Chapter 66 - Bladder

Question 1

1. What is the volume capacity of the bladder in an adult horse

Answer 1

• 4L or more

Question 2

2. What forms the round ligaments of the bladder?

Answer 2

• the cranial free edges of the lateral ligaments, which are remnants of the umbilical arteries

Question 3

3. The bladder is covered by ______ at the apex and _______ for the remainder

Answer 3

• peritoneum
• adventitial tissue

Question 4

4. What are the two muscle layers of the bladder and what type of muscle are they?

Answer 4

• outer layer of longitudinal to obliquely arranged muscle fibers
• inner layer of transversely or circularly arranged muscle fibers

Question 5

5. T/F: The muscle layers are interwoven around the bladder. At the dorsal aspect of the bladder, the circular layer is external to the longitudinal layer

Answer 5

• True

Question 6

6. Where is the bladder most likely to rupture?

Answer 6

• on the dorsad surface, where the muscle layers change

Question 7

7. What muscles form the urethral sphincter?

Answer 7

• muscles of the bladder wall, continuous to an outer longitudinal and inner circular layer of smooth muscle surrounding the pelvic urethra. Forms urethral sphincter together with the striated urethralis muscle laterally and ventrally

Question 8

8. The bladder is lined with what type of epithelium?

Answer 8

• transitional epithelium

Question 9

9. What provides sympathetic innervation to the bladder?

Answer 9

• hypogastric nerve, cholinergic and peptinergic nerve fibers, and preganglionic fibers from the spinal segments L1-L4 to synapse in the caudal mesenteric ganglion

Question 10

10. The hypogastric nerve arises from what spinal nerve roots?

Answer 10

• L1 to L4

Question 11

11. Where does the hypogastric nerve synapse?

Answer 11

• the caudal mesenteric ganglion and postganglionic nerve fibers

Question 12

12. The post ganglionic nerve supply supplies the bladder and urethra via what receptors?

Answer 12

• bladder (B2 adrenergic) and proximal urethra (1˚ α1 and some α2 adrenergic receptors)

Question 13

13. Parasympathetic supply to the bladder originates from?

Answer 13

• sacral segments of the spinal cord (S1-S2) with neurons joining to form the pelvic nerve

Question 14

14. Somatic innervation of the lower urinary tract is primarily via what?

Answer 14

• striated urethralis muscle via a branch of the pudendal nerve

Question 15

15. The smooth muscle of the bladder is the ______ muscle

Answer 15

• detrusor muscle

Question 16

16. The detrusor muscle is innervated by ______ and ______

Answer 16

• parasympathetic pelvic nerve
• B1 adrenergic postganglionic fibers

Question 17

17. Describe what occurs in the bladder during the filling phase

Answer 17

• increase in tone of the smooth and striated muscles of the urethral sphincter to maintain continence

Question 18

18. What type of nerve activity is active during the bladder filling phase?

Answer 18

• sympathetic nerve activity

Question 19

20. What nerve fibers are inhibited and stimulated to allow relaxation of the detrusor muscle during filling?

Answer 19

• a receptor mediated inhibition of pelvic nerve afferents and stimulation of sympathetic β-2 receptors in the smooth muscle of the bladder.

Question 19

19. What happens to the detrusor muscle during the filling phase?

Answer 19

• initially, relaxation is stimulated to allow for filling. as the detrusor muscle fibers reach their limit of stretch, intravesicular pressure starts to rise, and bladder fullness is sensed.

Question 20

21. When the detrusor is over stretched what is the signal transduction pathway to alert the body of the need to void the bladder?

Answer 20

• stretch receptors transmit signals via the pelvic nerve and ascending spinoreticular tracks to the pons, cerebrum, and cerebellum. Bladder fullness is sensed and signals for voluntary micuturition are initiated in the cerebrum, beginning the elimination phase.

Question 21

22. How is voluntary micturition signaled from the brain to bladder?

Answer 21

• Transmitted via the brainstem upper motor neurons descending in reticulospinal tacts to sacral parasympathetic nuclei, parasympathetic ganglia in the pelvic plexus or bladder wall, and postganglionic fibers, triggering detrusor contraction.

Question 22

23. As the detrusor muscle is stimulated to contract, what receptors are activated to allow urethral relaxation?

Answer 22

• concurrent inhibition of the pudendal nerve and hypogastric α and β-2 sympathetic activity leads to relaxation of the urethral sphincter.