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PCS 3 > Kidney > Flashcards

Kidney Flashcards

1
Q

How does filtration occur?

A

Some plasma flowing through the glomerular capillary is forced through the capillary wall and into Bowman’s space by the hydrostatic pressure of the blood/ glomerulus
(opposed by hydrostatic pressure of Bowman’s capsule and oncotic pressure of glomerular capillary protein)

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2
Q

Describe reabsorption

A

Substances move form the tubular fluid to the blood

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3
Q

Describe tubular secretion

A

Movement of a substance from the blood into the tubular fluid

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4
Q

What does transcellular route mean?

A

Passive diffusion/ active transport via tubular cells

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5
Q

What does paracellular route mean?

A

Diffusion between cells

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6
Q

What does the proximal tubule reabsorb?

A

All filtered glucose and a.a.

Most of the Na+/ Cl-/ HCO3-

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7
Q

What occurs at the loop of Henlé?

A

Sodium chloride is transported from tubular fluid to the interstitium

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8
Q

Distal tubule

A

regulates ionic balance of body by adjusting the amount of Na+ and other ions it reabsorbs
Secretes H+ that acidifies the urine

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9
Q

Collecting ducts

A

Water absorbed under influence of antidiuretic hormone (ADH)

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10
Q

Route of urine

A

Bowman’s capsule - proximal convoluted tubule - thin descending limb of loop of Henlé - thin ascending limb of loop of Henlé - thick ascending limb - distal convoluted tubule - collecting duct

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11
Q

Route of blood

A

Aorta - renal artery - afferent arteriole - glomerulus - efferent arteriole - peritubular capillaries - renal vein

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12
Q

Juxtamedullary nephron

A

Long loop of henlé, deep into medulla

Has vasa recta

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13
Q

Cortical nephron

A

Short loop of Henlé, mainly in cortex

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14
Q

Describe the process of ultrafiltration across glomerular capillaries

A

Pressure in glomerular capillaries forces a small proportion of plasma into Bowman’s space through fenestrae in endothelial cells
Small molecules and ions pass across capillary wall, leaving plasma proteins behind
Fluid formed is called glomerular filtrate

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15
Q

Composition of glomerular filtrate

A

Similar composition of small solutes to plasma
Almost impermeable to cells and larger molecules (so few proteins present)
No blood cells

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16
Q

Describe the reabsorption of Na+ in proximal convoluted tubule

A

Na+/K+-ATPase on basolateral surface of epithelial cells of proximal convoluted tubule provides the driving force for reabsorption of other substances (Na+ pumped out into interstitial fluid)

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17
Q

Describe the reabsorption of Na+ in proximal convoluted tubule coupled with a.a.

A

Amino acids are also con transported with Na+ across apical membrane

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18
Q

Describe the reabsorption of Na+ in proximal convoluted tubule coupled with bicarb

A

Reabsorption of HCO3- also linked to Na+ (Na+-H+ anti porter on brush border membrane, Na+ into tubule cell, H+ out so CO2 + H2O -> H+ + HCO3- shifts so more HCO3- made)

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19
Q

Describe the reabsorption of Na+ in proximal convoluted tubule coupled with chloride

A

Cl- diffuses down conc gradient with Na+ from lumen to interstitial fluid through tight junctions

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20
Q

Describe the reabsorption of Na+ in proximal convoluted tubule coupled with glucose

A

Inward movement of glucose on apical surface coupled to the movement of Na+ down its electrochemical gradient (secondary active transport)

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21
Q

Transcellular pathway of water

A

Uptake of solutes by tubular cells = inc in osmolality of fluid surrounding renal tubules
H2O moves tubular lumen to extracellular space down osmotic gradient via aquaporin channels in apical and basolateral membranes
Path of most water

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22
Q

Paracellular pathway of water

A

Uptake of solutes by tubular cells = inc in osmolality of fluid surrounding renal tubules
H2O moves tubular lumen to extracellular space down osmotic gradient via tight junctions
Only some water passes this way

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23
Q

What is the difference between water reabsorption in proximal tubule compared to distal tubule?

A

proximal tubule - regulation dependent on reabsorption of solutes
distal tubule - regulated independently of reabsorption of solutes

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24
Q

Is the descending limb permeable to water?

A

Yes

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25
Q

Is the ascending limb permeable to water?

