bladder, urethra and prostate gland Flashcards
what are the 2 main roles of the bladder?
- temporary storage of urine
- assists in the expulsion of urine
describe the bladder apex
located superiorly, pointing towards the pubic symphysis
what connects the bladder apex to the umbilicus?
median umbilical ligament = remnant of the urachus
what is the bladder fundus?
= the base
- located posteriorly
- it is triangular shaped, with the tip of the triangle pointing backwards
describe the bladder neck
formed by the convergence of the fundus and the two inferolateral surfaces. It is continuous with the urethra.
what are the orifices of the bladder marked by?
the trigone = a triangular area located within the fundus
- in contrast to the rest of the internal bladder, it has smooth walls — this is explained by the different embryological origin: the trigone is developed by the integration of two mesonephric ducts at the base of the bladder
what is the name of the specialised smooth muscle in the bladder wall?
detrusor muscle
the fibres of the detrusor muscle often become ___________ (presenting as _________ _________) in order to compensate for increased workload of the bladder emptying. This is very common in conditions that obstruct the urine outflow such as _______ _________ ________.
- hypertrophic
- prominent trabeculae
- benign prostatic hyperplasia
describe the internal urethral sphincter in the male
consists of circular smooth fibres, which are under autonomic control. It is thought to prevent seminal regurgitation during ejaculation
describe the itnernal urethra sphincter in females
thought to be a functional sphincter (i.e. no sphincteric muscle present). It is formed by the anatomy of the bladder neck and proximal urethra.
describe the external urethral sphincter
has the same structure in both sexes. It is skeletal muscle, and under voluntary control. However, in males the external sphincteric mechanism is more complex, as it correlates with fibres of the rectourethralis muscle and the levator ani muscle.
arterial supply of the bladder
Arterial supply is via the superior vesical branch of the internal iliac artery. In males, this is supplemented by the inferior vesical artery, and in females by the vaginal arteries. In both sexes, the obturator and inferior gluteal arteries may also contribute small branches.
venous drainage of the bladder
achieved by the vesical venous plexus, which empties into the internal iliac veins. The vesical plexus in males is in continuity at the retropubic space with the prostate venous plexus (plexus of Santorini), which also receives blood from the dorsal vein of the penis
lymphatic drainage of the bladder
- The superolateral aspect of the bladder drains into the external iliac lymph nodes.
- The neck and fundus drain into the internal iliac, sacral and common iliac nodes.
sympathetic supply of the bladder. effects?
- hypogastric nerve (T12 – L2) aka lumbar splanchnic
- It causes relaxation of the detrusor muscle, promoting urine retention.
parasympathetic supply of the bladder. effect?
- pelvic splanchnic nerve (S2-S4)
- increased signals from this nerve causes contraction of the detrusor muscle, stimulating micturition.
somatic supply of the bladder. effect?
- pudendal nerve (S2-4)
- it innervates the external urethral sphincter, providing voluntary control over micturition.
In addition to the efferent nerves supplying the bladder, there are _______________ nerves that report to the brain. They are found in the bladder _______ and signal the need to ________ when the bladder becomes ____.
In addition to the efferent nerves supplying the bladder, there are sensory (afferent) nerves that report to the brain. They are found in the bladder wall and signal the need to urinate when the bladder becomes full.
what is the bladder stretch reflex?
The bladder stretch reflex is a primitive spinal reflex, in which micturition is stimulated in response to stretch of the bladder wall
During toilet training in infants, this spinal reflex is overridden by the higher centres of the brain, to give voluntary control over micturition.
describe the reflex arc of the bladder stretch reflex
- Bladder fills with urine, and the bladder walls stretch. Sensory nerves detect stretch and transmit this information to the spinal cord
- Interneurons within the spinal cord relay the signal to the parasympathetic efferents (the pelvic nerve)
- The pelvic nerve acts to contract the detrusor muscle, and stimulate micturition
although the bladder stretch is non-functional post childhood, the bladder stretch reflex needs to be considered in what scenarios?
- spinal injuries — where the descending inhibition cannot reach the bladder
- neurodegenerative diseases — where the brain is unable to generate inhibition
what are the effects on the bladder of spinal cord transecting above T12?
In this case, the afferent signals from the bladder wall are unable to reach the brain, and the patient will have no awareness of bladder filling. There is also no descending control over the external urethral sphincter, and it is constantly relaxed.
There is a functioning spinal reflex, where the parasympathetic system initiates detrusor contraction in response to bladder wall stretch. Thus, the bladder automatically empties as it fills – known as the reflex bladder.
what are the effects on the bladder of spinal cord transecting below T12?
A spinal cord transection at this level will have damaged the parasympathetic outflow to the bladder. The detrusor muscle will be paralysed, unable to contract. The spinal reflex does not function.
In this scenario, the bladder will fill uncontrollably, becoming abnormally distended until overflow incontinence occurs.
