Unit 05 — Alimentary Canal · Question Bank

TMU Anatomy · Pharynx · Oesophagus · Stomach · Intestines · Peritoneum
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Q1
Where does the palatine tonsil lie?
2020 Past Paper MCQ Q15
A. In the tonsillar fossa of the oropharynx
B. In the roof of the nasopharynx
C. In the floor of the oropharynx
D. In the lateral wall of the nasopharynx
✓ Answer: A — In the tonsillar fossa of the oropharynx
The palatine tonsil lies in the tonsillar fossa on the lateral wall of the oropharynx, bounded anteriorly by the palatoglossal arch and posteriorly by the palatopharyngeal arch.
⚠ Traps: A = pharyngeal tonsil (adenoid) is in the roof of the nasopharynx. C = tubal tonsil is in the lateral wall of the nasopharynx (near the Eustachian tube opening). E = lingual tonsil is on the posterior 1/3 of the tongue. All four are members of Waldeyer's ring, but only the palatine tonsil is in the oropharynx tonsillar fossa.
Q2
The first oesophageal constriction is located at:
2020 Past Paper Essay Q7
A. 20 cm from upper incisors, level C5
B. 15 cm from upper incisors, level C6
C. 25 cm from upper incisors, level T4
D. 10 cm from upper incisors, level C5
✓ Answer: B — 15 cm, C6
The first (cricopharyngeal) constriction is at the commencement of the oesophagus where cricopharyngeus muscle forms the upper oesophageal sphincter, at the level of C6, 15 cm from the upper incisor teeth. It is the narrowest point of the oesophagus and the most dangerous for impacted foreign bodies.
⚠ Mnemonic: 15–25–40 (cm from incisors) = C6 → T4 → T10. 25 cm = aortic/bronchial constriction at T4/T5; 40 cm = diaphragmatic constriction at T10.
Q3
The second oesophageal constriction (25 cm from incisors) is caused by:
2020 Past Paper Essay Q7
A. The aortic arch crossing anteriorly only
B. The right main bronchus at T3
C. The left main bronchus crossing at T4/T5
D. The carina pressing posteriorly at T5
✓ Answer: C — Left main bronchus at T4/T5
The second constriction at 25 cm (T4/T5) is caused by the left main bronchus crossing anteriorly (and the aortic arch also compresses here). It is correctly called the aortic/bronchial constriction. It is at the level of the T4/T5 vertebral bodies.
⚠ The aortic arch crosses higher; the left bronchus is the specific structure at T4/T5 that causes the visible endoscopic narrowing. It is the LEFT bronchus, not the right (which diverges away from the oesophagus).
Q4
The left gastric artery arises directly from:
2020 Past Paper Essay Q5
A. The splenic artery
B. The common hepatic artery
C. The hepatic artery proper
D. The coeliac trunk
✓ Answer: D — Coeliac trunk directly
The left gastric artery is the smallest branch of the coeliac trunk and arises directly from it. It supplies the lesser curvature and the lower oesophagus. The coeliac trunk gives off three branches: left gastric + splenic + common hepatic.
⚠ All five arteries supplying the stomach ultimately trace back to the coeliac trunk, but only the left gastric comes off the trunk directly. Right gastric ← hepatic proper ← common hepatic ← coeliac.
Q5
The right gastroepiploic (gastro-omental) artery arises from:
A. Gastroduodenal artery
B. Splenic artery
C. Common hepatic artery
D. Left gastric artery
✓ Answer: A — Gastroduodenal artery
Right gastroepiploic artery: gastroduodenal artery → common hepatic → coeliac trunk. It supplies the greater curvature (right part). The left gastroepiploic arises from the splenic artery and supplies the greater curvature (left part).
⚠ Remember the greater curvature arcade: Left gastroepiploic (from splenic) + Right gastroepiploic (from gastroduodenal). Short gastric arteries = from splenic terminal branches to the fundus.
Q6
Short gastric arteries supplying the fundus of the stomach arise from:
A. Left gastric artery
B. Splenic artery (terminal branches)
C. Coeliac trunk directly
