vulvar cancer is in the groin (superficial inguinal). The technique involves peritumoral injection of radiotracer and blue dye. - Vulval cancer surgery: Radical vulvectomy with inguinofemoral lymphadenectomy.

Vagina

Key facts: - The vagina has a dual lymphatic drainage based on embryological origin. - This is a critical MRCOG concept: upper vagina (from Müllerian primordium) drains to pelvic nodes; lower 1/3 (from urogenital sinus) drains to inguinal nodes. - Vaginal cancer: Treatment depends on location — upper 1/3 treated like cervical cancer (pelvic RT + brachytherapy); lower 1/3 treated like vulval cancer (including groin nodes).

Cervix

The lymphatic drainage of the cervix is the most clinically important in gynaecological oncology.

Main Lymphatic Pathways

Summary of Cervical Lymphatic Drainage:

Cervix
  ↓
Parametrial nodes (first echelon in parametrium)
  ↓
Obturator nodes (medial to obturator nerve)
Internal iliac (hypogastric) nodes
  ↓
Common iliac nodes (at L5–S1 level)
  ↓
Para-aortic (lumbar) nodes (L1–L4 level)
  ↓
Cisterna chyli → Thoracic duct → Left subclavian vein

Sentinel nodes for cervical cancer: Typically found in the obturator and internal iliac regions. Detection rates >90% with combined radiotracer + blue dye technique.

Clinical significance: - Cervical cancer spreads stepwise: parametrial → obturator → internal iliac → common iliac → para-aortic. - Para-aortic nodal metastasis in cervical cancer indicates advanced disease (stage IIIC2 in FIGO 2018+). - Obturator nodes are the most common site of pelvic nodal metastasis from cervical cancer. - Bilateral drainage: False — the cervix drains primarily to ipsilateral nodes. However, advanced disease and the uterosacral pathway can lead to contralateral and presacral spread. - Parametrial invasion is a marker of poor prognosis (stage IIB).

Uterine Body (Corpus)

Key facts: - The fundus has a dual drainage pathway: para-aortic (via infundibulopelvic ligament) and inguinal (via round ligament through the inguinal canal). This is why endometrial cancer can rarely present with an inguinal node metastasis. - In endometrial cancer, the risk of nodal metastasis depends on histology (grade, type), myometrial invasion depth, and lymphovascular space invasion (LVSI). - Surgical staging: Pelvic and para-aortic lymphadenectomy is performed for high-risk endometrial cancer. - Sentinel node biopsy in endometrial cancer: SLNs are typically found in the obturator/internal iliac and para-aortic regions.

Ovaries

Key facts: - The primary lymphatic drainage of the ovary is to the para-aortic nodes, not the pelvic nodes. This is because the embryological origin of the ovary is near the developing kidney (L1–L2), and the lymphatics follow the gonadal vessels. - Ovarian cancer: Common sites of metastasis include the para-aortic nodes, omentum, peritoneal surfaces, and the contralateral ovary. - The right ovarian lymphatics drain to para-aortic nodes on both sides of the vena cava, while left ovarian lymphatics drain to nodes around the left renal hilus. - Surgical staging: Comprehensive staging includes infracolic omentectomy, peritoneal biopsies, and para-aortic lymphadenectomy.

Fallopian Tubes

Rectum

5.3 Lymphatic Drainage Summary Table

6. Nerve Supply of the Pelvis

The nerve supply of the pelvis includes both somatic nerves (supplying the pelvic wall, pelvic floor, and perineum) and autonomic nerves (supplying the pelvic viscera).

6.1 Somatic Nerves of the Pelvis

Lumbosacral Plexus

The lumbosacral plexus is formed by the ventral rami of L1–S4. It provides the somatic nerve supply to the lower limb, pelvic wall, perineum, and pelvic floor.

Lumbar Plexus (L1–L4)

Sacral Plexus (L4–S4)

Pudendal Nerve

The pudendal nerve is the most important nerve for the pelvic floor and perineum. It is the "nerve of the perineum."

Course of the Pudendal Nerve

1. Origin: Sacral plexus (S2–S4).
2. Exit: Leaves the pelvis via the greater sciatic foramen (between piriformis and ischiococcygeus).
3. Relation: Crosses the posterior surface of the ischial spine (just medial to the internal pudendal vessels).
4. Re-entry: Enters the perineum via the lesser sciatic foramen.
5. Canal: Runs in the pudendal (Alcock's) canal — a fascial tunnel on the lateral wall of the ischiorectal (ischioanal) fossa, formed by the split of the obturator internus fascia.
6. Termination: Divides into its three terminal branches at the posterior border of the perineal membrane.

Branches of the Pudendal Nerve

Key point: The dorsal nerve of the clitoris is the terminal branch of the pudendal nerve. It is purely sensory — it provides sensation to the clitoris (critical for sexual function). It does not supply the corpora cavernosa (which are supplied by parasympathetic fibres from the pelvic splanchnic nerves).

Pudendal Nerve Block

Indications: - Operative vaginal delivery (forceps, vacuum-assisted). - Episiotomy and repair of perineal tears. - Perineal suturing.

