Week 4 RNU Lectures Flashcards
What holds the bladder firmly at the bladder neck?
The puboprostatic or pubovesicle ligaments
What is the normal capacity of the bladder?
400-500ml
What type of epithelium is in the bladder?
transitional
What are the layers of the detrusor muscle?
Three smooth muscle layers (longitudinal, circular and spiral)
What are the layers of the bladder wall?
out in
Adventitia
Detrusor muscle
submucosa
mucosa - lamina propria + transitional epithelium
What is the venous drainage of the bladder?
The bladder is surrounded by a plexus of veins that ultimately drains into the internal iliac veins
What is the parasympathetic innervation of the bladder?
P=pee
- derived from the pelvic splanchnic nerves (S2-4)
- Motor to detrusor and inhibitory to internal sphincter
- When fibres are stretched the bladder contracts, the internal sphincter relaxes and urine passes
What is the sympathetic innervation to the bladder?
S=storage
- derived from T11-L2
- transmits sensations of pain, touch and temperature
- relaxes detrusor and contracts internal sphincter
- bladder fills up
What can cause injury to the bladder?
- Blunt lower abdominal trauma when bladder fully distended
- RTA and seat belt injury
- TURBT
- Intravesical pressure acutely elevated and bladder perforates at weakest point- DOME
What are the 2 main types of receptor in the bladder?
Cholinergic (muscarinic) and adrenergic
What are the muscarinic subtypes in the bladder and where are they?
M1-M3 in the bladder smooth muscle
M2 is 80% of the receptors but functionally M3 is most important
What do M3 receptors do?
Mediate bladder contraction
What are the adrenergic subtypes of receptor?
B1 and B2
What is the bladder base made up of?
Trigone and bladder neck
What is the structure of the bladder base?
2 distinct layers of smooth muscle:
- superior thin layer of longitudinal alpha-adrenergic smooth muscle contiguous with ureters
- deep layer of smooth muscle merges with detrusor
What is the pre-prostatic sphincter?
A circumferential collar of alpha-adrenergic smooth muscle surrounding bladder neck.
What is the predominant receptor subtype in the pre-prostatic sphincter?
Alpha 1A
What is the structure of the rhabdosphincter?
Small fibres, high numbers of mitochondria, packed with lipid droplets
What is the function of the rhabdosphincter?
Likely to be a major component in maintaining continence:
- Somatic innervation – S2/3 Onuf’s nucleus via pelvic nerves
- Cholinergic nicotinic receptors
What is the structure of the urethral sphincter?
Circular striated muscle horseshoe (rhabdosphincter) around inner longitudinal smooth muscle (internal urethral sphincter)
How is continence maintained?
- Alpha-blockade (sympathetic smooth muscle) reduce urethral sphincter pressure by only approx 30%
- Therefore continence likely to result from a combination of intrinsic striated muscle tone and sympathetic induced smooth muscle tone.
- Parasympathetic system has NO role in maintaining EUS tone
- Parasympathetic stimulation acts to inhibit sympathetic induced tone, and to cause relaxation of urethral smooth muscle, probably by release of NO, an inhibitory neurotransmitter
How is pain in the bladder transmitted?
Travels in the pelvic nerve to the dorsal horn of S2/3/4