D. Left gastroepiploic artery
✓ Answer: B — Splenic artery (terminal branches)
The short gastric arteries (5–7 in number) arise from the terminal branches of the splenic artery and pass through the gastrosplenic ligament to supply the fundus of the stomach.
⚠ The splenic artery gives: short gastric arteries (fundus) + left gastroepiploic (greater curvature left) + splenic branches to the spleen itself.
Q7
The major duodenal papilla (papilla of Vater) opens on the:
2020 Past Paper Definition
A. Anterolateral wall of the 1st (superior) part of the duodenum
B. Anterior wall of the 3rd (horizontal) part of the duodenum
C. Posteromedial wall of the 2nd (descending) part of the duodenum
D. Posterior wall of the 4th (ascending) part of the duodenum
✓ Answer: C — Posteromedial wall of 2nd part of duodenum
The major duodenal papilla is an elevation on the posteromedial wall of the descending (2nd) part of the duodenum at ~L2. The common bile duct + main pancreatic duct unite to form the hepatopancreatic ampulla (of Vater) and open here. The minor papilla (accessory pancreatic duct) lies 2 cm above it.
⚠ “Posteromedial” not “anterolateral” — the head of the pancreas is medial to the 2nd part, so ducts open on the medial wall. The 1st part (cap) is mobile and has no papillae.
Q8
Which statement is TRUE about structures BELOW the pectinate (dentate) line?
A. Supplied by the superior rectal artery (branch of IMA)
B. Innervated by autonomic nerves — visceral, no pain
C. Lined by columnar epithelium
D. Lymphatic drainage to superficial inguinal nodes
✓ Answer: D — Drains to superficial inguinal nodes
Below the pectinate line: epithelium = stratified squamous (ectodermal origin); blood supply = inferior rectal artery (from pudendal); lymphatics = superficial inguinal nodes; nerve = somatic (inferior rectal nerve = pain-sensitive → external haemorrhoids PAINFUL).
⚠ A, B, C all describe structures ABOVE the pectinate line (superior rectal artery, autonomic innervation, columnar epithelium → internal haemorrhoids are painless). External haemorrhoids below = painful.
Q9
McBurney's point is located at the:
A. Junction of the lateral 1/3 and medial 2/3 of the line from ASIS to umbilicus
B. Junction of the medial 1/3 and lateral 2/3 of the line from ASIS to umbilicus
C. Midpoint of the right inguinal ligament
D. 3 cm medial to the right anterior superior iliac spine
✓ Answer: A — Lateral 1/3 / medial 2/3 junction
McBurney's point: junction of the lateral 1/3 and medial 2/3 of the line drawn from the right ASIS to the umbilicus. This is the surface marking of the base of the appendix and the site of maximum tenderness in appendicitis.
⚠ “Lateral 1/3” means closer to the ASIS, not the umbilicus. B reverses this. The incision (grid-iron) is made at right angles to this line.
Q10
The most common position of the vermiform appendix tip is:
A. Pelvic (~30%)
B. Retrocaecal (~65%)
C. Subcaecal (~5%)
D. Pre-ileal (~2%)
✓ Answer: B — Retrocaecal (~65%)
The retrocaecal position (~65%) is most common. Pelvic position is second (~30%). The base of the appendix is constant (posteromedial wall of caecum, where the three taeniae coli converge) but the tip position varies. Retrocaecal appendicitis can present with psoas sign (pain on hip extension).
⚠ The BASE is fixed; only the TIP varies in position. Pelvic appendicitis → obturator sign (pain on hip internal rotation). The three taeniae coli are the intraoperative landmark to find the appendix base.
Q11
The watershed between SMA and IMA vascular territories in the colon is at the:
A. Hepatic (right colic) flexure
B. Mid-transverse colon
C. Splenic (left colic) flexure
D. Upper descending colon
✓ Answer: C — Splenic flexure
