---

Abdomen - Important Topics for MBBS 1st Year (Detailed Notes)

---

TOPIC 1: Boundaries and Surface Anatomy of the Abdomen

• Above: Costal margin (separates abdomen from thorax)
• Below: Pubic tubercle, Anterior Superior Iliac Spine (ASIS), iliac crest
• The inguinal ligament runs between ASIS and pubic tubercle, separating the anterior abdominal wall from the thigh
• The dome of the right diaphragm can reach as high as the 4th costal cartilage during forced expiration - so abdominal viscera in this upper region are protected by the thoracic cage

• Gray's Anatomy for Students, p. 466

---

TOPIC 2: Layers of the Anterior Abdominal Wall

1. Skin
2. Superficial fascia - has two layers:
   • Camper's fascia - superficial fatty layer
   • Scarpa's fascia - deep membranous layer (continues into the perineum as Colles' fascia)
3. Three flat muscles + their aponeuroses (see below)
4. Transversalis fascia - lines the inner surface of transversus abdominis
5. Extraperitoneal fascia - divided into preperitoneal (anteriorly) and retroperitoneal (posteriorly)
6. Parietal peritoneum - innermost lining

---

TOPIC 3: Muscles of the Anterolateral Abdominal Wall

Flat Muscles (Lateral Group)

Vertical Muscles (Medial Group)

Clinical Mnemonics

• The fiber direction of flat muscles: External oblique - "hands in pockets" (downward-medial); Internal oblique - perpendicular; Transversus - horizontal.
• Rectus abdominis has 3-4 tendinous intersections which are visible in developed individuals (the "six-pack").

Key Structures Formed by Aponeuroses:

• Above arcuate line: anterior wall = external oblique + anterior leaf of internal oblique; posterior wall = posterior leaf of internal oblique + transversus
• Below arcuate line: all three aponeuroses pass anterior to rectus, leaving the posterior wall covered only by transversalis fascia

• Gray's Anatomy for Students, p. 344

---

TOPIC 4: Innervation of the Anterior Abdominal Wall

• Intercostal nerves (T7-T11) leave their intercostal spaces and run between internal oblique and transversus abdominis, then enter the rectus sheath to supply skin via anterior cutaneous branches
• T12 = subcostal nerve
• L1 = gives iliohypogastric and ilio-inguinal nerves

• T7-T9 = above umbilicus
• T10 = at the umbilicus
• T11-T12 = below umbilicus
• L1 = groin

---

TOPIC 5: Inguinal Canal

Key Facts:

• Length: Approximately 4 cm
• Direction: Downward and medially, parallel to the lower half of the inguinal ligament
• Begins at: Deep (internal) inguinal ring
• Ends at: Superficial (external) inguinal ring

Deep Inguinal Ring

• Located midway between ASIS and pubic symphysis, just above the inguinal ligament
• Lies lateral to the inferior epigastric vessels (important for distinguishing indirect vs direct hernia)
• Not a true hole - it is an evagination of the transversalis fascia

Superficial Inguinal Ring

• Located superolateral to the pubic tubercle
• Triangular opening in the aponeurosis of external oblique
• Apex points superolaterally; base formed by pubic crest
• Two crura: medial crus (to pubic symphysis) and lateral crus (to pubic tubercle)
• Held together at apex by intercrural fibers

Walls of the Inguinal Canal

Contents:

Spermatic Cord Coverings (from outside in):

1. External spermatic fascia - from external oblique aponeurosis
2. Cremasteric fascia and cremasteric muscle - from internal oblique
3. Internal spermatic fascia - from transversalis fascia

Contents of Spermatic Cord:

• Ductus (vas) deferens
• Testicular artery (from aorta)
• Artery to ductus deferens
• Cremasteric artery (from inferior epigastric)
• Pampiniform plexus of veins
• Lymphatics
• Sympathetic nerves
• Genital branch of genitofemoral nerve

Clinical Application - Inguinal Hernias:

