Lecture 57 - Glomerulus, GFR, JGA, & autoregulation

Question 1

what is the renal corpuscle

Answer 1

glomerulus (capillaries) and bowman’s capsule

Question 2

blood pathways in the nephron provide

Answer 2

1. oxygen and nutrients
2. pathway for reabsorption and secretion

Question 3

describe the capillary network surrounding the nephron

Answer 3

1. peritubular capillaries at the cortex
2. vasa recta at medulla

Question 4

what are the 3 basic renal processes

Answer 4

1. glomerular filtration
2. tubular reabsorption
3. tubular secretion

Question 5

describe the glomerular filtration

Answer 5

primary filtration site to create ultrafiltrate

Question 6

what are the 3 layers of the kidney’s filtration barrier

Answer 6

1. fenestrated epithelium
2. basement membrane
3. podocytes

Question 7

describe fenestrated epithelium

Answer 7

filters by SIZE

small molecules are freely filtered, while cells and large molecules are not

Question 8

describe the basement membrane

Answer 8

filters by CHARGE

repels most negatively charged molecules except Cl- and HCO3-

Question 9

describe the podocyte layer

Answer 9

glomerular epithelial cells with a cell body and foot processes that interdigitate to prevent movement of large molecules

Question 10

Glomerular ultrafiltrate is like plasma with

Answer 10

water, glucose, amino acids, nitrogenous waste

Question 11

what does not get filtered

Answer 11

negatively charged, large molecules and cells

Question 12

what is the correct order and selectivity of the 3 major components of the glomerular filtration barrier (from inside to out)?

Answer 12

1. fenestrated endothelium (size)
2. basement membrane (charge)
3. podocytes (size)

Question 13

the creation of filtrate is due to

Answer 13

Starling forces (hydrostatic and oncotic pressure)

Question 14

hydrostatic pressure

Answer 14

• force that blood exerts on semi-permeable membrane
• “pushes” fluid and solutes through membrane
• roughly proportional to local blood/fluid pressure

Question 15

Oncotic pressure

Answer 15

• forces arising from large molecule
• favors retention of fluid in compartment
• roughly proportional to protein concentrations

Question 16

what are the ways to quantify glomerular filtration

Answer 16

1. glomerular filtration rate (GFR)
2. filtration fraction (FF)

Question 17

glomerular filtration rate

Answer 17

volume of fluid filtered from glomerular capillaries into bowman’s capsule per minute

directly proportional to net driving pressure

Question 18

filtration fraction

Answer 18

volume of ultrafiltration per unit time/volume of glomerular blood flow

Question 19

what are direct measurements of GFR

Answer 19

1. insulin
2. iohexol clearance

Question 20

what are indirect measurements of GFR

Answer 20

1. serum concentration of creatinine
2. BUN
3. SDMA

Question 21

what is needed to measure GFR directly

Answer 21

• freely filtered substance
• neither reabsorbed nor secreted
• substance quantified in urine/plasma

Question 22

creatinine as an estimation of GFR

Answer 22

• generated by metabolism in muscle
• most widely used surrogate maker to estimate
• GFR decreases, plasma creatinine increases

Question 23

T/F: plasma creatinine and BUN does not become increased until there is a 75% loss of function

Answer 23

TRUE

Question 24

T/F: plasma BUN is a good indicator of GFR in large animals

Answer 24

FALSE

Question 25

T/F: plasma BUN can be affected by factors like protein in diet, liver function, etc.

Answer 25

TRUE

Question 26

SDMA as an estimation of GFR

Answer 26

- produced by methylation of arginine residues in proteins - less impacted by extra-renal factors

Question 27

plasma SDMA increases at ____ loss of kidney function

Answer 27

25%

Question 28

azotemia

Answer 28

elevated amount of nitrogenous waste (BUN + creatinine) in blood

Question 29

uremia

Answer 29

azotemia that produces clinical signs

Question 30

what are the 3 types of azotemia

Answer 30

1. pre-renal = renal hypoperfusion 2. renal = acute or chronic renal disease 3. post-renal = obstruction of urine outflow

Question 31

which of the four starling forces most promotes the movement of fluid and solutes into the ultrafiltrate

Answer 31

capillary (plasma) hydrostatic pressure

Question 32

maintaining renal blood flow is vital to

Answer 32

1. create ultrafiltrate 2. provide oxygen to the kidney 3. provide nutrients to the kidney

Question 33

autoregulation of renal blood flow is maintained by

Answer 33

1. arterial blood pressure 2. renal vascular resistance

Question 34

what is the primary control of autoregulation? what causes response?

Answer 34

local/intrinsic baroreceptors and chemoreceptors

Question 35

what is systemic/extrinsic autoregulation controlled by

Answer 35

norepinephrine RAAS

Question 36

the juxtaglomerular apparatus is

Answer 36

mascula densa and granular cells

Question 37

macula densa

Answer 37

- distal convoluted tubule - chemo- and osmo- receptors - detect NaCl in urine (proportional to GFR)

Question 38

T/F: the macula densa responds to Na+ levels in filtrate

Answer 38

TRUE

Question 39

with high GFR, the macula densa

Answer 39

- less NaCl absorption (filtrate has high NaCl) - macula densa releases ATP - ATP constricts afferent arteriole and decreases GFR

Question 40

with low GFR, the macula densa

Answer 40

- more NaCl reabsorption (filtrate has low NaCl) - macula densa releases PGE2 and nitric oxide - vasodilation of afferent arteriole

Question 41

describe the cascade as a response to low blood pressure in the granular cells

Answer 41

1. baroreceptors sense blood pressure in the afferent arteriole 2. release renin 3. increases blood volume/pressure 4. increased renal blood flow 5. increased GFR

Question 42

T/F: NSAIDs block prostaglandin formation

Answer 42

TRUE

Question 43

which 2 parts if the nephron are physically close at the juxtaglomerular apparatus

Answer 43

1. glomerulus 2. distal convoluted tubule

Question 44

Prostaglandin

Answer 44

- released when GFR decreased - vasodilation of afferent arteriole - preserve GFR (sympathetic tone, angiotensin II, hypotension)