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Physiology Block 3 > Renal Lectures 1-2 > Flashcards

Renal Lectures 1-2 Flashcards

1
Q

Functions of the kidney

A

CENTRAL PHYSIOLOGIC ROLE: control volume and composition of body fluids

  1. Excretion of metabolic waste products and foreign chemicals
  2. Regulation of water and electrolyte balance
  3. Regulation of body fluid osmolality and electrolyte concentrations
  4. Regulation of arterial pressure
  5. Regulation of acid-base balance
  6. Secretion, metabolism, and excretion of hormones
  7. Gluconeogenesis
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2
Q

by weight, how much of the body is composed of water

A

50-70% (we will use 60%)

-this value is greater in leaner people (and lower in people with more fat)

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3
Q

what average values will we use for our calculation

A

70kg man

42L of total body water
(1L of water = 1kg mass)

-intracellular fluid (2/3 body water –40% body weight— 28L)

  • extracellular fluid (1/3 body water –20% body weight— 14L)
    1. interstitial fluid (11L)
    2. plasma volume (3L)
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4
Q

barrier b/w interstitial fluid and plasma volume

A

capillary wall

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5
Q

barrier between intracellular fluid and extracellular fluid is

A

cell membrane

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6
Q

normal blood volume of average individual and how to calculate it

A

~5L

Plasma volume / (1- hematocrit)

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7
Q

which compartment is first acted upon by intake or output mechanisms

A

plasma

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8
Q

order of blood fluid/cells

A
  1. Capillary has blood plasma in it
  2. then it crosses the capillary membrane to go into the interstitial fluid
  3. then it crosses the cell membrane to get into the intracellular fluid
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9
Q

capillary wall permeability

A

highly permeable to

  • water
  • electrolytes
  • small molecules

-NOT proteins

So the plasma volume (in the capillary) has more proteins in it than the interstitial fluid

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10
Q

what two forces oppose each other

A

oncotic pressure due to protein in the plasma (draws fluid into the capillary)

and

hydrostatic force int he blood vessels (pushes fluid out of the capillaries)

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11
Q

cell membrane permeability

A

highly permeable to
-water

-NOT electrolytes or proteins

ECF has high Na+, Cl-, and HCO3-

ICF has high K+, PO43-, and organic anions and proteins

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12
Q

Na+/K- pump

A

3Na+ out

2K+ in

*this is why you have more Na in ECF and more K in the ICF

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13
Q

measurement of body fluid volumes

A

Volume = Quantity remaining in body (amount) / Concentration (amount/volume)

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14
Q

how to measure intracellular volume

A

total body water - extracellular volume

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15
Q

how to measure interstitial volume

A

extracellular volume - plasma volume

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16
Q

osmolarity

A

function of total number of particles in solution

  • so if something doesnt dissociate it counts as 1 but if it does then it counts as however many parts it dissociates into
  • independent of mass, charge, or chemical composition
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17
Q

osmotic pressure

A

The dissolved particles (osmolytes) exert a force which tends to pull water across semi- permeable membranes (osmotic pressure)

-permeable to water only (no solutes)

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18
Q

osmosis

A

movement of water across a semi-permeable membrane due to differences in osmolarity (osmotic pressure gradient)

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19
Q

flux equation:

Where:
Kf = ultrafiltration coefficient (function of surface area for exchange)

Pc = capillary hydrostatic pressure

πif = interstitial oncotic pressure

πp=plasma oncotic pressure

Pif=interstitial hydrostatic pressure

A

Flux=(Kf)[Pc +πif -πp -Pif]

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20
Q

what happens when you add isotonic NaCl solution to extracellular fluid

A

TBW- increases

ECFV- increases

ICFV- same

Steady state osmolarity– same

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21
Q

what happens when you add hypertonic NaCl solution to extracellular fluid

A

TBW- increases

ECFV- increases

ICFV- decreases

steady state osmolarity- increases

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22
Q

what happens when you add hypotonic NaCl solution to extracellular fluid

A

TBW- increases

ECFV- increases

ICFV- increases

steady state osmolarity- decreases

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23
Q

Hypernatremia vs Hyponatremia

A
  • elevated plasma Na+ concentration > 150 mEq/l

- reduced plasma Na+ concentration <135mEq/l

24
Q

Hyperkalemia

Hypokalemia

A

-elevated plasma K+ concentration > 5.0 mEq/l

  • reduced plasma K+ concentration
    < 3.5 mEq/l
25
Q

Hypercalcemia vs. Hypocalcemia

A
  • elevated plasma Ca++ concentration > 10 mg/dl

- reduced plasma Ca++ concentration < 8 mg/dl

26
Q

Acidosis vs. Alkalosis

A
  • reduced plasma pH < 7.3

- elevated plasma pH > 7.5

27
Q

Edema

A

-condition in which there is excess fluid in the tissues

Common causes:

