Rectum (dave's notes) Flashcards
Describe the curves of the rectum
This could be added to from Prof Bissett’s lecture
Posteriorly, the rectum follows the posterior concavity of the sacrum, but also has three curves; the upper and lower to the right. Must know concave/convex what direction
What are the folds within the rectum called and what are they made of? What is their function?
The folds of Houston are made from the inner circular muscle layer of the wall. They help to separate flatus.
What is the lowest part of the rectum called?
The lowest, slightly dilated part of the rectum is the rectal ampulla.
At what point does sigmoid become rectum?
S3
How long is the rectum?
12cm
What marks the end of the rectum?
Where the muscle coat is replaced by anal canal sphincters
Why are there no sacculations in the rectum?
The three taenia coli have come together
Does the rectum leave mesentery? What fascia surrounds the rectum?
No, nor appendages epiploicae, fascia propria
What is the course of the rectum from S3?
Curves forward over coccyx and anococcygeal raphe behind the perineal body
Where is the anorectal junction located?
3cm above the cutaneous margin, 5cm from the coccyx
Describe the peritoneal coverings of the rectum
Anterior: The upper 2/3 is covered by peritoneum, the lower third is below the peritoneum that is reflected up to bladder/seminal vesicles or upper vagina.
Lateral: The upper 1/3 is covered by peritoneum
Posterior:
What are the potential spaces anterior to the rectum called? How far above the anal margin are they found?
Rectovesical, 7.5cm from anal margin, and rectouterine, 5.5cm from anal margin.
What is Denonvilliers?
A condensation of connective tissue intervening between the rectum and the anterior structures.
What constitutes the lateral ligaments of the rectum?
Retroperitoneal tissue around the middle rectal vessels
What are the posterolateral relations of the rectum?
S3,4,5 and coccyx, piriformis, lavator ani, ckoccygeus, anterior rami of lower 3 S/C(??) nerves, sympathetic trunk, pelvic splanchnic nerves and rectal vessels.
What anchors the lower part of the rectum? To what?
Waldeyer’s fascia, to the lower sacrum
What contributes to the rectourethralis muscles?
Some muscle fibres (from what?) leave the lower part of each side of the rectal ampulla to form the rectourethralis muscles
Describe the blood supply of the rectum
Principally the superior rectal artery (a continuation from the IMA) and middle and inferior, and median sacral arteries
What happens to the blood supply of the rectum at S3?
The superior rectal artery divides into various branches which supply the whole thickness of the muscle wall
How does the middle rectal artery reach the rectum? From what does it arise?
Through the lateral rectal ligaments
How does the inferior rectal artery reach the rectum? From what does it arise? Up to where does the inferior rectal artery supply?
The IRA penetrates the walls from the anal canal and may supply up to the peritoneal reflection.
Describe the venous drainage of the rectum
Veins correspond to arteries but anastomose freely forming the internal and external rectal plexus.
The superior and inferior rectal veins are the most important, with drainage to both portal and systemic systems.
Describe the lymphatic drainage of the rectum
Lymph passes back with the SRA, MRA and median sacral arteries. Lymphoid follicles ->
MSA: hollow of sacrum,
MRA: side wall of pelvis
Superior rectal and inferior mesenteric arterioes: pre-aortic nodes.
What nerve types supply the rectum?
Sympathetic and parasympathetic, pain.
Where does the sympathetic supply of the rectum come from?
From branches directly from the hyp0gastric plexus and fibres accompanying vessels
Where does the parasympathetic supply of the rectum come from?
From S2,3 from pelvic splanchnic nerves
What accompanies the sympathetic and parasympathetic nerves to the rectum?
Pain fibres appear to accompany both
What does the rectum develop from?
The anal canal, with the anal membrane breaking down at the pectinate line
What is the embryonic origin of the proximal part of the rectum?
What is the embryonic origin of the distal part of the rectum?
Endoderm, ectoderm.
