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Renal System > Physiology > Flashcards

Physiology Flashcards

1
Q

What passes through Fenestrated Capillary Cells?

A

Non-formed elements I.e. Not cells (less than 100 nm)

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2
Q

What drains the Glomerulus?

A

An efferent arteriole

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3
Q

What is the main function of the Kidney?

A

To maintain a stable internal environment

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4
Q

What processes are undergone by the kidney?

A

Filtration, reabsorption and secretion

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5
Q

What is the Glomerulus?

A

The filtering unit of the kidney

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6
Q

What is the Renal Blood Flow?

A

25% of cardiac output

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7
Q

How is blood flow changed in the kidney?

A

By changing Afferent and/or Efferent arteriolar resistance

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8
Q

How is Renal Blood Flow calculated?

A

Q = ΔP/R

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9
Q

What is the renal arterial pressure?

A

80 - 200 mm Hg

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10
Q

What happens if renal arteriole pressure increases?

A

Renal resistance will increase proportionally

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11
Q

What is the Myogenic Theory of autoregulation of RBF?

A

Increased arterial pressure stretches the blood vessels, causing reflex contraction of smooth muscle in the blood vessel walls and consequently increased resistance to blood flow

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12
Q

Where is autoregulation of RBF controlled?

A

At the level of the Afferent arteriole

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13
Q

What happens when blood pressure is increased according to the Myogenic theory of autoregulation of RBF?

A

Resistance is increased
RBF is kept constant
GFR is increased

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14
Q

What happens when blood pressure decreases according to the Myogenic theory of autoregulation of RBF?

A

Resistance is decreased
RBF is kept constant
GFR is increased

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15
Q

What are the effects of the SNS on RBF?

A

⍺1 receptors (more common on afferent arterioles) stimulate vasoconstriction, decreasing RBF and GFR

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16
Q

What are the effects of high levels of Angiotensin II on RBF?

A

It causes vasoconstriction of both afferent and efferent arterioles (efferent more than afferent), increasing resistance and decreasing RBF

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17
Q

What are the effects of low levels of Angiotensin II on RBF?

A

It produces an increase in GFR by preferentially constricting efferent arterioles

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18
Q

What are the effects of Atrial Natriuretic Peptide on RBF?

A

It causes dilation of afferent arterioles and constriction of efferent arterioles, increasing RBF and GFR

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19
Q

What are the effects of Prostoglandins on RBF?

A

It causes vasodilation of both afferent and efferent arterioles

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20
Q

What are the effects of Dopamine on RBF?

A

Low dosages dilate renal arterioles, increasing RBF

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21
Q

What is Ultrafiltrate composed of?

A

It is composed of Water and all of the small solute of blood (not proteins or blood cells)

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22
Q

What is the pathway for ultrafiltration of plasma from the glomerulus to the Bowman space?

A

Fenestrated capillary endothelium > Capillary basement membrane > Visceral epithelial cell layer (podocytes) of Bowman Capsule

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23
Q

What is the Ultrafiltration Coefficient determined by?

A

The hydraulic conductivity of the glomerular capillary wall and the total capillary surface area available for filtration

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24
Q

What determines the GFR?

A

The Starling Equation
SNGFR = Kf x (∆P-∆𝜋)
SNGFR = Kf x [(Pgc −Pbs)−(𝜋gc −𝜋bs)]

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25
Q

How is hydrostatic pressure in glomerular capillaries changed?

A

It is change by changing the resistance of the afferent and efferent arterioles

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26
Q

How is hydrostatic pressure changed in Bowman’s space?

A

it can be changed by obstructing urine flow

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27
Q

How is oncotic pressure in glomerular capillaries changed?

A

It is changed by changing the plasma protein concentration.

28
Q

What happens to oncotic pressure in glomerular capillaries when plasma protein concentration is increased?

A

It is increased

Net ultrafiltration and GFR is decreased

29
Q

What happens to oncotic pressure in glomerular capillaries when plasma protein concentration is decreased?

A

It is decreased

Net ultrafiltration pressure and GFR is increased

30
Q

What is the filtration fraction?

A

It is the fraction of the Renal Plasma Flow that is filtered across the glomerular capillaries
It expresses the relationship between the GFR and RPF

31
Q

What is the normal filtration fraction?

A

20%

32
Q

What happens if the filtration fraction is increased?

A

It produces increases in the protein concentration and oncotic pressure in glomerular capillaries of peritubular capillary blood

33
Q

What is Renal Clearance?

