Click image to view full screen
(3 of 4)
Inferior to the pectinate line identify the pecten and the white line (of Hilton) which separates the mucous portion from the cutaneous portion of the anal canal .
The anal canal contains two muscular sphincters, the internal anal sphincter and the external anal sphincter. Identify the external anal sphincter muscle, composed of striated muscle. It functions in voluntary control of the sphincter and maintains rectal continence. The involuntary internal anal sphincter is composed of a thick circular layer of smooth muscle fiber of the anal canal and is difficult to visualize in the dissection.
Links and References:
Netter (1ed.): 369 (2ed.): 365