Kidney physiology

Question 1

What is the main function of the kidney?

Answer 1

Excrete metabolic products (urea, creatinine)

Maintain internal environment (water, sodium, potassium, H+)

Secretes hormones (renin, erythropoietin, vit D)

Question 2

What is glomerular filtration rate?

Answer 2

The amount if blood that passes through the glomeruli per unit time

Question 3

What is osmolality measured in?

Answer 3

No. of particles per kilogram of solvent

mmol/kg

Question 4

What is osmolarity measured in?

Answer 4

No. of particles per litre of solution

mmol/l

Question 5

Draw a nephron (and label it).

Answer 5

:)

Question 6

What is the proximal convoluted tubule’s basic function?

Answer 6

Most of the reabsorption and secretion

Question 7

What is the loop of henle’s basic function?

Answer 7

Creates concentration gradient

Question 8

What is the distal convoluted tubule’s basic function?

Answer 8

Fine tuning!

Question 9

What is reabsorbed in the collecting duct?

Answer 9

Some urea, water and NaCl

Question 10

What is reabsorbed in the PCT?

Answer 10

K+
NaCl
water
amino acids
glucose
bicarbonate ions

Question 11

What is secreted in the PCT?

Answer 11

Uric acid
Organic acids
Antibiotics that need to be removed from the body

Question 12

What is reabsorbed in the descending limb of the loop of Henle?

Answer 12

water

Question 13

What is reabsorbed in the ascending limb of the loop of Henle?

Answer 13

NaCl

Question 14

What is reabsorbed in the DCT?

Answer 14

NaCl and water

Question 15

What is secreted in the DCT?

Answer 15

K+

H+

Question 16

What is hydrostatic pressure?

Answer 16

Force that compels a fluid to move out of a vessel.
The larger the volume of blood within the capillaries and the higher the BP, the more quickly fluid will move from blood to Bowman’s.

Question 17

What are podocytes?

Answer 17

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

Question 18

What is the structure of podocytes and how does this help them carry out their function?

Answer 18

They have long processes called pedicels which wrap around the capillaries. There are slits between the pedicels which is where blood is filtered through.

Question 19

What are the 2 functions of the glomerulus?

Answer 19

Ultrafiltration of plasma

Barrier to filtration of protein

Question 20

What is oncotic pressure?

Answer 20

A form of osmotic pressure exerted by proteins, notably albumin.
Usually pulls water into circulatory system.

Question 21

Name the three ‘pressures’ acting on the glomerulus and Bowman’s capsule.

Answer 21

Hydrostatic pressure of blood (Ph blood)
Hydrostatic pressure of filtrate (Ph filtrate)
Oncotic pressure (π)

Question 22

Which pressure(s) support movement of fluid out of blood into Bowman’s?

Answer 22

Hydrostatic pressure of blood

Question 23

Which pressure(s) support movement of fluid out of Bowman’s into blood?

Answer 23

Hydrostatic pressure of filtrate

Oncotic pressure

Question 24

Why is there not oncotic pressure supporting movement from blood to Bowman’s?

Answer 24

Oncotic pressure is exerted by presence of proteins - there shouldn’t be any protein in the filtrate

Question 25

What’s the equation to calculate net pressure (Pnet)?

Answer 25

Pnet = force out - force in

Pnet = Ph blood - (Ph filtrate + π)

Pnet = 55 - (15 + 30) = 10 mmHg

Question 26

Why is it that there’s an overall movement of fluid out of the glomerulus?

Answer 26

Because the pressures that are acting add up to mean the there is more pressure forcing fluid out than back in.

Question 27

What makes up the filtration barrier in the glomerulus?

Answer 27

Fenestrated endothelium of glomerular capillaries

Fused basal lamina of the endothelial cells and podocytes

Slits created by podocytes

Question 28

Where is the juxtaglomerular apparatus?

Answer 28

Structure between Bowman’s and the distal convoluted tubule - look up a picture!

Question 29

What is the juxtaglomerular apparatus made up of?

Answer 29

Juxtaglomerular cells
Macula densa
Mesangial cells

Question 30

What do the juxtaglomerular cells look like and what do they do?

Answer 30

Specialised smooth muscle cells of glomerular arteries

Produce and secrete renin

Question 31

What is the macula densa?

Answer 31

Area of closely packed specialised cells lining the thick ascending limb where it become the DCT

Question 32

What do macula densa cells look like and what do they do?

Answer 32

Columnar epithelium
Sense increase in NaCl concentration in the distal tubule.
Secretes a locally active vasopressor - which acts to decrease GFR

Question 33

What do Mesangial cells look like and what do they do?

Answer 33

Pericytes found outside the glomerulus near Bowman’s-ish. They resemble smooth muscle cells

Role in autoregulation of blood flow to the kidney and control of systemic blood pressure via Renin-Angio-Aldo pathway

Question 34

What effect does vasoconstriction of the afferent arteriole have on GFR? Explain briefly.

Answer 34

Decreases GFR

Less blood gets to glomerulus - less fluid can get to

↑resistance due to arteriolar constriction
↓ renal blood flow
↓ GFR

Question 35

What effect does vasoconstriction of the efferent artery have on GFR? Explain briefly.

Answer 35

Increases GFR

More blood gets to the glomerulus - so more fluid is forced out into Bowman’s.

↑ resistance due to arteriolar constriction
↓ renal blood flow
↑ GFR

Question 36

Normal value of oncotic pressure?

Answer 36

30 mmHg

Question 37

Normal value of hydrostatic pressure of blood?

Answer 37

55 mmHg

Question 38

Normal value of hydrostatic pressure of filtrate?

Answer 38

15 mmHg