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Case 10: Urinary System > Physiology: Urinary System > Flashcards

Physiology: Urinary System Flashcards

1
Q

What mechanism is responsible for the concentration gradient of the medulla of the kidney

A

Countercurrent multiplication

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2
Q

What is the two steps of the countercurrent multiplication

A
  1. Single effect
  2. Flow of fluid
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3
Q

How does the single effect of the countercurrent multiplication work

A

The ascending limb is impermeable to water
Na/K/2Cl transporter on the apical side of the ascending limb allowing ions to enter tubule cells
Na/K ATPase on basolateral surface allow for Na into interstitium
K & Cl enters interstitium
Osmosis cause ions in interstitium to diffuse into descending limb & fluid concentration increase

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4
Q

How does the flow of fluid step in the countercurrent multiplication work

A

Uses new fluids to distribute ions as it pushes the fluid around the loop allowing concentrated fluid moving to ascending limb
Single effect recur & fluid becomes more concentrated at the bottom of the ascending limb & step repeat until concentration gradient of 1200mOsm/L in inner medulla & 300mOsm/l at outer cortex

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5
Q

What is the important process of countercurrent exchange

A

Establish corticopapillary gradient

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6
Q

To what is the peritubular capillaries permeable to & where are they located

A

Permeable to water & solutes
Down ascending & descending limb

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7
Q

How does peritubular capillaries have a effect on water movement regarding ascending & descending limb

A

Descending limb: water is secreted & solutes reabsorbed
Ascending limb: water is reabsorbed & solutes secreted

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8
Q

What is the glomerular filtrate

A

Fluid that’s passes through glomerular filtrations barriers as it is size dependent filtration
Blood - RBC & plasma proteins

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9
Q

What is the effect of Starling forces on the glomerular filtration

A

Forces determine the movement of fluid through capillary wall

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10
Q

Where in the glomerulus does most of the filtration occur & why

A

At the beginning near the afferent arteriole
Oncotic pressure is the lowest

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11
Q

What is the 3 Starling forces that play a role in glomerular filtration barrier

A
  1. Hydrostatic P of blood in capillary
  2. Hydrostatic P of filtrate in Bowman’s capsule
  3. Oncotic pressure of proteins in capillary
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12
Q

How does the net filtration pressure change as moving along glomerular capillary

A

NFP decrease as fluid is removed & proteins remaining increase & eventually reaches equilibrium & no fluid is filtered

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13
Q

What is secreted by the juxtaglomerular apparatus

A

Renin

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14
Q

What is the 3 layers of glomerular filtration barrier

A
  1. Endothelium: capillary endothelium cells w/ fenestrations & allow for passage of solutes & proteins but blocks RBC
  2. Basement membrane: gel like layer w/ tiny pores & - membrane charge therefor blocks plasma protein passage
  3. Epithelium: podocytes which wraps around the basement membrane & block passage of proteins
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15
Q

Define glomerular filtration rate

A

Filtrate volume produced by all of the body’s glomeruli in one minute

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16
Q

What is the equation for glomerular filtration rate

A

GFR = NFP x Kf
Kf: capillary fluid permeability

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17
Q

What gives Kf a higher value

A

Fenestrations & large surface area

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18
Q

What 5 ions are reabsorbed back into the bloodstream at the PCT

A

Na, K, Ca, Cl, & Mg

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19
Q

Explain the movement of solutes in the PCT (3 transporters, para- & trans cellular & diffusion)

A

Na-glucose transporter into brush border cell Na down [ ] gradient while glucose against [ ] gradient
Na/K ATPase moves 3 Na into interstitium & 2 K into brush border to maintain low [ ] in cell
Na/H pumps Na into lumen & H into cell & bicarbonate get reabsorbed & converted into water & carbon dioxide & gets absorbed into blood
Leaky tight junctions increase permeability of Na paracellularly
Urea & water diffuse trans cellular
Glutamine breakdown inside cell into NH4+ (lumen) & bicarbonate (interstitium)
Organic acids & medication diffuse directly from capillaries into lumen

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20
Q

Why is there leaky tight junctions between cells in PCT

A

Due to less claudin proteins

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21
Q

What is the main function of Loop of Henle

A

To establish osmotic gradient & allow for varying urine

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22
Q

What is the peritubular capillaries that surrounds the Loop of Henle

A

Vasa recta

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23
Q

What is the main movement in the descending limb of Loop of Henle & what is the osmolarity effect

