Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 27Disorders of the Bladder and
Lower Urinary Tract
Chapter 27Disorders of the Bladder and
Lower Urinary Tract
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Micturition ReflexMicturition Reflex
• Begins when bladder contains 150–250 mL of urine
ureters
urine produced in
kidneys
bladder fills with urine
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Stretch Receptors in the BladderStretch Receptors in the Bladder
stretch receptors
stretch receptors
bladder fills with urine
micturition center in
pons stimulated
spinal reflex stimulated
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UrinationUrination
• Detrusor muscle of bladder contracts to push urine out
• Abdominal muscles may also be used
• Internal sphincter relaxes
• External sphincter relaxes
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question Question
Tell whether the following statement is true or false:
Abdominal muscles are used during forced urination.
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer Answer
True
Passive urination occurs when the bladder’s detrusor muscle contracts, and both internal and external sphincter muscles are relaxed. Abdominal muscles contract in order to force the excretion of urine.
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Parasympathetic NervesParasympathetic Nerves
M3 receptors
stretch receptors
M3 receptors
bladder fills with urine
detrusor muscle
contracts
internal sphincter relaxes and is pulled
open
parasympathetic neurons
spinal reflex stimulated
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Micturition Center Allows Conscious ControlMicturition Center Allows Conscious Control
stretch receptors
bladder fills with urine
detrusor muscle
contracts
internal sphincter relaxes and is pulled
open
micturition center in
pons stimulated
external sphincter
relaxes
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Question Question
All but which of the following stimulates urination?
a. Parasympathetic nervous system neurons
b. Micturition center
c. Sympathetic nervous center
d. Spinal reflex
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Answer Answer
c. Sympathetic nervous system
The micturition center in the pons and the spinal reflex respond to stretch receptors in the bladder to stimulate urination. The parasympathetic nervous system neurons are stimulated by the spinal reflex to cause urination.
SNS (fight-or-flight) decreases activity in both the excretory and digestive systems.
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ScenarioScenario
A 63-year-old woman complains of stress incontinence, and her 60-year-old husband complains of difficulty voiding.
Question:
• Why do people of the same age and lifestyle have opposite problems with urination?
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Male vs. Female UrethraMale vs. Female Urethra
• Female is urethra 2.5–3.5 cm long
• Allows urine to pass more freely
• Male urethra 16.5–18.5 cm long
• Passes through prostate
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Question Question
Tell whether the following statement is true or false:
Benign prostatic hypertrophy (BPH) has no effect on the elimination of urine.
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Answer Answer
False
Because the male urethra passes through the prostate gland, if the gland increases in size the urethra may become compressed or obstructed. This decreases the diameter of the urethra’s lumen, and the ability to urinate is diminished.
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
ScenarioScenario
Six months later, the husband develops urgency and incontinence…
• The doctor explains that it is due to his muscle strength.
Question:
• Which muscles is the doctor talking about?
• How did they cause incontinence?
Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins
Bladder Wall HypertrophyBladder Wall Hypertrophy
• The bladder may also pouch outward in diverticuli
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