The Kidneys

Question 1

Functions of the kidney.

Answer 1

1. Excrete waste products e.g. urea
2. Regulate the water potential of the blood.

Question 2

What is osmoregulation?

Answer 2

Maintaining the water potential of the blood.

Question 3

Stages of osmoregulation?

Answer 3

1. Ultrafiltration
2. Reabsorption by PCT
3. Maintenance of Na+ gradient by loop of Henle.
4. Reabsorption of water by DCT + collecting duct.

Question 4

What is ultrafiltration?

Answer 4

As the blood passes through capillaries in the cortex (outer layer) of the kidneys, substances are filtered out of the blood and into long tubules that surround the capillaries. = Ultrafiltration

Question 5

What is selective reabsorption?

Answer 5

Selective reabsorption - Useful substances, such as glucose and the right amount of water, are then reabsorbed back into the blood.

Question 6

What are nephrons?

Answer 6

Long tubules and a bundle of capillaries where the blood is filtered.

Question 7

Describe how blood is circulated between the heart and the kidneys.

Answer 7

Arteries carry (oxygenated) blood from the heart to the kidneys via the renal artery.

Veins take (deoxygenated) blood from the kidneys back to the heart via the renal vein.

Question 8

Structure of the kidneys?

Answer 8

Question 9

Basic diagram of a nephron?

Answer 9

Question 10

Label.

Answer 10

Question 11

Diagram of a nephron 2

Answer 11

1. Renal capsule
2. Glomerular capillary
3. Afferent arteriole
4. Efferent arteriole
5. Distal convoluted tubule
6. Collecting duct
7. Blood capillaries
8. Ascending limb of loop of Henle
9. Ascending limb of loop of Henle
10. Branch of renal vein
11. Proximal convoluted tubule
12. Branch of renal artery

Question 12

What is the glomerulus of a nephron?

Answer 12

Each arteriole splits into a bundle of capillaries.

Question 13

Where can the glomerulus be found?

Answer 13

Inside a hollow ball - the Bowman’s capsule.

Question 14

What do you need to remember about the glomerulus of a nephron?

Answer 14

• plural glomeruli
• site of ultracentrifugation
• arteriole that takes blood to the glomerulus = afferent arteriole
• arteriole that takes filtered blood out of the glomerulus = efferent.

Question 15

Why is there a high blood pressure in the glomerulus high?

Answer 15

The efferent arteriole has a smaller diameter than the afferent arteriole, so the blood in the glomerulus is under high pressure.

(- it can’t move out quickly enough, creating pressure)

The high pressure forces liquid and small
molecules in the blood out of the capillary and into the Bowman’s capsule.

Question 16

Describe ultrafiltration.

Answer 16

1. Afferent arteriole - blood into glomerulus. Efferent arteriole - filtered blood out.
2. efferent → smaller diameter than afferent arteriole = blood in the glomerulus is under high pressure.
   The high pressure forces liquid and small molecules in the blood out of the capillary and into the Bowman’s capsule.
3. The liquid and small molecules enter the nephron tubules through — the capillary wall, the basement membrane and the epithelium of the Bowman’s capsule.
4. Larger molecules like proteins and blood cells can’t pass through, so stay in the blood.
   The substances that can enter Bowman’s capsule = glomerular filtrate.
5. Glomerular filtrate passes through nephron and useful substances absorbed along the way.
6. It flows through the collecting duct and leaves the kidney via the ureter.

Question 17

How do substances pass through the capillary endothelium?

Answer 17

Pores in the endothelium

Question 18

When does selective reabsorption take place?

Answer 18

As the glomerulus filtrate flows along the proximal convoluted tubule (PCT), through the loop of Henle, and along the distal convoluted tubule (DCT).

Question 19

Where do the useful substances that are reabsorbed from the kidneys go?

Answer 19

Useful substances leave the tubules of the nephrons and enter the capillary network that’s wrapped around them.

Question 20

Where does reabsorption take place?

Answer 20

The epithelium of the wall of the PCT.

Question 21

How is the PCT adapted for the process of reabsorption?

Answer 21

The epithelium of the wall of the PCT has microvilli to provide a large surface area

This aids reabsorption of useful materials from the glomerular filtrate (in the tubules) into the blood (in the capillaries).

Question 22

How are specific substances reabsorbed?

Answer 22

Useful solutes, like glucose, are reabsorbed along the PCT by A.T and F.D.

Water enters the blood by osmosis because the water potential of the blood is lower than that of the filtrate.

Water is reabsorbed from the PCT, loop of Henle, DCT and the collecting duct.

Question 23

What happens to the filtrate that isn’t reabsorbed?

Answer 23

The filtrate that remains is urine, and passes along the ureter to the bladder.

Question 24

What is urine usually madeup of?

Answer 24

Urine is usually made up of:

• Water and dissolved salts.
• Urea.
• Other substances such as hormones and excess vitamins.

Question 25

What doesn’tvurine usually contain?

Answer 25

• Proteins and blood cells -they’re too big to be filtered out of the blood.
• Glucose because it’s actively reabsorbed back into the blood.

Question 26

Describe how epithelial cells along the wall of the PCT use co-transport for reabsorption.