Rectum And Anus

Front 1

Rectum

Back 1

Longitudinal muscle

Blood supply - superior rectal artery from inferior mesenteric

and middle rectal artery from the internal iliac

Sympathetic- hypogastric plexus

Parasympathetic - pelvic splanchnic nerves S2,3,4 via hypogastric plexus (motor to rectal muscle)

Front 2

Anus

Back 2

Circular muscle forming internal and external anal sphincters

Blood supply - upper part supplied by superior rectal vessels, lower part supplied by inferior rectal artery which is a branch of the internal pudendal

Nerve supply - inferior rectal nerve which is a branch of the pudendal nerve

Sympathetic supply is from pelvic plexus L1,2 —> contraction

Parasympathetic supply is from the pelvic splanchnic nerves (S2,3,4) —> relaxation

Front 3

Epithelium of anus

Back 3

The superior aspect of the anal canal has the same epithelial lining as the rectum (columnar epithelium) above the pectinate line.

Inferior to the pectinate line, the anal canal is lined by non-keratinised stratified squamous epithelium.

Above the pectinate line – derived from the embryonic hindgut.

Below the pectinate line – derived from the ectoderm of the proctodeum.

Front 4

External anal sphincter is innervated by

Back 4

Pudendal nerve

Front 5

Internal anal sphincter is innervated by

Back 5

The pelvic splanchnic nerves