• Indirect inguinal hernia: Passes through the deep inguinal ring (lateral to inferior epigastric vessels), traverses the inguinal canal, and exits through the superficial ring. More common, especially in males. Congenital.
• Direct inguinal hernia: Protrudes directly through the posterior wall of the inguinal canal (Hesselbach's triangle), medial to inferior epigastric vessels. Acquired, seen in older men with weak abdominal muscles.
• Hesselbach's triangle: Bounded laterally by inferior epigastric vessels, medially by lateral border of rectus abdominis, inferiorly by inguinal ligament.
• Gray's Anatomy for Students, p. 352

---

TOPIC 6: Peritoneum

Definition and Layers:

• The peritoneum is a thin serous membrane lining the abdominal cavity
• Parietal peritoneum: Lines the walls of the abdominal cavity
• Visceral peritoneum: Covers the abdominal viscera
• Peritoneal cavity: Potential space between the two layers. Closed in men; has two openings in women (via uterine tubes)

Peritoneal Cavity Subdivisions:

• Greater sac - main large portion
• Lesser sac (omental bursa) - posterior to the stomach, communicates with greater sac via the epiploic foramen (foramen of Winslow)

Visceral Positions:

• Suprarenal glands (adrenals)
• Aorta + IVC
• Duodenum (2nd-4th parts)
• Pancreas (except tail)
• Ureters
• Colon (ascending and descending)
• Kidneys
• Esophagus (lower part)
• Rectum

Peritoneal Folds and Ligaments:

• Mesentery: Fan-shaped fold connecting jejunum/ileum to posterior abdominal wall; root goes from left of L2 to right iliac fossa
• Greater omentum: Apron-like fold hanging from greater curvature of stomach; acts as "abdominal policeman" by walling off infections
• Lesser omentum: Between liver and lesser curvature of stomach + duodenum; contains hepatic artery, portal vein, bile duct in its free edge
• Falciform ligament: Connects liver to anterior abdominal wall; contains ligamentum teres (obliterated umbilical vein) in its free edge
• Coronary ligament: Connects liver to diaphragm

Innervation of Peritoneum:

• Parietal peritoneum - somatic innervation (spinal nerves T7-L1) → well-localized, sharp pain; tenderness and guarding
• Visceral peritoneum - autonomic/visceral innervation → poorly localized, dull, crampy pain; referred pain patterns

Pouches (Clinically Important):

• Hepatorenal pouch (Morrison's pouch): Between liver and right kidney; lowest point of peritoneal cavity when supine - fluid collects here first
• Recto-uterine pouch (Pouch of Douglas): In females, between uterus and rectum; lowest point of peritoneal cavity in females when standing - fluid, pus, blood collect here first
• Vesico-uterine pouch: Between bladder and uterus in females
• Paracolic gutters: On either side of the ascending/descending colon - allows fluid to spread up to the subphrenic space
• Gray's Anatomy for Students, p. 346, 362

---

TOPIC 7: Hernias of the Abdominal Wall

Types:

1. Inguinal hernia (most common overall) - see above
2. Femoral hernia: Below and lateral to pubic tubercle, through femoral canal. More common in females. High risk of strangulation.
3. Umbilical hernia: Through umbilicus - congenital (failure of bowel to return from umbilical cord) or acquired (para-umbilical in adults)
4. Incisional hernia: Through scar of previous surgery; wide neck, less risk of strangulation
5. Epigastric hernia: Through linea alba between xiphoid and umbilicus
6. Spigelian hernia: Through arcuate line into lateral border of posterior rectus sheath

Parts of a Hernia:

• Sac - peritoneum
• Contents - viscus (omentum, bowel)
• Coverings - layers of abdominal wall

Complications:

• Irreducible: Cannot be pushed back
• Obstructed: Bowel within hernia is obstructed
• Strangulated: Blood supply cut off - surgical emergency
• Gray's Anatomy for Students, p. 351-354

---

TOPIC 8: Stomach

Position:

• Located in the left hypochondrium and epigastric region
• Lies between esophagus (cardia) and duodenum (pylorus)

Parts:

1. Cardia - where esophagus joins (at T11)
2. Fundus - dome-shaped part above cardia, related to left dome of diaphragm
3. Body - largest part
4. Pyloric antrum and pyloric canal - leads to pylorus
5. Pylorus - at L1 vertebra level; contains pyloric sphincter

Curvatures:

• Lesser curvature - right border, related to lesser omentum
• Greater curvature - left border, related to greater omentum

