QS Study

Large Gut (or Large Intestine) is the hindermost part of alimentary canal which opens to the outside through the anus. The length of the large intestine is about 1.5 m. It begins at the ileocecal junction, where the ileum enters the large intestine and ends at the anus. It has 4 regions: caecum, colon, rectum, and anal canal.

Blood supply of large gut –

Arterial supply

(i) Front caecum to proximal 2/3 of the transverse colon – by the superior mesenteric artery and its branches. The superior mesenteric artery branches from the abdominal aorta inferior to the celiac trunk and provides oxygenated blood to most of the small intestine and the proximal large intestine.

(ii) From distal 1/3 of transverse colon to upper 15 mm of anal canal – by inferior mesenteric and middle rectal arteries. Blood flow to the rectum and anus below the internal anal sphincter is distinct from the blood flow to the other regions of the intestines.

Fig: Blood supply of large gut

Venous drainage

Corresponding veins drain into superior and inferior mesenteric veins. The proximal veins, which lie near the hepatic portal vein drain directly into it.

APPENDIX

Artery supply – by an appendicular branch of the inferior division of ileocolic artery, branch of the superior mesenteric artery.

Venous drainage – into

(a) Appendicular,

(b) Ileocolic &

(c) Superior mesenteric veins.

CAECUM

  • Arterial supply – by a caecal branch of the ileocolic artery.
  • Venous drainage – Veins drain into superior mesenteric vein.

Fig: Arterial supply of caecum and appendix

RECTUM

Arterial supply: By –

(a) Superior rectal artery branch of the inferior mesenteric artery.

(b) Middle rectal artery branch of the internal iliac artery.

(c) Median sacral artery dorsal branch of the abdominal aorta.

Venous drainage: Into –

(a) Superior rectal vein – drains into an inferior mesenteric vein.

(b) Middle rectal vein – drains into internal iliac vein.

ANAL CANAL

Arterial supply: by –

(a) Superior rectal artery (above pectinate line)

(b) Inferior rectal artery (below the pectinate line).

Venous drainage: Into –

(a) Upper part – superior rectal vein.

(b) Middle part – Middle rectal vein.

(c) Lower part – Inferior rectal vein.