Technique: - Transvaginal approach: The ischial spine is palpated vaginally. A needle is guided to the region of the ischial spine (just inferoposterior to the spine), through the vaginal wall, and into the pudendal canal. - Local anaesthetic (e.g., lidocaine 1%) is injected to block the nerve. - Alternative: Transperineal approach.

Coverage: Anaesthetises the lower 1/3 of the vagina, posterior perineum, perineal body, and external anal sphincter.

Complications: Intravascular injection (penetration of internal pudendal vessels), haematoma, ischiorectal fossa abscess, nerve damage.

6.2 Autonomic Nerves of the Pelvis

Sympathetic Innervation

Presacral Nerve (Superior Hypogastric Plexus)

• Location: Retroperitoneal, anterior to L5–S1, between the common iliac arteries, in the presacral space (triangle bounded by the two common iliac arteries and the sacral promontory).
• Root value: T11–L2 (preganglionic sympathetic fibres).
• Formation: Continuation of the intermesenteric plexus (aortic plexus) below the aortic bifurcation.
• Fibres:
• Preganglionic: T11–L2 → white rami communicantes → sympathetic chain → splanchnic nerves.
• Postganglionic: Relay occurs at the inferior mesenteric ganglion (for colon/rectum) and in the pelvic autonomic ganglia (for pelvic viscera).

Inferior Hypogastric Plexus (Pelvic Plexus)

• Location: On each side of the pelvis, adjacent to the rectum, bladder, and cervix.
• Formation: Continuation of the superior hypogastric plexus after division into right and left hypogastric nerves (which descend on each side of the pelvis).
• Inputs:
• Sympathetic: From superior hypogastric plexus → hypogastric nerve.
• Parasympathetic: From pelvic splanchnic nerves (S2–S4, erector nerves).
• Output: Forms organ-specific plexuses (e.g., uterovaginal plexus, vesical plexus, rectal plexus).

Frankenhäuser's Plexus (Uterovaginal Plexus / Inferior Hypogastric Plexus)

• Location: In the parametrium, at the base of the broad ligament, adjacent to the supravaginal cervix and vaginal fornices.
• Components: Mixed sympathetic and parasympathetic fibres.
• Supply: Uterus, cervix, upper vagina, bladder base, and rectum.
• Function:
• Sympathetic: Uterine contraction (α-receptors) and vasoconstriction.
• Parasympathetic: Uterine relaxation/vasodilatation, cervical secretion, vaginal lubrication.
• Surgical significance:
• Frankenhäuser's plexus can be damaged during radical hysterectomy (Wertheim's hysterectomy), leading to bladder dysfunction (loss of parasympathetic innervation → atonic bladder).
• Uterosacral nerve ablation (LUNA) was historically performed by transecting the uterosacral ligaments where they contain fibres from the uterovaginal plexus, to treat dysmenorrhoea.

Parasympathetic Innervation (Pelvic Splanchnic Nerves / Erector Nerves)

• Origin: S2–S4 (intermediolateral cell column of the sacral spinal cord).
• Course: Exit via the anterior sacral foramina → join the inferior hypogastric plexus (inferior hypogastric plexus) → travel with sympathetic fibres to pelvic viscera.
• Function:
• Bladder: Detrusor muscle contraction (emptying).
• Rectum: Internal anal sphincter relaxation (defecation).
• Uterus: Vasodilatation, cervical secretion.
• Vagina: Vasodilatation (vaginal lubrication during arousal).
• Erectile tissue: Vasodilatation of helicine arteries → clitoral erection and vestibular bulb engorgement.
• Sexual function: The pelvic splanchnic nerves are the nervi erigentes — they mediate the vascular component of female sexual arousal.

Autonomic Innovation of the Pelvic Viscera — Summary

Sympathetic Chain in the Pelvis

• The sympathetic trunks descend into the pelvis on the anterior surface of the sacrum, medial to the anterior sacral foramina.
• They contain four or five sacral ganglia and terminate in the ganglion impar (unpaired) on the anterior surface of the coccyx.
• The sympathetic trunks communicate with the sacral spinal nerves via grey rami communicantes (there are no white rami below L2).

Visceral Afferent (Sensory) Fibres

Pelvic visceral pain is conducted by sympathetic afferents (to T10–L2 spinal segments) and some parasympathetic afferents (to S2–S4).

Clinical significance: - Ovarian pain (e.g., mittelschmerz, ovarian cysts, torsion) is referred to the periumbilical region (T10). This is why ultrasonography is needed to differentiate ovarian from other lower abdominal pain. - Uterine pain (dysmenorrhoea, labour pain — first stage) is referred to the hypogastric/suprapubic region (T11–L1). - Labour pain: - First stage: Uterine contractions → afferent via T10–L1 (sympathetic) → referred to lower abdomen and back. - Second stage: Distension of the lower vagina, perineum, and pelvic floor → afferent via S2–S4 (pudendal nerve) → referred to perineum. - Epidural anaesthesia during labour blocks T10–S4 to provide effective pain relief.

