Bladder Anatomy and Physiology

Question 1

What is the specialized epithelium of the bladder called?

Answer 1

Urothelium

Question 2

What is unique about the epithelium that lines the bladder?

Answer 2

• It is waterproof so urine doesn’t get reabsorbed into the blood from the bladder
• It is transitional so it can be relaxed or distended (stretched)
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Question 3

Answer 3

Question 4

Describe the unique structure of the dome cells of the urothelium.

Answer 4

Dome cells contain urothelial plaques that line the apical surface making it impermeable to water. In the realxed state, some of these plaques are contained within the cells as fuisform vesicles. When the bladder needs to stretch, it can fuse the vesicles with the membrane to expand the membrane and allow it to stretch and grow in size. The outer leaflet of the membrane also contains a crystallized layer of uroplakins between the outer and inner leaflets which is responsible for the impermeable nature of the membrane.

Question 5

What signaling molecules are released in response to stretch of the urothelium?

Answer 5

Question 6

Answer 6

Question 7

The […] is the pacemaker of the urinary tract.

Answer 7

Renal pelvis - stretching of the pelvis stimulates action potentials that trigger peristaltic wave down ureter.

Question 8

Why are kidney stones so painful?

Answer 8

B/c the pelvis and ureters are innervated substnatially with pain fibers

Question 9

Describe the muscular layers of the ureter along its length.

Answer 9

Note: image is from lower 1/3 ureter b/c has 3 muscular layers

Question 10

What is the significance of smooth muscle and the uretero-vesicle junction?

Answer 10

In normal ureter/bladder junction, when bladder contracts, the smooth muscle of bladder pushes the ureter shut so there is no reflux during voiding. However, in some people where the angle is not as sharp and less of the ureter penetrates the bladder wall, there can be incomplete closure of ureter during voiding and there can be reflux.

Question 11

Why is reflux from bladder to ureter bad?

Answer 11

Ultimately can cause dilation of ureters, kidney failure, death.

More common in women, detected due to frequent bladder or UTI.

Question 12

Answer 12

Question 13

Describe the sympathetic innervation of the bladder.

Answer 13

SNS innervates bladder via hypogastric nerve (T11 - L2). Its functions will be to:

• Inhibit detrusor muscle contraction by releasing NE onto beta 2 receptors, causing relaxation of the detrusor muscle of the bladder.
• Stimulate internal sphincter contraction by releasing NE onto alpha 1 receptors

Question 14

Describe the parasympathetic innervation of the bladder.

Answer 14

PSNS innervates bladder via pelvic splanchnic nerves (S2 - S4). Its functions will be to:

• Stimulate detrusor contraction by releasing Ach (M3 recepetor) and ATP (P2X1 receptor) to cause contraction.
• Stimulate relaxation of internal sphincter by releasing NO

Question 15

Describe the somatic innervation of the bladder.

Answer 15

Somatic innervation by the pudendal nerve which stimulates external sphincter contraction by releasing Ach onto Nicotinic receptors to cause skeletal muscle contraction.

Question 16

Describe the sensory innervation of the bladder.

Answer 16

Viscercal sensory nerves travel with pelvic splanchnic (S2 - S4) and detect stretch, esp. at internal urethral orifice. Responsible for pain.

Question 17

What is the average daily production of urine?

Answer 17

800-2000mL

Question 18

When do you start to feel the urge to void? (@ what volume)

Answer 18

300-400 mL

Question 19

Answer 19

Question 20

Describe the process of bladder filling.

Answer 20

Question 21

Describe the process of bladder emptying.

Answer 21