Blood Supply:

Relations:

• Anterior: Left lobe of liver, diaphragm, anterior abdominal wall
• Posterior: Lesser sac (omental bursa), pancreas, left kidney, spleen

Nerve Supply:

• Parasympathetic: Vagus nerves (CN X) - left vagus = anterior, right vagus = posterior
• Sympathetic: T6-T10 via celiac plexus

---

TOPIC 9: Duodenum

• C-shaped structure, about 25 cm long
• Mostly retroperitoneal (except the first 2.5 cm which is intraperitoneal)
• Surrounds the head of the pancreas

Parts:

Blood Supply:

• Superior pancreaticoduodenal artery (from gastroduodenal = celiac)
• Inferior pancreaticoduodenal artery (from superior mesenteric artery)
• This junction marks the boundary between foregut and midgut

---

TOPIC 10: Liver

Position:

• Right hypochondrium + epigastric region
• Protected by lower ribs
• Lower border of liver is felt at the right costal margin at rest

Surfaces and Lobes:

• Diaphragmatic surface (anterior, superior, posterior) - smooth, convex
• Visceral surface (inferior) - has H-shaped fissures dividing into 4 lobes

• Right lobe (largest)
• Left lobe
• Caudate lobe (between IVC and ligamentum venosum)
• Quadrate lobe (between gallbladder and ligamentum teres)

Porta Hepatis (Gateway of the Liver):

1. Hepatic duct (bile duct - anterior)
2. Hepatic artery (middle)
3. Portal vein (posterior and largest)

Blood Supply:

• Hepatic artery proper (25% of blood flow, 50% of oxygen)
• Portal vein (75% of blood flow, 50% of oxygen)
• Drained by hepatic veins (right, middle, left) → IVC

Portal Vein:

• Formed behind the neck of pancreas by union of superior mesenteric vein + splenic vein
• Carries nutrient-rich blood from GI tract and spleen to liver
• No valves (important clinically - portal hypertension)
• Level: L1-L2

Portal-Systemic (Porto-caval) Anastomoses:

Ligaments of Liver:

• Falciform ligament - connects liver to anterior abdominal wall; contains ligamentum teres (obliterated left umbilical vein of fetus) in its free edge
• Coronary ligament - connects liver to diaphragm; the two layers separate to create the bare area of liver (not covered by peritoneum)
• Ligamentum venosum - fibrous remnant of ductus venosus (shunted blood from portal vein to IVC in fetus)

---

TOPIC 11: Gallbladder and Bile Duct

Gallbladder:

• Stores and concentrates bile (up to 10x)
• Located in gallbladder fossa on visceral surface of right lobe of liver
• Parts: Fundus, Body, Neck (neck has spiral valve of Heister; Hartmann's pouch is at the junction of neck and cystic duct - gallstones lodge here)

Calot's Triangle (Cystohepatic Triangle):

• Boundaries: Cystic duct (inferiorly), common hepatic duct (medially), inferior surface of liver (superiorly)
• Contents: Cystic artery (usually a branch of right hepatic artery)
• Critical for cholecystectomy - identify and ligate cystic artery here

Biliary Tree:

---

TOPIC 12: Pancreas

• Both exocrine (acini secrete digestive enzymes) and endocrine (islets of Langerhans: insulin/glucagon)
• Lies retroperitoneal across the posterior abdominal wall at L1-L2

Parts:

1. Head - in the C-loop of duodenum; uncinate process projects from head
2. Neck - anterior to portal vein (formed here); posterior to pylorus
3. Body - crosses L1-L2; posterior to lesser sac
4. Tail - tip enters the splenorenal ligament; only intraperitoneal part; related to hilum of spleen

Main Pancreatic Duct (Wirsung) + Accessory Duct (Santorini):

• Main duct runs from tail to head, joins CBD at ampulla of Vater
• Accessory duct opens separately at minor duodenal papilla above the major papilla

Blood Supply:

• Head: Superior + inferior pancreaticoduodenal arteries
• Body/tail: Splenic artery branches

---

TOPIC 13: Spleen

• Largest lymphoid organ in the body
• Located in left hypochondrium, at the level of ribs 9-11
• Long axis lies along the 10th rib
• Can only be felt clinically when enlarged more than 3 times normal size

