rectum and anal canal

Question 1

where does the rectum start

Answer 1

S3

Question 2

describe the shape of the rectum

Answer 2

has lateral concavities that form left, right, left rectal folds
the lower part is slightly dilated- the rectal ampulla
the middle concavity on the right is most pronounced

Question 3

why is the first concavity on the left

Answer 3

because the sigmoid leads to the rectum from the left

Question 4

what is found next to the rectum

Answer 4

pararectal fossae

Question 5

what is the pouch of douglas

Answer 5

the rectouterine pouch

Question 6

describe the peritoneal covering of the rectum

Answer 6

covered by mesorectum which is not a mesentery.
the upper third of the rectum is covered front and sides by peritoneum
the middle third is only covered in front
the lower third has no peritoneal covering

contains sup rectal artery and veins plus lymph nodes and nerves

Question 7

what is denonvilliers fascia

Answer 7

rectoprostatic fascia in the lower part of the rectovesical pouch

Question 8

how long is the rectum

Answer 8

12 cm

Question 9

what are the anterior relations of the rectum

Answer 9

bladder, vas, seminal vesical, prostate, pelvic floor

Question 10

what nerves are at risk in rectal surgery

Answer 10

urogenital nerves and vessels

Question 11

describe the internal sphincter

Answer 11

derived from circular smooth muscle, autonomic, ends at the intersphincteric groove

Question 12

describe the external sphincter

Answer 12

striated muscle, deep, superficial and subcutaneous parts

Question 13

what muscles surround the anus

Answer 13

puborectalis and pubococcygeus

Question 14

what muscle forms a sling around the anorectal junction

Answer 14

puborectalis

Question 15

what is the anococcygeal ligament

Answer 15

formed by the fused levator ani and attaches the anal canal to the coccyx

Question 16

what does the external sphincter fuse with in the female

Answer 16

puborectalis, anococcygeal ligament and the perineal body

Question 17

what are the features of the inside of the anus

Answer 17

mucous membrane and submucosa are loose, mobile and distensible
rich underlying vasculature

Question 18

how is anal closure maintained

Answer 18

anal cushions and internal sphincter

Question 19

what is the superior rectal artery a branch of

Answer 19

inferior mesenteric

Question 20

what is the middle rectal artery a branch of

Answer 20

internal iliac- may be absent

Question 21

what is the inferior rectal artery a branch of

Answer 21

internal pudendal

may also be a contribution from the median sacral which may bleed during surgery

Question 22

describe the rectoanal veins

Answer 22

mirror arteries
form external and internal venous plexuses which form a portosystemic anastomosis

this is due to sup. rect veins to inf. mesenteric and middle rectal veins going to the internal iliac

Question 23

what is the lymph drainage of the rectum

Answer 23

inf mesenteric nodes

internal iliac nodes

superficial inguinal nodes for distal anal canal

Question 24

what is the parasympathetic supply of the rectum

Answer 24

pelvic splanchnics from S2,3,4 Going to the pelvic plexus

Question 25

what is the function of the pelvic plexus

Answer 25

caries recto anal sensations and controls the internal sphincter

Question 26

what plexus forms the pelvic plexus

Answer 26

superior hypogastric plexus

Question 27

what controls the external sphincter and adjacent pelvic flood muscles and gives sensation to the distal anal canal

Answer 27

inferior rectal which is derived from the internal pudendal nerve from S2-4

Question 28

what happens during defecation

Answer 28

cortical inhibition is released
abdo pressure is increased
puborectalis relaxes, allows the rectal angle to straighten
external sphincter relaxes (s2-4)
lower colon and rectum contract while the internal sphincter relaxes

Question 29

what might cause incontinence

Answer 29

cord lesions above S2-4
loss of cortical control
damage to external sphincter during surgery
entrapment of the pudendal nerve

Question 30

what is the ischio anal fossa

Answer 30

fat filled pyramid region below levator ani and either side of the anal canal to allow distension during defecation

Question 31

where does the pudendal neurovascular bundle lie

Answer 31

laterally in alcock’s canal (obturator fascia)

Question 32

what does the inferior rectal NVB supply

Answer 32

external sphincter and anal canal sensation

Question 33

what muscle inserts onto the anococcygeal body

Answer 33

iliococcygeus, pubococcygeus and ishiococcygeus

Question 34

where is alcocks canal

Answer 34

overlies obturator internus and lateral to the rectum