The Kidneys

Question 1

Definition of osmoregulation:

Answer 1

The homeostatic control of the water potential of the blood

Question 2

Which blood vessel supplies the kidneys?

Answer 2

Renal artery

Question 3

3 ways salt is lost from the body:

Answer 3

1. Urine
2. Sweat
3. Faeces

Question 4

3 ways water is lost from the body:

Answer 4

1. Urine
2. Sweat
3. Exhaled air

Question 5

What are podocytes?

Answer 5

Specialised cells that make up the inner layer of the Bowman’s capsule

Question 6

What cells line the proximal convoluted tubule?

Answer 6

Epithelial cells

Question 7

What is the cortex?

Answer 7

The outer region of the kidney made up of renal (Bowman’s) capsules, convoluted tubules and blood vessels

Question 8

What is the medulla?

Answer 8

The inner region of the kidney made up of loops of Henle, collecting ducts and blood vessels

Question 9

What is the renal pelvis?

Answer 9

A funnel-shaped cavity that collects urine into the ureter

Question 10

What is the ureter?

Answer 10

A tube that carries urine to the bladder

Question 11

What is the basic functional unit of the kidney?

Answer 11

The nephron

Question 12

How does the kidney maintain osmoregulation?

Answer 12

1. Ultrafiltration
2. Reabsorption of glucose
3. Maintenance of sodium ion concentration
4. Reabsorption of water

Question 13

What cells line the glomerular capillaries?

Answer 13

Endothelial cells

Question 14

How is the filtrate formed?

Answer 14

The diameter of the afferent arteriole is larger than the efferent arteriole, increasing the hydrostatic pressure within the glomerulus, forcing water, glucose and other minerals out of the capillary

Question 15

What resists the movement of filtrate out of the glomerulus?

Answer 15

1. Capillary endothelial cells
2. Hydrostatic pressure of the fluid in the Bowman’s capsule
3. Low water potential of the blood in the glomerulus

Question 16

What adaptations does the proximal convoluted tubule have for reabsorbing substances?

Answer 16

1. Microvilli to increase surface area
2. Infoldings at bases to increase surface area
3. Mitochondria to provide ATP for active transport

Question 17

What is the concentration of urine directly linked to?

Answer 17

The length of the loop of Henle

Question 18

What are the two regions of the loop of Henle?

Answer 18

1. Descending limb

2. Ascending limb

Question 19

What is the structure of the descending limb like?

Answer 19

1. Narrow
2. Thin walls
3. Highly permeable to water

Question 20

What is the structure of the ascending limb like?

Answer 20

1. Wider
2. Thick walls
3. Impermeable to water

Question 21

What acts as a counter-current multiplier?

Answer 21

The loop of Henle

Question 22

What is actively transported out of the ascending limb and why?

Answer 22

Sodium ions to create a low water potential in the medulla, between the two limbs

Question 23

What happens to water in the ascending limb and why?

Answer 23

Very little water escapes as the thick walls are almost impermeable to water

Question 24

What happens to water in the descending limb and why?

Answer 24

It passes out of the filtrate by osmosis into the interstitial space as the walls are very permeable to water. It then enters the blood capillaries and carried away

Question 25

Which part of the loop of Henle will have the lowest water potential and why?

Answer 25

The tip of the hairpin as the filtrate progressively loses more water as it moves down the descending limb- this lowers the water potential

Question 26

What happens at the base of the ascending limb?

Answer 26

Sodium ions diffuse out of the filtrate

Question 27

Why are sodium ions actively transported out of the ascending limb?

Answer 27

To increase the water potential of the filtrate in the ascending limb as it goes higher up

Question 28

What are aquaporins?

Answer 28

Channel proteins that are specific to water that increase the membrane permeability to water.

Question 29

What alters the number of aquaporins?

Answer 29

Antidiuretic hormone (ADH)

Question 30

What adaptations does the distal convoluted tubule have to reabsorb substances?

Answer 30

1. Microvilli to increase SA | 2. Many mitochondria to produce ATP for reabsorption

Question 31

What are the main roles of the distal convoluted tubule?

Answer 31

1. Make final adjustments to water and salts reabsorbed | 2. Control pH of the blood by selective reabsorption of ions

Question 32

Which structure of the nephron reabsorbs the most water?

Answer 32

Proximal convoluted tubule

Question 33

Why is a longer loop of Henle desirable for animals living in the desert?

Answer 33

Longer loop of Henle means longer countercurrent multiplier so more reabsorption of water by the collecting duct

Question 34

What part of the nephron completely reabsorbs glucose?

Answer 34

Proximal convoluted tubule

Question 35

What part of the nephron makes final adjustments to the water and salts that are reabsorbed?

Answer 35

Distal convoluted tubule

Question 36

Where are osmoreceptors found?

Answer 36

In the hypothalamus

Question 37

How do osmoreceptors detect a fall in water potential?

Answer 37

Osmoreceptor cells shrink causing the hypothalamus to produce ADH

Question 38

Where is ADH secreted from?

Answer 38

Posterior pituitary gland

Question 39

What does ADH do?

Answer 39

Travels in the bloodstream to the kidneys, where it increases the permeability of the cell-surface membrane of the distal convoluted tubule and collecting duct to water

Question 40

When ADH binds to protein receptors on cells, what happens?

Answer 40

Activates phosphorylase that causes vesicles within the cell to fuse with the cell-surface membrane

Question 41

What do the vesicles activated by phosphorylase contain?

Answer 41

Aquaporins that are water channel proteins and therefore increase the uptake of water

Question 42

What happens when there is a rise in water potential?

Answer 42

1. Osmoreceptors detect a rise and increase frequency of nerve impulses to pituitary gland to reduce ADH secretion 2. Less ADH acting on the kidneys