Anal canal

Question 1

Where does the anal canal run from and to

Answer 1

From the rectal ampulla to the anus

Question 2

What does the anal canal run between (Anteroposteriorly)

Answer 2

Anococcygeal ligament (posterior) and the perineal body (anterior)

Question 3

What is the anal canal located within

Answer 3

The anal triangle of the perineum

Question 4

Length of the anal canal

Answer 4

4cm

Question 5

What direction does the anal canal follow

Answer 5

Posteroinferior

Question 6

What surrounds the anal canal and what is there function

Answer 6

Internal and external anal sphincters

They maintain faecal continence

Question 7

Which anal sphincters are voluntary and involuntary muscle

Answer 7

External is voluntary

Internal is involuntary

Question 8

Where is the internal anal sphincter

Answer 8

Surrounds the upper 2/3 of the anal canal

Question 9

Where is the external anal sphincter

Answer 9

Surrounds the lower 2/3 of the anal canal

Question 10

What does the external anal sphincter blend with

Answer 10

Puborectalis muscle

Question 11

What must occur to allow defecation

Answer 11

Relaxation of both anal sphincters

Question 12

What is at the anorectal junction

Answer 12

Anorectal ring (muscular ring formed by fusion of the internal anal sphincter, external anal sphincter and puborectalis muscle)

Question 13

What are anal canals

Answer 13

Series of longitudinal ridges in the superior aspect of the mucous membrane

Question 14

What do anal columns contain

Answer 14

Terminal branches of the superior rectal vessels

Question 15

What joins the anal columns inferiorly

Answer 15

Anal valves

Question 16

What’s superior to the anal valves and what do they contain

Answer 16

Anal sinuses which contain glands that secrete mucus

Question 17

When do anal sinuses secrete mucus

Answer 17

When compressed by faeces to aid defecation

Question 18

What do the anal valves form

Answer 18

The pectinate line

Question 19

Embryological origin above and below the pectinate line

Answer 19

Above - hindgut

Below - ectoderm of the proctodeum

Question 20

Epithelial lining above and below the pectinate line

Answer 20

Above - columnar

Below - non keratinised stratified squamous which transitions to keratinised (I.e skin) at the inter-sphincteric groove

Question 21

How does the anal canal superior to the pectinate line differ from the anal canal inferior to the pectinate line

Answer 21

Blood supply
Innervation
Lymphatic drainage
Embryological origin

Question 22

Arterial supply above the pectinate line

Answer 22

Aorta -> IMA -> Superior rectal artery

Question 23

Arterial supply below the pectinate line

Answer 23

Aorta -> common iliac -> internal iliac -> internal pudendal -> inferior rectal artery

Question 24

What other artery contributes to supply of the anal canal

Answer 24

Middle rectal arteries anastomose with the superior and inferior rectal arteries

Question 25

Venous drainage above and below the pectinate line

Answer 25

Above - superior rectal vein which drains into the IMV | Below - inferior rectal vein which drains into the internal pudendal vein

Question 26

Innervation above and below the pectinate line

Answer 26

Above (visceral) - inferior hypogastric plexus | Below (somatic) - inferior anal nerves which are branches of the pudendal nerve

Question 27

Where is pain above the pectinate line referred to

Answer 27

S2-4 dermatomes

Question 28

What is the anal canal sensitive to above and below the pectinate line

Answer 28

Above - stretch | Below - pain, touch, temperature and pressure

Question 29

What does lymph drain into from above and below the pectinate line

Answer 29

Above - internal iliac lymph nodes | Below - superficial inguinal lymph nodes

Question 30

What are haemorrhoids

Answer 30

Vascular cushions found within the anal canal which help with the maintenance of faecal continence

Question 31

What are pathological haemorrhoids

Answer 31

Swollen or distended haemorrhoids

Question 32

Who are pathological haemorrhoids seen in

Answer 32

People who suffer from: Constipation Prolonged straining when defecating Raised intra-abdominal pressure (pregnancy, ascites)

Question 33

Consequences of pathological haemorrhoids

Answer 33

Bleeding and pain on defecation