15.5- The Mammalian Kidney

Question 1

What are the three main parts of the kidney? (3 marks)

Answer 1

Cortex
Medulla
Pelvis

Question 2

How does blood get into the kidney? (1 mark)

Answer 2

Through the renal artery

Question 3

How does the blood pass out of the kidney? (1 mark)

Answer 3

Through the renal vein

Question 4

What does the pelvis do? (1 mark)

Answer 4

Collects urine before passing down the ureter.

Question 5

Describe the pathway of blood through the kidney and how this contributes to it’s function. (6 marks)

Answer 5

• Enters through renal artery.
• Passes through the capillaries in the cortex.
• Substances are filtered out of the blood into the tubules that surround it.
• Useful substances are reabsorbed back into the blood from the tubules into the medulla.
• The remaining, unwanted substances pass along the tubules, along the ureter to the bladder.
• The filtered blood passes out of the kidneys through the renal vein.

Question 6

What are kidneys made up of? (1 mark)

Answer 6

Nephrons

Question 7

Briefly describe what nephrons do. (2 marks)

Answer 7

Filter blood and balance water/mineral content of the blood.

Question 8

Is the Bowman’s capsule in the medulla or cortex of the kidney? (1 mark)

Answer 8

Cortex

Question 9

What does the Bowman’s capsule contain? and what is it? (2 marks)

Answer 9

Contains the glomerulus, which is a tangle of capillaries.

Question 10

Is the collecting duct in the medulla or cortex of the kidney? (1 mark)

Answer 10

medulla

Question 11

What is the function of the collecting duct? (1 mark)

Answer 11

Urine passes down the collecting duct through the medulla to the pelvis.

Question 12

Which parts of the nephrons are sensitive to ADH (the permeability of their membranes change)? (2 marks)

Answer 12

Distal convoluted tubule
Collecting duct

Question 13

Is the proximal convoluted tubule in the medulla or cortex? (1 mark)

Answer 13

Cortex

Question 14

What is the function of the proximal convoluted tubule? (1 mark)

Answer 14

It is where many substances are reabsorbed into the blood.

Question 15

Name four substances that are reabsorbed into the blood from the proximal convoluted tubule. (4 marks)

Answer 15

Glucose
Amino acids
Vitamins
Hormones

Question 16

Do the substances (that get reabsorbed into the blood stream) leave the proximal convoluted tubule by diffusion or active transport? (1 mark)

Answer 16

Active transport

Question 17

Is the distal convoluted tubule in the cortex or medulla of then kidney? (1 mark)

Answer 17

Cortex

Question 18

What is the function of the distal convoluted tubule? (4 marks)

Answer 18

It balances the water/salt content pf the blood.
If more ADH is released, the membrane becomes more permeable to water and it diffuses out via osmosis into the bloodstream.
If the body needs more salt, Na+ moves out of the tubule via active transport.

Question 19

What creates the glomerulus pressure? (2 marks)

Answer 19

The difference in width between the wide arteriole that leads into the glomerulus and the narrow efferent arteriole that leads out of the glomerulus.

Question 20

What does glomerulus pressure cause? (1 mark)

Answer 20

The blood to be forced out of the capillary walls.

Question 21

What 3 things does the blood pass through after entering the glomerulus, and what do these act as? (5 marks)

Answer 21

1. The capillary walls
2. The podocyte cells (in the Bowman’s capsule)
3. The basement membrane
   These act as sieves, they ensure red blood cells and proteins cannot get into the tubules.

Question 22

What is the name of the fluid that is produced from ultrafiltration? (1 mark)

Answer 22

Tissue fluid

Question 23

Is the loop of Henle in the medulla or cortex of the kidney? (1 mark)

Answer 23

Both- cortex and medulla

Question 24

What is the role of the descending loop of Henle? (2 marks)

Answer 24

As the fluid passes down the loop, water leaves into the tissue fluid in the medulla and then into the blood, via osmosis.

Question 25

How does the ascending loop of Henle alter the concentration and water potential in the medulla? (8 marks)

Answer 25

Only the first (bottom) part of the ascending loop of Henle is permeable to Na+ and Cl- ions, so they diffuse out of the tubule. This means the concentration of ions is high and water potential is low at the bottom.
The second part is not permeable to the ions, so they must be actively pumped out, as this requires energy, less of the ions move out of the tubule here.
This means there is a lower concentration of ions and higher water potential at the top of the ascending loop of Henle.

Question 26

How are the nephrons of an animal who lives in an environment with limited water action adapted, and why? (2 marks)

Answer 26

The loops of Henle are longer, so more water can move out of the nephron and into the bloodstream, making urine more concentrated and conserving water.