View Full Version : Musculature of Anal Canal

Medical Videos
05-30-2008, 03:57 PM
qGross Anatomy:
* The rectum is 12 - 15 cm in length .
* The anal canal is 4-5 cm in length.
* The Hauston’s valves are 3 valves, 2 in left and 1 on the right. They are mucosal folds which may hide a small lesions from endoscop.
* The peritoneum cover the ant. wall and sides of the upper 2/3 of rectum.
* At the ano-rectal junction there is 8-12 longitudinal folds called columns of Morgagni with depressions at its base what is called "Dentate line".
* Into small depressions between columns of Morgagni, open the ducts of anal glands. Anal glands are present in the interesphincteric space (between int. and Ext. sphincters).
q The anal canal is surrounded by 2 sphincters:
1- External sphincter: Voluntary muscle formed of 3 parts:
- Subcutaneous ext. sphincter. - Superficial ext. sphincter.
- Deep ext. sphincter.
2- Internal sphincter:

- Smooth muscle formed from the continuation of the circular muscle layer of rectum below pelvic diaphragm.
q Blood supply:
(I) Arterial supply:
1- Superior rectal artery (from inferior mesentaic artery).
2- Middle rectal artery (from anterior division of internal iliac artery).
3- Inferior rectal artery (from internal pudendal artery) supply the anal canal.
(II) Venous drainage:
1- Sup. rectal vein to inf. mesentric v.
2- Middle and inf. rectal to systemic venous drainage.
\ Anal canal is a site of porto-systemic communication.
So, increase in portal bl. pr. leads to dilated sup. rectal communications. (Haemorrhoidal vessels)® Haemorrhoids with minimal bleeding in comparison with oesophageal varices as it is supported by strong muscles.
q Lymph drainage: 3 Zones:
1- A zone of upward extension: to pararectal L.N. to sup. rectal artery L.N. to inf. mesentric L.N.
2- A zone of lateral extension: through middle rectal a ® to int. iliac ® to ® para-aortic L.N.
3- A zone of downward extension through the cutaneous L.N. to inguinal L.N.. (This group drains the anal canal).
The upper zone is the most important one in spread of malignancy of rectum.

So, it must be removed in high or low situated cancer rectum.

Copyright: Vascular Society of Egypt (www.vsegypt.org (http://www.vsegypt.org/)) &Medical Educational web (www.meduweb.com (http://www.meduweb.com/))
Not to be reproduced without permission of Vascular Society of Egypt