Features:

• Notched anterior border - distinguishes spleen from other masses on palpation
• Protected by ribs 9-11; rib fractures commonly injure the spleen
• Lies against the diaphragm, left kidney, and tail of pancreas

Blood Supply:

• Splenic artery (largest branch of celiac trunk; tortuous course along upper border of pancreas)
• Splenic vein (joins superior mesenteric vein → portal vein)

Functions:

• Filters blood (removes old/damaged RBCs)
• Immune function (production of IgM)
• In fetus: hematopoiesis
• Reservoir of blood/platelets

Clinical:

• Splenomegaly: Extends towards right iliac fossa following the line of the 10th rib
• Hypersplenism: Overactive spleen destroys blood cells
• Spleen vs. kidney distinction: Spleen has a notch, cannot "get above" it, moves with respiration, not ballottable, dull to percussion

---

TOPIC 14: Kidneys (Posterior Abdominal Wall)

Position:

• Retroperitoneal, on either side of vertebral column at T12-L3
• Right kidney is lower (pushed down by liver) - at L1-L3
• Left kidney is slightly higher - at T12-L2
• The hilus is at the level of transpyloric plane (L1)

Coverings (from inside out):

1. Fibrous capsule (renal capsule)
2. Perirenal fat (adipose capsule)
3. Renal (Gerota's) fascia - encloses kidney and adrenal gland
4. Pararenal fat (paranephric fat)

Relations of the Kidney:

• Anterior: Right suprarenal gland (superomedial), liver, hepatic flexure of colon, 2nd part of duodenum
• Posterior: Diaphragm, 12th rib, psoas major, quadratus lumborum, transversus abdominis

• Anterior: Left suprarenal gland, stomach, spleen, tail of pancreas, jejunum, splenic flexure of colon
• Posterior: Same muscles + 11th and 12th ribs

Blood Supply:

• Renal arteries from aorta at L1 level (right longer than left)
• Sequence: Segmental arteries → lobar → interlobar → arcuate → interlobular arteries
• Avascular plane (Brodel's line): Between anterior 4 and posterior 1 segment; used for incisions during pyelolithotomy

Ureter (Anatomy):

• ~25 cm long
• Three sites of narrowing (where stones lodge):
  1. Pelviureteric junction (PUJ) - most proximal
  2. Pelvic brim - where ureter crosses iliac vessels
  3. Vesicoureteric junction (VUJ) - where it enters bladder wall (narrowest point)

---

TOPIC 15: Posterior Abdominal Wall Muscles

---

TOPIC 16: Diaphragm

Structure:

• Musculotendinous partition separating thorax from abdomen
• Muscle fibers arise from periphery and converge on the central tendon in the middle

Origins (Three Parts):

• Sternal part: Posterior surface of xiphoid process
• Costal part: Inner surfaces of lower 6 costal cartilages and adjacent ribs
• Lumbar part: Medial and lateral arcuate ligaments + crura (from L1-L3)

Three Major Openings:

• I (IVC) = T8
• Ate (esophagus) = T10
• Eggs (aorta/EGG-orta) = T12

Nerve Supply:

• Motor: Phrenic nerve (C3, C4, C5 - "C3, 4, 5 keeps the diaphragm alive")
• Sensory: Central diaphragm = phrenic nerve (referred to C3-C5 dermatome = shoulder tip); Peripheral = lower intercostal nerves

Clinical:

• Hiatus hernia: Stomach slides through esophageal hiatus (sliding type - most common) or herniates alongside esophagus (rolling/para-esophageal type)
• Phrenic nerve irritation (e.g., blood under diaphragm) causes referred pain to the shoulder tip

---

TOPIC 17: Celiac, Superior Mesenteric, and Inferior Mesenteric Arteries

Celiac Trunk (T12/L1):

1. Left gastric artery - smallest; to stomach (lesser curvature) + lower esophagus
2. Splenic artery - largest; to spleen, gives short gastric and left gastroepiploic arteries, pancreatic branches
3. Common hepatic artery - to liver; gives off gastroduodenal artery (→ superior pancreaticoduodenal + right gastroepiploic) and right gastric artery, then becomes hepatic artery proper

