AN52.1-8 | Histology & Embryology (Abdomen & Pelvis) — Summary & Reflection

REFLECT

KEY TAKEAWAYS

Histology & Embryology of Abdomen and Pelvis — Key Points:

1. GIT histology keys: Brunner's glands = duodenum (submucosa); Peyer's patches = ileum; no villi = large intestine; Kupffer cells + space of Disse = liver
2. Liver zones: zone 1 (periportal) = hepatitis; zone 3 (centrilobular) = congestion/ischaemia/paracetamol toxicity
3. Testis: Sertoli cells (blood-testis barrier + AMH); Leydig cells (testosterone); Sertoli-cell-only = azoospermia
4. Corpus luteum: progesterone (large luteal cells) + oestrogen (small luteal cells); large pale folded cells on histology
5. Cardio-oesophageal junction: stratified squamous → simple columnar; site of Barrett's oesophagus
6. Diaphragm: 4 sources — septum transversum (main), pleuroperitoneal membranes, dorsal mesentery, body wall muscle; Bochdalek hernia = left posterolateral defect
7. Duodenal atresia: failure of recanalisation → double-bubble; associated with Down syndrome
8. Midgut rotation: 270° counterclockwise; malrotation → Ladd's bands + volvulus risk
9. Hirschsprung's disease: neural crest migration failure → distal aganglionosis → functional obstruction
10. Kidney development: ureteric bud (Wolffian duct) + metanephric mesenchyme; horseshoe kidney blocked at IMA; ARPKD = childhood, ADPKD = adults
11. Sex differentiation: SRY → Sertoli (AMH → Müllerian regression) + Leydig (testosterone → Wolffian + male genitalia); no SRY → female; undescended testis = orchidopexy before age 2