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The stomach is the most dilated portion of the muscular tube that forms the digestive tract. It is located between the oesophagus proximally, and the duodenum distally. Developmentally, the stomach is a derivative of the embryonic foregut, and this derivation is reflected in its arterial supply from the coeliac trunk – the artery to the foregut. Physiologically, the stomach acts simultaneously as a temporary food store, an organ of digestion, and a mechanism to control the rate of flow of digested food into the small intestine where absorption occurs. This article describes in detail the surgically relevant topographical anatomy of the stomach, including its blood supply and lymphatic drainage. [ABSTRACT FROM AUTHOR]

The small intestine, comprising the duodenum, jejunum, and ileum commences at the pyloroduodenal (gastroduodenal) junction and ends at the ileocaecal junction. The principal function of the small intestine is the digestion and absorption of ingested food, electrolytes, and vitamins. As might be expected from its very active role as a secretory and absorptive viscus, the small intestine has a rich blood supply and an extensive surface area of absorptive mucosa. The blood supply is derived chiefly from the superior mesenteric artery via its inferior pancreaticoduodenal, jejunal and ileal branches. Accompanying these arterial branches are corresponding venous tributaries that carry venous blood through the superior mesenteric vein to the portal vein and liver. This article describes the key surgically relevant anatomy of the small intestine. [ABSTRACT FROM AUTHOR]

The large intestine comprises the caecum and appendix, colon, rectum, and anal canal from proximal to distal. Embryologically, the proximal half of the large intestine is derived from the midgut, while the distal half develops from the hindgut. This dual derivation is reflected in the difference in arterial supply to its proximal (superior mesenteric artery) and distal (inferior mesenteric artery) portions. Physiologically, the large intestine primarily functions to absorb water and essential electrolytes (sodium and chloride) from its luminal contents leaving the unabsorbed residue to be excreted as faeces. Fibre-optic colonoscopy and MRI and CT colonography allow detailed internal inspection of the large intestine with relative ease and with minimal discomfort. This article highlights the clinically and surgically relevant aspects of the anatomy of the caecum, appendix, and colon. [ABSTRACT FROM AUTHOR]

The rectum and anal canal are the terminal portions of large intestine and the entire gastrointestinal tract. They are thus readily accessible to direct inspection and examination. The rectum functions as a distensible reservoir for faeces, while the anal canal possesses a powerful muscular sphincter in its wall which is important in maintaining faecal continence. Diseases of the rectum and anal canal, both benign and malignant, account for a very large part of colorectal surgical practice worldwide. This article emphasizes the clinically and surgically relevant aspects of the anatomy of the rectum and anal canal. [ABSTRACT FROM AUTHOR]