Superior Mesenteric Artery (SMA) (L1):

• Inferior pancreaticoduodenal artery
• Jejunal and ileal arteries (10-16 branches forming arterial arcades → vasa recta)
• Ileocolic artery (→ appendicular artery)
• Right colic artery
• Middle colic artery

Inferior Mesenteric Artery (IMA) (L3):

• Left colic artery
• Sigmoid arteries
• Superior rectal artery

---

TOPIC 18: Important Vertical Planes and Clinical Landmarks

---

Quick Revision Summary Table

---

---

THE PELVIS - Complete MBBS 1st Year Exam Notes

---

TOPIC 1: Introduction and Definition

• Bony pelvis - the skeletal framework
• Pelvic cavity - the space enclosed within it

---

TOPIC 2: Bony Pelvis

Bones Forming the Pelvis:

1. Two hip bones (os coxae) - each formed by fusion of ilium, ischium, and pubis
2. Sacrum
3. Coccyx

Hip Bone (Os Coxae):

Joints of the Pelvis:

Ligaments:

---

TOPIC 3: Greater Pelvis vs. Lesser Pelvis

Pelvic Brim (Linea Terminalis):

• Pubic symphysis (anteriorly) →
• Pubic crest + pectineal line (along superior pubic ramus) →
• Arcuate line of ilium →
• Sacral promontory (posteriorly)

Greater (False) Pelvis:

• Above the pelvic brim
• Part of the abdominal cavity
• Contains iliac fossae and lower abdominal viscera (sigmoid colon, ileum, cecum)
• Has no clinical "obstetric" significance

Lesser (True) Pelvis:

• Below the pelvic brim
• The true pelvic cavity proper
• Contains bladder, rectum, and reproductive organs
• Has an inlet (above), outlet (below), and cavity (between them)
• Clinically significant in obstetrics

---

TOPIC 4: Pelvic Inlet, Cavity, and Outlet

Pelvic Inlet (Superior Pelvic Aperture):

Pelvic Outlet (Inferior Pelvic Aperture):

• Anteriorly: Pubic arch (inferior pubic rami + ischial rami)
• Laterally: Ischial tuberosities + sacrotuberous ligaments
• Posteriorly: Tip of coccyx

Subpubic Angle:

• Males: 70° (narrow, V-shaped - android pelvis)
• Females: 100-110° (wide, U-shaped - gynecoid pelvis)

Pelvic Axis:

---

TOPIC 5: Male vs. Female Pelvis (Sex Differences)

Types of Female Pelvis (Caldwell-Moloy Classification):

1. Gynecoid (50%) - round inlet, wide arch - best for delivery
2. Android (30%) - heart-shaped inlet, narrow arch - poor for delivery, male type
3. Anthropoid (20%) - AP diameter > transverse, oval - delivery possible
4. Platypelloid (rare) - flat pelvis, transverse oval, wide arch - difficult delivery

---

TOPIC 6: Pelvic Walls

Anterior Wall:

Posterior Wall:

• Sacrum (S1-S5)
• Coccyx
• Piriformis muscle covering anterior sacrum

Lateral Walls:

• Inner surface of hip bone below the pelvic brim
• Obturator internus muscle + its fascia (covers most of lateral wall)
• Sacrospinous and sacrotuberous ligaments

Pelvic Wall Muscles:

1. Obturator Internus:

• Origin: Inner surface of obturator membrane + surrounding bone
• Insertion: Greater trochanter of femur (after turning 90° through lesser sciatic foramen)
• Nerve: Nerve to obturator internus (L5, S1, S2)
• Action: Lateral rotation of the extended thigh; abduction of flexed thigh
• Clinical: Its fascia forms the tendinous arch of levator ani and the pudendal canal (Alcock's canal)

2. Piriformis:

• Origin: Anterior surface of sacrum (S2-S4), sacrotuberous ligament
• Insertion: Greater trochanter of femur
• Nerve: S1, S2
• Action: Lateral rotation and abduction of thigh
• Exits: Through greater sciatic foramen, dividing it into:
  • Suprapiriform space - superior gluteal nerve and vessels pass through
  • Infrapiriform space - inferior gluteal nerve/vessels + sciatic nerve + pudendal nerve and vessels + nerve to obturator internus + nerve to quadratus femoris pass through
• Clinical: Piriformis syndrome - sciatic nerve compressed by piriformis → buttock pain + sciatica

