Bladder And Urethra Flashcards
How much liquid can the bladder hold?
400-500mls
What ligament holds the neck of the bladder in place?
Puboprostatic ligament in men
Pubovesicular ligament in women
What ligament extends from the top of the bladder?
The median umbilical ligament
What are the three layers of muscle found in the detrusor muscle?
Longitudinal (outer)
Circular
Spiral (inner)
What factors contribute to internal urethral closure?
Muscular occulsion by rhabdosphincter Transmission of abdominal pressure to proximal urethra Mucosal surface tension Anatomical configuration at bladder neck Submucosal vascular plexus Elasticity and length of urethra
Do women have an internal urethral sphincter?
No anatomically, but they do have a physiogical mechanism
What’s the venous drainage for the bladder?
A rich venous plexus that drains the the internal iliac veins
Where does the lymphatic drainage for the bladder drain to?
Vesical, external iliac, internal iliac and common iliac lymph nodes
What receptors play a role in micturition?
Muscarinic (M3) and B3 receptors on the detrusor muscle
Alpha-1 receptor found on the internal urethral sphincter
Nicotinic content receptor on the external urethral sphincter
Which parts of the CNS are used during micturition?
Sacaral and thoracic nuclei
Pontine and micturition centres in the brain
Name the three efferent nerves and which nerve fibres they contain.
From the sacral region arises the pudendal nerve, which contains somatic nerve fibres
From the sacral region arises the pelvic nerve, which contains sympathetic nerve fibres
From the thoracic region arises the hypogastric nerve, which contains parasympathetic nerve fibres
What hormone does the pelvic nerve release, which receptor does it bind to and what does it stimulate?
It releases ACh, which binds to the M3 receptor and stimulates contraction of the detrusor muscle
What hormone does the hypogastric nerve release, which receptor does it bind to and what does it stimulate?
The hypogastric nerve releases noradrenaline, which binds to two receptors
- the B3 receptor stimulating the relaxation of the detrusor muscle
- the alpha-1 receptors, stimulating the contraction of the internal urethral sphincter
What happens to the hypogastric nerve on the way to the bladder (why does it release noradrenaline, not ACh)?
It synapses with a ganglion, ACh is released from the pre-ganglionic fibres to stimulate the post-ganglionic fibres, which continue on the the bladder and release the post-ganglionic hormone NA.
What hormone does the puedendal nerve release, which receptor does it bind to and what does it stimulate?
The puedendal nerve releases ACh which binds to the Nicotinic receptor, stimulating the external urethral sphincter
When are the somatic and sympathetic nerves active?
Somatic - when we want to hold out urine, so the hormone is firing all the time
Sympathetic - all the time we are not urinating
Which response (parasympathetic or sympathetic) is responsible for holiday in our urine?
The sympathetic
- fight or flight
- can’t pee if your running like hell
What is the name of the single afferent nerve from the bladder?
The afferent pelvic nerve
What does the afferent nerve do when the bladder is empty?
Sends slow impulses to Onuf’s nucleus in the sacral region
What happens to the signal for an empty bladder when it reaches the sacral region?
It travels up to the hypogastric nerve in the thoracic region
- stimulates the contraction of urethral sphincter and relaxation of detrusor muscle
It carries on up to the pons so the brain knows we have an empty bladder
- pons sends stimulating messages down to hypogastric
- pons sends inhibitory messages down to the pelvic nerve
- sometimes sends stimulators messages to the puedendal nerve
What happens to the afferent pelvic nerve when the bladder is full?
It senses the stretched bladder and sends faster impulses down to Onuf’s nucleus in the pelvic region.
What happens to the message for a full bladder when it reaches the spinal cord
The messages travel so fast up the spinal cord the bypass the hypogastric nerve and arrive at the micturition centre
The neurons in the centre are stimulated
- inhibits the hypogastric nerve and pudendal nerve (if we allow)
- stimulates the pelvic nerve
What is the gating theory?
The restriction of the transmission of the messages from the afferent pelvic nerve
- Protects the parasympathetic fibres from afferent input until a threshold is reached
How can the bladder keep contracting until it is empty?
Positive feedback mechanism
What type of brain matter is the micturition centre located in?
Intermediolateral grey
Which neurological conditions can cause abnormal bladder and sphincter function?
Spinal cord injury
MS
Neuropathic detrusor hyperreflexia
Parkinson’s disease
What is spinal shock and what does it cause?
Period of decreased excitability at and below a signal cord injury.
Causes absent somatic reflexes, flaccid muscle paralysis and a decrease in autonomic activity
- in relation to the bladder, it is acontractile and areflexic with functional sphincters
- leads to urine retention
What is the bulbocavernosus reflux, and what does its absense mean?
It’s the contraction of the anal sphincter most people get when their glans/clitoris is pulled on
- its presence indicates that the sacral micturition centre is intact
What’s autonomic dysreflexia?
Exaggerated sympathetic activity in response to stimulus below the level of a spinal cord injury
- decreased blood pressure and heart rate
- sweating above lesion
- vasoconstriction below
What is detrusor hyperreflexia?
Bladder overactivity in a patient with an underlying neurological condition (Parkinson’s or MS)
- High pressure can cause hydronephrosis
- M3 receptor blockers are best treatment
List the causes of bladder outflow obstruction.
Enlarged prostrate (male) Pelvic organ prolapse, pelvic masses (women) Neurological disease Bladder tumours Bladder stone Urethral strictures
What are the pathological consequences of bladder outflow obstruction?
Increased irritability
Hydronephrosis
Acute and chronic retention
What is chronic retention of urine?
Painless retention of over 300mls of urine
What two groups are chronic retention separated into?
HPCR - residual volume remains at a pressure higher than the intra-abdominal pressure after urination (associated with hydronephrosis)
LPCR
What is the pathophysiology of the upper urinary tract dilation in chronic retention?
Diuresis and bladder filling cause an increase in upper tract pressure
Dilation of ureters leads to loss of peristalsis and ureteric drainage becomes reliant on gravity
Associated with
- hypertension
- peripheral oedema
Why does diuresis occur?
Patients with prolonged diuresis are unresponsive to ADH
Sodium reabsorption has been impaired for too long
How is chronic diuresis managed?
Strict hourly urine output Daily weights U+Es BP (orthostatic hypotension) Most don't need volume replacement