The splenic flexure is the watershed: SMA territory covers caecum → ascending → transverse colon (to splenic flexure); IMA territory covers splenic flexure → descending → sigmoid → upper rectum. The splenic flexure is therefore the most vulnerable site for ischaemic colitis (e.g. after aortic aneurysm repair with IMA ligation).
⚠ The marginal artery of Drummond connects the two systems, but may be inadequate at the splenic flexure — hence the clinical vulnerability.
Q12
Oesophageal varices in portal hypertension result from anastomosis between:
A. Superior mesenteric vein ↔ inferior vena cava
B. Splenic vein ↔ left renal vein
C. Portal vein ↔ hepatic vein
D. Left gastric vein (portal) ↔ azygos vein (systemic)
✓ Answer: D — Left gastric vein ↔ azygos vein
The portosystemic anastomosis at the lower oesophagus: left gastric vein (portal) ↔ oesophageal veins ↔ azygos vein (systemic). In portal hypertension, blood is shunted retrogradely into this anastomosis → submucosal oesophageal veins dilate → oesophageal varices → risk of torrential haematemesis (mortality up to 30% per bleed).
⚠ The other portosystemic sites: anterior abdominal wall (paraumbilical ↔ epigastric → caput medusae); rectum (superior rectal ↔ middle/inferior rectal → rectal varices); retroperitoneum (veins of Retzius).
Q13
Which set of features is unique to the colon (absent from small intestine)?
A. Taeniae coli, haustra, appendices epiploicae
B. Plicae circulares, villi, Peyer's patches
C. Mesentery, ileocaecal valve, lacteals
D. Circular folds, Auerbach's plexus, goblet cells
✓ Answer: A — Taeniae coli, haustra, appendices epiploicae
The three unique features of the colon: (1) Taeniae coli — 3 longitudinal muscle bands (shorter than the wall → puckering); (2) Haustra — sacculations between taeniae; (3) Appendices epiploicae — fat-filled peritoneal tags on outer surface.
⚠ A = features of the small intestine (plicae circulares + villi = absorption surface; Peyer's patches = ileum). Auerbach's plexus and goblet cells are present in both. Mesentery is present for parts of both.
Q14
In congenital hypertrophic pyloric stenosis, vomiting is non-bilious because the obstruction is:
A. Distal to (below) the major duodenal papilla
B. Proximal to (above) the major duodenal papilla
C. At the hepatopancreatic ampulla itself
D. At the gastro-oesophageal junction
✓ Answer: B — Proximal to (above) the major duodenal papilla
The pyloric sphincter is in the 1st part of the duodenum, above the major duodenal papilla (which is in the 2nd part). Bile and pancreatic juice enter at the papilla — since the obstruction prevents gastric content from reaching the 2nd part, bile cannot reflux back into the stomach → non-bilious vomit. Any obstruction BELOW the papilla produces bilious (green) vomiting.
⚠ “Bilious vs non-bilious” is determined by whether the obstruction is above or below the major duodenal papilla. Non-bilious = above papilla (e.g. pyloric stenosis, oesophageal atresia). Bilious = below papilla (duodenal atresia, malrotation, jejunal atresia).
Q15
The isthmus of fauces is bounded laterally (on each side) by the:
A. Palatopharyngeal arches (posterior pillars)
B. Palatine tonsils
C. Palatoglossal arches (anterior pillars of fauces)
D. Uvula
✓ Answer: C — Palatoglossal arches
The isthmus of fauces (gateway between oral cavity and oropharynx) boundaries: Superior = uvula + free margin of soft palate; Lateral (each side) = palatoglossal arches (anterior pillars); Inferior = root of the tongue. The tonsillar fossa lies between the palatoglossal (anterior) and palatopharyngeal (posterior) arches, posterior to the isthmus.
⚠ The palatoglossal arch is the ANTERIOR boundary of the tonsillar fossa and also forms the LATERAL boundary of the isthmus of fauces. The palatopharyngeal arch is POSTERIOR to the tonsil.
Q16
Pringle's manoeuvre controls hepatic inflow bleeding by compressing the:
A. Hepatogastric ligament
B. Gastrosplenic ligament
C. Transverse mesocolon
D. Hepatoduodenal ligament (free edge of lesser omentum)