6.3 Nerve Injuries in Pelvic Surgery

Prevention of Nerve Injuries in Surgery

• Obturator nerve: Visualise the nerve during pelvic lymphadenectomy. The nerve runs on the medial side of the obturator vessels. During transobturator tape (TOT) procedures, the tape passes through the obturator membrane — the nerve must be avoided.
• Femoral nerve: Avoid placing deep retractor blades on psoas muscle. Ensure proper positioning in lithotomy (avoid excessive hip flexion/external rotation).
• Common peroneal nerve: Protect the fibular neck with padding in lithotomy.
• Iliohypogastric/Ilioinguinal nerves: Identify and retract during Pfannenstiel incision closure. These nerves run between internal oblique and transversus abdominis.
• Pudendal nerve: Minimise prolonged second stage of labour; avoid excessive traction during forceps delivery.

7. Anatomy of the Pelvic Ureter

The ureter is a critical structure in gynaecological surgery. Ureteric injury is one of the most feared complications of pelvic surgery (especially hysterectomy), with an incidence of 0.5–1.5% in routine gynaecological surgery and higher in radical surgery.

7.1 General Features

7.2 Segments of the Ureter

Three Constrictions of the Ureter

7.3 Course and Relations in the Pelvis

Right Ureter vs. Left Ureter

The Ureter in the Pelvis: Detailed Course

1. Crossing the pelvic brim: The ureter crosses the bifurcation of the common iliac artery (at L5–S1, the level of the pelvic brim). It lies anterior to the internal iliac artery as it descends into the pelvis.

2. Ovarian fossa: The ureter descends in the posterior part of the ovarian fossa (fossa of Waldeyer). It is related posteriorly to the internal iliac vessels and obturator vessels/nerve, and anteriorly to the ovary and infundibulopelvic ligament.

3. Parametrium (Cardinal ligament): The ureter enters the base of the broad ligament, passing through the parametrium (the fibroareolar tissue at the base of the broad ligament). It is surrounded by the uterine venous plexus (paracervical venous plexus) — the "ureteric tunnel".

4. Uterine artery crossing: The ureter passes underneath the uterine artery ("water under the bridge") approximately 1.5–2.0 cm lateral to the cervix at the level of the internal os. The uterine artery crosses anteriorly to the ureter, passing from lateral to medial (the uterine artery is above, the ureter is below).

5. Vesicouterine ligament: The ureter runs anteriorly and medially, passing through the vesicouterine ligament in a fibromuscular tunnel (the ureteric tunnel). At this point, it is closely related to the anterior vaginal fornix.

6. Entry into bladder: The ureter pierces the bladder wall obliquely at the vesicoureteric junction (VUJ). The oblique course provides a flap-valve mechanism preventing vesicoureteric reflux.

"Water Under the Bridge" — The Ureter and Uterine Artery Relationship

This is arguably the single most important anatomical relationship for MRCOG Part 1 and for gynaecological surgery.

Lateral pelvic wall
         |
    Internal iliac artery
         |
    Uterine artery
         |          ← Uterine artery crosses ABOVE the ureter
    -----+-----
         |
     *** URETER ***   ← Ureter runs BELOW the uterine artery
         |
    Supravaginal cervix (1.5–2 cm medial)

Why this matters: - During hysterectomy: The uterine artery is ligated at the isthmus level. If the ureter is not identified and protected, it can be clamped, ligated, or transected when the uterine artery pedicle is taken. - Safe technique: The ureter should be identified (palpated or visualised) before ligating the uterine artery. The uterine artery is skeletonised and clamped above the ureter (away from the ureter). - During ureteric surgery or when stenting is needed, the uterine artery crossing is a key landmark.

Summary: Five Sites Where the Ureter is at Risk in Gynaecological Surgery

7.4 Blood Supply of the Ureter

Note: The ureteric arteries run longitudinally in the adventitia and anastomose freely. Therefore, ureteric devascularisation during surgical dissection (stripping the adventitia) can lead to ureteric ischaemia and fistula formation. Minimal dissection of the adventitia is crucial during pelvic surgery.

Venous Drainage of the Ureter

• Corresponding veins follow the arterial supply.
• The peristaltic action of the ureter assists venous return.

7.5 Nerve Supply of the Ureter

7.6 Ureteric Injuries in Gynaecology

Incidence

• Gynaecological surgery accounts for ~75% of all iatrogenic ureteric injuries.
• Incidence: 0.5–1.5% for routine hysterectomy; up to 10–30% for radical hysterectomy.
• Laparoscopic hysterectomy has a slightly higher risk than abdominal hysterectomy.

Types of Injury

Presentation

Prevention of Ureteric Injury

The following strategies are employed: 1. Identify the ureter: Open the retroperitoneal space and visualise/palpate the ureter on the psoas. The "ureteric peristalsis" sign (gentle stroking causes contraction) confirms identification. 2. Ureteric stenting: Pre-operative ureteric stent placement may help in high-risk cases (large fibroids, severe endometriosis, pelvic mass, previous pelvic surgery, distorted anatomy). 3. Use of "ureteric tunnel" dissection: In radical hysterectomy, the ureter is dissected out of the paracervical tunnel to push it laterally. 4. Intra-operative cystoscopy: After complex pelvic surgery, cystoscopy can confirm bilateral ureteric patency (visualised by observing ureteric jets of urine). 5. Minimal adventitial dissection: Preserving the ureteric blood supply. 6. McCall's culdoplasty: Palpate the ureter before placing uterosacral sutures.

