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A&P 303 > 5/1 Lecture E2 > Flashcards

5/1 Lecture E2 Flashcards

1
Q

Where does filtration occur?

A

Bowman’s capsule

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2
Q

What is glomerular filtrate?

A

the fluid in the capsular space

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3
Q

What is tubular fluid?

A

fluid from the proximal convoluted tubule through the distal convoluted tubule; after having been added or removed by tubular cells.

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4
Q

What is urine?

A

fluid that enters the collecting duct.

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5
Q

What substances are able to pass through glomerular filtration?

A

water, electrolytes, glucose, amino acids, fatty acids, vitamins, urea, uric acid, creatinine

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6
Q

What substances are not able to pass through glomerular filtration?

A

blood cells, plasma proteins, large anions, protein-bound minerals and hormones; most molecules > 8nm in diameter

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7
Q

in glomerular filtration, where do water and solutes pass from and to?

A

from the blood plasma of the capillaries of the glomerulus into the capsular space of the nephron.

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8
Q

How many barriers do water and solutes need to pass through during glomerular filtration? and what are they?

A

3:

1) fenestrated (perforated) endothelium of glomerular capillaries
2) basement membrane
3) filtration slits

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9
Q

Is the basement membrane positively or negatively charged?

A

negatively charged:

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10
Q

What is the basement membrane made of?

A

protoglycan gel

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11
Q

In what case does protein pass into the urine?

A

only in the case of disease (proteinuria)

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12
Q

What forms filtration slits?

A

podocyte cell extensions (pedicels) that wrap around capillaries to form a barrier layer with 30 nm filtration slits

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13
Q

Are filtration slits positively or negatively charged?

A

negatively

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14
Q

Give 3 examples of substance of low molecular weight that are bound to the plasma proteins and cannot get though the membrane.

A

1) calcium
2) iron
3) thyroid hormone

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15
Q

kidney infections or trauma can damage the filtration membrane and allow what to filter?

A

albumin or blood cells

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16
Q

what is proteinuria (albuminuria)?

A

the presence of protein in the urine

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17
Q

What is hematuria?

A

The presence of blood in the urine

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18
Q

What is perfusion?

A

blood flow

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19
Q

What can cause perfusion of the kidney?

A

prolonged, strenuous exercise

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20
Q

what can deteriorate under prolonged hypoxia (oxygen deficiency in the tissues)?

A

the glomerulus

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21
Q

what does filtration pressure depend on?

A

hyrdrostatic and osmotic pressures on each side of the filtration membrane

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22
Q

Why is blood hydrostatic pressure higher in glomerular capillaries than in most other capillaries?

A

Because of the large inlet (large afferent arteriole) and the small outlet (small efferent arteriole)

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23
Q

What is the hydrostatic pressure of the capsular space?

A

18 mmHg

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24
Q

What is colloid osmotic pressure?

A

pressure exerted by proteins

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25
Q

What is the colloid osmotic pressure of blood?

A

32 mmHg

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26
Q

Does glomerular filtrate contain protein?

A

No, it is nearly protein-free.

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27
Q

What is the net glomerular filtration pressure?

A

10 mmHg out

28
Q

What can high BP in the glomerulus lead to?

A

hypertension in the kideys, which can lead to the rupture of glomerular capillaries, producing scarring of the kidneys, and atherosclerosis of renal blood vessels, and ultimately renal failure.

29
Q

What are the three forces involved in glomerular filtration?

A

1) blood hydrostatic pressure (BHP): 60 mmHg out
2) Colloid osmotic pressure (COP): -32 mmHg in
3) Capsular pressure (CP): -18 mmHg in

30
Q

How many liters of urine are excreted per day?

A

1-2 L

31
Q

What does the filtration coefficient (Kf) depend on?

A

permeability and surface area of the filtration barrier

32
Q

What is the glomerular filtration rate (GFR)?

A

The amount of filtrate formed per minute by the two kidneys combined: GFR=NFP X Kf

33
Q

What is the approximate GFR for males and females?

A

males: 125 mL/min or 180 L/day
females: 105 mL/min or 150 L/day

34
Q

What can happen if GFR is too high?

A

1) fluid flows too fast through renal tubules for them to reabsorb the usual amount of water and solutes
2) urine output rises
3) risk of dehydration and electrolyte depletion

35
Q

What can happen if GFR is too low?

