Renal Tubules

Question 1

Describe the urinary capsule (bowmans)

Answer 1

where glomerular filtration takes place forming the glomerular filtrate that is similar to blood plasma with almost no protein. This filtrate then enters the renal tubules for reabsorption.

Question 2

Describe the proximal convoluted tubule

Answer 2

2/3 of the filtrate is reabsorbed here because of microvilli, tight junctions, mitochondria, etc.
- both active and passive transport
- sodium reabsorption is the key
- secondary active transport using Na+ gradient
- resorption of filtered bicarb

Question 3

describe the loop of henle thin descending limb

Answer 3

squamous cell layer that is highly permeable to water allowing for simple diffusion of water and small solutes. The tubular fluid becomes hyperosmotic here

Question 4

describe the ascending limb of the loop of henle

Answer 4

thin segment: impermeable to water allowing for reabsorption of NaCl and making tubular fluid hypoosmotic

thick segment: impermeable to water with lots of mitochondria allowing for reabsorption of Na+
- Na+/2Cl/K+ is the site of action for many loop diuretics

Question 5

which segment of the loop of henle is a common site for loop diuretics?

Answer 5

thick segment of the ascending limb because of the Na+/2Cl/K+ co-transporter

Question 6

describe the distal tubule

Answer 6

variable reabsorption of Na, K, and MG and dilution of the tubule fluid
- impermeable to water
- ADH
- thiazide diuretics work on the Na+/Cl- co-transporter to inhibit reabsorption
- Late DCT is responsive to aldosterone
- intercalated cell is key to acid/base

Question 7

describe the collecting duct

Answer 7

the last area with urine concentrating abilities
- responsive to ADH to produce dilute/concentrated urine
- K sparing diruetics
- acid/base

Question 8

aldosterone

Answer 8

salt retaining hormone that activated transcription of Na/K pump gene
- tubules reabsorb more sodium and secrete more hydrogen and potassium
- water and Cl passively follow sodium

Question 9

ANP and BNP

Answer 9

inhibit sodium and water reabsorption, and the secretion of renin and ADH

Question 10

PTH

Answer 10

decreased urinary excretion of calcium, increased excretion of phosphate

Question 11

renal clearance

Answer 11

volume of plasma cleared of a substance per unit time
Cs= Us x V / Ps

Question 12

Fractional Excretion

Answer 12

fractional excretion of substance x (FEx) is the ratio of urinary excretion rate (Ex) to the filtration rate of x (Fx)