Difference between revisions of "Rectum - Anatomy & Physiology"

From WikiVet English
Jump to navigation Jump to search
Line 41: Line 41:
 
*The circular layer of the tunica muscularis forms the internal anal sphincter.
 
*The circular layer of the tunica muscularis forms the internal anal sphincter.
 
*The external anal sphincter is formed from skeletal muscle.
 
*The external anal sphincter is formed from skeletal muscle.
 +
*Epithelium changes from
  
 
===Rectum===
 
===Rectum===

Revision as of 14:38, 14 July 2008

BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY
BACK TO LARGE INTESTINE - ANATOMY & PHYSIOLOGY

Introduction

Structure

  • Exists dorsal to the reproductive organs, bladder and urethra.
  • The cranial portion of the rectum is attached to the dorsal body wall by a short mesorectum which is a continuation of the mesocolon.
  • The mesorectum is reflected to continue with the parietal peritoneum of the pelvic cavity and to cover the urogenital organs ventrally.
    • This forms the rectogenital pouch.
    • Therefore the most distal part of the rectum is retroperitoneal.
      • This distal, retroperitoneal part is directly attached to the vagina in the female and to the urethra in the male.
      • The retroperitoneal space is filled with soft tissue rich in fat.
  • The anal canal joins the bowel to the exterior.
    • This is a short passage derived from the proctodeum (formed by invagination of the surface ectoderm).
    • Before joining the anal canal, the rectum becomes dilated to form the rectal ampulla.
  • At the rectoanal junction, the lumen is constricted by longitudinal folds in the mucosa.
    • These are normally pressed together to occlude the lumen.
  • There are two anal sphincters:
    • Internal anal sphincter, formed by thickening of the circular smooth muscle of the gut and under autonomic control.
    • External anal sphincter, formed from striated skeletal muscle and under voluntary control.

Function

Vasculature

Innervation

Lymphatics

Histology

Recto-Anal Junction

  • Termination of the lamina muscularis and longitudinal layer of the tunica muscularis.
  • The circular layer of the tunica muscularis forms the internal anal sphincter.
  • The external anal sphincter is formed from skeletal muscle.
  • Epithelium changes from

Rectum

  • Epithelium is columnar.
  • Goblet cells are present in the mucosa.

Species Differences

Links