11.3 The Kidney Flashcards

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1
Q

Define Excretion

A

Excretion is the removal from the body of the waste products of metabolic processes

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2
Q

Outline the function of the Afferent Arteriole

A

Brings blood to the nephron to be filtered

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3
Q

Outline the function of the Efferent Arteriole

A

Removes filtered blood from nephron

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4
Q

Outline the function of the Glomerulus

A

A group of branching capillaries where filtration occurs

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5
Q

Outline the function of the Bowman’s Capsule

A

First part of the nephron where filtration occurs and the filtrate is collected

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6
Q

Outline the function of the Proximal Convoluted Tubule

A

Where selective reabsorption occurs

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7
Q

Outline the function of the Loop of Henle

A

Important for establishing a salt gradient in the medulla

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8
Q

Outline the function of the Distal Convoluted Tubule

A

Final site of selective reabsorption

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9
Q

Outline the function of the Collecting Duct

A

Leftover filtrate goes to the ureter; where osmoregulation occurs

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10
Q

Outline the function of the Vasa Recta

A

Blood network which reabsorbs components from the filtrate

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11
Q

Explain the process of ultrafiltration

A
  • Ultrafiltration occurs in the Bowman’s capsule in the cortex of the kidney
    • Blood enters the afferent arteriole and leaves the efferent arteriole
    • The afferent arteriole is larger than the efferent arteriole, causing high pressure in the glomerulus
    • Water, glucose, amino acids and solutes (WAGS) are forced out of blood through the fenestrated capillaries and the basement membrane
    • Podocyte cells act as a filter
    • Plasma proteins, platelets and red/white blood cells are large, so remain in blood
    • Glomerular filtrate is carried through the nephron, where selective reabsorption takes place in the proximal convoluted tubule
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12
Q

Define osmoregulation

A

The control of the water balance of the blood, tissue or cytoplasm of a living organism

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13
Q

Explain selective reabsorbtion in the kidney

A
  • Water, salts, amino acids and glucose in glomerular filtrate need to be reabsorbed
    • Selective reabsorption occurs in proximal convoluted tubule (PCT) of nephron
    • Convolution and microvilli increase surface area for reabsorption
    • Large numbers mitochondria present in PCT cells generate ATP
    • Active transport pumps Na+ ions from PCT cells into capillaries, generating concentration gradient between PCT cells and filtrate in lumen
    • Na+ ions move from lumen to PCT cells by facilitated diffusion
    • Glucose and amino acids follow by cotransport
    • Solute concentration increases in PCT cells, leading to osmosis of water from lumen into PCT cells
    • Facilitated diffusion carries glucose and amino acids into blood
    • Flow of blood maintains concentration gradient
    • ~80% of water is reabsorbed by osmosis
    • 100% glucose and amino acids recovered
    • Active transport used for the transport of glucose and amino acids, so there are large number of mitochondria to provide the required ATP
      • Some urea also diffuses back into the blood
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14
Q

State the two locations in the kidney where osmoregulation occurs

A

The Loop of Henle and the Collecting Duct

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15
Q

Explain the role of the Loop of Henle in maintaining the water balance of the blood

A
  • Descending limb is permeable to water but not to Na+
    • Ascending limb is permeable to NA+, but not to water
    • Na+ is pumped out of the ascending limb into the medulla, generating osmotic potential between the nephron and medulla
    • Some water leaves descending loop by osmosis
    • Output is reduced volume, reduced salt concentration
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16
Q

Explain the role of the Collecting Duct in maintaining the water balance of the blood

A
  • Filtrate enters collecting duct from distal convoluted tubule
    • Countercurrent flow of blood in capillaries and filtrate in duct maintains concentration gradient, allowing for osmosis of water into blood
    • Dehydration (detected by hypothalamus) leads to an increased level of ADH (released by pituitary)
    • ADH opens aquaporins (water channels) in walls of duct
    • Increased transfer of water into blood, therefore hypertonic urine
    • Excess water in blood leads to break down of aquaporins and hypotonic urine
17
Q

Outline the function of the kidneys

A

The two kidneys act as filters for the blood, removing harmful toxins