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Physiology > Urinary > Flashcards

Urinary Flashcards

1
Q

What are the functions of the kidneys?

A

-Excrete nitrogenous waste (urea, uric acid, creatine)
-Regulate blood volumes (H2O balance and release of erythropoietin)
-Regulates blood pressure (renin release)
-Regulates chemical composition of blood
-Stabilizes pH
-Converts Vitamin D to active form

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2
Q

What is the flow of blood through the renal blood vessels in the capillary system?

A

Afferent arteriole > Glomerulus > Efferent arteriole > Pertibular capillaries OR vasa recta

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3
Q

What is the functional unit of the kidney?

A

The nephron

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4
Q

What are the tubular components of the nephron?

A

Tubular components: Bowman’s capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule, collecting duct

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5
Q

What are the vascular components of the nephron?

A

Afferent arterioles, glomerulus (a capillary knot), efferent arterioles, peritubular capillaries (around cortex) , vasa recta (in medulla)

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6
Q

What is the difference between a cortical nephron and a juxtamedullary nephron?

A

Cortical - in cortex, short loop of Henlea

Juxtamedullary - Glomulerii are deep in cortex and long loop of Henles extends into the medulla

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7
Q

What is the purpose of the juxtaglomerular apparatus?

A

At the beginning of the distal convoluted tubule.

Contains cells that regulate filtration rate and blood pressure

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8
Q

Where are macula densa and what are their purpose?

A

In JGA, in distal convoluted tubule, contain osmoreceptors (chemoreceptors) that monitor solute concentration (specifically Na+) and flow rate of filtrate

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9
Q

What makes granular cells of JGA granular?

A

They contain renin

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10
Q

What are the granular cells of the JGA?

A

Smooth muscle cells in the afferent arteriole that contain barioreceptors that monitor blood pressure, synthesizes and secretes renin

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11
Q

What are the four basic processes of the nephron?

A

Glomerular Filtration(F), Tubular Reabsorption (R), Tubular Secretion (S), and Excretion (E)

F - R + S = E

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12
Q

What is the main component of the body contributing to osmotic pressure?

A

Plasma proteins

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13
Q

How often do the kidneys filer the blood plasma?

A

60x per day

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14
Q

What is filtrate?

A

Blood plasma minus proteins: everything in the nephron to the tip of the papillary duct

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15
Q

How much of filtrate winds up as urine?

A

Less than 1%

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16
Q

What is the filtration fraction?

A

The amount of fluid reabsorbed from filtrate. 20% of fluid from plasma is pushed through the glomerulus, 19% will be reabsorbed

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17
Q

Where is filtrate formed?

A

Glomerulus

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18
Q

Why is glomerular filtration more efficient at filtration than other capillary beds?

A

Fenestration makes it more permeable to solutes

Blood pressure is higher due to a wider afferent arteriole than efferent

Higher net filtration pressure

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19
Q

What is the Glomerular Filtration Rate?

A

The total amount of filtrate formed per minute by the kidneys

125 mL/min or 180L/day

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20
Q

What are the factors that govern filtration rate?

A

Net filtration pressure
Total surface area available (#of nephrons)
Filtration membrane permeability

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21
Q

What are the forces involves in glomerular filtration?

A

Glomerular capillary pressure (55mmHg)
Plasma-colloid osmotic pressure (30mmHg)
Hydrostatic pressure in Bowman (15mmHg)
Osmotic pressure in Bowman (mmHg, due to lack of proteins)

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22
Q

What happens if GFR is too high?

A

Necessary substances cannot be reabsorbed and are lost in urine

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23
Q

What happens if GFR is too low?

A

Everything is reabsorbed, including wastes

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24
Q

What are the extrinsic controls of the GFR?

A

Sympathetic nervous system and the renin-angiotensin-aldosterone system

Increased BP increases Glom BP, increases GFR

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25
Q

What are the intrinsic controls of the GFR?

A

Autoregulation by kidneys, maintains BP between 80-180mmHg

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26
Q

What is myogenic regulation?

A

Autoregulation of GFR that responds to changes in pressure in renal blood vessels and (constriction and dilation) arteriole smooth muscles

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27
Q

If arteriole pressure increases afferent arterioles constrict or dilate?

A

They construct, which lowers the GFR

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28
Q

If arteriole pressure is low what happens to the aretioles?

A

The myogenic mechanism dilates the arterioles to increase GFR

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29
Q

If macula densa cella detect increased NaCl flow what happens?

A

Releases vasoactive chemicals which cause vasoconstriction of afferent arteriole, decreasing GFR

30
Q

What is sympathetic control of the GFR?

A

If blood pressure drops barioreceptors trigger vasoconstriction, less blood flows and lowers GF, which reduces urine volume and conserves plasma volume (which increases blood volume)

31
Q

What triggers the release of renin?

A

Reduced stretch of granular cells (MAP below 80)

Stimulation of granular cells by macula densa

Stimulation of granular cella by Beta adrenergic receptors

32
Q

What are the effects if angiotensin II?

A

Constriction of arteriolar smooth muscle (increases MAP)
Stimulates reabsorption of Na+
Triggers release of aldosterone from adrenal cortex
Stimulates release of ADH
Activates thirst center

33
Q

What is tubular reabsorption?

A

The selective transfer of substances from filtrate back into peritubular capillaries

Note: Rates are very high

34
Q

What is transepitheleal transport?

A

A substance is reabsorbed. It crosses the tubule wall, enters interstitial fluid, passes through the wall of the peritubular capillaries, and enters the blood

35
Q

True or false: Sodium reabsorption is mostly driven by active transport because of the Na+/K+ pump at the basolateral membrane

A

True

36
Q

Where is most of Sodium reabsorbed?

