Fecal continence

Question 1

Rectum

• function
• location

Answer 1

The storage area for faeces

Located in the pelvic cavity

Question 2

What do visceral afferent (sensory) nerves do in the rectum?

Answer 2

Sense fullness of rectum

Question 3

Pelvic cavity - where is it located?

Answer 3

Lies within pelvis
- between pelvic inlet and pelvic floor
Continuous with abdo cavity

Question 4

Pelvic floor

Answer 4

Openings allow distal parts of the alimentary, renal and reproductive tracts to pass from the pelvic cavity into the perineum
The bridge between the pelvis and perineum
Levator ani muscle

Question 5

Levator ani muscle (3 muscles)

Answer 5

iliococygeous
pubococcygeous
puborectalis - most important

Question 6

Puborectalis - levator ani muscle

Answer 6

Acts as a sling around the rectum

Voluntary contraction helps maintain faecal continence when rectal ampulla is full of faeces

Question 7

What type of muscle is the levator ani?

Answer 7

Skeletal - under voluntary control
Tonically contracted most of the time
Must relax to allow defecation

Question 8

Levator ani muscle - nerve supply

Answer 8

Nerve to levator ani

- branch of the sacral plexus and pudendal (S2,3,4)

Question 9

Nerve supply to pelvis (3)

Answer 9

Sympathetic
Parasympathetic
Visceral afferent (sensory)

Question 10

Nerve supply to perineum (2)

Answer 10

Somatic motor - pudendal nerve, nerve to levator ani

Somatic sensory

Question 11

At which SC level does the sigmoid colon become the rectum

Answer 11

Anterior to S3

Question 12

Sympathetic nerve supply to rectum/anal canal

Answer 12

Fibres from T12-L2 
Travel from IM ganglia and synapse here
Post synaptic neurone travels via plexus 
Contraction of internal anal sphincter
Slows down peristalsis in GIT

Question 13

Parasympathetic nerve supply to rectum/anal canal

Answer 13

Fibres from S2-S4 
Travels via pelvic splanchnic nerves 
Synapses close to organ 
Inhibits contraction of internal anal sphincter 
Increased peristalsis

Question 14

Visceral afferents nerve supply to rectum/anal canal

Answer 14

Travel to S2-S4 (run with parasympathetics)

They signal that it’s time to tell brain to defecate

Question 15

Somatic motor nerve supply to rectum/anal canal

Answer 15

Fibres from S2-S4 (pudendal nerve)

Contracts external anal sphincter and puborectalis

Question 16

What causes damage to the pudendal nerve or sphincter?

Answer 16

Labour

Question 17

Anal canal - pectinate line

Answer 17

Divides the anal canal into upper and lower
Upper - superior 2/3rds of anal canal
Lower - inferior 1/3 of anal canal

Question 18

Arterial and venous drainage above and below pectinate line

Answer 18

Above: portal venous system
Below: systemic venous system

Question 19

Lymphatics of pelvis

Answer 19

Internal iliac nodes - drain inferior pelvic structures
External iliac nodes - drain lower limbs
The lymph from these places drains to common iliac nodes

Question 20

Defecation reflex

Answer 20

When rectum is full (distended) with faecal matter

• activation of afferents towards SC which activates parasympathetic efferents resulting in relaxation of internal anal sphincter
• activation of afferents towards brain give us urge to defecate via the pudendal nerve
• relaxation of external anal sphincter results in defecation
• contraction of internal anal sphincter delays defecation until appropriate