Dr Kiran Kumar C
• Once urine has been formed by the kidneys,
• Smooth–muscle walled ureters to the urinary bladder.
• Urine does not flow through the ureters by gravitational pull alone.
• Peristaltic (forward-pushing) contractions of the smooth muscle
within the ureteral wall propel the urine forward from the kidneys to
• The ureters penetrate the wall of the bladder obliquely, before they
open into the bladder cavity.
• Prevents backflow of urine from the bladder to the kidneys when
pressure builds up in the bladder.
• As the bladder fills, the ureteral ends within its wall are compressed
• Urine can still enter, however, because ureteral contractions generate
enough pressure to overcome the resistance and push urine through
the occluded ends.
• Parasympathetic :
- Sacral detrusor nucleus
- Intermediolateral grey horn of spinal
- Pelvic splanchnic nerve
- Excitatory to detrusor muscle
- Inhibitory to sphincter vesicae
• Sympathetic :
- Intermediolateral grey horn T10- L2
segments of spinal cord
- Bladder, bladder neck and urethra
- Inhibitory to detrusor
- Excitatory to sphincter vesicae
• Somatic motor supply
- Sacral pudental nucleus
- Nucleus of ONUF
- Supply to external sphincter
- BLADDER WALL: T10-T12 through pelvic splanchnic nerve &
- URETHRA: pudental nerve
- Stretch receptor in the detrusor
- Imminent voiding : periurethral striated muscle
- Pontine and Suprapontine micturition centre
- Pain fibres: anterolateral column of spinal cord
- Is a process by which urinary bladder empties when it
• It involves two steps
1. Filling of bladder until the tension in the bladder increases
above the threshold level
2. Micturition reflex which empties the bladder
• FILLING OF URINARY BLADDER
• Transport of urine into urinary bladder through ureters
• As urine collects in the renal pelvis,
• The pressure in the pelvis increases and initiates a peristaltic
contraction along the ureter
• To force urine towards the bladder.
• Capacity of the bladder
• Physiological capacity of the bladder varies with age,
• 20–50 mL at birth,
• 200 mL at 1 year,
• 600 mL in young adult males.
• This refers to the process of studying the relationship between the
intravesical volume and pressure,
• The cystometrogram refers to a graphical record of this relationship
• Normal cystometrogram have 3 phases
1. Phase 1
2. Phase 2
EMPTYING OF BLADDER
• Normal voiding is a spinal reflex
• Modulated by CNS( brain and spinal cord)
• Coordinates the function of bladder and urethra
• Urethra and bladder is controlled by
2. Brain stem
3. Spinal cord
Emptying of bladder
1. The sacral micturition centre
- Spinal centre for micturition
- Sacral pudental nucleus: relaxation of external sphincter
- Sacral detrusor nucleus : contraction of detrusor muscle
2. Pontine micturition center
- Aka BARRINGTON CENTRE
- Reticulospinal tract
- Exert control over sacral micturition centre
3. Cerebral cortex
- Detrusor area is located in the medial frontal lobe
- Excite detrusor nucleus
4. Basal Ganglia:
- Inhibits sacral detrusor nucleus
REFLEX CONTROL VOLUNTARY CONTROL
Bladder fills Cerebral cortex
Parasympathetic Motor neuron to external
Detrusor contraction External urethral sphincter
Opening of internal sphincter
Urination No urination
• Atonic neurogenic urinary bladder
- Destruction of sensory nerve fibres from bladder to spinal cord
- Absence of awareness of bladder filling and desire to urinate
- Over distention of bladder
- Overflow incontinence
- Degeneration and traumatic injury of the spinal cord
- Aka RETENTION AND OVERFLOW INCONTINENCE, PARALYTIC
• AUTOMATIC URINARY BLADDER
- Complete destruction of spinal cord above sacral segments
- Complete loss of micturition reflex, bladder sensation
- Also called as reflex neurogenic bladder
• AUTONOMUS URINARY BLADDER
- Lesion in the sacral portion of the spinal cord
- Interruption of the reflex arc
- Loss of normal reflex
- Inability to initiate urination normally
- Stress incontinence
Notas do Editor
Gross anatomy External features: The urinary bladder, a hollow muscular viscus, is a temporary reservoir for urine. The main body of empty bladder is pyramidal having an apex and a base. The lowest part of the bladder is called neck, which continues as urethra. Interior of the bladder. In an empty bladder, the greater part of the mucosa shows irregular folds The interior of the base (posterior surface) of the bladder presents a triangular area, the trigone where the mucosa is smooth due to its firm attachment. Internal urethral orifice is located at the apex (inferior angle) of the trigone. The ureters open into the bladder at superior angles of the trigone (Fig. 6.7-1). The ureters pierce the bladder wall obliquely, and this provides a valve-like action, which prevents a reverse flow of urine towards the kidneys as the bladder fills.
The wall of the urinary bladder consists of three layers: an outer serous layer, a thick coat of smooth muscle, and the inner mucous membrane. Mucous membrane is lined by the transitional epithelium. Its characteristic features are: It stretches when the bladder distends, It forms a complete barrier to the passage of fluid and electrolytes. Therefore, urine stored in the bladder remains unchanged in chemical composition. Muscular layer is formed by smooth muscle fibres, which constitute the detrusor muscle. Contraction of this muscle coat is responsible for emptying of the bladder.
Sphincters of the urethra 1. Internal sphincter. The circular smooth muscle fibres in the area of the neck of bladder are thickened to form the internal sphincter (sphincter vesicae). The natural tone of the internal sphincter prevents emptying of the bladder until the pressure in the body of bladder rises above a threshold level. 2. External sphincter. Beyond the bladder neck, it is encircled by a ring of voluntary (skeletal type) muscle known as external sphincter of the bladder. The external sphincter provides voluntary control over micturition.
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