Diagnosis of Ureteric Injury

Management

8. Anterior Abdominal Wall

8.1 Layers of the Anterior Abdominal Wall

From superficial to deep:

Inguinal Canal

• Length: ~4 cm.
• Direction: Oblique — runs from deep inguinal ring (midpoint of inguinal ligament) to superficial inguinal ring (superior to pubic tubercle).
• Contents in the female: Round ligament of uterus, ilioinguinal nerve, genital branch of genitofemoral nerve.
• Contents in the male: Spermatic cord (vas deferens, testicular vessels, pampiniform plexus, nerves, lymphatics), ilioinguinal nerve.
• Walls:
• Anterior: External oblique aponeurosis.
• Posterior: Transversalis fascia (reinforced laterally by conjoint tendon).
• Roof: Internal oblique and transversus abdominis (from the conjoint tendon medially).
• Floor: Inguinal ligament (Poupart's) and lacunar ligament (at the medial end).

8.2 Rectus Sheath

The rectus sheath encloses the rectus abdominis and pyramidalis muscles.

Formation Above the Arcuate Line

Above the arcuate line: - Anterior sheath: External oblique + anterior leaf of internal oblique. - Posterior sheath: Posterior leaf of internal oblique + transversus abdominis.

At and Below the Arcuate Line

At the arcuate line (Douglas' line), located ~midway between the umbilicus and the pubic symphysis (approximately 5 cm below the umbilicus):

• The posterior sheath ends (transversus abdominis and the posterior leaf of internal oblique pass anteriorly).
• Below the arcuate line: All three aponeuroses pass anterior to the rectus muscle. The posterior sheath consists only of transversalis fascia and peritoneum.

Rectus Abdominis Muscle

• Origin: Pubic crest and pubic symphysis.
• Insertion: Costal cartilages of ribs 5–7 and xiphoid process.
• Innervation: Intercostal nerves T7–T12.
• Action: Flexes the trunk; compresses abdominal contents.
• Tendinous intersections: The rectus abdominis is crossed by 3–4 tendinous intersections (at the xiphoid, umbilicus, and midway). These are fused to the anterior rectus sheath.

Pyramidalis Muscle

• A small triangular muscle anterior to the lower part of rectus abdominis.
• Origin: Pubic crest; Insertion: Linea alba.
• Innervation: T12.
• Surgical significance: The pyramidalis is present in ~80% of people and is used as a landmark during Pfannenstiel incision (midline identification).

8.3 Blood Supply of the Anterior Abdominal Wall

Arterial Supply

Venous Drainage

Portocaval anastomosis at the umbilicus: Para-umbilical veins (portal) communicate with superficial abdominal veins (systemic → IVC) — clinically evident as caput medusae in portal hypertension.

Lymphatic Drainage

8.4 Surgical Incisions of the Anterior Abdominal Wall

1. Pfannenstiel Incision

• Description: Transverse, slightly curved, ~2–3 cm above the pubic symphysis.
• Length: ~10–15 cm.
• Layers divided:
• Skin.
• Camper's + Scarpa's fascia.
• Anterior rectus sheath (incised transversely along the full width).
• Rectus abdominis muscles are separated in the midline (not cut).
• Peritoneum (opened vertically in the midline).
• Advantages:
• Good cosmetic result (scar hidden by pubic hair).
• Strong fascial closure (low risk of incisional hernia).
• Less postoperative pain than midline incision.
• Adequate access for caesarean section, vaginal hysterectomy, and many gynaecological procedures.
• Disadvantages:
• Limited access to upper abdomen.
• Risk of injury to iliohypogastric and ilioinguinal nerves (L1) — which run between internal oblique and transversus abdominis in this region.
• Bleeding from superficial epigastric vessels.
• Nerves at risk: The iliohypogastric nerve and ilioinguinal nerve run through the layers between internal oblique and transversus abdominis at the level of the incision. They can be entrapped in sutures during closure, causing nerve entrapment syndrome (chronic groin pain/numbness).

2. Midline (Vertical) Incision

• Description: From xiphisternum to pubic symphysis (full) or from umbilicus to pubis (lower midline).
• Layers divided:
• Skin.
• Camper's + Scarpa's fascia.
• Linea alba (decussation of aponeuroses) — incised in the midline.
• Transversalis fascia and peritoneum.
• Advantages:
• Rapid entry.
• Excellent exposure of the entire abdomen.
• Extensile (can be extended up or down).
• No muscle cutting.
• Minimal nerve injury.
• Disadvantages:
• Poorer cosmetic outcome.
• Higher risk of incisional hernia (especially in lower midline if improperly closed).
• More postoperative pain (due to tension on the midline closure).
• Gynaecological indications: Large pelvic masses, ovarian cancer staging, emergency laparotomy, suspected ruptured ectopic.

3. Maylard Incision

• Description: Transverse incision similar to Pfannenstiel, but the rectus abdominis muscles are divided transversely.
• Advantages: Wider exposure than Pfannenstiel (especially lateral access to the pelvis). Muscle division allows access to the paracolic gutters.
• Disadvantages: Division of rectus abdominis increases blood loss and postoperative pain. Slower recovery. May require division of the inferior epigastric vessels.
• Indications: Radical hysterectomy with pelvic lymphadenectomy, where wider lateral access is needed.

