Glomerular Filtration (1.5)

Question 1

Afferent =

Efferent =

Answer 1

Carry towards

Carry away from

Question 2

How is filtration brought about?

Answer 2

Blood enters the glomerulus through the wide afferent arteriole and leaves through the narrower efferent arteriole. More blood will therefore enter the glomerulus than can leave it. (This will create a similar situation to a traffic jam in the glomerulus) In this way pressure is built up, forcing the filterable contents of the blood through the glomerular membrane into the cavity of Bowman’s Capsule.

Question 3

How much blood is filtered?

Answer 3

Every minute 120ml of blood plasma (10% of the blood in the glomerulus), filters from the blood in the capillaries into the cavity of Bowman’s capsule in each kidney.

Question 4

What is ultrafiltration?

Answer 4

Ultrafiltration occurs at the barrier between the blood and the filtrate in the glomerular capsule (Bowman’s capsule) in the kidneys. It is known as ultrafiltration because it is filtration under pressure, through a very fine filter called the glomerular membrane.

Question 5

How is the glomerular membrane adapted for filtration?

Answer 5

It is made up of two layers of cells:
1. The endothelial cells making up the wall of the glomerular capillaries are porous allowing the plasma (plus its proteins) through but the pores are too small to allow the blood cells to pass through.
2. Podocyte layer of Bowman’s capsule, made up of flattened cells, podocytes (footed cells), that have spaces between them called filtration slits. These filtration slits are too small to allow plasma protein molecules through.
A very thin basement membrane covers each capillary, so it occurs between these two layers.

Question 6

What is the glomerular filtrate?

Answer 6

The plasma is known as glomerular filtrate. It is blood plasma without the blood cells or plasma proteins, which have been held back as they are too large to pass through the glomerular membrane.

Question 7

What makes up the glomerular filtrate? (2)

Answer 7

• Useful substances: water, glucose, amino acids, vitamins, hormones and ions
• Waste substances: nitrogenous waste such as urea, uric acid and creatinine

Question 8

The cup shape of ____ capsule and the many capillaries forming the glomerulus provide a larger ___ ___ (about 1.5 square metres), through which the maximum amount of ___ can take place.

Answer 8

Bowman’s
Surface Area
Filtration

Question 9

Define Glomerular filtration.

Answer 9

It is a passive, non-selective process in which fluids and solutes are forced through the glomerular membrane by hydrostatic pressure.