---

TOPIC 7: Pelvic Floor (Pelvic Diaphragm)

Definition:

Components:

1. Levator ani muscle (main component)
2. Coccygeus muscle
3. Superior and inferior fasciae covering them

Levator Ani Muscle - Three Parts:

• In females: Urethra, vagina
• In males: Urethra pass out of the pelvis

Coccygeus (Ischiococcygeus):

• Origin: Ischial spine
• Insertion: Lateral margins of coccyx and S5
• Nerve: S4, S5
• Action: Supports pelvic floor; pulls coccyx forward after defecation

Nerve Supply of Pelvic Floor:

• Levator ani: Nerve to levator ani (branches of S3, S4) from above + perineal branches of pudendal nerve from below
• Coccygeus: S4, S5

Functions of the Pelvic Floor:

1. Supports abdominal and pelvic organs against gravity and raised intraabdominal pressure
2. Maintains urinary and fecal continence (sphincter function)
3. Controls the genital hiatus (important in childbirth)
4. Resists peristaltic pressures

Clinical Relevance of Pelvic Floor:

• Pelvic floor weakness (after childbirth, in multiparous women) → uterine prolapse, cystocele, rectocele, stress urinary incontinence
• Puborectalis dysfunction → loss of anorectal angle → fecal incontinence
• Pudendal nerve injury during delivery → damage to external anal and urethral sphincters

---

TOPIC 8: Perineum

Boundaries (Diamond-shaped):

• Anteriorly: Pubic symphysis
• Posteriorly: Tip of coccyx
• Laterally: Ischial tuberosities
• Sides: Ischiopubic rami (anterior) and sacrotuberous ligaments (posterior)

Division of Perineum:

1. Anterior - Urogenital triangle (nearly horizontal, faces inferiorly)
2. Posterior - Anal triangle (more vertical, faces posteriorly)

Urogenital Triangle:

• External genitalia (penis + scrotum in males; vulva in females)
• External urethral opening
• In females: Vaginal opening (introitus)

Anal Triangle:

• Anal canal and anus
• Ischiorectal (ischoanal) fossae on each side

Ischiorectal (Ischoanal) Fossa:

• Wedge-shaped fat-filled space on each side of the anal canal
• Boundaries:
  • Medially: External anal sphincter + levator ani
  • Laterally: Obturator internus muscle and its fascia
  • Roof: Pelvic floor (levator ani)
  • Base: Skin
• Contents:
  • Ischiorectal fat (allows distension during defecation)
  • Pudendal nerve and internal pudendal vessels (in pudendal canal on lateral wall)
  • Inferior rectal nerve and vessels
• Clinical: Common site of perianal/ischiorectal abscess; the two fossae communicate behind the anal canal through the postanal space - abscess can track from side to side creating a horseshoe abscess

Pudendal Canal (Alcock's Canal):

• A fascial canal within the lateral wall of the ischiorectal fossa
• Formed by splitting of the obturator internus fascia
• Contents: Pudendal nerve + internal pudendal artery and vein
• Pudendal nerve block is given here for perineal anesthesia during episiotomy

---

TOPIC 9: Pudendal Nerve

1. Arises from the sacral plexus (S2, S3, S4)
2. Exits pelvis through the infrapiriform part of greater sciatic foramen
3. Crosses behind the ischial spine and sacrospinous ligament
4. Re-enters the perineum through the lesser sciatic foramen
5. Runs forward in the pudendal canal (Alcock's canal) on the lateral wall of the ischiorectal fossa

1. Inferior rectal nerve - supplies external anal sphincter, anal skin, perianal skin
2. Perineal nerve - supplies perineal muscles + scrotal/labial skin
3. Dorsal nerve of penis/clitoris - sensory to glans penis/clitoris

• Pudendal nerve block: Needle directed to the ischial spine - used in obstetric procedures
• Pudendal nerve injury in childbirth → fecal and urinary incontinence

