Micturition

What forms the male genitalia

Mesonephric duct → Wolffian duct

What forms the female genitalia

Paramesonephric duct → Mullerian duct

How do gonads differentiate into the wolffian duct

Y chromosome → SRY gene → TDF → Testis formation → Testosterone + AMH

How do gonads differentiate into the mullerian duct

No Y chromosome, SRY or TDF → Ovary form → Estrogen

How does the uterus form

Mullerian duct → Fallopian tubes → Both Lt and Rt side join together

What does urine storage depend on

Lumbosacral reflex

What does micturition depend on

Spino-bubo-spinal reflex from the PMC

What happens in the resting/filling stage

Voluntary contraction of external sphincter, sympathetic contraction of internal and detrusor distension

What happens during the voiding stage

Detrusor muscle contract, urinary sphincter relax

What controls the internal and external sphincter and detrusor

Internal and detrusor controlled by the ANS, external sphincter controlled by somatic

When are the first urge to urinate felt, when does the urge become uncomfortable

First urge is felt when there is 100-150 ml of urine; becomes uncomfortable at 350-400 ml

What characterizes micturition

Relaxation of striated (somatic) sphincter, relaxation of smooth muscle sphincter (sympathetic) and detrusor contraction (PNS)

Pontine micturition center function

Activate by afferent signal from bladder as it fills → PROMOTE voiding

How does CNS regulate micturition

Cortical signals are triggered when bladder is filled → Inhibition of voiding reflex until time and place is right

PAG function

Detect bladder distension and relay of afferent to higher brain center → Activate PMC to INHIBIT micturition

How do efferent nerves mediate detrusor

S2-S4 act on detrusor by muscarinic receptor

PNS ACh action

Pelvic nerve → ACh stimulate M3 (muscarinic receptor) contraction in detrusor

SNS NA action (detrusor)

Hypogastric nerve → NA → Act on beta 3 in detrusor to inhibit contraction (relaxation)

SNS NA action (internal sphincter)

Hypogastric nerve → NA → act on alpha 1 in internal sphincter to cause contraction

Somatic ACh function

Pudendal nerve → ACh → Act on nicotinic/cholinergic external sphincter to cause contraction

What causes incontinence

Impaired function, cognition, presence of comorbid condition that affect neural control

Effect of beta adrenergic drug

Detrusor muscle relax → No voiding

Effect of anti beta drug

Blocks beta → Detrusor contract → Voiding

Effect of alpha adrenergic drug

Internal sphincter contract → No voiding

Effect of alpha blocker drug

Internal sphincter relax → Voiding

Effect of cholinergic drug

Stimulate M3 → Detrusor contract → More voiding

Effect of anti-cholinergic drug

Inhibit M3 → Detrusor relax → No voiding

What are hospital acquired causes of incontinence

Long use of catheter (urethral damage), anesthesia, decreased mobility

What is acute urinary retention

Sudden inability to urinate with lower abdominal pain/distension; common in elderly men with prostatic hyperplasia → Catheter needed

How do you treat acute urinary retention

Give alpha adrenergic blocker → Internal sphincter relax → Increase urinary flow