Rectum and anal canal
Upon completing this study unit you will be able to:
- Name and recognize the main anatomical features of the rectum, anal canal and its lining.
- List the structures anatomically related to the terminal part of the gastrointestinal tract.
- Understand the function of the rectum and anal canal.
The rectum and anal canal are located in the pelvic cavity and are the terminal structures of the gastrointestinal tract. The rectum is a direct continuation of the sigmoid colon and is followed by the anal canal, which opens itself to the external environment through the anus. The main functions of these structures is to absorb water and electrolytes, and store feces prior to defecation.
The rectum and anal canal lie posteriorly against the sacrum and coccyx, the anococcygeal ligament and the median sacral vessels. In males, the urinary bladder, distal parts of the ureters, ductus deferens, seminal glands, and prostate are found anterior to the rectum and anal canal, whereas in females the vagina occupies this position.
The video below will help you understand more about the rectum and the anal canal:
Take a quiz
You can complete this quiz to test your recently acquired knowledge:
Learn about the rectum and anal canal structure, vascularization, and innervation with a custumizible quiz:
Review the parts and related structures of the rectum and anal canal in our atlas gallery:
Superior third of rectum: intraperitoneal
Middle third of rectum: retroperitoneal
Inferior third of rectum and anal canal: infraperitoneal
Rectum: absorption of water and electrolytes and feces storage
Anal canal: absorption of water and electrolytes and defecation
|Major landmarks of rectum||
Vertical flexures: sacral flexure (dorsal bend) and anorectal flexures (ventral bend)
Lateral flexures: superior flexure (convexes to the right), intermediate flexure (convexes to the left) and inferior lateral flexure (convexes to the right)
|Major landmarks of anal canal||
Columnar zone: contains anal columns, valves and sinuses
Intermediate zone: separeted from the columnar zone by the pectinate (dentate) line
Cutaneous zone: made of perianal skin and progresses to the anus