2. • 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 bladder.
3. • 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
closed.
• Urine can still enter, however, because ureteral contractions generate
enough pressure to overcome the resistance and push urine through
the occluded ends.
7. Innervation
• MOTOR
• Parasympathetic :
- Sacral detrusor nucleus
- Intermediolateral grey horn of spinal
cord S2-S4
- Pelvic splanchnic nerve
- Excitatory to detrusor muscle
- Inhibitory to sphincter vesicae
8. • Sympathetic :
- Intermediolateral grey horn T10- L2
segments of spinal cord
- Bladder, bladder neck and urethra
- Inhibitory to detrusor
- Excitatory to sphincter vesicae
9. • Somatic motor supply
- Sacral pudental nucleus
- Nucleus of ONUF
- S2,3,4
- Supply to external sphincter
10. • SENSORY
- BLADDER WALL: T10-T12 through pelvic splanchnic nerve &
hypogastric 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
11. Micturition
• Definition:
- Is a process by which urinary bladder empties when it
become filled
• 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
12. • 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.
13. CYSTOMETRY
• 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
3. Phase3
14.
15. 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
1. Brain
2. Brain stem
3. Spinal cord
16. 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
17. 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
18. REFLEX CONTROL VOLUNTARY CONTROL
Bladder fills Cerebral cortex
Stretch receptor
Parasympathetic Motor neuron to external
sphincter
Bladder
Detrusor contraction External urethral sphincter
closed
Opening of internal sphincter
Urination No urination
External
urethral
sphincter opens
when motor
neuron is
inhibited
21. • 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
BLADDER
22. • AUTOMATIC URINARY BLADDER
- Complete destruction of spinal cord above sacral segments
- Complete loss of micturition reflex, bladder sensation
- Also called as reflex neurogenic bladder
23. • 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.