AN52.1-8 | Histology & Embryology (Abdomen & Pelvis) — Gate Quiz

Correct. Brunner's glands are submucosal mucous glands found exclusively in the duodenum (and to a small extent the proximal jejunum). They secrete alkaline mucus to neutralise the acid chyme entering from the stomach. Their presence in the submucosa is the definitive histological marker of the duodenum.

Brunner's glands (submucosal, alkaline-secreting) are unique to the duodenum. Villi, crypts, and goblet cells are present throughout the small intestine. Peyer's patches (submucosal lymphoid nodules) are unique to the ileum. Use these two markers — Brunner's = duodenum; Peyer's = ileum — to identify small bowel segments histologically.

Correct. In the hepatic acinus (Rappaport), zone 1 is periportal (best oxygenation, first exposure to hepatotoxins from portal blood, affected in hepatitis and ingested toxins), zone 3 is centrilobular (lowest O2 tension, most susceptible to hypoxia and metabolic toxins including alcohol and paracetamol). Alcoholic hepatitis and congestion (right heart failure) cause zone 3 (centrilobular) necrosis.

Zone 1 = periportal = best oxygenation = first affected in viral hepatitis and ingested poisons. Zone 3 = centrilobular = least oxygen = most vulnerable to ischaemia, congestion (right heart failure), alcohol, and paracetamol. This zonal pattern on biopsy guides the aetiology.

Correct. The corpus luteum develops from the ruptured Graafian follicle after ovulation. On histology: large, pale, vacuolated granulosa lutein cells (derived from granulosa cells — secrete progesterone) and smaller theca lutein cells (derived from theca interna — secrete oestrogen). The structure is folded (collapsed follicle), often with a central haemorrhagic clot. The large pale cells are the hallmark.

Corpus luteum = post-ovulatory structure. Key histology: large, pale, lipid-laden granulosa lutein cells (progesterone) + smaller theca lutein cells (oestrogen) in a folded, haemorrhagic structure. It regresses into the corpus albicans (white fibrous scar) at the end of an infertile cycle.

Correct. Barrett's oesophagus is the replacement of the normal stratified squamous epithelium of the lower oesophagus with intestinal metaplasia (specialised columnar epithelium with goblet cells). It is caused by chronic GORD. It is a premalignant condition — risk of progression to oesophageal adenocarcinoma. The cardio-oesophageal junction normally shows an abrupt transition from squamous to simple columnar (gastric) epithelium without goblet cells.

Barrett's oesophagus = columnar metaplasia (specialised intestinal type with goblet cells) replacing the normal squamous epithelium of the lower oesophagus, caused by chronic acid reflux. It is premalignant (risk of adenocarcinoma 0.5–1% per year). The normal Z-line at the cardio-oesophageal junction shows squamous → simple columnar (not intestinal columnar with goblet cells).

Correct. The right pleuroperitoneal membrane closes slightly earlier than the left during development. The left side closes last — hence any defect in membrane closure occurs more commonly on the left. Additionally, the liver on the right side may provide some protection against right-sided herniation. This explains the 85:15 left-to-right ratio in Bochdalek hernias.

The right pleuroperitoneal membrane closes earlier than the left, leaving the left side more susceptible to delayed or failed closure. The liver also helps 'protect' the right side from herniation. Therefore Bochdalek CDH is overwhelmingly left-sided — and left-sided CDH has a worse prognosis because the small bowel, stomach, and spleen herniate and cause greater pulmonary compression.

Correct. Hirschsprung's disease is caused by premature arrest of neural crest cell craniocaudal migration. Neural crest cells normally colonise the bowel from the oesophagus downward, reaching the distal rectum by week 12. Failure of migration stops at some level — the segment distal to this is aganglionic (no Auerbach's or Meissner's plexus). The aganglionic bowel cannot relax → functional obstruction → explosive decompression on rectal examination (as the obstructed proximal stool is released past the aganglionic segment).

Hirschsprung's = neural crest migration failure → absence of enteric ganglia (Auerbach's + Meissner's) in the distal bowel. Absent ganglion cells on rectal biopsy is diagnostic. The aganglionic segment cannot relax peristaltically → functional obstruction. Treatment: resect aganglionic segment + pull-through of ganglionic bowel to anus.

Correct. The metanephros (permanent kidney) develops from two components: (1) the ureteric bud — an outgrowth from the mesonephric (Wolffian) duct that forms the collecting system (ureter, renal pelvis, calyces, collecting tubules), and (2) metanephric mesenchyme (blastema) — surrounds the ureteric bud and forms the secretory units (nephrons: glomerulus through distal convoluted tubule). Mutual induction between these two primordia drives kidney development.

Kidney development requires two primordia: ureteric bud (from Wolffian duct → collecting system) and metanephric mesenchyme (→ nephrons). Failure of either to develop or interact causes renal agenesis or dysplasia. This is also why Wolffian duct anomalies (e.g., absent ureteric bud) predict ipsilateral renal agenesis AND Wolffian duct derivatives (vas deferens, seminal vesicle) are often absent on the same side.

Correct. Sertoli cells (the supporting cells of the testis, derived from the sex cords) produce Anti-Müllerian Hormone (AMH), also called Müllerian Inhibitory Substance (MIS). AMH causes regression of the Müllerian (paramesonephric) ducts in male embryos, preventing development of uterus, uterine tubes, and upper vagina. Leydig cells produce testosterone, which drives Wolffian duct differentiation and external genitalia masculinisation (via DHT).

Two key hormones in male differentiation: (1) AMH from Sertoli cells → Müllerian duct regression (no uterus/tubes); (2) Testosterone from Leydig cells → Wolffian duct persistence (epididymis, vas, seminal vesicles) + DHT → external genitalia masculinisation. In females: no AMH → Müllerian ducts persist; no testosterone → Wolffian ducts regress.

Correct. Cryptorchidism (undescended testis) has two main long-term complications: (1) Infertility — the higher intra-abdominal temperature (37°C vs 34°C in scrotum) causes progressive failure of spermatogenesis from the end of year 1; bilateral undescended testes = near-certain infertility if not treated. (2) Increased risk of testicular malignancy (seminoma) — 5–10× higher than the normal population; even orchidopexy reduces but does not fully eliminate the risk. Treatment: orchidopexy before 2 years of age.

Undescended testis → two major concerns: (1) infertility (heat-related spermatogenic failure — the testis must be 2–3°C below body temperature for spermatogenesis); (2) testicular cancer (5–10× increased risk of seminoma — even in the contralateral descended testis). Orchidopexy before 2 years of age preserves fertility potential and allows early cancer detection.

Correct. In male penile development, the urethral plate (endodermal groove) forms on the ventral surface of the phallus. The urethral folds then fuse in the midline from the base of the penis toward the glans, enclosing the urethra. Failure of this fusion at any point results in hypospadias — the orifice is at the site where fusion stopped. Glanular hypospadias = fusion failure at the distal end. Perineal hypospadias = failure throughout (associated with ambiguous genitalia).

Hypospadias = failure of urethral fold fusion on the ventral surface of the penis. The process of urethral formation goes from proximal to distal (except the terminal part, which is formed by canalization of the ectodermal glanular plate). Hypospadias is the most common urogenital malformation (1:250 live male births). It is associated with an underdeveloped prepuce (dorsal hood) and ventral chordee (penile curvature).