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Endeavour - Human Bio 2 > Session 18 - Urinary system - Tubular Reabsorption and Secretion > Flashcards

Session 18 - Urinary system - Tubular Reabsorption and Secretion Flashcards

1
Q

purpose of tubular reabsorption

A

return filtered water and solutes to blood stream

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2
Q

how is reabsorption achieved

A

Proximal convoluted tubule have microvilli - this is how most is reabsorbed.

  • Solutes are reabsorbed by both active and passive transport
  • Water follows by osmosis
  • Small proteins by pinocytosis
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3
Q

tubular secretion definition

A

transfer of materials from blood and tubule cells into glomerular filtrate

  • controls blood pH
  • elimate certain substances
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4
Q
A

A - renal corpuscle

B - renal tubule and collecting duct

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5
Q

Two routes of reabsorption routes

A
  • paracellular reabsorption
    • movement between adjacent tubule cells
    • via osmosis
  • transcellular reabsorption
    • movement through an individual tubule cells
    • via active transport
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6
Q

transport mechanisms

A
  • two main mechanisms
    • active transport
      • primary and secondary
    • passive transport
      • osmosis
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7
Q

primary sctive transport

A

ATP used to pump across membrane

  • sodium potassium ATPase pumps in basolateral membrane
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8
Q

secondary active transport

A
  • ion electrochemical gradient drive substances across the membrane
    • symporters: membrane proteins moving two or more substances in the same direction across a membrane
    • antiporters: membrane proteins moving two or more substances in opposite directions across membrane
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9
Q

passive transport

A
  • osmosis
    • obligatory water reabsorption
      • ​water is obliged to follow the solutes which are being reabsorbed
      • occurs in proximal convoluted tubule and descending limb of the loop of Henle
    • facultative water reabsorption
      • ​adapted to specific needs
      • occurs in the collecting duct
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10
Q

facultative water reabosption controlled by

A
  • antidiuretic hormone
    • if more water is needed to be reabsorped by the body, ADH is released for insertion of aquaporins in the collecting duct
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11
Q

largest amount of solutes and water are reabsorped where

A

reabsorption in proximal convulted tubule

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12
Q

secretion from the proximal convoluted tubule

A
  • deamination of the glutamine by PCT cells
  • ammonia and urea in blood
    • secreted into tubules
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13
Q

how and where is sodium reabsorbed

A

Achieved by several mechanisms in the proximal convoluted tubule:

  1. by sodium glucose symporters
  2. sodium/hydrogen antiporters
    • sodium reabsorp into blood and H secretion into tubular fluid
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14
Q

bicarbonate (HCO3-) reabsorption

A
  • facilitated diffusion
    • filtered through simulataneously with hydrogen
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15
Q

how are sodium, potassium, calcium, magnesium and urea reabsorped

A

passive diffusion into peritubular capillaries via both paracellular and transcellular routes

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16
Q

water reabsorption in proximal convoluted tubule

A
  • osmosis followed by solute reabsorption
    • via both paracellular and transcellular routes
    • aquaporin-1
17
Q

the loop of henle reabsorps a large proportion

A

of chloride, sodium, potassium and water

18
Q

loop of henle controls..

A

regulation of volume and osmolarity of body fluids

19
Q

sodium , chloride and postassium reabsorption occurs where in the loop of henle

A
  • apical membrane by symporters, leakage channels or paracellular route
    • blue square in image
  • basolateral membrane by active sodium transport and leakage channels for chloride
    • red square in image
20
Q

what is

  1. I,
  2. II,
  3. VII and
  4. VIII
A
  1. afferent arteriole
  2. efferent arteriole
  3. glomerulus
  4. bowmans capsule

Glomerulus and bowmans capsule where filtration occurs

21
Q

label

  1. III
  2. VI
  3. V
  4. IV
A
  1. proximal convoluted tubule
  2. descending loop of henle
  3. ascending loop of henle
  4. distal convoluted tubule
22
Q

What two regions can the descending and ascending loop of henle be divided in to

A
  • thick descending and thin descending
    • thin descending freely permeable to water
  • thick ascending and thin ascending
    • ascending permeable to sodium chloride
23
Q

water reabsorption in loop of henle

A
  • descending limb = 15%
  • ascending limb = little/no water reabsorbed
24
Q

reabsorption in early distal convoluted tubule

A
  • reabsorp of calcium under control of parathyroid hormone (PTH)
  • reabsorp of very little/no water
25
Q

late distal convoluted tubule and collecting duct reabsorp/secretions

A
  • water and solute reabsorp depend on bodys needs
    • eg ADH
26
Q

What cells compose the distal convoluted tubule DCT and collecting duct

A
  • principal cells
    • sodium reabsorption
      • sodium leakage channels or sodium potassium pump depending on side of cell
    • secretion of potassium via leakage channels
      • major source of potassium in urine
  • intercalated cells
    • Bicarbonate reabsorption which regulates body fluid pH
    • H secretion (H+ATPase pump) which can make urine more acidic than blood
27
Q

how is urine buffered

A
  • hydrogen phosphate and ammonia
  • this allows the body to excrete more hydrogen through the urine
28
Q

what 5 hormones regulate tubular reabsorption and secretion

A
  • angtiotensin 2
  • aldosterone
  • ADH (antidiuretic hormone)
  • atrial natriuetic peptide
  • parathyroid hormone
29
Q

angiotensin 2

A
  • increases reabsorption of sodium and water
    • -> increses blood volume and BP
  • Works on PCT (proximal convoluted tubule)
30
Q

aldosterone

A
  • increases secretion of potassium
  • increses reabsorp of sodium and chloride
    • this increases water reabsorp -> increasing blood volume and pressure
  • Acts on DCT and collecting duct
31
Q

atrial natriuretic peptide

A
  • incresaes excretion of sodium in urine
    • increases fluid loss and therefore urine output
    • lowers blood volume and BP
32
Q

parathyroid hormone

A
  • increases calcium reabsorp
33
Q

antidiuretic hormone (ADH)/ vasopressin

A
  • increases facultative reabsorption of water, decreasing osmolarity of body fluids
  • works on collecting duct
34
Q

how does ADH act and how is it regulated

A
  • ADH secretion leads to aquaporin-2 channels into the membrane allowing water molecules to move more rapidly
  • increased osmolarity of plasma = ADH secretion
    • principal cells more permeable to water increasing water reabsorption
35
Q

tubular reabsorption brings how much renal filtrate back into use

A

99%

36
Q

renin-angiotensin aldosterone system (RAS)

A
  • renin from kidney
    • converts angiotensinogen to angiotensin 1
  • ACE is released from lungs which converts angiotensin 1 to angiotensin 2
    • angiotensin 2 stimulates release of aldosterone (also causes vasoconstriction)
  • = reabsorption of water and salt
37
Q
A

Endeavour - Human Bio 2 (20 decks)

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