✓ Answer: D — Hepatoduodenal ligament
Pringle's manoeuvre: surgeon passes index finger through the epiploic foramen of Winslow and compresses the hepatoduodenal ligament (free right edge of the lesser omentum) between finger and thumb. This occludes the portal vein + hepatic artery proper + bile duct simultaneously. Normal liver tolerates ~60 minutes of warm ischaemia.
⚠ The hepatoduodenal ligament contains the portal triad: portal vein (posterior), hepatic artery proper (left), bile duct (right). Compressing this free edge = compressing all hepatic inflow at once.
Q17
A 4-week-old male presents with projectile non-bilious vomiting after every feed. An “olive” mass is palpable in the epigastrium. Electrolytes show hypochloraemic hypokalaemic metabolic alkalosis. Diagnosis:
A. Hypertrophic pyloric stenosis
B. Duodenal atresia
C. Intussusception
D. Hirschsprung's disease
✓ Answer: A — Hypertrophic pyloric stenosis
Hypertrophic pyloric stenosis: hypertrophy of pyloric circular muscle, 2–6 weeks age, M>F (4:1), first-born males. Triad: projectile non-bilious vomiting + olive mass + hypochloraemic hypokalaemic metabolic alkalosis (losing HCl in vomit). Ultrasound confirms (muscle thickness >3 mm, length >16 mm). Treatment: Ramstedt's pyloromyotomy.
⚠ Duodenal atresia = bilious vomiting on day 1 of life (“double bubble” on AXR). Intussusception = 6–18 months, redcurrant jelly stool. Hirschsprung's = delayed meconium (>48h) + abdominal distension.
Q18
Regarding the two sagittal curves of the rectum, which statement is CORRECT?
A. The sacral flexure is convex anteriorly, following the lumbar lordosis
B. The perineal (anorectal) flexure is maintained by the puborectalis sling of levator ani
C. The perineal flexure is maintained by the external anal sphincter (pudendal nerve)
D. Both curves are in the same direction — both concave anteriorly
✓ Answer: B — Perineal flexure maintained by puborectalis
The two sagittal curves: (1) Sacral flexure — convex posteriorly, follows the concavity of the sacrum; (2) Perineal (anorectal) flexure — convex anteriorly, sharp ~90° bend at the anorectal junction maintained by the puborectalis sling (levator ani, origin and insertion on pubis, loops behind the anorectal junction). This angle is critical for faecal continence; relaxation during defaecation straightens it.
⚠ A = wrong: sacral flexure is convex posteriorly (follows sacral hollow). B = wrong: puborectalis (not external sphincter) maintains the anorectal angle. External sphincter = voluntary continence but does not maintain the angle.
Q19
The most dependent part of the peritoneal cavity in the SUPINE position is:
A. Pouch of Douglas (rectouterine pouch)
B. Lesser sac (omental bursa)
C. Morrison's pouch (hepatorenal recess)
D. Left paracolic gutter
✓ Answer: C — Morrison's pouch (hepatorenal recess)
Morrison's pouch (hepatorenal recess, between right lobe of liver and right kidney) is the most dependent part of the peritoneal cavity in the supine position — free fluid (blood, bile, pus) collects here first. Detected by FAST ultrasound in trauma. In the erect/upright position, the pouch of Douglas (rectouterine in F; rectovesical in M) is the most dependent point.
⚠ Position matters: SUPINE = Morrison's; ERECT = pouch of Douglas. Examination scenario: “patient lying down in trauma” = Morrison's; “pelvic abscess drained per vaginum” = pouch of Douglas.
Q20
Which of the following is NOT a component of Waldeyer's tonsillar ring?
A. Pharyngeal tonsil (adenoid)
B. Palatine tonsil
C. Lingual tonsil
D. Sublingual tonsil
✓ Answer: D — Sublingual tonsil (does not exist)
Waldeyer's ring has four components: (1) Pharyngeal tonsil (adenoid) — nasopharynx roof; (2) Tubal tonsils (×2) — nasopharynx lateral wall; (3) Palatine tonsils (×2) — oropharynx tonsillar fossa; (4) Lingual tonsil — posterior 1/3 of tongue. There is no “sublingual tonsil”. The sublingual region contains the sublingual salivary gland and the submandibular duct opening at the sublingual caruncle — not a tonsil.