4. Cherney Incision

• Description: A transverse suprapubic incision with detachment of the rectus abdominis tendons from the pubic bone (instead of dividing the muscle bellies).
• Advantages: Excellent exposure of the retropubic space (space of Retzius) and deep pelvis. Rectus tendons heal well.
• Disadvantages: Higher risk of symphysis pubis periostitis. Requires careful reattachment of the rectus tendons.
• Indications: Retropubic procedures (e.g., Burch colposuspension, sling procedures), exenteration.

5. Joel-Cohen Incision

• Description: A straight transverse incision higher than Pfannenstiel (approximately 3–5 cm below the umbilicus). The skin and subcutaneous tissue are incised. The rectus sheath is opened in the midline and then stretched transversely (using finger dissection). The rectus muscles are separated (not cut). The peritoneum is opened transversely.
• Advantages:
• Faster than Pfannenstiel (reduced operating time).
• Less blood loss.
• Reduced fever and postoperative pain.
• Faster recovery.
• Popularised for caesarean section (particularly in some low-resource settings and by the Misgav-Ladach method).
• Disadvantages: Higher incision may be less cosmetic; limited access to the deep pelvis.

6. Laparoscopic Port Placements

Common gynaecological laparoscopic port sites: - Umbilical: For the camera (10 mm). - Suprapubic (McBurney's points): For accessory instruments (5 mm) — placed lateral to the inferior epigastric vessels. - Midline suprapubic: For uterine manipulator or additional instruments (5 mm).

Inferior epigastric vessel injury is a risk during lateral trocar placement. The vessels are visualised transabdominally or via transillumination.

Incision Comparison Table

9. Perineum & Vulva

9.1 The Perineum

Definition and Boundaries

The perineum is the region of the body below the pelvic diaphragm (pelvic floor). It corresponds to the pelvic outlet.

Boundaries: - Anterior: Inferior border of the pubic symphysis. - Anterolateral: Inferior pubic rami, ischial rami. - Lateral: Ischial tuberosities. - Posterolateral: Sacrotuberous ligaments. - Posterior: Coccyx and sacrum.

Perineal Triangles

The perineum is divided into two triangles by a transverse line connecting the ischial tuberosities (through the perineal body):

Boundaries of Triangles

Perineal Body

• As described in section 1.11.
• Located midway between the anus and the vaginal introitus.
• Attachments: bulbospongiosus, superficial transverse perineal, deep transverse perineal, levator ani (pubococcygeus), external anal sphincter.
• The perineal body is a critical support structure — it fuses the pelvic floor muscles and maintains the integrity of the posterior vaginal wall.
• Clinical significance: Obstetric tears of the perineal body (third and fourth degree tears) involve the anal sphincter complex. Repair is essential.

Superficial Perineal Pouch

Boundaries: - Floor: Perineal membrane (inferior fascia of urogenital diaphragm). - Roof: Colles' fascia (deep membranous layer of the superficial perineal fascia). Colles' fascia is continuous with Scarpa's fascia of the anterior abdominal wall. - Lateral: Ischiopubic rami.

Contents (Female): | Structure | Description | |-----------|-------------| | Ischiocavernosus muscle | Covers the crus of the clitoris. Origin: ischial ramus. Insertion: pubic ramus/crus. Function: maintains clitoral erection by compressing the crus | | Bulbospongiosus muscle | Covers the vestibular bulb. Origin: perineal body. Insertion: clitoris. Function: compresses the bulb, constricts the vaginal introitus | | Superficial transverse perineal muscle | Origin: ischial ramus. Insertion: perineal body. Function: stabilises the perineal body | | Crus of clitoris (2) | Attached to ischiopubic rami; covered by ischiocavernosus | | Vestibular bulb (2) | Erectile tissue on each side of the vaginal introitus; covered by bulbospongiosus | | Greater vestibular glands (Bartholin's glands) | Posterior to the vestibular bulb; ducts open into the vestibule |

Deep Perineal Pouch

Boundaries: - Floor: Perineal membrane (inferior fascia). - Roof: Superior fascia of the urogenital diaphragm. - Lateral: Ischiopubic rami.

Contents (Female): | Structure | Description | |-----------|-------------| | Deep transverse perineal muscle | Origin: ischial ramus. Insertion: perineal body. Function: stabilises the perineal body (with superficial transverse perineal) | | Compressor urethrae | Female-specific muscle; compresses the urethra | | Sphincter urethrovaginalis | Female-specific; encircles urethra and vagina | | External urethral sphincter (rhabdosphincter) | Striated muscle surrounding the mid-urethra; responsible for voluntary continence | | Dorsal nerve and vessels of the clitoris | Terminal branches of pudendal nerve and internal pudendal vessels | | Proximal part of the vestibular bulb | Small extension into the deep pouch | | Paraurethral (Skene's) glands | Open into the urethra (not strictly within the deep pouch but adjacent) |

Ischiorectal (Ischioanal) Fossa

• Shape: Wedge-shaped space on each side of the anal canal.
• Base: Skin of the perineum.
• Apex: Junction of the obturator internus fascia and the levator ani fascia.
• Medial wall: Levator ani and external anal sphincter.
• Lateral wall: Obturator internus muscle (with its fascia containing the pudendal canal/Alcock's canal).
• Anterior boundary: Transversus perinei muscles.
• Posterior boundary: Sacrotuberous ligament and gluteus maximus.

