Rectum and Anal Canal

Question 1

How long is the rectum

Answer 1

13-15cm

Question 2

Where does the rectum commence?

Answer 2

Rectosigmoid junction anterior to S3

Question 3

What is the difference in orientation between the rectum of a monkey and that of a human

Answer 3

The rectum is straight in a monkey and sigmoid shaped in humans

Question 4

Where does the rectum end

Answer 4

2-3cm anterior and inferior to the tip of the coccyx

Question 5

How is peritoneum related to the rectum

Answer 5

Upper 3rd- peritoneum is present anteriorly and laterally
Middle 3rd- peritoneum only present anteriorly
Lower third- Devoid of peritoneum

Question 6

How far is the rectovesical pouch of proust (lower extent) from the anus in males?

Answer 6

7.5cm

Question 7

How far is the Rectouterine pouch of Douglas (lower extent) from the anus in females?

Answer 7

5.5cm above anus
7.5cm above the externa orifice of the vagina

Question 8

State the Antero-posterior curvatures of the rectum

Answer 8

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

Question 9

Lateral curve?

Answer 9

3 in number, 2 are convex to the right side and one to the left

Question 10

State the positions and locations of the upper , middle and lower curves

Answer 10

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

Question 11

Which curve of the rectum is the most prominent?

Answer 11

Middle curve

Question 12

What runs along the concavities of the curves of the rectum?

Answer 12

Horizontal/Transverse rectal valves of houston
and they project into the lumen of the rectum

Question 13

What is the function of the folds in the rectum

Answer 13

Support the faecal mass
To prevent over distention of the rectal ampulla

Question 14

Length of the Anal Canal

Answer 14

2.5-5cm; usually around 3.8cm in length

Question 15

What keeps the anal canal closed except during defecation

Answer 15

Tonic contraction

Question 16

What surrounds the anal canal

Answer 16

Sphincter ani muscles and in part by Ischiorectal fat (which will allow for its expansion)

Question 17

What does the upper part of the anal canal contain

Answer 17

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

Question 18

What lies in between the Anal Columns

Answer 18

Anal Sinuses ( anal glands of ball end on the floor of these sinuses)

Question 19

What is the Pectinate/Dentate line

Answer 19

Free margines of the Anal valves that appear wavy

Question 20

Which epithelium lines the lower surface of the anal valves

Answer 20

Stratifies squamous epithelium

Question 21

The pectinate line serves as a border because above and below it are different blood, nerve supply and lymphatic drainage; True or False

Answer 21

True

Question 22

What type of epithelium is below the pectinate line

Answer 22

Non-keratinized epithelium WITHOUT sebaceous or sweat glands

Question 23

What forms the internal sphincter of the rectum

Answer 23

Circular muscle layers

Question 24

Which 2 muscles blends and goes into the formation of the Sphincter Ani Externus

Answer 24

Longitudinal coat blends with Puborectalis muscle

Question 25

What are the 3 parts of the Sphincter Ani Externus

Answer 25

Deep part- which blends with the puborectals
Superficial part
Subcutaneous part

Question 26

Which artery supplies the entire mucus membrane t the level of the Anal valves

Answer 26

Superior Rectal Artery

Question 27

Location of 3 sites of primary pile

Answer 27

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

Question 28

List the blood supply for the rectum

Answer 28

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

Question 29

Venous drainage of the anal canal

Answer 29

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

Question 30

The pectinate line is a site of portosystemic anastomosis; True or False

Answer 30

True

Question 31

What is the parasympathetic innervation to the rectum

Answer 31

S2 and S4 - stimulate peristalsis and relax the sphincters

Question 32

Nerve supply below the pectinate line

Answer 32

Somatic nerve supply- Inferior rectal nerve

Question 33

List the supports of the rectum

Answer 33

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