Renal physiology

Question 1

What does GFR stand for?

Answer 1

glomerular filtration rate

Question 2

What is glomerular filtration rate?

Answer 2

the volume of fluid filtered from the glomerulus to the Bowmann’s space per unit time

Question 3

What is the average GFR is a 70Kg person?

Answer 3

125ml/min

Question 4

What is the oncotic pressure into the bowmann’s space?

Answer 4

zero!

Question 5

Why is the oncotic pressure into the bowmann’s space zero?

Answer 5

there are no proteins in the bowmann’s space

Question 6

What is the renal blood flow per minute?

Answer 6

1 L

Question 7

What is PGC?

Answer 7

hydrostatic pressure in the glomerular capillary

Question 8

What is PBS?

Answer 8

hydrostatic pressure in the bowman’s space

Question 9

What is πGC?

Answer 9

oncotic pressure into the glomerular capillary

Question 10

What is KF?

Answer 10

the filtration coefficiant

Question 11

What is the equation for glomerular filtration rate?

Answer 11

GFR= KF (PGC-PBS)-(πGC-πBS)

Question 12

How can the afferemt and efferent arteriole decrease GFR?

Answer 12

constrict afferent arterioles

dilate efferent arteriole

Question 13

How is GFR measured clinically?

Answer 13

creatinine used as a marker substance

Question 14

What factors affect GFR?

Answer 14

blood pressure 
size of substance 
Charge of substance 
Surface area 
Attatchment to plasma proteins e.g albumin

Question 15

If pressure within the afferent arteriole rises, how does it respond?

Answer 15

responds by constricting

Question 16

When measuring GFR using a marker substance, what important qualities must the marker substance have?

Answer 16

be freely filtered
not be secreted or absorbed in the tubules
not metabolised

Question 17

What equation do we use when calculating GFR from a marker substance?

Answer 17

GFR= Um x urinary flow rate /Pm 
Um= concentration of m in urine 
Pm= concentration of m in plasma

Question 18

What is renal clearance?

Answer 18

the volume of plasma from which a substance is completely removed by the kidney per unit time

Question 19

How do we calaculate renal clearance?

Answer 19

clearance= urine concentration x urine volume / plasma concentration

Question 20

What is the filtration fraction?

Answer 20

GFR/ renal plasma flow

Question 21

Describe the charge of the foot processes of podocytes

Answer 21

negative

Question 22

What are the three basic layers of the filtration barrier in the kidneys?

Answer 22

1. endothelium
2. basement membrane
3. epithelium

Question 23

How much of the filtrate is reabsorbed in the proximal convoluted tubule?

Answer 23

2/3rds

Question 24

Where in the kidney is most of the filtrate reabsobed?

Answer 24

proximal convoluted tubule

Question 25

Where in the nephron does bulk reabsorption of glucose and amino acids occur?

Answer 25

the proximal convoluted tubule

Question 26

Which tubule is the longest?

Answer 26

the proximal convoluted tubule

Question 27

Does the proximal convoluted tubule have microvilli?

Answer 27

yes

Question 28

What are the two parts of the loop of Henle? What do they do?

Answer 28

Ascending: impermiable to ions, H2O reabsorption Descending: Na, K and Cl reabsorption

Question 29

Where in the nephron does fine tuning occur?

Answer 29

the distal convoluted tubule

Question 30

ADH acts on which type of cell at the collecting duct?

Answer 30

principal cells

Question 31

The macula densa detects the concentration of which ion?

Answer 31

Na+

Question 32

What happens if the macula densa detects low Na+ concentration?

Answer 32

a low Na+ concentration implies low GFR macula densa sends signals to increase renin renin causes an increase in blood pressure via RAAS this increases GFR

Question 33

What is the anion gap?

Answer 33

the difference between anions and cations

Question 34

How do we calculate the anion gap?

Answer 34

cations- anions

Question 35

describe the anion gap in a case of acidosis

Answer 35

acidosis- low anions | so wide anion gap

Question 36

How do the kidneys control water and ultimately blood pressure?

Answer 36

ADH RAAS Atrial natriuretic peptide

Question 37

Describe how a decrease in plasma volume is corrected for by ADH

Answer 37

decrease in plasma volume detected by baroreceptors posterior pituitary increases ADH secretion Increases collecting duct permeability to H2O More H2O is absorbed at the collecting duct and less is excreted