L32. Urinary 2

Question 1

What is the macula densa ?

Answer 1

• columnar thickening of the distal tubule
• responds to high urine volume and low salt content
• stimulates the juxtaglomerular cells via gap junction

Question 2

What are juxtaglomerular cells?

Answer 2

• modified pericytes
• secrete renin into the bloodstream
• are stimulated by the macula densa

Question 3

What is the role of renin

Answer 3

• decreases urine volume by:
• cleaving angiotensinogen and setting up the angiotensin cascade, causes the increase NaCl pumps in the ascending loop of Henle and distal tubule
• increases ADH which leads to a greater resorption of water in the collecting ducts

Question 4

Describe the collecting tubules

Answer 4

• respond to ADH and vassopressin by increasing the amount of aquaporins present in the plasma membrane (that facilitate water flow out into the medulla)
• drains into the renal pelvis which leads to the ureters that leave the kidney

Question 5

What is diuresis

Answer 5

high volume of urine

Question 6

Describe how the collecting duct changes its permeability from being in diuresis to anti-diuresis

Answer 6

1. ADH causes G-protein coupled reaction
2. cAMP/PKA induces aquaporin channels to be inserted into the membrane
3. cells become H2O permeable

Question 7

What kind of epithelium do collecting ducts possess

Answer 7

low columnar epithelium

Question 8

Where do collecting tubules expel urine

Answer 8

renal pelvis

Question 9

What are the 3 excretory passages

Answer 9

1. ureters
2. bladder
3. urethra

Question 10

Describe the ureter (tissue layers)

Answer 10

• distensible mucosa
• contractile mucosa externae
• peristaltic

Question 11

Describe the bladder (tissue layers)

Answer 11

• distensible mucosa
• contractile m. externae
• non-peristaltic

Question 12

Describe the tissue layers of the urethra

Answer 12

• thickening of the m. externae ( forms the sphincters)

- distensible mucosa

Question 13

Describe the cellular layer of the ureter

Answer 13

have desmosomes to hold the cells together
transitional epithelium
modulatable membrane domains
cytoskeleton of the transitional epithelium is very dynamic which facilitates cell change

Question 14

Describe the cellular level of the bladder cells

Answer 14

1. transitional epithelium in contracted state
2. apical cells are cubodial
3. lamina propria has fibroeleastic connective tissues

Question 15

Describe what happens when the bladder starts to fill

Answer 15

• Desmosomes become clearly visible and they help anchor the cell
• folds stretch as the bladder fills

Question 16

Describe the muscularis externa in the bladder

Answer 16

contains a thickening : internal sphincter which is a smooth muscle
interlaced smooth muscle , non -persitaltic

Question 17

Describe the external sphincters in the bladder

Answer 17

Skeletal muscles control voluntary motion, wraps around proximal urethra – relaxes for micrturition

Question 18

Describe the tissue layers of the urethra

Answer 18

epithelium: (stratified squamous non keratinized at the distal end and at the proximal: transitional epithelium)
lamina propria: fibroelastic with mucous gland ( lubricating purposes)
submucosa: erectile tissue
muscularis externa: inner longitudinal, outer circular (smooth muscles)