Stomach and Intestines

Stomach - The Acidic Mixer

• Parts: Cardia, Fundus, Body, Pylorus (Antrum, Canal). J-shaped.
• Curvatures: Lesser (R. gastric a.), Greater (R & L gastro-omental a.). Incisura angularis on lesser.
• Relations (Posterior - Stomach Bed): Pancreas, spleen, L kidney, L suprarenal, transverse mesocolon, splenic a., diaphragm.
• Arterial Supply (Celiac Trunk branches): L&R Gastric, L&R Gastro-omental, Short Gastrics.
• Venous Drainage: Parallels arteries; drains to Portal system.
• Lymphatics: Follow arteries to celiac, gastric, gastro-omental nodes.
• Innervation:
  • Parasympathetic: Vagus (Ant/Post trunks of Latarjet) - ↑motility, ↑secretion.
  • Sympathetic: Greater Splanchnic n. (T6-T9) via celiac plexus - ↓motility, vasoconstriction.
• Key Cells:
  • Parietal (oxyntic): HCl, Intrinsic Factor (for Vit B12 absorption).
  • Chief (peptic): Pepsinogen.
  • G-cells (antrum): Gastrin.

⭐ Posterior gastric ulcers may erode the splenic artery, causing major hemorrhage (commonest artery involved).

Small Intestine - Absorption Ace

• Segments (Proximal to Distal): 📌 "Dow Jones Industrials"
  • Duodenum: ~25 cm; C-shaped; Brunner's glands (alkaline mucus); major iron absorption.
  • Jejunum: ~2.5 m; feathery appearance (prominent plicae circulares & villi); main site for nutrient absorption (carbs, fats, proteins, Ca).
  • Ileum: ~3.5 m; Peyer's patches (lymphoid aggregates); absorbs Vitamin B12 & bile salts.
• Vascular Supply: Superior Mesenteric Artery (SMA) branches.
• Absorption: Vast surface area via plicae circulares, villi, and microvilli.

  ⭐ The terminal ileum is the principal site for Vitamin B12 and bile acid reabsorption. A

Large Intestine - Water Warden

• Parts: Cecum & appendix, Colon (ascending, transverse, descending, sigmoid), Rectum, Anal canal.
• Key Features:
  • Taeniae coli: Three longitudinal muscle bands.
  • Haustra: Sacculations of the colon wall.
  • Appendices epiploicae: Small fatty projections.
• Blood Supply:
  • Arteries: Superior Mesenteric Artery (SMA) branches (ileocolic, right colic, middle colic); Inferior Mesenteric Artery (IMA) branches (left colic, sigmoidal, superior rectal).
  • Marginal artery of Drummond: Anastomotic arcade.
• Primary Function: Water & electrolyte absorption; formation & storage of feces.

⭐ McBurney's point: Located one-third of the distance from the anterior superior iliac spine (ASIS) to the umbilicus; tenderness here is a sign of acute appendicitis. 📌

Gut Development & Clinicals - Twists & Troubles

• Gut Development:
  • Foregut: Esophagus to D2, liver, pancreas.
  • Midgut: D2 to prox 2/3 TC. Rotates 270° CCW (SMA axis).
  • Hindgut: Distal 1/3 TC to upper anal canal.
• Clinical Issues:
  • Meckel's: True diverticulum. Rule of 2s (📌 2% pop, 2ft ICV, 2in long, 2 ectopic tissues).
  • Hirschsprung's: Aganglionosis (neural crest failure); rectosigmoid.
  • Volvulus: Bowel twist (sigmoid/cecum); obstruction/ischemia.
  • Intussusception: Telescoping bowel (ileocolic); currant jelly stool.

⭐ Meckel's diverticulum, the most common congenital GI anomaly, results from incomplete obliteration of the vitelline duct.

High‑Yield Points - ⚡ Biggest Takeaways

• Stomach's rich arterial supply from celiac trunk branches.
• Meckel's diverticulum: most common GI anomaly, follows Rule of 2s.
• Second part of duodenum contains major duodenal papilla; SMA crosses third part.
• Jejunum: prominent plicae circulares, long vasa recta. Ileum: Peyer's patches.
• Large intestine: characterized by Teniae coli, haustra, omental appendices.
• Ligament of Treitz suspends the duodenojejunal (DJ) flexure.
• Griffith's point (splenic flexure) is a key watershed area for colonic ischemia.