Urination/Micturition

Question 1

What are the general layers of excretory passageways?

Answer 1

• Mucosa
• Submucosa
• Muscularis externa
• Adventitia or serosa

Question 2

What makes up the mucosal layer?

Answer 2

Sheet of epithelium - transitional
Laminal propria (CT)

Question 3

What types of muscle fibres are found in the muscularis externa?

Answer 3

Smooth muscle

Question 4

Outflow of urine is controlled by what 3 structures?

Answer 4

1) Contraction of the detrusor muscle – smooth muscle
2) Internal urethral sphincter – smooth muscle
3) External urethral sphincter – striated muscle

Question 5

How does each nervous system affect the bladder?

Answer 5

• Parasympathetic - contacts detrusor muscles
• Sympathetic - relaxation of detrusor muscle (to accommodate filling)
- contraction of internal sphincter
• Somatic - the external sphincter is skeletal muscle and can prevent bladder emptying

Question 6

What happens when filling is sufficient to stretch the smooth muscle?

Answer 6

There is a myogenic reflex

Question 7

Which two reflexes are caused by the myogenic reflex?

Answer 7

1) Activation of the parasympathetic motor nerves to the bladder (contraction of detrusor, passive pressure induced relaxation of the internal sphincter)
2) Inhibition of the somatic motor drive to the external sphincter.