Part 12: Rectum Flashcards
Describe the course of the rectum
Continuous with sigmoid colon, beings where mesocolon ends. Follows posterior concavity of sacrum with 3 lateral curves (upper to the R, middle to L then upper to R)
What produces the folds of Houston?
Circular muscle of wall projecting into lumen. May help seperate flatus from stool
How long is the rectum?
12cm
Describe the muscle wall of the rectum
2 layers - circular and longitudinal. The 3 taeniae of colon come together over rectum, no sacculations and no appendices epiploicae
Where is the anorectal junction?
3cm above cutaneous margin, 5cm from coccyx
What parts of the rectum are covered by peritoneum?
Anterior: Upper 2/3 covered by peritoneum, lower 1/3 is below reflected margin over bladder/seminal vesicles/vagina
Sides: Upper 1/3 covered with peritoneum
Posterior: Only covers upper 1/3
What is Waldeyer’s fascai relationship to the rectum?
Anchors lower part of the rectum to lower sacrum
What is the blood supply of the rectum?
Superior rectal (continuation of IMA) Middle and inferior rectal arteries and small portion from median sacral
Describe the course of superior rectal artery and margin of supply
S3 SRA divides into branches to supply thickness of muscles wall of upper and middle rectum
Where do middle rectal and inferior rectal arteries arise?
Middle rectal - internal iliac (supplies lower rectum)
Inferior rectal - internal pudendal artery (penetrates wall anal canal to supply lower rectum)
Where is the pouch of douglas?
Rectouterine pouch in females
Rectovesical pouch in males (not called the pouch of douglas)
Dependent area therefore often source for collections of infection
What is the lymph drainage of the rectum?
Pass back along SRA, MRA and median sacral arteries
What is the nerve supply of the rectum?
Sympathetic branches from hypogastric plexus, accompany vessels
Parasympathetic S2,3 from pelvic splanchnic nerves
Briefly describe development of rectum
Rectum is developed from anorectal canal, with the anal membrane breaking down at the pectinate line. Above pectinate line is endoderm and below is ectoderm (hence the different blood supply between upper and lower part of canal)