Contents: - Fat (allows distension during defaecation). - Pudendal nerve and internal pudendal vessels (in Alcock's canal on the lateral wall). - Inferior rectal nerve and vessels (cross the fossa horizontally). - Lymphatics (draining anal canal).

Clinical significance: - Ischiorectal abscess: Infection in the ischiorectal fossa. Presents with severe perianal pain, swelling, and systemic signs. Requires surgical drainage. - Pudendal nerve block: The pudendal nerve and internal pudendal vessels are accessed in the ischiorectal fossa (at the level of the ischial spine). - Posterior sagittal approach: Used for some gynaecological reconstructive procedures (e.g., for rectovaginal fistula repair).

9.2 The Vulva

The vulva (external female genitalia) comprises all structures visible externally.

Blood Supply of the Vulva

Venous drainage: Via the internal pudendal veins → internal iliac veins. Also communicates with the vaginal venous plexus and vesical venous plexus.

Lymphatic Drainage of the Vulva

Primary: Superficial inguinal nodes (superomedial group). Secondary: Deep inguinal nodes → external iliac nodes.

Key facts: - The vulva has rich lymphatic anastomoses crossing the midline. - Midline structures (clitoris, perineum, fourchette) drain bilaterally. - The clitoris has a direct drainage pathway to the deep inguinal nodes (bypassing the superficial nodes). - Vulval cancer: The sentinel node is the first-echelon node in the groin; if negative, groin dissection may be avoided (GROINSS-V trial results). - Inguinofemoral lymphadenectomy: Removal of superficial inguinal nodes (above the cribriform fascia) and deep inguinal nodes (medial to the femoral vein in the femoral canal).

Nerve Supply of the Vulva

Clinical Correlations of Vulval Anatomy

OASIS Classification of Perineal Tears

10. Male Reproductive Anatomy

While MRCOG Part 1 focuses on female anatomy, knowledge of male reproductive anatomy is essential for understanding embryological development, homologous structures, and certain clinical conditions (e.g., intersex disorders, testicular feminisation, congenital adrenal hyperplasia).

10.1 The Testes

Histology of the Testis

Blood Supply

Venous drainage: Pampiniform plexus → testicular vein. - Right testicular vein → IVC. - Left testicular vein → left renal vein (same as left ovarian vein).

Clinical: Varicocele is more common on the left (longer course, drainage into left renal vein at right angle).

Lymphatic Drainage

• Para-aortic nodes (L1–L2) — same as the ovary.
• Key fact: The testis drains to para-aortic nodes, not inguinal nodes. This is because the testis embryologically originates at L1–L2 (like the ovary). Scrotal skin, however, drains to inguinal nodes.

Homologous Structures

10.2 Epididymis

10.3 Vas Deferens (Ductus Deferens)

10.4 Seminal Vesicles

10.5 Prostate Gland

Prostatic Secretions

• Alkaline (pH ~7.3) — helps neutralise acidic vaginal environment.
• Contains PSA (prostate-specific antigen), acid phosphatase, citric acid, zinc.
• ~25–30% of seminal fluid volume.

10.6 Penis

Erection Physiology

• Parasympathetic (S2–S4, pelvic splanchnic/nervi erigentes): Vasodilatation of helicine arteries → increased blood flow into corpora cavernosa → expansion compresses emissary veins → venous occlusion → rigidity.
• Nitric oxide (NO) is the primary neurotransmitter (released by non-adrenergic, non-cholinergic [NANC] neurons and endothelium).
• Sympathetic (T11–L2): Vasoconstriction → detumescence.

10.7 Spermatic Cord

Layers of the spermatic cord (from outside in): 1. External spermatic fascia (from external oblique aponeurosis). 2. Cremasteric fascia + cremaster muscle (from internal oblique). 3. Internal spermatic fascia (from transversalis fascia).

11. The Breast

11.1 Overview

The breast (mamma) is a modified sweat gland (apocrine gland) located on the anterior chest wall, extending from the 2nd to the 6th ribs vertically and from the sternal edge to the mid-axillary line horizontally. It lies over the pectoralis major (deep), serratus anterior (lateral), and external oblique (inferolateral) muscles.

11.2 Structure

Cooper's (Suspensory) Ligaments

• Fibrous bands running from the dermis to the deep fascia (pectoral fascia).
• They support the breast architecture.
• Clinical significance: Invasion by breast carcinoma causes tethering and peau d'orange (lymphatic obstruction causing skin oedema with prominent hair follicles).

Anatomical Extensions

• Tail of Spence (axillary tail): The superolateral quadrant of the breast extends into the axilla, through the axillary fascia in the foramen of Langer (opening in the axillary fascia). This is why breast tissue can be present in the axilla and may be involved in breast cancer.

11.3 Blood Supply

Arterial Supply

Dominant supply: The breast receives approximately 60% of its blood supply from the internal thoracic artery and 30% from the lateral thoracic artery.

Venous Drainage

Batson's vertebral venous plexus: A valveless venous plexus connecting the intercostal veins, pelvic veins, and the vertebral venous system. This provides a route for metastatic spread of breast and prostate cancers to the vertebral column and brain, bypassing the pulmonary circulation.

