Anal Canal Anal Canal

Definition :- The last part of the GIT Commences at the level where the rectum passes through the pelvic diaphragm and ends at the anal verge Parts : - Anorectal ring – the muscular junction between the rectum and anal canal – can be feltas a thickened ridge Internal sphincter Thickened continuation of the circular muscle coat of the rectum. Pearly white Spasm of this muscle is the cause of increased pain in many painful conditions of the anus.

The external sphincter Longitudinal muscle fibres – fan out to get attached to the skin of the anal verge. The external sphincter Some of its fibres are attached posteriorly to the coccyx, anteriorly inserted into the midperineal point in the male and in the female fuse with the sphincter vaginae Pink The intersphincteric plane The potential space between the internal and external sphincter Contains 8-12 apocrine glands – can cause infections Puborectalis This muscle maintains the angle between the rectum and the anal canal The ano rectal ring Junction between the rectum and the anal canal Formed by the joining of the puborectalis muscle, the deep external sphincter, conjoined longitudinal muscle and the highest part of the internal sphincter

Anal valves situated at the lower end of the columns of Morgagni Division of the anorectal ring permanent incontinence of faeces The mucous membrane 8-12 longitudinal folds known as the columns of Morgagni Red Anal valves situated at the lower end of the columns of Morgagni Just below the level of the anal valves transition of columnar epithelium to squamous epithelium – wavy margin – called the dentate line The squamous epithelial lining of the anal canal is called the anoderm Lower down the pale anoderm becomes pigmented

superior, middle and inferior haemorrhoidal veins Arterial supply By branches from the superior, middle and inferior haemorrhoidal arteries Venous drainage superior, middle and inferior haemorrhoidal veins Lymphatic drainage Hpper half to the para-aortic nodes Lower half to the inguinal lymph nodes