Gross Anatomy
? External features :Bladder is a hollow
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muscular viscous organ .?pyramidal in shape having apex base & 3
surfaces.
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?Neck- lowest part, continues as urethra.
? Interior of bladder : mucosa shows irregular
folds, & smooth trigone.
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Urinary Bladder
? Urinary bladder is a sac like structure in the
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pelvic cavity.
? It is a distensible organ made up of smooth
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muscle called detrusor muscle , depicting theLatin word "pushes down".
? Smooth muscles are arranged in three
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bundles: spiral, longitudnal, and circular.
? The bladder epithelium has superficial layer of
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flat cells and deep layer of cuboidal cells.Urethral Sphincters
? There are 2 sphincters
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?Internal sphincter :located at the neck of thebladder ,made up of bundle of smooth muscle
(sphincter vesicae) ,and innervated by
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sympathetic (hypogastric) and
parasympathetic(pelvic) nerves. Therefore, it is
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under autonomic control.?External sphincter : present around urethra in its
proximal part ,made up of skeletal
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muscle(sphincter urethrae) ,innervated by
somatic (pudendal) nerves . Therefore under
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voluntary control.? Male urethra -20cm,3 parts ?
? Female urethra -4cm ,traverses external sphincter,
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lies in front of vagina.INNERVATION OF URINARY BLADDER
Parasympathetic(S2,3,4) Sympathetic T11-L2
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via pelvic nerves via hypogastric nervesSomatic fibres(S2,3,4)
? Via pudendal nerves
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? Innervates external sphincterTransport of urine from kidney
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Urine from collecting ducts flows into renalcalyces
Stretches calyces & es pacemaker activity
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Initiates peristaltic contraction in renal pelvis &
along the length of ureter
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Urine enters bladder? In adults ureter is 25-35cm long.
? Peristaltic activity in ureter are enhanced by
parasympathetic stimulation and inhibited by
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sympathetic stimulation.
? There is no significant change in composition of
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urine as it flows from renal calyces and ureter tothe bladder.
? Trigone of bladder
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? Vesicouretric reflux ?? Uretrorenal reflex (explain)
Micturition reflex
? Micturition is the process by which urinary
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bladder empties when it becomes filled.
? It is a reflex phenomenon, integrated in spinal
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cord.? This spinal reflex is influenced by activities of the
higher center.
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? Urine enters the bladder without producing much
increase in intravesical pressure untill well filled,
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because smooth muscle exhibit property ofplasticity
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Mechanism Of Micturition
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Filling of the bladder stimulates its stretchreceptors
Impulses travel in afferent(pelvic) nerve
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Reaches S2,3,4 spinal segment (center)
Parasympathetic fibers form efferent limb which
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travel in pelvic nervesParasympathetic stimulation causes contraction of
detrusor and relaxation of internal sphincter
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Urine passes into the urethraAlso external sphincter relaxes due to cortical
influences
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Urine finally comes out of urethra and is completely
emptied by effect of gravity in females
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And by contraction of bulbocavernous muscle inmales
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? Contraction of abdominal muscle and descent of
diaphragm es intra-abdominal pressure which
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helps in expulsion if urine.? Pelvic , perineal, and levator ani muscle relaxes
which causes downward pull of detrusor muscle
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and aids in initiation of contraction.
? Voluntary control of micturition is influenced by
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cortical activities and by learning to contract theexternal sphincter.
Control Of Micturition
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? Micturition reflex is controlled by centers in thebrainstem.
? Facilitatory area is present pons and inhibitory
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area is in midbrain.
? What is the effect of neurexis above 1. pons
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2.midbrain on micturition ?? Posterior hypothalamus also contain facilitatory
area for micturition.
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? Cortex has voluntary inhibitory control on
micturition.
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? Control of urination starts to develop at about2yrs
Bladder Dysfunctions
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? 3 major types of bladder dysfunctions are due to
neural lesions:
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1. Interruption of the afferent nerve.2. Interruption of both afferent & efferent nerves.
3. Interruption of facilitatory & inhibitory pathways
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descending from brain.
? In all 3 types the bladder contracts , but
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contractions are not sufficient so residual urineis left .
Deafferentation
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When sacral dorsal roots are cut inexperimental animals or interrupted by
disease of dorsal root , such as tabes dorsalis .
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? All reflex contraction of bladder are abolished.
? Bladder is distended, thin walled,and
hypotonic.
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? Some contractions occurs because of intrinsic
response of smooth muscle to stretch.
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? Overflow incontinence occurs.Denervation
When both afferent and efferent fibers are
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destroyed as in tumor of cauda equina or filumterminale.
? Bladder is flaccid and distended for a while.
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? Gradually the muscle of `decentralised bladder'become active ,with many contraction waves that
expel dribbles of urine.
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? Bladder is shrunken and its wall is hypertrophied .
? This hyperactive bladder is due to denervation
hypersensitivity.
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.
Spinal cord transection
? During spinal shock bladder is flaccid and
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unresponsive , there is overflow incontinence .
? In recovery phase , voiding reflex returns but
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there is no voluntary control and no inhibitionor facilitation from higher center.
? How Mass reflex helps paraplegic patients ?
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? Sometimes voiding reflex is hyperactiveleading to spastic neurogenic bladder
? Reflex hyperactivity is worsen by infection .
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? Nocturnal enuresis/Bed wetting : Involuntarymicturition during sleep, normal phenomenon
in children below 3yrs ,due to incomplete
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myelination of motor nerve fiber of bladder.
? It may be primary or secondary type .
? If present beyond 5yrs need proper evaluation
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and treatment.
Urinary incontinence : is any
involuntary leakage of urine
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