Control Of Micturition

Question 1

What are the layers of the bladder

Answer 1

Urothelium
Lamina propria
Detrusor muscle
Serosa

Question 2

Features of the urothelium

Answer 2

Tight junctions of prevent any movement of fluid or substances between the urine and the interstitium
Umbrella cells which protect the underlying epithelium covering them also act to stretch when the bladder fills
Underlying epithelial is transitional epithelium so as the bladder fills it changes shape from more rounded cells to a flatter shape
Detect chemical constituents of the urine

Question 3

Features of the lamina propria

Answer 3

Contains BV, nerves and lymphatics
Chemical constituents detected in the urine lamina propria conveys the signals to the detrusor muscle - contract or relax
Interstatial cells of cajal
These are through to act to transmit the chemical detection signals to the detrusor with no nerves

Question 4

Features of the detrusor muscle

Answer 4

Basket weave of smooth muscles cells
Innervated with sympathetic and parasympathetic fibres
Sympathetic relax - continence
Parasympathetic contract in voiding

Question 5

What are the receptors for the sympathetic input and the NT

Answer 5

B3 noradrenaline

Relaxation of the muscle

Question 6

What are the receptors for the parasympathetic input and the NT

Answer 6

M3
Ach
Contraction

Question 7

Feature of the serosa

Answer 7

Acts to maintain the integrity of the bladder when full

Question 8

Where do sensory input go to in the brain about the state of filing of the bladder

Answer 8

Pontine micturition centre

Question 9

Internal urethral sphincter - muscle

Answer 9

Smooth muscle

Circular fibres

Question 10

External urethral sphincter muscle

Answer 10

Skeletal muscles

Longitudinal

Question 11

Which nerve supplies the EUS

Answer 11

Pudendal nerve

Question 12

IUS nerve supply

Answer 12

Sympathetic alpha receptors of NA to contract it

Question 13

What is the storage reflex - higher centre involvement

Answer 13

Inc in pressure detected

Pontine micturition centre fibres descend and synapse with the skeletal muscle causing contraction

Question 14

What is the storage reflex- local

Answer 14

Increasing pressure stretched bladder wall
Local reflex from pelvic afferents to the pudendal nerve which contracts the EUS
Also sympathetic reflex causing relaxation of the detrusor

Question 15

What happens in voiding

Answer 15

Inactivation of sympathetic and somatic
Activation of parasympathetic
Results in relaxation of EUS
Contraction of detrusor

Question 16

When is urinary continence affected

Answer 16

UTI chemical stimuli increase the eed for micturition
Spinal cord transection different levels cause different problem - continence and voiding
Strokes
Pelvic floor injury - following childbirth damage to the anterior vaginal wall
Detrusor over activity- outflow obstructions -smooth muscle hypertrophy -bladder contraction too forceful to control
Atonic Bladder syndrome -bladder fills until pressure high, slow leak of urine

Question 17

How is overactive bladder managed pharmacologically

Answer 17

Anti muscarinic drugs - oxybutynin useful but show tolerance
Botulinum toxin injections into bladder prevent Ach release and stop contraction - ongoing and repeated process
Target sensory nerves prevent reflex generation resiniferatoxin
B3 agonists mirabegron
Type 5 PDE inhibitors - sildenafil
K+ channel activators

Question 18

What most commonly causes urinary outflow obstruction

Answer 18

Benign prostatic hyperplasia

Question 19

Treat BPH

Answer 19

Surgically - transurethral resection of the prostate
Medication-
Alpha adrenoceptor antagonists relax smooth muscle in prostate - tamsulosin
5 alpha reductase inhibitors finesteride reduce hypertrophy