A

67% occurs in the proximal tubule at a constant rate

37
Q

What is true about the rate of Sodium in the distal tubule?

A

It varies depending on aldosterone: more or leas is reabsorbed based on the needs of the body

38
Q

How does aldosterone increase Na+ absorption in the distal collecting tubule?

A

It increases membrane permeability by promoting additional Na+ channels in the luminal membrane and Na-K pumps in the basolateral membrane

39
Q

What happens to sodium in the distal convoluted tube if no aldosterone is present?

A

It gets lost in the urine

40
Q

What is the effect of ANP on sodium reabsorption?

A

Inhibits it by acting directly on the ducts to decrease blood volume and lower blood pressure.

It also dilates the afferent arteriole, increasing GFR and decreasing absorption rate

41
Q

What causes tubular reabsorption of water?

A

Accumulation of sodium in lateral spaces produces an osmotic gradient that drives water into the peritubular capillaries (water follows)

42
Q

Where does most water get reabsorbed?

A

Loop of Henle - 80% occurs via osmosis (no control)

43
Q

Where does facultative reabsorption of water take place?

A

Distal tubule and collecting duct: about 20%, based on body’s needs and regulated by ADH

44
Q

What are the two key hormones for reabsorption?

A

Aldosterone: sodium
ADH: water

45
Q

How does ADH affect water reabsorption?

A

Promotes aquaporin production on luminal membrane, which increases water reabsorption (means concentrates urine)

46
Q

How are glucose and amino acids reabsorbed?

A

Secondary active transport. GLUT protein and Co-transported with Sodium on luminal membrane.

47
Q

What is a transport maximum?

A

The number of carriers available in a renal tubules: when the carriers are saturated excess is excreted

Note: This is the reason for “sweet urine” in diabetes

48
Q

What prevents a substance like urea, creatinine, and other nitrogen wastes from begin reabsorbed?

A

Lack carriers
Water soluble instead of lipid soluble
Too large to pass through pores

49
Q

What is absorbed in the proximal collecting tubule?

A

Most reabsorption occurs here.
2/3 of water and Na+
All nutrients, ions, and small proteins

50
Q

What gets absorbed in the loop of Henle?

A

Descending Limb: Water

Ascending Limb: Na+, K+, Cl-

51
Q

What is absorbed in the distal convolutes tubule and collecting duct? What is noteworthy about this absorption?

A

Reabsorption is hormonally regulated.

Ca2+ (PTH), Water (ADH), Na+ (Aldosterone and ANP)

52
Q

What is the purpose of tubular secretion?

A

It speeds up the elimination of substances from the blood by skipping the glomerulus

53
Q

What is tubular secretion important for?

A

-Disposing of substances not already in the filtrate

-Eliminating undesirable substances

-Ridding excess K+ ions

-Controlling blood pH

54
Q

What is the effect of aldosterone on potassium?

A

Stimulates distal tubule to secrete it and increases excretion

55
Q

True or false: Potassium is almost entirely reabsorbed in the distal tubule

A

False. This occurs in the proximal tubule

56
Q

How is the vertical osmotic gradient eatablished?

A

The countercurrent system: the movement of filtrate in opposite directions in the ascending and descending loop of Henle

57
Q

What are the properties of the limbs of the loop of Henle?

A

Descending: impermeable to solutes, permeable to water

Ascending: permeable to solutes, impermeable to water

58
Q

Where does the ascending limb of the loop of Henle teansport NaCl?

A

Into interstitial fluid. Water cannot follow because the limb is impermeable to water, so the fluid becomes hypertonic and is reabsorbed by the descending loop

59
Q

What is true about blood when it enters the medulla of the vasa recta and when it leaves?

A

It is isotonic

60
Q

What hormone signals the production of concentrated urine?

A

ADH

61
Q

What changes about the distal convolutes tubule and collecting ducts in the presence of ADH?

A

Allows them to be permeable to water and 99% is reabsorbed

62
Q

What are osmotic diuretics?

A

High glucose levels - Water leaves with glucose

Alcohol - Inhibits the release of ADH

Caffeine - Inhibits Na+ reabsorption

63
Q

Where is H+ and NH4+ secreted and HCO3 reabsorbed to maintain blood pH?

A

The proximal convoluted tubule

64
Q

Where is H+ and HCO3 reabsorbed to maintain blood pH

A

The collecting duct

65
Q

What is the term for elimination of the remains in the tubular lumen?

A

Urine excretion

66
Q

What is renal clearance?

A

The volume of plasma cleared of a particular substance in a given time

67
Q

What are renal clearance tests used to detect?

A

GFR
Any damage to glmoerulus
The progression of renal disease

68
Q

True or false: Inulin clearance is equal to GFR

A

True.

69
Q

What are the Renal Clearance numbers?

A

If GFR = 125ml/min
RC < 125 the substance is reabsorbed
If RC = 0 the substance is COMPLETELY rebsorbed
If RC > 125 the substance is secreted (this is true of most drugs)

70
Q

How does urine leave the kidneys?

A

Through ureters to bladder, which has stretch receptors that fill until micturition is triggered and urine is forced past the internal sphincter and put the external sphincter (voluntarily)

71
Q

What is the name of the underdeveloped control center in infants that matures between ages 2 and 3

A

Pontine control centers.

-Storage - inhibits micturition by inhibiting PSNS and exciting SNS and somatic paths

-Micturition center - promotes micturition by exciting PSNS and inhibiting SNS and somatic paths

Physiology (14 decks)

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