⚠ Mnemonic: P-T-P-L = Pharyngeal · Tubal · Palatine · Lingual. Any 5th option is the trap. Sublingual gland ≠ sublingual tonsil.
D1 Duodenal major papilla (Papilla of Vater) +
An elevation on the posteromedial wall of the descending (2nd) part of the duodenum (at ~L2). It is the site where the common bile duct and the main pancreatic duct (of Wirsung) unite to form the hepatopancreatic ampulla (of Vater) and open into the duodenum. The opening is guarded by the sphincter of Oddi. The minor duodenal papilla (~2 cm above) carries the accessory pancreatic duct (of Santorini). Clinical: obstruction here (carcinoma of head of pancreas, impacted gallstone) causes obstructive jaundice; ERCP cannulates this papilla.
Gray's Anatomy 4e · Unit 05 Notes
D2 Isthmus of Fauces +
The narrow opening connecting the oral cavity proper posteriorly to the oropharynx. Boundaries: superior = uvula + free margin of the soft palate (palatine velum); lateral (each side) = palatoglossal arches (anterior pillars of fauces); inferior = root of the tongue. The tonsillar fossa lies lateral to it, between the anterior (palatoglossal) and posterior (palatopharyngeal) pillars.
TMU Slide 5 · Unit 05 Notes
D3 McBurney's Point +
The surface marking for the base of the vermiform appendix: the junction of the lateral 1/3 and medial 2/3 of the line drawn from the right anterior superior iliac spine (ASIS) to the umbilicus. It is the site of maximum tenderness in acute appendicitis (somatic pain once the parietal peritoneum overlying the appendix is irritated). The grid-iron incision for appendicectomy is made perpendicular to this line at McBurney's point.
Gray's Anatomy 4e · Unit 05 Notes
D4 Pectinate Line (Dentate Line) +
A line across the anal canal formed by the bases of the anal columns and the anal valves, approximately halfway along the anal canal. It marks the embryological boundary between endoderm (above) and ectoderm (below). Above: columnar epithelium, superior rectal artery, autonomic (visceral) innervation, internal iliac lymph nodes → internal haemorrhoids (painless). Below: stratified squamous epithelium, inferior rectal artery, somatic (inferior rectal nerve) innervation, superficial inguinal lymph nodes → external haemorrhoids (painful).
Gray's Anatomy 4e · Unit 05 Notes
D5 Epiploic Foramen of Winslow +
The only natural communication between the greater peritoneal sac and the lesser sac (omental bursa). Boundaries: anterior = hepatoduodenal ligament (free right edge of lesser omentum; contains portal vein, hepatic artery proper, bile duct); posterior = IVC (covered by parietal peritoneum); superior = caudate lobe of liver; inferior = 1st part of duodenum. Clinical: Pringle's manoeuvre — surgeon passes index finger through this foramen to compress the hepatoduodenal ligament (hepatic inflow control during liver surgery).
Gray's Anatomy 4e · Unit 05 Notes
D6 Waldeyer's Tonsillar Ring +
A circular arrangement of lymphoid tissue at the entrance to the pharynx forming a defensive barrier against inhaled and ingested pathogens. Four members (P-T-P-L): (1) Pharyngeal tonsil (adenoid) — roof/posterior wall of nasopharynx; (2) Tubal tonsils (×2) — lateral nasopharynx near Eustachian tube opening; (3) Palatine tonsils (×2) — tonsillar fossa, lateral wall of oropharynx; (4) Lingual tonsil — posterior 1/3 of tongue dorsum. Clinical: adenoid hypertrophy → Eustachian tube block → glue ear; tonsillar hypertrophy → OSA in children.
TMU Slide 5 · Unit 05 Notes
Essay 1
Name the three constrictions of the oesophagus. For each, give the name, the vertebral level, and the distance from the upper incisor teeth. Why are these clinically important?
6 marks

