Continence and Micturition Flashcards
The bladder is a balloon like organ with walls of smooth muscle called …
The detrusor muscle
Name and give a brief descriptio of the 4 external features of the bladder
- Apex - superiorly, pointing upwards towards pubic symphysis
- Body - Main part
- Fundus (base) - Posterior, triangular shaped.
- Neck - Joins the bladder to the urethra
What is the trigone?
A triangular area of the located on the fundus
- Between the internal urethral oriface and the 2 orifaces of the ureters
- Smooth wall (not like the rest of the bladder)
Describe the internal and external urethral sphincters
Internal urethral sphincters = Male only
- Circular smooth muscle fibers under autonomic control
- Thought to prevent seminal regurgitation during ejaculation
External urethral spincters = Male & Female
- Voluntary muscle
- Contraction can prevent urination even if the bladder contracts very strongly
Which artery is the primary blood supply for the bladder in both sexes?
The internal iliac vessels (Superior vesical branch)
Fill out the table: Innervation
Type During filling During Micturition
Detrusor (smooth muscle) _______ _________ ____________
Internal urethral sphincter (smooth muscle) _______ _________ ____________
External urethral sphincter (skeletal muscle) ______ _________ ____________
Parasympathetic Inhibited Stimulated
Sympathetic Stimulated Inhibited
Somatic motor Stimulated Inhibited
Which of the following is true about the sympathetic nervous supply of the bladder:
a) Via the hypogastric nerve (T12-L2)
b) Via the pelvic nerve (S2-S4)
c) Increased signals cause contraction of the detrusor muscle
d) The signals indicated the need to urinate
Sympathetic to bladder = the hypogastric nerve (T12-L2) - relaxation of the detrusor
Parasympathetic = pelvic nerve (S2-S4) - contraction of the detrusor
Sensory afferent report to the brain about how full the bladder is
Describe the bladder stretch reflex arc that leads to micturition
Bladder fills with urine - bladder walls stretch - stretch receptors stimulated - send info to spinal cord - interneurones relay signal to parasympathetic efferents (the pelvic nerve) = contraction of the detrusor muscle and micturition
Where is Onuf’d nucleus?
Anterior horn of the spinal cord
S 2,3,4
- Involved in micturition and continence
Describe the affect of the sympathetic nervous system on the bladder
Bladder + sympathetic = Receptive relaxation (fight/flight, can’t do either if your weeing)
Where do the C fibers project?
a) Onuf’s nucleus
b) Sacral Micturition Centre
b) Pontine Micturition Centre
c) Periaquductal Gray
C Fibres - local afferents to the Sacral Micturition Centre
Reflex bladder contractions
Where do the Aδ fibers project?
a) Onuf’s nucleus
b) Sacral Micturition Centre
b) Pontine Micturition Centre
c) Periaquductal Gray
Periaqueductal gray
Concious centres
Describe the effects of the bladder when there is a spinal cord transection above S2
Spinal cord transection above S2:
Afferent can’t reach brain = no awareness of the bladder filling
- No descending control over the external urethral spincter so it is constantly relaxed.
- Functioning spinal reflex - Parasympathetic causes the detrusor to contract - bladder empties as it fills
Describe what happens with a flaccid bladder due to a spinal cord transection S2-S4
Ppinal cord transection S2-S4
- Parasympathetic damaged = no spinal reflex
- Detrusor muscle will be paralysed & can’t contract
- Over flow incontinence
Describe the differences between stress and urge incontinence
Incontinence = the involuntary release of urine
Stress incontinence = due to coughing/sneezing/exercise
Urge incontinence = associated with the desire to urinate