---

TOPIC 10: Pelvic Viscera

A. Urinary Bladder

• Apex - anterosuperiorly (connected to umbilicus by median umbilical ligament = obliterated urachus)
• Body
• Base (fundus) - posteroinferiorly
• Neck - at the bottom, continuous with urethra; in contact with prostate in males

• Triangular smooth area on the posterior wall of the bladder
• Boundaries: Two ureteric orifices (posterolateral corners) + urethral orifice (anterior apex)
• The interureteric crest/ridge runs between the two ureteric orifices
• Trigone is always smooth (no rugae) because it is formed from incorporated mesonephric duct tissue (different embryological origin)
• Clinically important: Tumors tend to occur here; first area examined on cystoscopy

• Anteriorly: Pubic symphysis (retropubic space/cave of Retzius between them)
• Posteriorly: Seminal vesicles, vas deferens, rectum
• Inferiorly: Prostate gland

• Posteriorly: Uterus and vagina (vesico-uterine pouch between bladder and uterus)
• Inferiorly: Pelvic floor

• Superior vesical artery (from patent part of umbilical artery = internal iliac)
• Inferior vesical artery (males) / Vaginal artery (females) - from internal iliac

• Parasympathetic (S2-S4) via pelvic splanchnic nerves - contracts detrusor, relaxes sphincter = micturition
• Sympathetic (T10-L2) via hypogastric plexus - fills bladder (relaxes detrusor, contracts sphincter = continence)
• Somatic: Pudendal nerve (S2-S4) - controls external urethral sphincter

B. Urethra

1. Subclavicular bend (at junction of membranous and penile) - fixed
2. Puboprostatic bend - can be straightened during catheterization

C. Rectum and Anal Canal

• Continuous with sigmoid colon at S3
• Three lateral flexures (curvatures): Right, Left, Right
• Three internal transverse folds (Houston's valves/rectal valves) correspond to the lateral flexures
• No mesentery, no haustrations, no taeniae coli (unlike colon)
• Ends at the anorectal junction (anorectal flexure), held by puborectalis sling

• ~90° between rectum and anal canal, maintained by puborectalis sling
• When puborectalis relaxes during defecation, the angle straightens to ~130° allowing passage of feces

• Internal hemorrhoids: Above pectinate line (painless, bleed)
• External hemorrhoids: Below pectinate line (painful, rarely bleed)
• Carcinoma above line: Spreads to internal iliac nodes
• Carcinoma below line: Spreads to inguinal nodes

1. Internal anal sphincter (IAS): Involuntary (smooth muscle); thickened circular layer; innervated by autonomic nerves; maintains resting tone (~80% of resting anal pressure)
2. External anal sphincter (EAS): Voluntary (skeletal muscle); three parts (subcutaneous, superficial, deep); innervated by inferior rectal nerve (branch of pudendal, S2-S4); important for voluntary control

D. Prostate Gland

• Male accessory sex gland, size of a walnut (4 x 3 x 2 cm; weight ~20g)
• Located below the bladder neck, surrounding the prostatic urethra

• Traditionally described: Anterior, Posterior, Two lateral lobes, Middle (median) lobe
• McNeal's zones:
  • Peripheral zone (70%): Most gland; site of carcinoma and prostatitis
  • Transition zone (5-10%): Surrounds urethra; site of BPH (benign prostatic hyperplasia)
  • Central zone (25%): Around ejaculatory ducts

• Superior: Bladder neck
• Inferior: Urogenital diaphragm / pelvic floor
• Anterior: Puboprostatic ligaments, retropubic space
• Posterior: Rectum (separated by Denonvilliers' fascia/rectovesical septum)
• On each side: Levator ani

• Parasympathetic (S2-S4): Secretomotor
• Sympathetic (T10-L2): Smooth muscle contraction (ejaculation)

E. Uterus

1. Fundus - dome above uterine tubes
2. Body (corpus) - main part; uterine tubes enter at uterine cornu
3. Isthmus - narrow part between body and cervix; becomes the lower uterine segment in pregnancy
4. Cervix - lower cylindrical part; internal os (above) and external os (below); projects into vagina

• Anteriorly: Covers only the body (not the cervix)
• Posteriorly: Covers fundus, body, and upper cervix, then reflects onto rectum forming the Pouch of Douglas (recto-uterine pouch) - the most dependent part of the peritoneal cavity in females

Position of Uterus:

• Uterine artery (main) - branch of internal iliac
• Ovarian artery - from aorta
• Important relation: The uterine artery crosses above the ureter at the base of the broad ligament, at the level of the cervix ("water under the bridge"). This is the landmark to avoid during hysterectomy - the ureter can be injured.

