Urinary bladder Flashcards
What are the two main roles of the bladder?
Temporary storage of urine-accomidate 300-400ml
Assists in expulsion of urine- musculature of the bladder contracts during micturition
What are the four main features of the bladder?
Apex- located superiorly pointing towrds pubic symphysis, it is connected to the umbillicus by the median umbilical ligament
Body- main part of the bladder, located between the apex and fundus
Fundus(base)- located posteriorly it is triangluar shaped with the tip of the triangle pointing backwards
Neck- formed by the convergence of the fundus and the two interolateral surfaces, it is continuous with the urethra
How does urine enter ad exit through the bladder?
What is the trigone?
Left and right ureters, exits through the urethra. these orifices are makred by the trigone, atriangluararea of the fundus.
Smooth walled, formed from integration of two mesonephric ducts
What is the major muscle of the bladder used to void urine
The detrusor, specialised smooth muscle thats fibres spread in every direction. Recieves innervation from both parasympathetic and sympathetic sources. Contracts to void urine
What are the two sphicnters involved in the urethra?
Male- circular sooth fibres under autonomic control. Prevents seminal regurgitation
Female- Functional sphincter (no muscle present)
External urethral sphincter- skeletal msucle udner voluntary control
Where is the vasculature of the bladder mainly derived from?
What is the arterial supply to the bladder in males and females?
internal iliac vessels
Superior vesical artery-both
vaginal arteries-female
Inferior vesical artery- male
How is venous drainage achieved?
What is different in men?
Vesical venous plexus which empties into the internal ilaic veins.
In males this is found in the retropubic space with the prostate venous plexus which also receives blood from the penis
How does the bladder drain its lymphs
Drains into external iliac nodes. Neck and fundus drain into the internal iliac, sacral and common iliac nodes.
What is the nerve supply of the bladder
Sympathetic- hypogastric nerve (T12-L2) causes relaxation of detrusor muscle, promting uine retention
Parasympathetic-pelvic nerve (S2-S4)- increased signals cause contraction of the detrusor stimualting micturition
Somatic- Puedendal nerve (S2-S4)- innervates external urethral sphincter providing voluntary control over micturition
What is the bladder stretch reflex?
Why is it important?
A primitive stretch reflex, micturition is stimulated in response to stretching of the bladder wall
During toilet training in infants the spinal reflex is overridden by the higher centres of the brain
Spinal injuries and neurodegenrative conditions
What is the reflex arc of the bladder?
Bladder fills with urine, bladder walls stretch. Sensory nerves detect stretch and transmits this information to the spinal cord
Interneurons within the spinal cord relay this information to the parasympathetic efferents (pelvic nerve)
Pelvic nerve acts to contract the detrusor muscle and stimulate micturition
What is involved in a spinal injury that causes a reflex bladder injury. (above T12)
The patient has no awareness of bladder filling. There is no descending control over the external urethral sphincter and it is constantly relaxed
This leads to a spinal reflex causing the bladder wall to stretch
What is involved in a spinal cord injury that causes a reflex bladder injury (below T12)
Spinal cord transection at this level will damage parasympathetic outflow to the bladder. The detrusor muscle will be paralysed meaning it wont be able to contract. This leads to overflow incontinence
What is acute retention?
A medical emergency, typically presenting in males due to BPH or a stone in the way. The bladder is filled to its limit.