A

It is the volume of plasma completely cleared of a substance by the kidney per unit time

34
Q

What does it mean if a substance has high renal clearance?

A

It is completely removed on a single pass of blood through the kidneys

35
Q

What substances have high renal clearance?

A

Inulin, Fructose, Polymers, Para-aminhippuric acid

36
Q

What does it mean if a substance has a low renal clearance?

A

It is not removed well

37
Q

What substances have low renal clearances

A

Protein, Glucose

38
Q

How is GFR measured?

A

Using a substance that:

  1. Is freely filtered across the glomerular capillaries without size or charge restrictions
  2. Cannot be reabsorbed or secreted by the renal tubule
  3. cannot alter the GFR when infused
39
Q

What can be used to measure GFR?

A

Inulin (must be injected intravenously)

40
Q

What are the patterns of reabsorption?

A

Complete Reabsorption - The filtered substance is completely reabsorbed and is not present in urine
Zero Reabsorption - The Filtered substance is not reabsorbed and is present in its entirety (or close to) in the kidney
Regulated and Variable reabsorption - Reabsorption is dependant on the circumstances

41
Q

How does tubular transport work?

A

Through Vectorial transport - the net movement of substance from tubular fluid to blood or vice versa

42
Q

How is the proximal tubule adapted to bulk reabsorption of glomerular filtrate?

A

The epithelial cells have microvilli on their apical surface to provide large area and the basolateral membrane has folds

43
Q

How is Na+ absorbed in the early proximal tubule?

A

Na+ is mainly absorbed with HCO3- and organic solutes, i.e. glucose and amino acids

44
Q

How is Na+ in the late proximal tubule?

A

Na+ is mainly absorbed with Cl-

45
Q

How much Na+ and what else is reabsorbed in the same amount?

A

67%, water is reabsorbed in the same amount

46
Q

What is isosmotic reabsorption?

A

The tight coupling between Na+ and water reabsorption

47
Q

What is reabsorbed in the proximal tubule?

A

65% of water, sodium, potassium and chloride
100% of glucose and amino acids
85%-90% of bicarbonate

48
Q

What is the purpose of secretion in the proximal tubule?

A

To rapidly clear endogenous solutes and medications from the circulation

49
Q

What is absorbed in the thick ascending limb of the loop of henle and what are the effects?

A

Sodium, potassium, chloride, bicarbonate and magnesium are reabsorbed. Water is not absorbed. This lowers tubular osmolarity.

50
Q

What are the types of Nephrons?

A

Cortical (superficial) and Juxtamedullary (deep)

51
Q

What is a nephron?

A

The functional unit of the kidney

52
Q

What are the nephron segments?

A

The Bowman’s capsule, the Proximal Convoluted Tubule, the Proximal Straight Tubule, the Loop of Henle, the Distal Convoluted Tubule, the Collecting Duct

53
Q

What is Renal Plasma Flow?

A

The portion of RBF that Is only plasma

54
Q

What is the Paracellular transport pathway?

A

Passive transport where molecules travel between individual cells

55
Q

What is the Transcellular Transport Pathway?

A

When molecules travel through cells

56
Q

What does Sodium/Potassium ATPase transport?

A

It transports 3 Na+ out of the cell and 2 K+ into the cell

57
Q

What is the purpose of Sodium/Potassium ATPase?

A

It creates a Na+ concentration gradient and a voltage gradient

58
Q

What modes of transport are utilised by Sodium/Potassium ATPase?

A

Both active and passive transport mechanisms

59
Q

What are the methods of water transport in the tubule?

A

Paracellular, transcellular and solvent drag/bulk transport

60
Q

What is the renal threshold of reabsorption

A

The maximum amount of any given substance to be reabsorbed

61
Q

What happens if the renal threshold is exceeded?

A

The additional substances are lost to the urine

62
Q

What is the difference between Peritubular Capillary absorption and regular capillary absorption?

A

Peritubular capillaries reabsorb fluid across their entire length whereas regular capillaries filer along their 1st half and reabsorb along their 2nd half

63
Q

What is the primary function of the Proximal Tubule?

A

To reabsorb as much of those substances the body needs as possible

64
Q

What is the transport mechanism of Cl- reabsorption in the Proximal Tubule?

A

The Paracellular mechanism

65
Q

How much HCO3- is reabsorbed by the Proximal Tubule?

A

About 80%

66
Q

What is the function of the parathyroid hormone in the proximal tubule?

A

It inhibits Phosphate reabsorption

Renal System (3 decks)

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