Rectum and Anal Canal Flashcards
Gardener
How long is the rectum
13-15cm
Where does the rectum commence?
Rectosigmoid junction anterior to S3
What is the difference in orientation between the rectum of a monkey and that of a human
The rectum is straight in a monkey and sigmoid shaped in humans
Where does the rectum end
2-3cm anterior and inferior to the tip of the coccyx
How is peritoneum related to the rectum
Upper 3rd- peritoneum is present anteriorly and laterally
Middle 3rd- peritoneum only present anteriorly
Lower third- Devoid of peritoneum
How far is the rectovesical pouch of proust (lower extent) from the anus in males?
7.5cm
How far is the Rectouterine pouch of Douglas (lower extent) from the anus in females?
5.5cm above anus
7.5cm above the externa orifice of the vagina
State the Antero-posterior curvatures of the rectum
Sacral curve- is convex backwards towards the hollow of the sacrum.
Perineal curve- is convex forwards at the ano-rectal junction and is maintained by the pubo-rectal sling of the levator ani muscle
Lateral curve?
3 in number, 2 are convex to the right side and one to the left
State the positions and locations of the upper , middle and lower curves
Upper curve- is convex to the right at S3 and S4
Middle curve- IS CONVEX TO THE LEFT, occurring at the upper border of the coccyx
Lower curve- is convex to the right at the tip of the coccyx
Which curve of the rectum is the most prominent?
Middle curve
What runs along the concavities of the curves of the rectum?
Horizontal/Transverse rectal valves of houston
and they project into the lumen of the rectum
What is the function of the folds in the rectum
Support the faecal mass
To prevent over distention of the rectal ampulla
Length of the Anal Canal
2.5-5cm; usually around 3.8cm in length
What keeps the anal canal closed except during defecation
Tonic contraction
What surrounds the anal canal
Sphincter ani muscles and in part by Ischiorectal fat (which will allow for its expansion)
What does the upper part of the anal canal contain
Anal Columns (6-10 permanent longitudinal folds formed by a duplication of the mucosa)
-Internal rectal venous plexus
-radicles of superior rectal vessels
-AV Shunt of Haller- bleeding of bright red blood from piles
What lies in between the Anal Columns
Anal Sinuses ( anal glands of ball end on the floor of these sinuses)
What is the Pectinate/Dentate line
Free margines of the Anal valves that appear wavy
Which epithelium lines the lower surface of the anal valves
Stratifies squamous epithelium
The pectinate line serves as a border because above and below it are different blood, nerve supply and lymphatic drainage; True or False
True
What type of epithelium is below the pectinate line
Non-keratinized epithelium WITHOUT sebaceous or sweat glands
What forms the internal sphincter of the rectum
Circular muscle layers
Which 2 muscles blends and goes into the formation of the Sphincter Ani Externus
Longitudinal coat blends with Puborectalis muscle
What are the 3 parts of the Sphincter Ani Externus
Deep part- which blends with the puborectals
Superficial part
Subcutaneous part
Which artery supplies the entire mucus membrane t the level of the Anal valves
Superior Rectal Artery
Location of 3 sites of primary pile
Where the ant and post branches of the right superior rectal artery produces AV shunts which drain to radicles of the superior rectal veins at positions 3, 7 and 11o’clock
List the blood supply for the rectum
Superior rectal artery- branch of rectosigmoid which is a branch of the inferior mesenteric
Middle rectal artery- branch of internal iliac artery
Below the pectinate line:
Inferior Rectal Artery- branch of pudendal artery from the internal iliac artery
Venous drainage of the anal canal
Internal rectal plexus- surrounds anal canal in its upper part; drains to radicles of the superior rectal vein
External Rectal Plexus- surrounds the anus between Peri-anal skin and the subcutaneous part of the sphincter ani externus muscle
The pectinate line is a site of portosystemic anastomosis; True or False
True
What is the parasympathetic innervation to the rectum
S2 and S4 - stimulate peristalsis and relax the sphincters
Nerve supply below the pectinate line
Somatic nerve supply- Inferior rectal nerve
List the supports of the rectum
Puborectal sling of the Levator Ani
Pelvic floor
Fascia of Waldeyer- attaches rectum to the sacrum
Pelvi-rectal and Ishiorectal fat
Fascia of Denovillers- only in males
