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A level Biology OCR A > 15.5 Structure & Function of the Mammalian Kidney > Flashcards

15.5 Structure & Function of the Mammalian Kidney Flashcards

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1
Q

What 2 homeostatic roles is the kidney responsible for?

A

EXCRETION (regulation of waste)

OSMOREGULATION (regulation of water)

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2
Q

Blood ⟶ kidneys using what vessel?

A

Renal artery

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3
Q

Blood from kidney ⟶ inferior vena cava using what vessel?

A

Renal vein

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4
Q

Urine from kidney ⟶ bladder using what vessel?

A

Ureter

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5
Q

What are the 3 main parts within the kidneys?

A

CORTEX

MEDULLA

PELVIS

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6
Q

What happens in the cortex of the kidney?

A

Area of dense capillary network

providing blood from renal artery

to nephrons

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7
Q

What is the function of the pelvis of the kidney?

A

Central chamber

where urine collects before entering ureter

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8
Q

What is a nephron?

A

TUBULES

making up the main FUNCTIONAL STRUCTURES

of the KIDNEY.

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9
Q

What is the Bowman’s capsule?

A

CUP-SHAPED structure

containing GLOMERULUS.

Site of ULTRAFILTRATION.

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10
Q

What is a glomerulus?

A

Entangled capillaries found in each Bowman’s capsule

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11
Q

What is the proximal convoluted tubule?

A

1st twisted section of nephron

after Bowman’s capsule

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12
Q

What occurs in the proximal convoluted tubule?

A

SELECTIVE REABSORPTION

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13
Q

What processes occur in the proximal convoluted tubule?

A
  • selective reabsorption
  • active transport (Na+ actively transported out of pct cell)
  • diffusion (Na+ diffusing into vasa recta, glucose diffusing into vasa recta)
  • facilitated diffusion (Na+ & Glucose using cotransport protein moving from filtrate into pct cell)
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14
Q

Outline the process of selective reabsorption in the proximal convoluted tubule:

A
  1. Na+ actively transported out of pct cell by sodium pump into tissue fluid
    - concentration of ions in pct cell ￬
  2. Na+ & glucose in filtrate move into pct cell by facilitated diffusion using cotransport protein
    - concentration of glucose in pct cell ￪
  3. Glucose diffuses from pct cell ⟶ vasa recta/surrounding capillaries
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15
Q

What are the features of the ascending and descending limb of the loop of henle?

A

DESCENDING: permeable to water molecules only

ASCENDING: permeable to ions only, Na+ Cl-

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16
Q

What is the role of the ascending limb?

A

to create a water potential gradient

in the tissue fluid

for water to move out of the descending limb by osmosis.

(Done by active transport of Na+ Cl- out, since permeable to ions.)

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17
Q

Outline the steps of osmoregulation which occur in the loop of henle:

A

DESCENDING LIMB: permeable to H2O ONLY

  1. H2O moves out of tubule ⟶ tissue fluid ⟶ vasa recta, by osmosis.
    - (due to water potential gradient created by ascending limb actively transporting ions out)
  2. Further down, less water present in tubule, ∴ filtrate increasingly concentrated.

ASCENDING LIMB: permeable to IONS ONLY

  1. actively transports ions out ⟶ medulla tissue fluid
    - creates low water potential in tissue fluid
  2. Further up, less ions present, ∴ filtrate decreasingly concentrated
18
Q

What is the name of the system in which the 2 limbs of the loop of Henle function?

A

Countercurrent multiplier system

19
Q

Why is the loop of Henle described as a “countercurrent multiplier” system?

A

COUNTERCURRENT - solutions in each limb travel in opposite directions.

MULTIPLIER - concentration of filtrate decreases while tissue fluid increases. Allows production of urine more concentrated than blood.

20
Q

At what point in the loop of henle is the filtrate most concentrated?

A

the bend.

(after the bend, ion concentration of filtrate decreases in ascending limb)

21
Q

Outline the general process which occurs in the distal convoluted tubule/collecting duct in response to ADH:

A

(Wall permeability varies with ADH concentration)

  • More ADH produced by posterior pituitary gland:
    • Tubule walls more permeable to water
    • More water reabsorbed
    • Urine becomes lower in volume + more concentrated
22
Q

In the loop of Henle, water is moved by osmosis as a result of…

A

water potential gradient being created

by the active transport of ions by the ascending limb

23
Q

What occurs in the Bowman’s Capsule?

A

Ultrafiltration

24
Q

What occurs in the proximal convoluted tubule?

A

selective reabsorption

25
Q

What process occurs in the loop of Henle/distal convoluted tubule/collecting duct?

A

osmoregulation

26
Q

What are the 2 functions of the nephron?

A

ULTRAFILTRATION

SELECTIVE REABSORPTION

27
Q

What is ULTRAFILTRATION?

A

process by which

blood plasma FILTERED through BOWMANS CAPSULE

under HIGH PRESSURE

28
Q

What is SELECTIVE REABSORPTION?

A

REABSORPTION of selected substances

those which are needed by the body

in KIDNEY tubules

29
Q

What 2 factors maintain a high pressure in the glomerulus during ultrafiltration?

A
  • Arterial blood is under high pressure
  • The lumen of the efferent arteriole is narrower than that of the afferent arteriole, causing buildup of pressure in glomerulus
30
Q

Outline the process of ultrafiltration in the Bowman’s Capsule:

A
  1. Blood enters Bowman’s capsule through AFFERENT arteriole & leaves via efferent.
    - afferent lumen > efferent lumen, so blood in glomerulus is under high pressure.
  2. HIGH PRESSURE in glomerulus >> ULTRAFILTRATION
    - Some blood solutes forced through FENESTRATIONS in:
    - Capillary walls
    - Basement membrane
    - Podocyte layer
    - Forms FILTRATE
31
Q

What is a podocyte?

A

CELLS which form a part of the wall of the Bowmans capsule.

Have PROCESSES called PEDICITES, which wrap around glomerular capillaries, only allowing filtering of small molecules.

32
Q

What are the layers through which ultrafiltration in the Bowman’s capsule occurs in?

A
  1. capillary
  2. basement membrane
  3. podocyte layer
33
Q

Which solutes are NOT filtered out of the blood during ultrafiltration?

A

large plasma proteins (albumin, fibrinogen, globulins)

red blood cells

34
Q

What does glomerular filtrate consist of?

A

urea

glucose

amino acids

hormones

nutrients

other small molecules

35
Q

Should glucose be found in urine?

A

no

ALL glucose reabsorbed + any excess is stored as glycogen in liver + muscle cells

36
Q

Which substance(s) is/are NOT selectively reabsorbed in the proximal convoluted tubule?

A

urea

37
Q

How are the epithelial cells of the proximal convoluted tubule specialised?

A
  • Contain many MITOCHONDRIA
    • ATP, for active transport of Na+
  • Has MICROVILLI on apical side only
    • increases surface area for reabsorption, which occurs in 1 direction only
38
Q

What is the function of the renal artery?

A

supply oxygenated blood to the kidney

39
Q

What is the function of the renal vein?

A

carry deoxygenated blood from the kidneys to inferior vena cava

40
Q

What is the function of the ureter?

A

carry urine from kidneys to bladder

41
Q

In which section of the kidney does ultrafiltration & selective reabsorption occur?

A

renal cortex

A level Biology OCR A (103 decks)

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