A

Aquaporins & water moves into interstitium
Increases osmolarity from 300 to 1200mOsm/L

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24
Q

What is the main movement in the thin ascending limb of Loop of Henle & what is the osmolarity effect

A

No aquaporins but numerous Na Cl transport channels & ions move from Lume onto interstitium along [ ] gradient
Decrease in osmolarity from 1200 to 600mOsm/L

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25
Q

What is the main movement in the thick ascending limb of Loop of Henle & what is the osmolarity effect

A

Na/K/Cl transporter & moves ions from lumen into cell
Na/K ATPase maintain Na [ ] gradient
Osmolarity decrease from 600 to 325mOsm/L

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26
Q

What is the two part of DCT

A
  1. Early DCT
  2. Late DCT
27
Q

What is the movement of ions in the early DCT

A

Impermeable to water
Na/Cl cotransporter use Na [ ] gradient to move ions into cell & Cl move into interstitium via direct channels
Ca moves into cell via direct channels
Na/Ca cotransporter transport Ca into interstitium & into capillary
Na/K ATPase maintain Na [ ] gradient

28
Q

What regulates calcium reabsorption in early DCT

A

Parathyroid hormone can increase absorption by increasing Na/Ca channels

29
Q

What is the movement of ions in the late DCT regarding principle & intercalated cells

A

Principle cells:
K pumps from cell into lumen against [ ] gradient
Na pumps/ENaC pumps Na from lumen into cells
Na/K ATPase pumps Na into interstitium
Aquaporins in response to ADH
Alpha-intercalated:
H ATPase moves from cell into lumen
H/K ATPase moves H into cell & K out of cells
Na/K ATPase pumps Na into interstitium

30
Q

With what is Ca reabsorption coupled with/ & where is it reabsorbed

A

Na reabsoprtion via electrochemical gradient created
PCT, Loop of Henle (thick ascending limb) & DCT

31
Q

What is the effect of loop diuretics on Ca reabsoprtion

A

Decrease reabsorption & increase secretion

32
Q

Where is magnesium reabsorbed

A

PCT, thick ascending limb of Loop of Henle & DCT

33
Q

What is the effect of loop diuretics on Mg reabsoprtion

A

Decrease reabsorption & increase excretion

34
Q

With what is phosphate reabsorption coupled with/ & where is it reabsorbed

A

Na/P cotransporter in luminal membrane
PCT

35
Q

What is the effect of of PTH on phosphate reabsorption

A

Inhibits Na/P cotransporter & decrease phosphate transport leading to phosphaturia

36
Q

On what is the filtration rate of glucose in the kidneys dependent

A

Plasma glucose concentration

37
Q

Where does glucose reabsorption occur

A

PCT

38
Q

Explain the effect of normal plasma glucose levels on glucose reabsorption

A

Glucose reabsorption = filtration

39
Q

Explain the effect of high plasma glucose levels on glucose reabsorption

A

Limited number of glucose transporter proteins prevent reabsorption into blood

40
Q

Explain the effect of high glucose levels on glucose reabsorption

A

Glucose transporter proteins fully accurate & reabsorption rate ca not increase as transport maximum reached

41
Q

How is glucose reabsorbed in the kidneys

A

Glucose move into cell via SGLT using Na [ ] to move glucose against [ ] gradient (inside higher)
Glucose diffuse across basolateral membrane into peritubular capillaries via GLUT1/2

42
Q

What is the 5 factors that affect vascular tone

A
  1. Auto regulation
  2. Real sympathetic activity
  3. RAAS
  4. Endothelial factors
  5. Humoral factors
43
Q

What is the effect of humoral factors on vascular tone

A

ANF is released from cardiac atrial cells when stretched & dilate real afferent arteriole & constrict efferent increasing GFR

44
Q

What is the effect of RAAS on vascular tone

A
  1. Decrease of arterial pressure of Na [ ] cause decrease in Na perfusion
  2. Cells of macula densa sense change in blood volume/osmolarity & stimulate renin production
  3. Renin is secreted by juxtaglomerular cells & converts **angiotensinogen* secreted from the liver into angiotensin 1
  4. ACE in lungs & kidneys convert to angiotensin 2
  5. Angiotensin 2 stimulate synthesis & secretion of aldosterone in glomerulosa cells of adrenal gland
  6. Aldosterone cause increase in Na reabsorption in principle cells of DCT & collecting ducts
  7. Increase Na [ ] leads to increased osmolarity & increase in ECF & blood volume
45
Q

