Anal Canal Flashcards
above pectinate line vs below pectinate line arterial supply
Superior rectal artery (branch of inferior mesenteric artery)
Anastomosing branches from the middle rectal artery.
Inferior rectal artery (branch of the internal pudendal artery)
Anastomosing branches from the middle rectal artery.
above pectinate line vs below pectinate line venous drainage
Superior rectal vein, which empties into the inferior mesenteric vein. Inferior rectal vein, which empties into the internal pudendal vein.
above pectinate line vs below pectinate line nerve supply
Visceral innervation via the inferior hypogastric plexus.
Sensitive to stretch.
Somatic innervation via the inferior anal nerves (branches of the pudendal nerve)
Sensitive to pain, temperature, touch and pressure.
above pectinate line vs below pectinate line lymphatics
internal iliac lymph nodes Superficial inguinal lymph nodes
anterior and posterior lat to the anal canal male
Perineal body
Urogenital diaphragm
Urethra
Bulb of the penis
Post.Anococcygeal ligament
Coccyx and sacrum
Lat Ischioanal fossae
anterior and posterior lat to the anal canal female
Perineal body
Urogenital diaphragm
Vagina
Post.Anococcygeal ligament
Coccyx and sacrum
Lat
Ischioanal fossae
function of the anal canal
the final segment of the gastrointestinal tract, that has an important role in defecation and maintaining faecal continence.
postion of the anal canal
he anal canal is located within the anal triangle of the perineum between the right and left ischioanal fossae. The anal canal is the final segment of the gastrointestinal tract, and is around 4cm in length.
It begins as a continuation of the rectum, and passes in an infero-posterior direction to terminate at the anus.
except during defeachation the anal canal is collapesd by the internl and external sphincters. wht doe sthis do
prevent the passage of faecal material.
descibe the external and internal anal sphincters
Internal anal sphincter – surrounds the upper 2/3 of the anal canal. It is formed from a thickening of the involuntary circular smooth muscle in the bowel wall.
External anal sphincter – voluntary muscle that surrounds the lower 2/3 of the anal canal (and so overlaps with the internal sphincter). It blends superiorly with the puborectalis muscle of the pelvic floor.
what happens At the junction of the rectum and the anal canal and how is this thing formed
there is a muscular ring – known as the anorectal ring. It is formed by the fusion of the internal anal sphincter, external anal sphincter and puborectalis muscle, and is palpable on digital rectal examination.
describe the inernal tructe of the anal canal
The superior aspect of the anal canal has the same epithelial lining as the rectum (columnar epithelium). However, in the anal canal, the mucosa is organised into longitudinal folds, known as anal columns. These are joined together at their inferior ends by anal valves. Above the anal valves are small pouches which are referred to as anal sinuses – these contain glands that secrete mucus.
The anal valves collectively form an irregular circle – known as the pectinate line (or dentate line). This line divides the anal canal into upper and lower parts, which differ in both structure and neurovascular supply. This is a result of their different embryological origins:
Above the pectinate line – derived from the embryonic hindgut.
Below the pectinate line – derived from the ectoderm of the proctodeum.
Inferior to the pectinate line, the anal canal is lined by non keratinised stratified squamous epithelium (known as the anal pecten). It is a pale and smooth surface, which transitions at the level of the inter-sphinteric groove to true skin (keratinised stratified squamous).
