Basic Kidney Function

Question 1

What is osmolarity?

Answer 1

The sum of the moles of each component of a solution: 2mM solution of MgCl2=6mM per liter (2x3(Cl) + 2x 1(Mg))

Question 2

Major difference in osmolality and osmolarity?

Answer 2

Osmolality: the moles of solute per kilogram of solvent
Osmolarity: number of moles per liter in solution

Question 3

What is osmolality?

Answer 3

Moles of a solute per kilogram of solvent

Question 4

What concentration of NaCl is isosmotic to cells?

Answer 4

150mM

Question 5

How many liters of water is filtered by kidneys each day?

Answer 5

180L

Question 6

What is the process of producing hypo-osmotic urine?

Answer 6

Thick ascending limb of Henle’s loop reabsorbs more solute than water

Question 7

What is the process of producing hyper-osmotic urine?

Answer 7

Water reabsorbed from lumen into a hyper-osmotic medullary interstitium

Question 8

How are medullary interstitial cells made hyper-osmotic?

Answer 8

1. ) Addition of Na+ to interstitium
2. ) Vasculature that minimizes removal of Na+
3. ) Recycling urea between medullary collecting ducts and deep portions of loops of Henle

Question 9

What are the seven major renal functions?

Answer 9

1. ) Water of and electrolyte balance
2. ) Acid base balance
3. ) Excretion of waste
4. ) Arterial blood pressure
5. ) Red blood cell
6. ) Vitamin D production
7. ) Gluconeogenesis

Question 10

What are the three fundamental elements of renal function?

Answer 10

1. ) Glomerular filtration
2. ) Tubular secretion
3. ) Tubular reabsorption

Question 11

What are podocytes?

Answer 11

Cells that wrap around the capillaries of the Bowman’s capsule

Question 12

What are the macula densa?

Answer 12

A sensor of tubular Na+ content that exerts renal control of granular cells

Question 13

Where are the macula densa (juxtaglomerular apparatus) located?

Answer 13

Between the afferent arteriole and the distal convoluted tubule

Question 14

What innervates the macula densa and what does it release?

Answer 14

Sympathetic innervation for release of renin

Question 15

What is the macula densa response to blood sodium levels being too high?

Answer 15

Contraction of the afferent arteriole

Question 16

What is the Bowman’s filtrate most similar to?

Answer 16

Blood plasma minus large proteins

Question 17

What does the descending limb do?

Answer 17

Reabsorbs water out of the tubule (impermeable to ions)

Question 18

What does the ascending limb do?

Answer 18

Reabsorbs ions out of the tubule (impermeable to water)

Question 19

What is meant by counter current?

Answer 19

As ions are absorbed out into the tubule from the ascending limb the ions pull water out from the descending limb

Question 20

What is the distal convoluted tubules function?

Answer 20

To reabsorb more ions (Na, Cl, etc.)

Question 21

Function of the proximal convoluted tubule?

Answer 21

Reabsorb water, Na+, glucose, AA

Question 22

What does the collecting duct reabsorb?

Answer 22

Water, Urea

Question 23

What is the function of the juxtaglomerular apparatus?

Answer 23

Control blood pressure

Question 24

How do the kidneys regulate Ca++ and phosphate?

Answer 24

Excrete Ca++ in urine

Activates vitamin D

Question 25

How do kidneys regulate acid-base balance?

Answer 25

By excreting or producing H+

Question 26

What is renal excretion rate dependent on?

Answer 26

Rate of filtration
Rate of reabsorption
Rate of secretion

Question 27

Formula for excretion rate:

Answer 27

Ux x V
Ux= [x]
V= urine flow per unit time

Question 28

What is renal clearance?

Answer 28

The virtual amount of plasma that would be completely cleared of a solute in a given amount of time (mL/min)

Question 29

Example: what does it mean if the renal clearance of urea is 65mL/min?

Answer 29

That the kidneys remove all of the urea present in 65mL of plasma each minute

Question 30

Renal clearance formula:

Answer 30

Cx= (Ux x V)/Px

Px= [x] in systemic blood plasma

Question 31

Function of PTH?

Answer 31

Ca++ reabsorption
Phosphate (i) excretion
Hydroxylation of Vitamin D precursor into active Vitamin D