Rectal and anal canal Flashcards
What is the peritoneum like on the different sections of the rectum
Upper third = peritoneum on front and sides
Middle third = peritoneum on front
Lower third = devoid of peritoneum
What points make up the anal triangle
Ischial tuberosities + coccyx
What is in the pudendal canal
int pudendal artery
pudendal vein
pudendal nerve
What is the ischioanal fossa
Fatty space = cusioning
What makes up the external anal sphincter
The deep superficial and subcutaneous muscles of the sphincter
What nerve supplies the anus
inf rectal nerve
What muscle has to relax to allow defaecation
levator ani
What is the shape of the rectum
smooth apart from 3 folds; two to the left and one to the right
What is the difference between the upper and lower anal canal
Upper has anal columns + sinuses; longitudinal folds
lower is smooth
What is the blood supply of the rectum
superior rectal artery (branch of the IMA)
middle rectal artery (branch of int. iliac)
inferior rectal artery (branch of int. pudendal)
What is the source of the superior rectal artery
interior mesenteric artery
What is the source of the middle rectal artery
int iliac
What is the source of the inferior rectal artery
int. pudendal
Describe the neurology of defaecation
stretch receptors (p’sympathetics S2-4)
ascending sacral spinal nerves inhibit lumbar sympathetics (L1, 2) to relax the involuntary sphincter
somatic nerves are inhibited in spinal cord - pudendal nerve relaxes voluntary sphincter
parasympathetic efferents (S2-4) trigger peristalsis, mass movements.
