Formation of filtrate

Question 1

What is the ultrafiltrate?

Answer 1

Blood filtered as it enters from glomerulus into the Bowman’s capsule

Question 2

What is the diameter of the glomerular capillaries?

Answer 2

200 micrometers

Question 3

What is the length of the glomerular capillaries?

Answer 3

19 km in total

1 nephron = 1 cm

Question 4

What is the surface ares of the capillaries?

Answer 4

1 metre squared

Question 5

What is the histology of the filtration barrier on the side of the glomerulus?

Answer 5

Endothelial cells contain endothelial pores

Allow small molecules to move across the filtration barrier

Fenestrae can be plugged with glycocalyx

Glycocalyx is attached to the basal lamina

Question 6

What is the role of the glycocalyx?

Answer 6

Prevent macromolecules from entering Bowman’s capsule

Question 7

What is glycocalyx made of?

Answer 7

Glycoprotein - polysaccharide covering

Question 8

What is the basal lamina made up of?

Answer 8

Negatively charged glycoprotein sheets

Question 9

What is the histology of the filtration barrier on the side of the Bowman’s space?

Answer 9

Glomerular capillary is surrounded by podocytes

Between the podocytes is a diaphragm made by the protein nephrin

Question 10

How do the podocytes surround the glomerular capillaries?

Answer 10

Podocytes are made up of arm-like structures called primary processes

The primary processes -> secondary processes -> finger-like projections that extend over all capillaried to form a sheet

Question 11

What is the diaphragm of podocytes made up of?

Answer 11

The protein nephrin

Question 12

What disease is caused by a mutation in the protein nephrin?

Answer 12

Congenital nephrotic syndrome

Question 13

How wide is the diaphragm of the podocytes?

Answer 13

4 nm

Question 14

Which factors determine glomerular filterability of molecules?

Answer 14

Electrical charge

Molecular weight

Question 15

How does electrical charge determine filterability of a molecule?

Answer 15

Filtration membrane is made up of negatively charged glycoproteins

Repels negatively charged solutes

Attract positively charged solutes

Question 16

How does molecular weight determine filterability of a molecule?

Answer 16

Small molecules are freely filtered

As molecules increase in size - filtration ratio decreases

Question 17

What is the equation for net ultrafiltration pressure?

Answer 17

Net ultrafiltration pressure = net hydrostatic pressure - net oncotic pressure

Question 18

What creates net hydrostatic pressure in the capillaries?

Answer 18

Heart

Question 19

What creates net oncotic pressure in the capillaries?

Answer 19

Proteins

Question 20

What is the equation for net hydrostatic pressure?

Answer 20

Glomerular hydrostatic pressure - Bowmans space hyrdrostatic pressure

Question 21

What happens to the net hydrostatic pressure as you go from the afferent to the efferent arterioles?

Answer 21

Net hydrostatic pressure = net oncotic pressure

Question 22

What does net hydrostatic pressure do?

Answer 22

Drives filtration of salt, water and other components from the glomerulus to the Bowman’s space

Question 23

What happens when net hydrostatic pressure = net oncotic pressure?

Answer 23

No filtration happens

Question 24

What can alter the rate of glomerular filtration?

Answer 24

Change in any pressure can alter ultrafiltrate pressure

Decrease in hydrostatic pressure following haemorrhage

Increase in hydrostatic pressure following kidney stone

Increase in oncotic pressure folowing dehydration