15.5 Structure & Function of the Mammalian Kidney Flashcards

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
What process occurs in the loop of Henle/distal convoluted tubule/collecting duct?
osmoregulation
26
What are the 2 functions of the nephron?
ULTRAFILTRATION SELECTIVE REABSORPTION
27
What is ULTRAFILTRATION?
process by which blood plasma FILTERED through BOWMANS CAPSULE under HIGH PRESSURE
28
What is SELECTIVE REABSORPTION?
REABSORPTION of selected substances those which are needed by the body in KIDNEY tubules
29
What 2 factors maintain a high pressure in the glomerulus during ultrafiltration?
* 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
Outline the process of ultrafiltration in the Bowman's Capsule:
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
What is a podocyte?
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
What are the layers through which ultrafiltration in the Bowman's capsule occurs in?
1. capillary 2. basement membrane 3. podocyte layer
33
Which solutes are NOT filtered out of the blood during ultrafiltration?
large plasma proteins (albumin, fibrinogen, globulins) red blood cells
34
What does glomerular filtrate consist of?
urea glucose amino acids hormones nutrients other small molecules
35
Should glucose be found in urine?
no ALL glucose reabsorbed + any excess is stored as glycogen in liver + muscle cells
36
Which substance(s) is/are NOT selectively reabsorbed in the proximal convoluted tubule?
urea
37
How are the epithelial cells of the proximal convoluted tubule specialised?
* 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
What is the function of the renal artery?
supply oxygenated blood to the kidney
39
What is the function of the renal vein?
carry deoxygenated blood from the kidneys to inferior vena cava
40
What is the function of the ureter?
carry urine from kidneys to bladder
41
In which section of the kidney does ultrafiltration & selective reabsorption occur?
renal cortex