Rectum and Anal Canal

Question 1

Rectum location

Answer 1

Sits in curvature of sacrum, retroperitoneal
2 indentations, 1 on R, 2 on L
In the pelvis

Question 2

Female rectal pouches

Answer 2

Rectouterine pouch, lowest part of peritoneal cavity, back of vagina
Vesiculouterine pouch, top of bladder

Question 3

Peritoneal coverings of rectum

Answer 3

Upper 1/3, peritoneum on front and sides of rectum
Middle 1/3, peritoneum only on the front
Lower 1/3, no peritoneum

Question 4

Male rectal pouches

Answer 4

Rectovesicular pouch, between rectum and behind bladder

Question 5

Anal triangle

Answer 5

Puborectalis muscles wrap around the anus and external anal sphincter, towards sacrum
Muscles here form the pelvic floor

Question 6

Where is the perineum and what does it cover

Answer 6

Urogenital triangle, the anterior side

Question 7

Ischioanal fossa structure

Answer 7

Internal smooth sphincter, with external skeletal sphincter around anal canal
Fat filled ischiorectal space under levator ani
Obturator internus next to ischium, internal pudendal artery, vein in pudendal canal

Question 8

Function of the pudendal nerve

Answer 8

Supplies external anal sphincter

Question 9

Innervation of the external sphincter and levator ani

Answer 9

Inferior rectal nerve, branch of the pudendal nerve

Question 10

Anorectal junction

Answer 10

Puborectalis surrounds the anorectal junction, part of the levator ani
Anococcygeal ligament attaches to external anal sphincter muscles and puborectalis, changes angle between rectum and anal junction
Perineal body, anchorage of some muscle fibres

Question 11

Bones and tendon around the anorectal junction

Answer 11

Pubis symphysis at anterior side
Ischio pubic ramus on anterior side
Ischial tuberosity on corner , attaches to the sacrotuberous ligament on the posterior side

Question 12

What occurs at rest during defaecation

Answer 12

Rectum follows curve of sacrum
Obtuse anorectal angle
Puborectalis forms sling around rectum

Question 13

What occurs during straining during defaecation

Answer 13

Rectum becomes straighter
Almost 180 degree anorectal angle
Puborectalis relaxes, pelvis floor descends

Question 14

Internal structure of the rectum and anal canal
Sigmoid
Rectum
Rectal ampulla
Upper anal canal
Lower anal canal

Answer 14

Sigmoid, plicae circularis, teniae coli, epiploici

Rectum, coat of longitudinal muscle, 3 plicae folds, form rectal valves

Rectal ampulla, marks end of rectum

Upper anal canal, has folds of mucosa between columns, form anal valves
Pectinate line at bottom upper canal anal

Lower anal canal, pecten

Question 15

What can you see in a rectal endoscopy

Answer 15

Yellow masses, colon cancer

Polyps can turn cancerous

Question 16

Anal sphincters
Internal sphincter
External sphincter

Answer 16

Internal sphincter, longitudinal muscle from rectum joins with levator ani muscle (puborectalis) to form the conjoined longitudinal muscle.
Internal anal sphincter from white line upwards

External anal sphincter skeletal fibres under pudendal branch of pudenda nerve, tonic contraction until relaxed

Question 17

Arterial supply of rectum

Answer 17

IMA, branches into superior rectal artery
Internal iliac, branches into middle rectal artery, supplies hindgut above pelvic floor
Internal pudendal, branches into inferior rectal artery, below pectinate line

Question 18

Venous drainage of the rectum

Answer 18

Veins match arteries
Superior rectal veins join splenic veins
Internal pudendal vein => internal iliac => common iliac

Question 19

Formation of haemhorrhoids
Internal
External

Answer 19

Internal, forms in anal sinus, collection of mucosal veins bulge out

External, collection of mucosal veins below pectinate line, proctodeal drainage

Question 20

Lymphatic drainage
Anal
Middle rectal
Hindgut

Answer 20

Anal, superficial inguinal
Middle rectal, internal iliac
Hindgut, inferior mesenteric => preaortic

Superficial inguinal => external iliac and internal iliac => both join common iliac => para aortic

Question 21

Neural control of defaecation

Answer 21

Sigmoid colon in mass contraction, moves faces to rectum
Rectal wall stretches, sensed by afferent parasympathetic (pelvic splanchnic and inferior hypogastric)=> S2-S4 => brain
At the same time, somatic afferents from S2-S4 (pudendal) from anal sphincter => spinal cord

Inhibition of sympathetic L1-2 (lumbar splanchnic and inferior hypogastric) to relax involuntary sphincter
Pudendal nerves control somatics, puborectalis => straighten rectum
Transversus abdominus applies anterior pressure

Parasympathetic (pelvic splanchnic and inferior hypogastric), splanchnic nerve, contract smooth sigmoid and rectal muscle

Question 22

Difference between preaortic and paraaortic lymph nodes

Answer 22

Preaortic
-Drain GI lymphatics

Paraaortic
-Drain pelvic organs

Question 23

What is the Pectinate line

What is the White line

Answer 23

Pectinate line
-Represents the hindgut proctodeum junction

Hilton’s White line
-Marks transition between internal and external anal sphincter muscles

Question 24

What is the function of the superior hypogastric plexus
What is the function of the inferior hypogastric plexus
What is the relationship between the 2?

Answer 24

Autonomic pelvic nerves
Superior - sympathetic lumbar and visceral afferents
Anterior to aortic bifurcation

-SNS function of pelvic organs

Branches out into right and left hypogastric

Inferior - formed from pelvic splanchnic branches (PNS) and sacral splanchnic branches (SNS)

-SNS, PNS to pelvic organs
Lateral to rectum, bladder and vagina