Renal Physiology 1 - Checked and Completed

Question 1

Why are kidneys overperfused?

Answer 1

Blood is needed for more than metabolic needs - blood is filtered

Question 2

Define GFR

Answer 2

Glomerular Filtration Rate

Rate at which fluid moves from blood into kidney

Typically ~125 ml/min or about 180 L per day

Question 3

What hormones are produced by the kidney?

Answer 3

Renin

Prostaglandins

Erythropoietin

vitamin D (calcitriol)

Question 4

Define difference between Osmolality and Osmolarity

Answer 4

Osmolality defined as solutes per kilogram of water

NOT per liter of solution

Similar but osmolality is slightly higher because solutes displace liquid slightly - more than 1 liter of a solute-containing solution is needed for it to have 1 kilogram of water.

Question 5

How do kidneys regulate blood pressure?

Answer 5

**1) Can increase/decrease blood volume; increase in volume increases central venous pressure, increasing venous return and hence cardiac output. **

2) Hormonal regulation: renin secretion increases angiotensin II which acts as a vasoconstrictor

Question 6

Describe how kidneys regulate RBC production.

Answer 6

Low blood O2 levels trigger interstitial cells in the renal cortex to produce EPO

Erythropoietin stimulates RBC precursor cells in bone marrow to mature

Question 7

Describe the kidney’s role in Vitamin D production.

Answer 7

Vitamin D is converted into its active form (calcitriol) by two hydroxilation reactions, one of which occurs in the kidney

** Calcitriol promotes Ca2+ absorption in the GI tract**

Question 8

Define renal papilla

Answer 8

Point of each renal pyramid which empties into minor calyxes

Question 9

Describe artieries of kidney

Answer 9

**Renal artery - Interlobar arteries - arcuate arteries - interlobular arteries - afferent arterioles - glomerular capillaries - efferent arterioles - peritubular capillaries **

Question 10

Define and describe 2 types of nephrons

Answer 10

Cortical (superficial) nephrons = arise high in the cortex and have loops of Henle that do not reach the inner medulla; NOT associated with vasa recta

Juxtamedullary nephrons = arise in lower cortex (near the cortex-medulla border) and have loops of Henle that extend into the inner medulla; associated with peritubular capillary called the vasa recta

Question 11

Describe 3 filtration layers from lumen of capillary to Bowman’s space

Answer 11

Filter Layer 1 : fenestrated capillary endothelial cells ( ~70 nm gaps allow solutes/proteins to pass but not RBCs)

Filter Layer 2 : glomerular basement membrane ( < ~ 3 nm allowance because of net negative charge)

Filter Layer 3 : the podocytes ( ~8 nm gaps)

Question 12

What is the result of constricting an afferent arteriole? afferent arteriole?

Answer 12

Afferent Arteriole Vasoconstriction reduces GFR by putting a kink in the system before filtration (promoting reabsorption as coping method)

Efferent Arteriole Vasoconstriction increases pressure in the glomerular capillaries resulting in increased filtration.

Question 13

Describe the juxtaglomerular apparatus (JGA)

Answer 13

Composed of macula densa and granular cells

Granular cells are specialized smooth muscle cells of glomerular afferent arteriole

Macula Densa cells are columnar epithelium thickening of the distal tubule (in close proximity of renal corpuscle)

Question 14

Describe how the JGA regulates kidney filtration

Answer 14

Increased blood pressure means increased GFR, which means more tubular flow past macula densa cells

Densa cells sense this and constrict afferent arterioles, decreasing GFR (kink in hose before kidney)

Question 15

Define excretion in mathematical terms

Answer 15

Excretion = Filtration + Secretion - Reabsorption