A

No

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26
Q

What occurs under influence of aldosterone?

A

Na+ and Cl- reabsorbed from distal convoluted tubule

K+ and H+ secreted into distal convoluted tubule

27
Q

Effect of ADH

A

Acts to retain water in the body by enabling water to be reabsorbed back into blood (decreasing osmolality and increasing blood volume)
Osmoreceptors in hypothalamus detects ↑ in plasma osmolality
Released from posterior pituitary gland in response to increased blood osmolality/ significant decrease in blood volume
Causes vasoconstriction in afferent arteriole
If dehydrated, ADH secretion stimulated → smaller vol of urine produced
ADH increases the permeability of the last 1/3 of distal tubule & collecting duct to water (Otherwise impermeable to water)

28
Q

What is hydrostatic pressure?

A

The force a fluid exerts on the walls of it’s comportment

29
Q

What is oncotic pressure?

A

Pressure exerted by plasma proteins on the walls of it’s comportment

30
Q

What is GFR

A

Total amount of filtrate formed by all renal corpuscles in both kidneys per minute

31
Q

What does GFR take account of?

A

Net filtration pressure

Kf (Surface area available for filtration + Permeability of glomeruli)

32
Q

What occurs if the afferent arteriole is constricted?

A

Decrease in hydrostatic pressure of glomerular blood (reduction in blood available for filtration)
Decrease in net filtration rate
= decrease in GFR

33
Q

What is osmolarity?

A

Conc of solute

34
Q

What does countercurrent multiplication mean?

A

Filtrate flowing in opposite directions in the limbs of loop of Henlé enable effects of gradient to be increased
Interstitial fluid becomes more concentrated/ inc osmolarity the deeper down in medulla
Results in passive movement of water out of collecting duct = more conc urine

35
Q

How does loop of Henlé create an osmotic gradient?

A 
Ascending limb (impermeable to water) pumps Na+ out of tubule into interstitial fluid (increasing osmolarity in interstitial fluid )
Osmolarity in ascending limb decreases 
Water leaves descending limb (impermeable to ions) passively to equilibrate with interstitial fluid until they become equal in osmolarity 
Filtrate continually enters descending limb creating greater osmolarity lower down interstitial fluid
36
Q

What occurs if the afferent arteriole vasoconstricts?

A

Reduces the hydrostatic pressure in the subsequent glomerular capillaries
= reduced GFR
(if you step on a hosepipe, upstream pressure will increase, downstream pressure will decrease)

37
Q

What occurs if the afferent arteriole vasodilates?

A

Increases blood flow into glomerulus
Increases the hydrostatic pressure in the subsequent glomerular capillaries
= increased GFR
(if you step on a hosepipe, upstream pressure will increase, downstream pressure will decrease)

38
Q

What occurs if the efferent arteriole vasodilates?

A

Reduces the hydrostatic pressure in the previous glomerular capillaries
= reduced GFR
(if you step on a hosepipe, upstream pressure will increase, downstream pressure will decrease)

39
Q

What occurs if the efferent arteriole vasoconstricts?

A

Increases the hydrostatic pressure in the previous glomerular capillaries
= increased GFR
(if you step on a hosepipe, upstream pressure will increase, downstream pressure will decrease)

40
Q

What does vasoconstriction of an arteriole cause ?

A

Increased resistance
Increased mean arterial blood pressure
(vasodilation = opposite)

41
Q

How is a decrease in GFR compensated for?

A

Efferent arteriole constriction
Increases the hydrostatic pressure in the previous glomerular capillaries
Increases GFR

42
Q

How is an increase in GFR when afferent arterioles are stretched during high mean arterial blood pressure prevented?

A

myogenic reflex
afferent arteriole contracts
Reduces the hydrostatic pressure in the subsequent glomerular capillaries
prevents increase in GFR

43
Q

GFR equation

A

GFR = Kf x NFP

44
Q

Tubuloglomerular feedback

A

A decrease in arterial pressure, decreases glomerular hydrostatic pressure and also GFR
More NaCl reabsorbed by proximal convoluted tubule
Low tubular Na+ detected by macular densa Causes release of Renin from granule cells
Renin activates angiotensinogen to Angiotensin I
that is converted to angiotensin II
which causes vasoconstriction and inc in efferent arteriolar resistance
dilation and a decrease in afferent arteriolar resistance

45
Q

What does aldosterone do and where?

