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Anatomy II > M24: Tubular Reabsorption & Regulation > Flashcards

M24: Tubular Reabsorption & Regulation Flashcards

1
Q

At what point does glomerular filtrate become tubular fluid?

A

once it enters the proximal convoluted fluid

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2
Q

Where does most reabsorption occur?

A

proximal convoluted tubule

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3
Q

tubular secretion

A

transfer of materials from blood into glomerular filtrate
- controls blood pH (H+ ions)
- eliminate substances (ammonia, creatinine, K+, some drugs)

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4
Q

transport mechanisms for tubular reabsoprtion

A

PRIMARY ACTIVE TRANSPORT
- ATP dependent

SECONDARY ACTIVE TRSNAPORT
- driven by ions electrochemical gradient
- SYMPORTERS move substances in same direction (e.g. Na+-glucose symporters move Na+ AND glucose into cell)
- ANTIPORTERS move substances in opposite directions

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5
Q

paracellular reabsorption

A

passive transport mechanism between cells

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6
Q

obligatory water reabsorption

A
  • process where water follows solutes that are reabsorbed
  • 90% of water reabsorbed this way
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7
Q

Water reabsorption processes

A

OBLIGATORY WATER REABSORPTION
- 90% reabsorbed this way
- water follows solutes that are reabsorbed
- facilitated by AQUAPORIN-1: protein water channel found in apical and basolateral membranes of proximal convoluted tubule and descending limb

FACULTATIVE WATER REABSORPTION
- 10% reabsorbed this way
- regulated by anti-diruetic hormone (ADH)

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8
Q

Reabsorption in the first half of proximal convoluted tubule

A

Na+ Symporters
- help reabsorb materials from the tubular fluid
- includes: glucose, amino acids, lactic acid, water soluble vitamins
- all completely reabsorbed in first half of PCT

Na+ Antiporters
- help reabsorb Na+
- also secrete H+ ions which aides bicarbonate reabsorption

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9
Q

Reabsorption in the second half of proximal convoluted tubule

A

passive reabsorption
- several different ions: Cl-, K+, Ca2+, Mg2+, urea

water taken up via osmosis

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10
Q

What does PCT stand for in the urinary system?

A

Proximal convoluted tubule

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11
Q

cell type in descending nephron loop

A

simple squamous

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12
Q

reabsorption in nephron loop

A

Everything is reabsorbed into the vasa recta

Descending limb
- 15% of water reabsorbed
- small diffusion of solutes into

Ascending limb
- water not reabsorbed, but solutes are
- thin region - passive ion diffusion
- thick region - Na+, K+, Cl- active transport out

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13
Q

why is reabsorption of water high in descending nephron loop?

A
  • solute concentration in interstitial fluid gets higher as loop descends
  • therefore, more water is reabsorbed as a result of osmosis
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14
Q

what end of nephron loops are solutes reabsorbed?

A

ascending
via active and passive transport

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15
Q

How much water and solutes are reabsorbed in proximal convoluted tubute?

A

65% of water
ALL glucose and amino acids

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16
Q

reabsorption in the early distal convoluted tubule

A
  • reabsorption of Na+ and Cl- continues via symporters
  • 10-15% water reabsorbed
  • PARATHYROID HORMONE (PTH) acts on cells to control Ca2+ reabsorption here
17
Q

reabsorption and secretion in late distal convoluted tubule and collecting duct

A
  • By the end of DCT, 95% of water and solutes reabsorbed
  • Cells in collecting duct make final concentration adjustments for urine production

PRINCIPLE CELLS
- reabsorb Na+ and secrete K+
- controlled by ADH and Aldosterone

INTERCALATED CELLS
- reabsorb K+ and bicarbonate ions, secrete H+

18
Q

name cells in collecting duct that make final adjustments to urine concentration

A

Principle cells
Intercalated cells

19
Q

name 5 hormones that regulate Na+, Cl-, Ca2+ and water reabsorption and K+ secretion in renal tubules

A
  1. Angiotensin II
  2. Aldosterone
  3. Antidiuretic hormone (ADH)
  4. Atrial natriuretic hormone (ADH)
  5. Parathyroid hormone (PTH)
20
Q

Renin-Angiotensin system

A
  • Activated if blood volume and pressure decrease
  • Produces Angiotensin II

Process
a) less stretch in afferent arterioles (increases SNS response)
b) juxtaglomerular cells secrete RENIN into blood
c) renin converts ANGIOTENSINOGEN (from liver) into ANGIOTENSION I (still not the active hormone)
d) ANGIOTENSIN CONVERTING ENZYME (ACE) (released from lungs) converts angiotensin I into ANGIOTENSIN II

21
Q

Role of Angiotensin III

A
  • ↓ GFR via vasoconstriction of afferent arterioles
  • ↑ Na+, Cl- and water reabsorption in PCT by stimulating Na+/H+ antiporters
  • causes adrenal cortex to secrete ALDOSTERONE - causes principle cells in collecting ducts to reabsorb more Na+, Cl- and water and secrete K+
22
Q

Role of Antidiuretic hormone (ADH)

A
  • Increases water permeability of principle cells -> increased facultative water reabsorption
  • How? On demand water protein channels! Signals insertion of AQUAPORIN-2 channels into membrane (bring up to apical surface of principal cells)

Keys:
increased facultative waterr reabsorption in principle cells via aquaporin-2

23
Q

where is antidiuretic hormone (AHD) released

A

Pituitary gland

Receptors: osmoreceptors in to hypothalamus
Control centre: hypothalamus and posterior pituitary
Effectos: principle cells

24
Q

alcohol inhibits the release of which hormone? What are the effects?

A

Antidiruetic hormone (ADH)
- increases urine production because water is not reabsorbed int blood supply

25
Q

role of atrial natriuretic peptide

A
  • helps regulate blood pressure: decreases water reabsorption and suppresses secretion of water reabsorption increasing hormones
  • released if high blood pressure/volume detected
  • inhibits reabsorption of Na+ and water in the proximal convoluted tubule and collecting ducts
  • suppresses secretion of aldosterone and antidiuretic hormone: therefore ↑ Na+ excretion in urine, ↓ blood volume
26
Q

role of parathyroid hormone (PTH)

A
  • regulates Ca2+ ion concentrations
  • released from parathyroid glands in response to low blood Ca2+
  • stimulates cells in early distal convoluted tubule to increases Ca2+ reabsorption
  • inhibits phosphate reabsorption in proximal convoluted tubule
27
Q

paracellular reabsorption

A

movement of solutes between the cells of the renal tubule

28
Q

what ion are solutes co-transported with in the kidney nephron cells?

A

Na+ ions

29
Q
A

Anatomy II (34 decks)

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