254. Anatomy of the bladder

Question 1

What is the normal capacity for urine storage in the bladder?

Answer 1

400-500ml

Question 2

What ligaments firmly hold the bladder by its neck?

Answer 2

Puboprostatic or pubovesical ligaments

Question 3

What is the median umbilical ligament?

Answer 3

Remnants of an obliterated urachus which was for draining the bladder to the umbilical cord before birth

Question 4

What epithelium lines the bladder and why?

Answer 4

Transitional epithelium - can expand upon distension

Question 5

What tissues are present in the bladder submucosa?

Answer 5

Connective and elastic

Question 6

What are the 3 smooth muscle layers of the bladder?

Answer 6

Longitudinal, circular and spiral

Question 7

Men have an internal and external urethral sphincter whereas in women they only have one urethral sphincter.

Name and describe the two muscles that make up the external urethral sphincter.

Answer 7

Intramural “rhabdosphincter”

• striated muscle
• small ‘slow twitch’ fibres, mitochondria/lipid droplets, rich in myosin ATP-ase

Peri-urethral striated muscle (pelvic floor)
- mixture of fast and slow twitch larger fibres

Question 8

What are the factors which contribute to urethral closure?

Answer 8

Muscular occlusion by rhabdosphincter
Transmission of abdominal pressure to proximal urethra
Mucosal surface tension
Anatomical configuration at bladder neck
Submucosal vascular plexus
Inherent elasticity
Urethral length

Question 9

What is the venous drainage of the bladder?

Answer 9

Rich plexus of veins which drain into the internal iliac veins

Question 10

What is the lymphatic drainage of the bladder?

Answer 10

Vesical, internal iliac, external iliac, and common iliac lymph nodes

Question 11

Describe the pathway of afferent neurones in the bladder and their role (simple nerve endings)

Answer 11

Simple nerve endings in lamina propria/detrusor
Travel with parasympathetic neurones back to the cord and then to the pontine and micturition centres

Responsible for sensing stretch, bladder filling, and pain
Have ‘polymodal receptors’ (more than one stimulus) which can be sensitised or desensitised

Question 12

What is the afferent sympathetic innervation of the bladder?

Answer 12

Hypogastric nerve - responsible for pain, touch, temperature

Question 13

What is the parasympathetic motor innervation of the bladder? Describe its pathway

Answer 13

Sacral pre-ganglionic parasympathetic nuclei in intermediolateral columns of S2, 3, 4

Run with PELVIC nerves via pelvic plexus to synapse with ganglion cells close to and within bladder wall
Post ganglionic axons provide cholinergic excitatory input to detrusor smooth muscle

Question 14

What is the sympathetic motor innervation of the bladder? Describe its pathway

Answer 14

Pre-ganglionic sympathetic nerve fibres arise from T10-12 and L1-2

Travel in HYPOGASTRIC nerves and innervate trigone/blood vessels of bladder and smooth muscle of prostate in men

In females there is a sparse innervation of bladder neck and urethra

In both sexes: some post-sympathetic nerves terminate in parasympathetic ganglion and exert ‘inhibitory’ effect (Gating theory)

Question 15

Describe the dual innervation of the urethral sphincter

Answer 15

Pre-ganglionic somatic nerve fibres innervate striated muscle
PLUS
Parasympathetic nerves from S2-4 from ONUF’s nucleus which lies in medial aspect of anterior horn of spinal cord

These somatomotor nerves run via the perineal branch of the PUDENDAL nerve

Question 16

Where is the pontine micturition centre located and what is its function?

Answer 16

In the dorsolateral region of the pons
PMC sends axons, via lateral columns, to sacral micturition centre (which is both the intermediolateral nucleus and Onuf’s nucleus)

Critical level of integration of storage and voiding