A

Inc NaCl and water reabsorption (increasing blood volume)
and K+ secretion in the collecting duct
Released from adrenal gland in response to decreased blood volume

46
Q

What does angiotensin II do and where?

A

Inc NaCl and water reabsorption

and H+ secretion in the PCT, thick ascending limb and collecting duct

47
Q

What does antidiuretic hormone do and where?

A

Inc water reabsorption in the DCT and collecting duct

48
Q

What does atrial natriuretic peptide do and where?

A

Dec NaCl reabsorption in the DCR and collecting duct
Dilates the afferent glomerular arteriole, constricts the efferent glomerular arteriole
Increases pressure in the glomerular capillaries, thus increasing the glomerular filtration rate (GFR), resulting in greater excretion of sodium and water
Inhibits renin secretion (and also renin-angiotensin-aldosterone system)

49
Q

What does parathyroid hormone do and where?

A

Dec PO4 reabsorption

Inc Ca reabsorption in the PCT, thick ascending limb and DCT

50
Q

What makes up extracellular fluid?

A

Plasma and interstitial fluid

51
Q

What is a hypotonic solution and what is a cells fate in this solution?

A

Cell has a lower osmotic pressure and conc of solutes that its surroundings
Cell swells
Water moves from hypotonic to hypertonic, towards region of higher solute conc

52
Q

What is a hypertonic solution and what is a cells fate in this solution?

A

Cell has a higher osmotic pressure and conc of solutes that its surroundings
Cell shrinks
Water moves from hypotonic to hypertonic, towards region of higher solute conc

53
Q

What is osmotic pressure?

A

The pressure required to prevent water from passing into the cell/ solution

54
Q

What has an affect on tonicity?

What is tonicity used to describe

A

Solutes that cannot cross the membrane

2 solutions separated by a membrane

55
Q

Describing 1 solution

What is the difference between molality/ osmolality and molarity/ osmolarity?

A

molality/ osmolality - moles/ osmoles in 1 kg solvent

molarity/ osmolarity - moles/ osmoles in 1 L solution

56
Q

What is the juxtaglomerulus apparatus?

A

Where the distal convoluted tubule passes the glomerulus

Role in controlling blood pressure

57
Q

If a person takes 3 grams of salt with little water, what changes, if any will occur to the blood osmolality, ADH levels and GFR in a hydrated individual?

A

Blood osmolality increases because blood solute concentration increases
ADH level increases to increase permeability of collecting duct to reabsorb more water
GFR increases as blood volume increases

58
Q

If a person drinks 600ml of tap water, what changes, if any, will occur to the blood osmolality, ADH levels and GFR in a hydrated individual?

A

Blood osmolality decreases as the blood solute concentration decreases
ADH levels decrease to decrease H2O reabsorption from the collecting duct
GFR increases because the blood volume increases

59
Q

Angiotensin

A

Angiotensin is a peptide hormone derived from angiotensionogen
Overall the action is to increase blood pressure by various ways:
Reabsorption of Na+, H2O follows
vasoconstriction to increase the blood pressure
increases secretion of ADH in the posterior pituitary to increase water reabsorption
Angiotensin II has a direct effect on the proximal tubules to increase Na+ reabsorption
Angiotensin II acts on the adrenal cortex, causing it to release aldosterone, a hormone that causes the kidneys to retain sodium and lose potassium

60
Q

What causes renal inulin (or creatinine) clearance to increase?

A

Both dilation of the afferent arteriole and constriction of the efferent arteriole would increase glomerular capillary hydrostatic pressure and thus increase GFR. (Note that inulin (or creatinine) clearance is a measure of GFR).

61
Q

How do Mesengial cells react to rise in blood pressure?

A

They are smooth muscle cells which contract in response to high blood pressure to constrict the afferent arteriole
Prevents the high pressure being passed on the glomerular capillaries and maintains GFR around 80-160 mmHg

62
Q

What type of cell in the distal convoluted tubule reabsorbs Na+ + H2O?

A

Principal cells

63
Q

What type of cell in the distal convoluted tubule reabsorbs K+ and secrete H+?

A

Intercalated cells

PCS 3 (11 decks)

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