11.4 Lymphatic Drainage of the Breast

The lymphatic drainage of the breast is critically important for understanding the spread of breast cancer.

Lymphatic Plexuses

1. Subareolar plexus (Sappey's plexus): Under the areola and nipple — receives lymph from the nipple, areola, and central ducts.
2. Cutaneous (subepidermal) plexus: Drains the skin of the breast.
3. Deep parenchymal (intraglandular) plexus: Drains the glandular tissue.
4. Submammary plexus: Deep to the breast, on the pectoral fascia — communicates with the parasternal lymphatics and the subdiaphragmatic/subhepatic lymphatics.

Lymphatic Pathways

Axillary Lymph Nodes — Berg's Levels

The axillary lymph nodes are divided into three levels relative to the pectoralis minor muscle:

Sentinel lymph node: The first axillary node(s) receiving lymph from the breast. Identified by peritumoral injection of blue dye and/or radiotracer. Sentinel lymph node biopsy (SLNB) has replaced axillary lymph node dissection (ALND) for clinically node-negative breast cancer.

Axillary lymph node dissection (ALND): Removal of Level I and II nodes (usually preserving Level III unless involved). Complications include: lymphoedema, axillary cording (lymphatic thrombosis), brachial plexus injury, long thoracic nerve injury (winged scapula), and thoracodorsal nerve injury (latissimus dorsi weakness).

Rotter's Nodes

• Location: In the interpectoral fascia between pectoralis major and minor.
• Significance: Part of the mid-axillary (Level II) group. They receive lymph from the breast and also communicate with the internal mammary chain.
• Clinical: Rotter's nodes can be involved in breast cancer and are sometimes included in the axillary dissection specimen.

Lymphoedema

• Pathophysiology: Disruption of axillary lymphatics after ALND or radiotherapy → impaired lymphatic drainage of the arm → accumulation of protein-rich fluid in the subcutaneous tissue.
• Presentation: Ipsilateral arm swelling, heaviness, limited range of motion, recurrent cellulitis.
• Risk factors: Complete ALND, radiotherapy, obesity, infection.
• Management: Compression garments, manual lymphatic drainage (MLD), exercise.

11.5 Nerve Supply of the Breast

Surgical significance: The intercostobrachial nerve (T2) runs from the axilla to the medial arm. It is often sacrificed during ALND, resulting in sensory loss/paresthesia over the medial upper arm.

11.6 Clinical Anatomy of the Breast

12. Embryological Anatomy

Understanding the embryological origins of the female reproductive tract is essential for MRCOG Part 1. Many anatomical anomalies and pathological conditions are explained by abnormal embryological development.

12.1 Early Development (Weeks 1–6)

Indifferent Stage

Up to ~6 weeks of gestation, the embryo has the potential to develop into either male or female reproductive systems (the "indifferent stage").

12.2 Gonadal Development

12.3 Müllerian (Paramesonephric) Duct Development

Normal Development

Müllerian Duct Fusion Abnormalities

Failure of normal fusion or resorption of the paramesonephric ducts results in a spectrum of Müllerian anomalies. The American Fertility Society (AFS, now ASRM) classification:

Key embryological facts: - The fallopian tubes develop from the unfused cranial portions of the Müllerian ducts. - The uterus develops from the fused middle portions of the Müllerian ducts. - The upper 2/3 of the vagina develops from the uterovaginal primordium (fused Müllerian ducts). - The lower 1/3 of the vagina develops from the urogenital sinus (sinovaginal bulbs). - The hymen is the remnant of the urogenital sinus membrane that separates the vaginal lumen from the vestibule.

Clinical significance: - MRKH syndrome: Absent uterus and upper vagina (agenesis of Müllerian ducts). Presents with primary amenorrhoea. Normal secondary sexual characteristics and normal ovaries. Treated with vaginal dilation or surgical creation of a neovagina (McIndoe's procedure or Vecchietti procedure). - Transverse vaginal septum: Failure of canalisation of the vaginal plate → can cause haematocolpos (cyclic pain, primary amenorrhoea with an otherwise normal uterus). - Longitudinal vaginal septum: Incomplete resorption of the septum between fused Müllerian ducts → can cause dyspareunia or obstructive symptoms (double vagina). - Imperforate hymen: The urogenital sinus membrane fails to perforate → presents at menarche with haematocolpos (bulging blue-tinged hymen, cyclic abdominal pain, primary amenorrhoea).

12.4 Wolffian (Mesonephric) Duct Remnants

In female embryos, the Wolffian (mesonephric) ducts regress in the absence of anti-Müllerian hormone (AMH) and testosterone. However, remnants persist in specific locations:

Key fact: Gartner's duct cysts are located in the anterolateral vaginal wall (the course of the embryological mesonephric duct). They must be differentiated from Bartholin's duct cysts (posterolateral, at 4 and 8 o'clock) and Skene's duct cysts (anterior, adjacent to the urethra).