• Fundus → para-aortic nodes
• Body → iliac nodes
• Cervix → iliac and sacral nodes

F. Ovaries

• Almond-shaped; ~3 x 1.5 x 1 cm
• Located in the ovarian fossa (shallow depression on lateral pelvic wall, between external and internal iliac vessels)
• Not covered by peritoneum - the only pelvic organ not covered by peritoneum; covered by germinal epithelium (simple cuboidal/columnar)

• Mesovarium - posterior fold of broad ligament to hilum (vessels + nerves enter here)
• Ligament of the ovary - from medial pole to uterine cornu
• Suspensory ligament (infundibulopelvic ligament) - from lateral pole to pelvic brim; contains ovarian vessels and nerves

---

TOPIC 11: Blood Supply of the Pelvis

Internal Iliac Artery (Hypogastric Artery):

Anterior Division:

• Superior vesical artery → bladder (patent part of umbilical artery)
• Inferior vesical artery (males) / Uterine artery (females)
• Obturator artery (sometimes from inferior epigastric - "aberrant obturator artery" = corona mortis)
• Middle rectal artery → rectum
• Vaginal artery (females)
• Internal pudendal artery → perineum (main artery)

• Obturator artery
• Inferior gluteal artery → gluteal region (inferior)

Posterior Division:

• Iliolumbar artery → iliacus + psoas
• Lateral sacral arteries → sacral canal
• Superior gluteal artery (largest branch of internal iliac) → gluteal region (superior)

• Iliolumbar (actually posterior), Superior vesical, Uterine/Inferior vesical, Middle rectal, Renal (no), Vaginal, Internal pudendal, Inferior gluteal (parietal)

Internal Iliac Vein:

---

TOPIC 12: Nerve Supply of the Pelvis

Sacral Plexus (L4, L5, S1, S2, S3):

Autonomic Supply of Pelvic Viscera:

• Injury to pelvic splanchnic nerves (e.g., during AP resection of rectum) → erectile dysfunction + bladder dysfunction
• Sympathetic injury → retrograde ejaculation

Obturator Nerve:

• Arises from lumbar plexus (L2, L3, L4)
• Runs along lateral pelvic wall, exits through obturator canal
• Supplies: Adductor compartment of thigh + skin of medial thigh
• Clinical: Pelvic tumor or ovarian cyst can compress the obturator nerve → pain/numbness along medial thigh; also tender on hip adduction

---

TOPIC 13: Pelvic Peritoneum and Pouches

In Females (Anterior to Posterior):

1. Anterior abdominal wall (median/medial umbilical folds over urachus/umbilical arteries)
2. Bladder - peritoneum covers superior + posterior surfaces
3. Vesico-uterine pouch - between bladder and uterus (NOT the most dependent pouch)
4. Uterus - peritoneum covers anterosuperior body, fundus, posterior body, cervix → becomes broad ligament laterally
5. Recto-uterine pouch (Pouch of Douglas) - between uterus + vagina posteriorly and rectum; MOST DEPENDENT part of peritoneal cavity in erect posture in females
6. Rectum

In Males (Anterior to Posterior):

1. Bladder
2. Rectovesical pouch - between bladder and rectum; most dependent peritoneal recess in males
3. Rectum

Clinical significance:

• Blood, pus, or peritoneal fluid collect in the Pouch of Douglas in females (ectopic pregnancy rupture, peritonitis)
• Can be drained by posterior colpotomy (needle through posterior vaginal fornix)
• Felt on per vaginal examination (tenderness = pelvic peritonitis)

---

TOPIC 14: Sacral Plexus - Quick Overview

• Lumbosacral trunk (L4 + L5)
• Anterior rami of S1, S2, S3 + part of S4

---

Quick Revision Table - HIGH-YIELD EXAM POINTS

---