Three constrictions (mnemonic: 15–25–40)

  • 1st — Cricopharyngeal (upper oesophageal sphincter): Where cricopharyngeus muscle (inferior pharyngeal constrictor) joins the oesophagus. Level: C6. Distance from upper incisors: 15 cm. Narrowest point — most dangerous site for impacted foreign bodies.
  • 2nd — Aortic/bronchial constriction: Where the oesophagus is crossed by the aortic arch and then indented by the left main bronchus. Level: T4/T5. Distance: 25 cm. Endoscopy landmark; site of aorto-oesophageal fistula in aortic aneurysm.
  • 3rd — Diaphragmatic constriction (lower oesophageal sphincter): Where the oesophagus passes through the oesophageal hiatus of the diaphragm. Level: T10. Distance: 40 cm. The GOJ (gastro-oesophageal junction) is at T11 (~45 cm from teeth).

Clinical importance

  • NGT insertion: confirm tip in stomach at ~50 cm. Position at 15 cm = oropharynx (too high); 40 cm = LOS (just entering stomach).
  • Foreign bodies most commonly impact at the 1st constriction (15 cm, C6).
  • Oesophageal carcinoma levels are reported relative to these distances (upper/middle/lower third).
  • Oesophageal varices form at the 3rd constriction (lower oesophagus, portosystemic anastomosis).
Marking (6 marks): Name + level + distance for each constriction = 1 mark each (3 marks total) · Any 2 clinical applications = 1 mark each (2 marks) · NGT tip position knowledge (1 mark)
Essay 2
Describe the arterial blood supply to the stomach. Name each artery, its origin (tracing back to the coeliac trunk), and the region of the stomach it supplies.
8 marks

All supply traces to the coeliac trunk

The stomach has an extraordinarily rich blood supply from five named arteries, all ultimately arising from the coeliac trunk (1st unpaired branch of abdominal aorta at T12).

Lesser curvature arcade

  • Left gastric artery → coeliac trunk directly → lesser curvature (left part) + lower oesophagus. Largest of the two lesser curvature arteries.
  • Right gastric artery → hepatic artery proper → common hepatic → coeliac trunk → lesser curvature (right/pyloric part).

Greater curvature arcade

  • Left gastroepiploic (gastro-omental) artery → splenic artery → coeliac trunk → greater curvature (left part).
  • Right gastroepiploic (gastro-omental) artery → gastroduodenal artery → common hepatic → coeliac trunk → greater curvature (right part).

Fundus

  • Short gastric arteries (5–7) → terminal branches of splenic artery → fundus (via gastrosplenic ligament). Posterior gastric artery also from splenic.

Veins

Corresponding gastric veins drain into the portal venous system. The left gastric (coronary) vein is especially important in portal hypertension → oesophageal varices.

Marking (8 marks): Left gastric origin (1) · Right gastric origin (1) · Left gastroepiploic origin (1) · Right gastroepiploic origin (1) · Short gastric origin (1) · Correct regions for each (1.5) · All ultimately from coeliac trunk stated (0.5) · Portal venous drainage + variceal significance (1)
Essay 3
Describe the pectinate (dentate) line of the anal canal: its location, the differences above and below it in terms of epithelium, blood supply, nerve supply, and lymphatic drainage. What is its clinical significance?
8 marks

Location

The pectinate line is formed by the bases of the anal columns and the anal valves, approximately halfway along the anal canal (~2 cm above the anus). It marks the embryological junction between endoderm (above) and ectoderm (below).

Above the pectinate line

  • Epithelium: Columnar (transitional zone immediately above)
  • Blood supply: Superior rectal artery (branch of IMA) / superior rectal vein → inferior mesenteric vein → portal system
  • Nerve supply: Autonomic (visceral) — pain-insensitive (only stretch detected)
  • Lymphatics: Internal iliac nodes
  • Haemorrhoids: Internal haemorrhoids — painless

Below the pectinate line

  • Epithelium: Stratified squamous (keratinised)
  • Blood supply: Inferior rectal artery (branch of internal pudendal) / inferior rectal vein → internal iliac → IVC (systemic)
  • Nerve supply: Somatic (inferior rectal nerve from pudendal) — exquisitely pain-sensitive
  • Lymphatics: Superficial inguinal nodes
  • Haemorrhoids: External haemorrhoids — painful

Clinical significance

  • Internal haemorrhoids above → painless bright red rectal bleeding. External haemorrhoids below → painful, tender lump.
  • Anal cancer: squamous cell carcinoma below the line; adenocarcinoma above the line.
  • Lymphatic drainage change: rectal cancer above → internal iliac nodes; anal canal cancer below → inguinal nodes (key for staging and biopsy).
  • Portosystemic anastomosis: superior rectal vein (portal) ↔ inferior/middle rectal veins (systemic) → rectal varices in portal hypertension.
Marking (8 marks): Location/definition (1) · Epithelium above and below (1) · Blood supply above and below, with named vessels (2) · Nerve supply + explanation (1) · Lymphatics above and below (1) · Internal vs external haemorrhoids (1) · One further clinical point (1)
Essay 4
Describe the four main portosystemic anastomoses. For each, name the portal vessel, the systemic vessel, and the clinical consequence when portal pressure rises.
8 marks

What is portal hypertension?