Comparison: Vaginal Cysts

12.5 Development of the Vagina

Vaginal Plate Theory (Meyer-Bulmer Theory)

The vagina develops from two embryological sources:

Stages of Vaginal Development

Clinical significance: - Vaginal agenesis (MRKH): Failure of development of the uterovaginal primordium. The vagina may be absent or represented by a shallow dimple. Ovaries are normal. - Transverse vaginal septum: Failure of the vaginal plate to canalise completely. Can occur at the upper, middle, or lower vagina. Can cause haematocolpos/hematometra at menarche. - Longitudinal vaginal septum: Incomplete resorption of the fused Müllerian duct walls. Associated with uterus didelphys or bicornuate/septate uterus. - Vaginal atresia: Congenital absence of the lower 1/3 of the vagina (urogenital sinus contribution fails). Upper vagina and uterus are normal.

12.6 Development of the External Genitalia

Clinical Correlations

12.7 Descent of the Ovaries

Clinical: Ovarian descent is less dramatic than testicular descent. The ovaries remain in the pelvis; they do not exit through the inguinal canal. However, the round ligament does traverse the inguinal canal (remnant of the female gubernaculum), which explains why the round ligament can be a site of endometriosis (ectopic endometrial tissue tracking along the ligament) and why indirect inguinal hernias in females contain the round ligament (or sometimes an ovary or fallopian tube).

12.8 Remnants of Embryological Structures — Summary Table

Appendix: High-Yield Exam Facts — Quick Reference

Top 20 Must-Know Facts for MRCOG Part 1 Anatomy

1. Obstetric conjugate is the shortest AP diameter of the pelvic inlet (~10.5 cm). It cannot be measured clinically; it is estimated from the diagonal conjugate (minus 1.5–2.0 cm).

2. Interspinous diameter (~10.5 cm) is the narrowest fixed pelvic diameter. An interspinous diameter <9.5 cm = mid-cavity contraction.

3. Gynaecoid pelvis is the most favourable for vaginal delivery; android is funnel-shaped, unfavourable; platypelloid has a narrow AP inlet.

4. Uterine artery crosses above the ureter ~1.5–2 cm lateral to the cervix ("water under the bridge").

5. Ureter crosses the pelvic brim at the bifurcation of the common iliac artery. It is most at risk during ligation of the infundibulopelvic ligament and ligation of the uterine artery.

6. Cardinal (Mackenrodt's) ligaments provide primary support for the cervix and upper vagina. They contain the uterine artery.

7. Uterosacral ligaments maintain uterine anteversion. They contain fibres from the inferior hypogastric plexus and are a common site of endometriosis.

8. The ureter runs in the parametrium, surrounded by the uterine venous plexus. It is at risk during hysterectomy.

9. Vulva → superficial inguinal nodes; Lower 1/3 vagina → superficial inguinal nodes; Upper 2/3 vagina → internal iliac nodes; Cervix → parametrial → obturator → internal iliac → common iliac → para-aortic; Uterine fundus → para-aortic (and inguinal via round ligament); Ovary → para-aortic (L1–L2).

10. Ovarian artery arises from the aorta at L2. Right ovarian vein → IVC; Left ovarian vein → left renal vein.

11. Pelvic splanchnic nerves (S2–S4) = nervi erigentes. Parasympathetic supply to pelvic viscera. Their damage during radical hysterectomy causes atonic bladder.

12. Pudendal nerve (S2–S4) supplies the perineum, external anal sphincter, and clitoris. It runs in Alcock's canal (on the lateral wall of the ischiorectal fossa). Blocked at the level of the ischial spine.

13. Frankenhäuser's plexus (uterovaginal plexus) is located in the parametrium at the base of the broad ligament. It innervates the uterus, cervix, and upper vagina.

14. Round ligament passes through the inguinal canal to the labia majora. It contains the genital branch of the genitofemoral nerve (cremasteric reflex in males).

15. Broad ligament is a double layer of peritoneum. Subdivisions: mesometrium (largest), mesosalpinx (contains fallopian tube), mesovarium (contains ovary).

16. Müllerian duct fusion abnormalities: septate uterus (Class V — highest risk of reproductive failure), bicornuate (Class IV), didelphys (Class III), unicornuate (Class II). MRKH syndrome (Class I) = absent uterus and upper vagina.

17. Gartner's duct cyst = anterolateral vaginal wall (mesonephric duct remnant). Bartholin's cyst = posterolateral vestibule (urogenital sinus origin).

18. Breast lymphatic drainage: ~75% to axillary nodes (Levels I, II, III). The sentinel node is at Level I (low axillary, lateral to pectoralis minor).

19. Portocaval anastomosis in the pelvis: Superior rectal vein (portal) ↔ middle/inferior rectal veins (systemic) → rectal varices in portal hypertension.

20. Cooper's ligaments (breast) — tethering by carcinoma causes skin dimpling. Corona mortis — anastomosis between obturator and inferior epigastric arteries; can cause life-threatening bleeding if injured during surgery.

Important Anatomical Relations — Quick Table

Diameter Reference Card

Lymph Node Levels — Quick Reference

End of Document

This comprehensive guide has covered all anatomical topics required for MRCOG Part 1.

Key revision strategy: Focus on the relationships (ureter-uterine artery), lymphatic drainage pathways, pelvic dimensions, and embryological development — these are the highest-yield topics consistently tested in the exam.

Good luck with your MRCOG Part 1 preparation!