What is the 4 effects of angiotensin 2

A
  1. Stimulate Na/H exchange & increase Na reabsorption
  2. Stimulate ADH secretion
  3. Acts on hypothalamus to stimulate thirst & water intake
  4. Vasoconstriction of arteriole as leading to increased total peripheral resistance
46
Q

Where is urea from

A

A waste products that forms from amino acid breakdown

47
Q

How does urea recycling work

A

Urea is freely filtered across kidneys glomerular capillaries & travels through renal tubule
Part of reabsorbed urea is secreted back in to the loop of Henle
Establishment corticopapillary gradient in reabsorption of water from kidneys back into blood

48
Q

What is the 4 steps of urea recycling

A
  1. 50% of urea reabsorbed by simple diffusion in PCT w/ water
  2. Urea from the medullary interstitium is secreted back into tubule in descending limb of Loop of Henle due to higher urea [ ] in medullary interstitium
  3. Ascending limb of Loop of Henle & early DCT are impenetrable to urea & water
  4. 70% of initial urea is reabsorbed into interstitium in late DCT & collecting ducts due to ADH induced water reabsorption via aquaporins causing [ ] gradient of urea towards interstitium
49
Q

How much of the cardiac output does the kidney receive

A

20% - 500ml/min/kidney

50
Q

How much blood does the cortex & medulla receive & who is at greater risk for ischaemia

A

Cortex receives 80% w/ more nutrients & oxygen
Medulla receives 20% less nutrients & oxygens & slow blood flow therefore at higher risk of ischaemia

51
Q

What is two factors that increase renal blood flow

A
  1. Increased blood pressure resulting in increase pressure in renal artieries
  2. Decrease arteriole resistance
52
Q

What is the relationship between GFR & renal blood flow

A

Increase in renal blood flow results in increase GFR

53
Q

How is renal blood flow regulated

A

Increase or decrease in arteriole resistance

54
Q

What is the effect of adenosine released by macula densa cells

A

Increase resistance can afferent arteriole when more Na & Cl are detected in DCT (increase GFR & renal blood flow)
Increase arteriole resistance & reduce GFR

55
Q

What is the 5 signals the hypothalamus integrate to control renal sympathetic nervous stimulation

A
  1. Atrial & cardiopulmonary baroreceptor (low pressure)
  2. Carotid sinus & aortic arch baroreceptor (high pressure)
  3. Somatosensory receptors (muscle, joints & skin)
  4. Visceral receptors (liver & gut)
  5. Renal mechano- & chemoreceptors
56
Q

What is the sympathetic innervation of the kidneys

A

T11-l2

57
Q

What stimulate a1 & B1 adrenergic receptors

A

Noradrenaline

58
Q

What is stimulated by a1 & b1 adrenergic receptors

A

a1 smooth muscles cell in walls of blood vessels
b1 granulosa cells (renin containing)

59
Q

What is the effect of auto regulation on vascular tone

A

Smooth muscle cells in arteriole automatically contract when stretched by high blood pressure & decrease blood flow
Increased transluminal pressure causes stretch activated Ca pressure sensors to open & Ca causes cells to constrict
Once pressure is lowered the muscles relax & more blood flow through

60
Q

What is the 3 measuring technique of blood flow in the kidneys

A
  1. Fick principle
  2. Electromagnetic/ultrasound flow meter
  3. Laser Doppler flowmetry
61
Q

What is the Fick principle

A

Amount of substance in blood that flows into the organ is equal to the amount that flows out

62
Q

What is the Fick’s principle in the kidneys

A

Amount of PAH into the kidney = amount of PAH flows out via urine & renal vein
True renal plasma flow = [PAH]urine x urine flow/[PAH] artery - [PAH] veins
[PAH] measured in blood, urine & amount of urine
Assumed that [PAH] artery = [PAH] vein therefor
Effective renal plasma flow = [PAH]urine x urine flow/[PAH]

63
Q

What is the Fick’s principle in the kidneys

A

Amount of PAH into the kidney = amount of PAH flows out via urine & renal vein
True renal plasma flow = [PAH]urine x urine flow/[PAH] artery - [PAH] veins
[PAH] measured in blood, urine & amount of urine
Assumed that [PAH] artery = [PAH] vein therefor
Effective renal plasma flow = [PAH]urine x urine flow/[PAH]

Case 10: Urinary System (8 decks)

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