Repro Topic 4 - Bladder Flashcards
Describe the afferent and efferent pathways for control of bladder function
- Efferent
- Sympathetic - hypogastric nerve (T12-L2)
- Parasympathetic - pelvic nerve (S2, 3, 4)
- Afferent - pelvic, hypogastric and pudendal nerves from bladder wall
- A delta (normal) and C (pathological) fibres
How does urine retention lead to hydronephrosis?
- Bladder filling, increased upper tract pressure
- Ureters dilate, peristalsis lost, ureteric drainage dependent on gravity
- Increasing pressure = decreasing renal function
Describe the voiding phase of micturition
- Voluntary relaxation of external sphincter
- Pontine micturition relaxes internal first
- Parasympathetic action causes detrussor contraction, bladder empties
- Assissted by contraction of abdominal muscles - increases the pressure in the bladder
What is the role of higher centres in the brain in the micturition reflex?
- Keep micturition reflex inhibited except when micturition is desired
- Contraction of external sphincter
- When time to urinate high centres send signals to sacral micturition centre which stimulates the micturation reflex
- Coordinates: spino-bulbar-spinal reflex, detrussor contraction, urethral relaxation
Describe the structure of the male urethra
- 15-20cm long, carries urine and semen
- 4 parts - pre-prostatic, prostatic, membraneous, spongey
- Prostatic - prostatic and ejaculatory glands empty into
- Membraneous - surrounded by external urethra sphincter
- Spongey - through bulb and corpus spongeosum, ends at external urethral orifice, bulbourethral glands empty into
Describe the venous drainage of the ureters
Follows arteries
Describe the higher centres in the brain involved in micturition
- Pontine micturition (Barrington’s nucleus)
- Dorsolateral pons, collection of neuronal cell bodies
- Send axons via lateral columns to sacral micturition centre (intermediolateral nucleus and Onuf’s nucleus)
Describe the structure of the walls of the bladder
- Rugae (folds) allow for expansion - volume can increase without pressure changing
- Mucosa - transitional epithelium, lamina propria
- Submucosa
- Detrussor muscle
- Adventitia
Describe the process of the micturition reflex
- Bladder fills until it reaches critical pressure, stretch receptors activated, signals from bladder to spinal cord via sensory afferents (pelvic nerves)
- Activates autonomic spinal reflex (parasympathetic + sympathetic activity), can be overriden by higher centres in the brain
- Causes contraction of the detrussor muscle, at partial filling contractions relax spontaneously - allows more filling
- With continued filled reflexes become more frequent
- If signals from brain are stronger than voluntary contraction of the external sphincter micturition occurs
- If not, bladder fills further and further and reflex becomes stronger
What is the effect of the parasympathetic efferent pathway on the bladder?
Contraction of detrussor muscle - micturition
Describe the innervation of the ureters
Renal, testicular/ovarian and hypogastric plexus
Sensory fibres –> T11-L2
Describe the arterial supply of the ureters
- Renal and testicular/ovarian arteries from the abdominal aorta
- Superior and inferior vesical arteries from the internal iliac artery
List the stages of micturition
- Filling
- Micturition reflex
- Voiding
List the functions of the bladder
- Store urine at low pressure (no sensation)
- Empty fully at socially convenient time
- Reciprocal contraction/relaxation
Describe the arterial supply of the male urethra
- Prostatic - inferior vesicle from internal iliac artery
- Membraneous/spongey - bulbourethral from internal pudendal artery
Describe the lymphatic drainage of the bladder
Vesical, external iliac, internal iliac and common iliac nodes
What are the causes of bladder outflow obstruction?
- Men - prostatic hyperplasia
- Women - pelvic organ prolapse (pregnancy), pelvic masses
- Both -
- Neurological disease - failure of relaxation of external sphincter
- Bladder tumours, stones, urethral strictures (e.g. scar tissue)
Describe the musculature of the bladder
- Lined by smooth muscle - detrussor
- Spiral, longitudinal and circular layers
- Bundles around neck = internal urethral sphincter (involuntary)
- More distal = external urethra sphincter (after prostate in males) - voluntary, skeletal muscle, in ureogenital diaphragm
- Internal controlled by ANS, external by voluntary control
Describe the innervation of the female urethra
Vesical plexus and pudendal nerve, visceral afferent nerve in pelvic splanchnic nerves
What is the function of the urethra?
