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Introduction to
Micturition
Clinical Science Team
Objectives
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Differentiate between the gross anatomical
features of the male and female urinary
tracts
Briefly describe the structure and function
of the ureters
Describe the gross structure, layers, nerve
supply and function of the urinary bladder
Describe the structure and function of the
urethra and urethral sphincters
Briefly explain the process of micturition
Gross Anatomy of the Urinary Tract
Male
Female
Gross Anatomy of the Urinary Tract
Male
Gross Anatomy of the Urinary Tract
Female
What structure is superior
to the bladder in this
diagram?
What structure is anterior
to the bladder?
What structure is posterior
to the urethra?
The Ureters
Function of the ureters
is to convey urine
from the kidney to
the urinary bladder.
The angle that the
ureters pass through
the bladder wall
prevents reflux of
urine from the
bladder).
The Urinary Bladder
Transitional Epithelium Lining of
the Urinary Bladder
The Urinary Bladder
Is a spherical hollow sac
Consists of three layers:
Inner mucosa, composed of transitional epithelium
Middle layer of involuntary detrusor muscle
Outer layer of loose connective tissue
Function:
Reservoir for urine
Evacuation of urine (under control of ANS)
The Male Urethra
The Male and Female Urethra
Male Urethra:
Female Urethra:
18-20 cm long
3-5 cm long
Tortuous in configuration
Straight in
configuration
Composed of three parts
(see previous diagram)
The Female Urethra
Structure of the Urethra
What is different
about transitional
epithelial tissue?
Structure of the Urethra
Layers:
• Essentially the same as the remainder of
the urinary tract
• Lined with mucous membrane
Function:
Conveys urine from the bladder to the
exterior
Questions
• What gland lies next to the urinary bladder
in men?
• How is the male urethra different to the
female urethra?
• What membrane covers the superior
aspect of the bladder?
Questions
• What is the name of the triangular area
between the entry point of the two ureters
and the internal urethral orifice?
• What are the ‘pelvic floor muscles’ and
what do they have to do with micturition?
Urethral Sphincters
The Internal Sphincter:
• Forms part of the bladder neck outlet
• Composed of circular smooth muscle
(involuntary)
• Is under the control of the ANS
Urethral Sphincters
The External Sphincter:
• Forms part of the pelvic floor muscles
• Composed of circular striated muscle
(voluntary)
• Is under the control of the somatic
nervous system
Involuntary (Autonomic) Control
of Micturition
Spinal Cord
Sensory
Neurone
Stretch
Receptor
Parasympathetic Motor Neurone (contracts
Detrusor muscle & opens internal sphincter)
Bladder
Detrusor
Muscle
Internal urethral
sphincter
Voluntary Control of Micturition
Sensory
Cortex
Motor
Cortex
Pons
Voluntary (Somatic) Pudendal
Nerve: Controls opening &
closure of external sphincter
External Urethral
Sphincter
Questions
• What sort of muscle is contained in the wall of
the ureter (and bladder)?
• What sort of pain is experienced when the
ureters are inflamed?
• What is the maximum volume of urine that the
adult bladder can hold comfortably?
Questions
• How much urine (normal range) is produced
daily in an adult?
• What is the minimum amount of urine that
should be produced per hour in an adult
• What structure does the urethra pass through?
• Why is glucose an abnormal constituent of
urine?
Micturition animation
Please watch the following short animation,
it summaries the micturition reflex nicely
1anim0081.exe
Conclusion
In this session we have:
1. Discussed the anatomical features of male and
female urinary tracts
2. Discussed the structure, function, layers, and
nerve supply of the bladder and the urethra
3. Illustrated the control of micturition
Maintaining Continence
• What knowledge and skills are needed by
the nurse in relation to maintenance of
continence in patients?