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A-Level Biology > 15.5 The Functions of the Nephrons > Flashcards

15.5 The Functions of the Nephrons Flashcards

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1
Q

What is ultrafiltration?

A

First stage in removal of nitrogenous waste and osmoregulation of blood

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2
Q

Can you explain the steps involved in blood entering the glomerulus?

A
  1. Renal artery supplies blood to glomerulus via wide afferent arteriole
  2. Blood leaves through narrower efferent arteriole
  3. Causes pressure in capillaries of glomerulus
  4. Blood forced out of capillary wall
  5. Fluid passes through basement membrane
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3
Q

What does ‘afferent’ mean?

A

Incoming

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4
Q

What does ‘efferent’ mean?

A

Outward

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5
Q

What is the basement membrane?

A

Made up of network of collagen fibres and other proteins that make up a second ‘sieve’

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6
Q

What are podocytes?

A

Special cells in wall of Bowman’s capsule that act as additional filter

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7
Q

What are pedicels?

A

Extensions of podocytes that wrap around capillaries to form slits

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8
Q

What is the glomerular filtration rate?

A

Volume of blood that is filtered through kidneys in a given time

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9
Q

What is urea?

A

Waste product of protein breakdown

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10
Q

What does hypotonic mean?

A

Less concentrated than

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11
Q

What is the concentration of the ultrafiltrate compared to the blood plasma?

A

Ultrafiltrate is hypotonic than blood plasma

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12
Q

What is the main function of the nephron after the Bowman’s capsule?

A

To return most filtered substances back to blood

E.g. water, glucose, salt

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13
Q

What happens in the proximal convoluted tubule?

A

All glucose, amino acids, vitamins and hormones are moved from filtrate back into blood by active transport

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14
Q

What happens to the ions of the sodium chloride salt?

A

The sodium ions are moved by active transport

Chloride ions and water follow passively down concentration gradients (passive transport)

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15
Q

What are the adaptions of the cells lining the proximal convoluted tubule?

A

Covered with microvilli to greatly increase surface area over which substances can be reabsorbed

Many mitochondria to provide ATP needed in active transport systems

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16
Q

What does ‘isotonic’ mean?

A

At same concentration

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17
Q

What is the loop of Henle?

A

Section of kidney tubule that allows mammals to produce urine more concentrated than their own blood

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18
Q

What does a countercurrent multiplier do?

A

Uses energy to produce concentration gradients resulting in the movement of substances from one area to another
E.g. water

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19
Q

What does the loop of Henle act as?

A

A countercurrent multiplier

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20
Q

Where is the diffusion gradient produced by the loop of Henle acting as a countercurrent multiplier?

A

Diffusion gradient in medulla

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21
Q

What is the descending limb of the proximal convoluted tubule?

A

Region where water moves out of filtrate down a concentration gradient

22
Q

Can you describe the permeability of the descending limb?

A

Upper part is impermeable to water

Lower part of descending limb is permeable to water and runs down into medulla

23
Q

Can you describe the change in concentration of the sodium and chloride ions in the tissue fluid of the medulla?

A

Concentration of sodium and chloride ions increases as you move from cortex to the pyramids

24
Q

Can you describe the concentration of the blood entering the descending limb of the loop of Henle?

A

Isotonic with blood

25
Q

What are the surrounding capillaries of the descending limb called?

A

Vasa recta

26
Q

What is the fluid that reaches the hairpin bend like?

A

Very concentrated and hypertonic to the blood in the capillaries

27
Q

What passes through the basement membrane and what cannot?

A

Most plasma contents can pass through

Blood cells and many proteins retained in capillary because of their size

28
Q

What do pedicels help do?

A

Ensures any cells, platelets or large plasma proteins that managed to pass epithelial cells AND basement membrane do not get through into the TUBULE

29
Q

What percentage of water and solutes are removed from the plasma as it passes the glomerulus?

A

20% of water and solutes

30
Q

What does ultrafiltration also remove apart from urea?

A

Water, gluocose, salts and other substances needed in plasma

31
Q

What percentage of the sodium chloride and water is reabsorbed in the proximal convoluted tubule?

A

85% of sodium chloride and water

32
Q

How are sodium and chloride ions and water moved in the proximal convoluted tubule?

A

Sodium ions moved by active transport

Chloride ions and water follow passively down concentration gradients

33
Q

What happens to the substances that have been removed from the nephron?

A

Diffuse down steep concentration gradients into capillary network surrounding tubules

34
Q

How are the steep concentration gradients of the capillary network surrounding the tubules maintained?

A

Maintained by constant flow of blood through capillaries

35
Q

What is the concentration of the filtrate reaching the end of the distal convoluted tubule compared to the tissue fluid surrounding the tubule and the blood?

A

Filtrate is ISOTONIC with tissue fluid surrounding tubule and ISOTONIC with the blood

36
Q

Can you describe the movement of the filtrate entering the descending limb?

A

Filtrate enters descending limb

Water passes out of loop into tissue fluid by osmosis as it travels down limb

Moves down concentration gradient into blood of vasa recta

36
Q

Is the descending limb permeable to sodium and chloride ions?

A

No, so no active transport takes place

37
Q

How permeable is the FIRST section of the ascending limb?

A

Very permeable to SODIUM and CHLORIDE ions

38
Q

How do the sodium and chloride ions move out of the first part of the ascending limb?

A

Diffuse down concentration gradient

39
Q

What happens in the second section of the ascending limb?

A

Sodium and chloride ions are actively pumped out AGAINST a concentration gradient into medulla tissue fluid

40
Q

Can you describe the involvements of water in the SECOND part of the ascending limb?

A

Ascending limb is IMPERMEABLE to water

So water cannot follow sodium and chloride ions down concentration gradient

Means fluid left in ascending limb becomes increasingly dilute

Tissue fluid gains high concentration of ions that are essential to produce urine MORE concentrated than blood (COUNTERCURRENT MULTIPLIER SYSTEM)

Dilute fluid HYPOTONIC to blood and enters distal convoluted tubule and collecting duct

41
Q

What part of the loop of Henle is impermeable to water?

A

Ascending limb

Water cannot follow sodium and chloride ions down concentration gradient

42
Q

Where does balancing the water needs of the body take place?

A

Distal convoluted tubule and collecting duct

43
Q

Where does ADH have an effect?

A

Collecting duct and distal convoluted tubule

44
Q

What is an adaptation of the cells in the distal convoluted tubule?

A

Many mitochondria to carry out active transport

45
Q

What happens if the body lacks salt?

A

Sodium ions are actively pumped out of DISTAL convoluted tubule with chloride ions following down an electrochemical gradient

46
Q

What happens if the body needs water?

A

ADH

Water LEAVES distal convoluted tubule

Urine becomes more concentrated

47
Q

What is another role of the distal convoluted tubule apart from water balance?

A

Balancing blood pH

48
Q

Where is the collecting duct located?

A

Passes down concentrated tissue fluid of renal medulla

49
Q

What is the purpose of the collecting duct?

A

Area where volume and concentration of urine is determined

50
Q

How does water move out of the collecting duct?

A

Diffusion down concentration gradient as it passes through renal medulla

Urine becomes more concentrated

51
Q

What happens to the sodium ions regarding the collecting duct?

A

Level of sodium ions in SURROUNDING FLUID increases through medulla, from cortex to pelvis

Means water can be removed ALL ALONG collecting duct’s length

Hypertonic urine produced to save water when needed

A-Level Biology (35 decks)

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