Elimination

Question 1

What is micturition?

Answer 1

Release of urine from the urinary bladder into urethra to be eliminated via urethral meatus

Question 2

How is urine passed down the ureters?

Answer 2

Peristalsis

Question 3

How do ureters enter the bladder?

Answer 3

At an acute angle- prevents reflux of urine from the bladder back in the ureter and kidneys

Question 4

What is the function of transitional epithelium in the bladder?

Answer 4

Allows the bladder to expand when filling

Special type of stretchy epithelium

Question 5

What does the bladder contain to enable it to respond to stretching?

Answer 5

Bare sensory nerve endings of parasympathetic system

Question 6

What are the components of the closure mechanism?

Answer 6

Smooth and striated muscle

Forms internal and external sphincter

Internal controls autonomic NS

External under voluntary control

Question 7

What are the 4 centres involved in storage/voiding of urine?

Answer 7

Spinal micturition centre

Pontine micturition centre

Cerebral cortex

Hypothalamus

Question 8

What is the function of the spinal micturition centre?

Answer 8

Acts as relay centre

Organises incoming sensory info from bladder and outgoing motor responses to brain

Sense of bladder fullness

Question 9

What is the function of the pontine micturition centre?

Answer 9

Neural switch between bladder storage and voiding

Inhibits descending signals to SMC during filling and releases descending signals to SMC to facilitate voiding

Question 10

What is the function of the cerebral cortex?

Answer 10

Houses relay centre

Allows voluntary inhibition of micturition reflex

Question 11

What is the function of the hypothalamus?

Answer 11

Integrates with micturition centres

Under hormonal control

Question 12

What occurs when the bladder is beginning to refill?

Answer 12

PNS is inhibited

SNS stimulated- relax bladder wall and constrict sphincters in readiness for next ‘cycle’

Question 13

What occurs when micturition is terminated?

Answer 13

Contraction of external and internal urinary sphincters

Bladder neck closes- returns to normal position

Any residual urine above level of external sphincters squeezed back into the bladder

Question 14

What is the process of normal voiding?

Answer 14

1) bladder fills (stretch receptors stimulated)
2) afferent signals to sacral segments in SC (SMC) via pelvic nerves
3) integration of signals in SC
4) efferent signals from SC to bladder (parasympathetic)
5) efferent signals cause bladder contraction and internal (smooth muscle)/ external (skeletal muscle) sphincters to relax
6) urinary bladder contacts and empties

Question 15

What is the process of voluntary delay of normal voiding?

Answer 15

1) Bladder fills
2) afferent signals to sacral segments of SC via pelvic nerves
3) integration of signals in SC
4) efferent signals from SC to pons (neural switch)
5) pons send descending signals via SC to reduce intensity of bladder contractions and stimulate efferent neurones that keep external urinary sphincter contracted
6) when convenient to urinate, higher brain centres send impulses via pons to SC to inhibit urinary sphincter
7) desire to urinate initiates micturition reflex
8) pons switches off signals that decrease bladder contractions allowing efferent impulses to cause bladder contraction and internal/external sphincters to relax
9) urinary bladder contracts and empties

Question 16

What are the 2 main functions of the pelvic floor?

Answer 16

Provides support for contents of the abdominal cavity

Contributes to maintaining continence by supporting closure of the urethra and anus

Question 17

What 3 factors are urinary continence dependent upon?

Answer 17

1) relaxation if bladder as it fills- produces low pressure reservoir
2) inhibition of bladder contractions during filling
3) creation of higher closing pressure in urethra than in the bladder