A

1) wastes are reabsorbed

2) azotemia may occur (abnormally high levels of nitrogen-containing compounds)

36
Q

What three homeostatic mechanisms control GFR?

A

1) renal autoregulation
2) sympathetic control
3) hormonal control

37
Q

What is renal autoregulation?

A

the ability of the nephrons to adjust their own blood flow and GFR WITHOUT external (nervous or hormonal) control

38
Q

What are two methods of autoregulation?

A

1) myogenic mechanism

2) tubuloglomerular feedback

39
Q

What is myogenic mechanism?

A

a method of autoregulation of GFR, based on the tendency of smooth muscle to contract when stretched. For example, if arterial blood pressure increases, the afferent arteriole is stretched, and the vessel responds by contracting to prevent blood flow changes.

40
Q

What is tubuloglomerular feedback?

A

a method of autoregulation of GFR, where the glomerulus receives feedback on the status of downstream tubular fluid and adjusts filtration rate accordingly.

41
Q

What is the juxtaglomerular apparatus?

A

a complex structure found at the end of the nephron loop that comes into contact with the afferent and efferent arterioles at the vascular pole of the renal corpuscle

42
Q

How does tubuloglomerular feedback work?(4 steps)

A

1) When GFR is high, the filtrate contains higher NaCl. The macula densa absorbs more Na Cl, water follows, and it secretes ATP.
2) ATP is metabolized by nearby mesangial cells into adenosine
3) Adenosine stimulates nearby granular cells (juxtaglomerular cells)
4) granular cells respond to adenosine by constricting afferent arterioles, reducing blood flow with corrects the high GFR.

43
Q

Where is renin found?

A

granular cells

44
Q

Why is renin released?

A

in response to a drop in blood pressure

45
Q

What happens if the mean arterial pressure drops below 70 mmHg?

A

filtration and urine output stops

46
Q

Describe how the sympathetic nervous system helps to control GFR

A

The SNS and adrenal epinephrine constrict the afferent arterioles in strenuous exercise or acute conditions like circulatory shock.

47
Q

What is the response to SNS control?

A

1) GFR and urine output are reduced

2) Blood is redirected from the kidneys to the heart, brain, and skeletal muscle

48
Q

What is the renin-angiotensin-aldosterone system

A

a system of hormones that helps control blood pressure and GFR

49
Q

What is the renin-angiotensin-aldosterone system in response to?

A

a drop in blood pressure

50
Q

What occurs in the renin-angiotensin-aldosterone system

A

1) baroreceptors in carotid and aorta stimulate the sympathetic nervous system
2) sympathetic fibers trigger the release of renin by kidneys’ granular cells
3) renin converts angiotensinogen into angiotensin 1

51
Q

What is angiotensinogen

A

a liver blood protein

52
Q

Within the lungs and kidneys, what converts angiotensin 1 to angiotensin 2?

A

angiotensin-converting enzyme

53
Q

What is angiotensin 2?

A

An active hormone that increases BP by constricting efferent arterioles, raising GFR despite having a low BP

54
Q

What does angiotensin 2 stimulate the adrenal cortex to secrete?

A

aldosterone

55
Q

What does aldosterone promote?

A

The reabsorption of Na+ and H2O (increases BP!), stimulates thirst

56
Q

What secrets ADH?

A

the posterior pituitary

57
Q

What are the steps of urine formation?

A

1) tubular reabsorption
2) tubular secretion
3) water conservation

58
Q

What is tubular reabsorption?

A

the process of reclaiming water and solutes from tubular fluid and returning them to the blood.

59
Q

how much glomerular filtrate is reabsorbed into the PCT?

A

about 65%

60
Q

What are the two routes of reabsorption?

A

1) transcellular

2) paracellular

61
Q

What is transcellular reabsorption?

A

substances pass through the cytoplasm of PCT epithelial cells and out their base

62
Q

What is paracellular reabsorption

A

substances pass between PCT cells in gaps

63
Q

Where is reabsorbed fluid ultimately taken up?

A

by peritubular capillaries, back into the body

64
Q

What is key for tubular reabsorption?

A

Sodium!! reabsorption

65
Q

What is the most abundant cation in filtrate?

A

Sodium!

A&P 303 (18 decks)

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