QS Study

Rectum is the distal part of the large gut, placed between the sigmoid colon above and the anal canal below. It is the last part of the large intestine and connects the sigmoid colon to the anal canal. It has an important role as a temporary store of faeces.

Blood Supply – The rectum receives its autonomic nerves with its arterial blood supply, the superior rectal artery.

(a) Arterial supply:

  • superior rectal artery: terminal branch of an inferior mesenteric artery and forms the major blood supply to the mucosa of the rectum.
  • middle rectal artery: a branch of an internal iliac artery and forms the major blood supply to the muscular coat.
  • inferior rectal artery: a branch of the internal pudendal artery. It anastomoses with the middle rectal artery at the anorectal junction.

(b) Venous return: via similarly named veins to both the portal venous system and systemic venous system

Fig: Blood supply of rectum

Nerve supply

  • Upper rectum: inferior mesenteric plexus
  • Middle and lower rectum: superior and inferior hypogastric plexus
  • Sympathetic – (L 1, 2) and,
  • Parasympathetic – (S 2, 3, 4) through superior rectal and inferior hypogastric plexus.

CLINICAL SIGNIFICANCE

The semilunar transverse folds of the rectum, especially the 3rd valve, cause hindrance in passing an instrument from the anus. Thus, the cannula for rectal sigmoidoscope is generally passed in the left lateral position of the patient to prevent injury to Houston’s third valve and give a wide berth to unnecessary suffering to the patient.

Development

(i) Above the middle transverse fold – from hindgut.

(ii) Below the middle transverse fold – from the endodermal cloaca.