Drain urine from bladder to external opening (in perineum)
Describe the lining of the male urethra
- Pre-prostatic, prostatic - transitional
- Membraneous, proximal spongey - pseudostratified columnar
- Distal spongey - stratified squamous
Where is Onuf’s nucleus found? What is its function?
S2, 3, 4 - somatic, anterior horn
Maintains continence
What is the function of the afferent pathway from the bladder?
Signals to brain when bladder is full
Describe the gross anatomy of the bladder
- Hollow muscular organ - body, neck and apex
- Neck connects to urethra
- Normal capacity - 400-500ml (can hold more - backflow risk)
- Held at neck by puboprostatic (male) or pubovescical (female) ligaments, attach to pubic symphysis
- Base is trigone, has ureteric openings, less mobile and more sensitive to pain
Describe the structure of the female urethra
- 4 cm long (increased risk of UTI/incontinence e.g. due to pregnancy)
- Opening external urethral orifice = vestibule
- 2 mucous glands at distal end - Skene’s glands
What is the effect of the sympathetic efferent pathway on the bladder?
Causes relaxation of detrussor muscle - urine retention
Describe the path of the ureters
- Begin abdominally as continuation of the renal pelvis, end in pelvic cavity where they drain into the bladder
- Descend through abdomen, along anterior surface of psoas major, retroperitoneal
- At sacroiliac joint cross pelvic brim into pelvic cavity
- Run down lateral pelvic wall
- Peirce lateral wall of bladder
Describe the innervation of the male urethra
Prostatic plexus - parasympathetic, sympathetic + viseral afferent fibres
What are the consequences of chronic urine retention?
- Upflow from bladder can cause irreversible kidney damage - hydronephritis
- Usually only 1 kidney affected
- Irreversible tubular atrophy if obstruction not recognised + corrected - blunting of papillae, interstitial fibrosis
- Increased susceptibility to UTIs/urolithiasis (struvite) - stagnant urine
Describe the arterial supply of the bladder
Superior and inferior vesical branches of the internal iliac artery
+ uterine/vaginal arteries in females
How can the intactness of the sacral micturition reflex be tested?
Check the bulbocavernous reflex
Describe the filling phase of micturition
Increasing volume of urine, walls stretch to accommodate, little increase in pressure (= compliance)
Describe the lining of the female urethra
Proximal 2/3 = transitional epithelium
Distal 1/3 = Stratified squamous epithelium
Describe the blood supply of the female urethra
Arteries = Internal pudendal, vaginal and inferior vesical branches of vaginal arteries
Veins follow arteries
What is the function of the ureters?
Transport urine from the kidneys to the bladder
How does spinal shock cause bladder dysfunction?
- Decreases excitability below injury
- No somatic reflexes and flaccid muscle paralysis
- Acontractile, areflexic bladder, sphincter functioning
- Urine retention
- Lasts days-months
How is bladder dysfunction in spinal shock treated?
Catheter - suprapubic or clean intermittent self catheterisation
What controls the micturition reflex?
Autonomic reflex under partial voluntary control
How is the entry of the uterers of the bladder functionally beneficial?
Pierce lateral wall of bladder at oblique angle - one-way valve to prevent backflow
List causes of bladder dysfunction
- Spinal shock
- Multiple sclerosis
- Neuropathic detrussor hyperreflexia e.g. in spina bifida
- Parkinson’s
What is the function of the sacral micturition centre?
Parasympathetic, relaxation of sphincter, voiding
Describe the venous drainage of the bladder
Vesical venous plexus, drains to the internal iliac vein
Describe the structure of the ureters
- 2 bilateral thick tubes
- 25cm long
- Stratified transitional epithelium
- Walls lined with smooth muscle, contracts to produce peristaltic waves, push urine to bladder
Describe the venous drainage of the male urethra
Inferior vesicle vein, middle rectal vein, internal pudendal vein
