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Digestive system

Not medically reviewed · Content last updated · 1 min read ·

This is the date the draft was written, not a medical review date.

The digestive system is the alimentary canal from mouth to anus together with its accessory organs. It ingests, digests and absorbs nutrients and water, and eliminates undigested residue.

Terminologia Anatomica (Latin): Systema digestorium

Components

The tube comprises the oral cavity, pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, ileum) and large intestine (caecum, colon, rectum, anal canal). The accessory organs are the salivary glands, liver, gallbladder with biliary tree, and pancreas; the wall has mucosa, submucosa, muscularis externa and serosa or adventitia.

Function

Mechanical and chemical digestion, controlled by enteric, autonomic and hormonal mechanisms, reduces food to absorbable molecules, mostly absorbed in the small intestine. The liver metabolises absorbed nutrients and secretes bile, and the colon reabsorbs water and electrolytes.

Clinical correlations

Gastro-oesophageal reflux, peptic ulcer, inflammatory bowel disease, gallstones, hepatitis, cirrhosis, pancreatitis and gastrointestinal cancers are common. The acute abdomen and gastrointestinal bleeding need prompt assessment under local protocols.

Common exam points

  • Foregut, midgut and hindgut derivatives with their arterial supply (coeliac, superior and inferior mesenteric arteries).
  • Four layers of the gut wall and the enteric plexuses (submucosal and myenteric).
  • Peritoneal relations: intraperitoneal versus retroperitoneal organs.
  • Portal venous system and the sites of portosystemic anastomosis.
  • Sites of absorption: iron in the duodenum, vitamin B12 and bile salts in the terminal ileum.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology. Elsevier, 14th edition (2020) — Tier 3 (textbook)
  4. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. Elsevier, 11th edition (2020) — Tier 3 (textbook)

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