Portal hypertension is defined as portal venous pressure >10 mmHg (normal 5–10 mmHg). Most common cause: liver cirrhosis (increased resistance to portal flow). Blood is redirected through the four portosystemic anastomoses.

1. Lower oesophagus

  • Portal: Left gastric (coronary) vein → oesophageal submucosal veins
  • Systemic: Azygos vein
  • Clinical: Oesophageal varices — dilated submucosal veins; risk of catastrophic haematemesis (mortality 30% per bleed). Managed by endoscopic banding, TIPS, propranolol.

2. Anterior abdominal wall (umbilicus)

  • Portal: Paraumbilical veins (run in falciform ligament, connect to left branch of portal vein)
  • Systemic: Superior and inferior epigastric veins (systemic)
  • Clinical: Caput medusae — dilated tortuous veins radiating from the umbilicus, visible on inspection. Flow is away from umbilicus (distinguishes from inferior vena cava obstruction where flow is upward on the flanks).

3. Rectum

  • Portal: Superior rectal vein → inferior mesenteric vein
  • Systemic: Middle rectal and inferior rectal veins → internal iliac → IVC
  • Clinical: Rectal varices (not haemorrhoids — varices extend into the rectum). Much less likely to bleed than oesophageal varices.

4. Retroperitoneum

  • Portal: Splenic/mesenteric tributaries → veins of Retzius (retroperitoneal)
  • Systemic: Lumbar and phrenic veins
  • Clinical: Usually asymptomatic; may cause collateral vessels visible on CT. Relevant during retroperitoneal surgery in portal hypertension (bleeding risk).
Marking (8 marks): Oesophageal site with correct portal/systemic vessels + variceal consequence (2) · Umbilical site + caput medusae (2) · Rectal site + vessels (2) · Retroperitoneal site (1) · Definition of portal hypertension / cause (1)
Essay 5
Describe the rectum: its two sagittal curves, peritoneal relations, blood supply, and the anatomical basis of faecal continence at the anorectal junction.
8 marks

Two sagittal curves

  • Sacral flexure: The rectum curves posteriorly in its upper part to follow the concavity of the sacrum and coccyx. Convex posteriorly. Relevant for insertion of sigmoidoscope (must angle posteriorly).
  • Perineal (anorectal) flexure: At the anorectal junction, the rectum bends anteriorly (~80–90°). Convex anteriorly. Created and maintained by the puborectalis sling (pubococcygeus portion of levator ani: origin pubis, loops posteriorly behind the anorectal junction, insertion pubis — a “U” sling that pulls the anorectal junction anteriorly). This angle is critical for continence.

Peritoneal relations

  • Upper 1/3: peritoneum covers anterior surface and both sides
  • Middle 1/3: peritoneum covers anterior surface only
  • Lower 1/3: no peritoneal cover (extraperitoneal)
  • The peritoneal reflection forms the rectouterine pouch of Douglas (females) / rectovesical pouch (males) — the most dependent peritoneal space in the erect position.

Blood supply

  • Superior rectal artery: Terminal branch of IMA — supplies upper rectum; portal venous drainage → portosystemic anastomosis site
  • Middle rectal arteries: Internal iliac arteries (both sides)
  • Inferior rectal arteries: Internal pudendal arteries (from internal iliac)

Faecal continence mechanism

  • Puborectalis: maintains anorectal angle at ~80–90° at rest. Tonic contraction = continence. Voluntary relaxation during defaecation straightens the angle.
  • Internal anal sphincter (IAS): smooth muscle, involuntary. Tonically contracted at rest (main contribution to resting pressure). Relaxes when rectal distension is detected (rectoanal inhibitory reflex — RAIR).
  • External anal sphincter (EAS): striated muscle, voluntary (inferior rectal branch of pudendal nerve). Provides the “squeeze” pressure for voluntary continence.
Marking (8 marks): Sacral flexure described correctly (1) · Perineal flexure + puborectalis mechanism (2) · Peritoneal relations (upper/middle/lower thirds) (1.5) · Three blood supply arteries named with origins (1.5) · IAS + EAS + anorectal angle in continence (2)
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