  • elevation in capillary hydrostatic pressure/elevated venous pressure (heart failure)
  • a drop in capillary oncotic pressure/loss of plasma protein (cirrhosis of liver, nephrotic syndrome)
  • lymphatic blockade
28
Q

first couple step in urine formation

A

bulk filtration in glomerulus
-filters ~100-125ml/min of plasma in a normal human

tubule is where reabsorption occurs
-returns 99% of filtered fluid to extracellular fluid space

29
Q

secretion

A

when some substances are transported from ECF into tubular lumen

30
Q

excretion =

A

filtration - reabsorption + secretion

31
Q

parts of the nephron

A
  1. Bowman’s Capsule (which combines with the glomerular capillaries to form the glomerulus),
  2. Proximal Tubule
  3. Loop of Henle (thin descending limb, thin ascending limb, and thick ascending limb)
  4. distal tubule (early distal tubule)
  5. connecting tubule (late distal tubule)
  6. collecting duct system (cortical, outer medullary, and inner medullary segments).
32
Q

kidney divided into…

A

8-18 pyramids consisting of cortex, outer medulla, and inner medulla

-kidney is approximately 0.5% body weight, yet receives 20-25% of cardiac output

33
Q

Common renal parameters

Blood Flow
renal arterial blood flow (how much cardiac output do the kidneys receive)
renal arterial plasma flow

A

20-25% of cardiac output ~1200ml/min

~700ml/min

34
Q

Common renal parameters

Filtration
glomerular filtration rate
filtration fraction
filtered load

A

Glomerular Filtration Rate (GFR) ~ 125 ml/min

Filtration Fraction (GFR/RPF=125/700=18%) Range- 15-25%

Filtered Load (GFR X Plasma Concentration= mass/time)

35
Q

Common renal parameters

Reabsorption

A

99% of filtered solute and water ~ 124 ml/min

36
Q

Common renal parameters

Secretion

A

Transport of solutes from blood into tubular lumen

37
Q

Common renal parameters

Excretion

A

Urine Flow ~1 ml/min

38
Q

Common renal parameters

Venous blood flow

A

~ 1199 ml/min

39
Q

two types of nephrons

A
  1. Cortical nephrons (90% of nephrons)- peritubular capillaries
  2. Juxtamedullary nephrons (10% of nephrons) - vasa recta capillaries
40
Q

glomerular capillaries

A

have high hydrostatic pressure which favors ultrafiltration (net filtration out of these capillaries)

41
Q

2 renal capillaries

A
  1. glomerular capillaries
    - high hydrostatic pressure
    - favors net filtration out
  2. postglomerular capillaries
    - peritubular and vasa recta
    - low hydrostatic pressure
    - favors reabsorption

Resistance vessels are located before and after the high pressure glomerular capillaries

42
Q

initial step in the formation of urine

A

glomerular filtration which is a bulk process (approximately 100-125 ml/min is filtered every minute–Step 1)

43
Q

steps in urine composition

A
  1. filtration
  2. reabsorption
  3. secretion
  4. excretion
44
Q

concentration of salts/organic substances in plasma vs. filtered fluid

A

they are around the same concentrations

45
Q

glomerular filtrate

A

bulk filtration process

  • ~3L every .5hour
  • excluded: large proteins, substances bound to protein, cellular elements
46
Q

3 kidney forces that are analogous to other capillaries around the body?

A
  1. glomerular hydrostatic pressure (like capillary pressure)
  2. glomerular COP
  3. bowman’s capsule pressure (like interstitial fluid pressure)
47
Q

in a healthy 700kg man how much plasma flows in the glomeruli every minute?

A

700ml flows into glomeruli

  • 125 is filtered every minute
  • 575 leaves via efferent arteriole every minute
48
Q

size of glomerulus

A

really small

approximately 100microns in diameter

49
Q

filtration barrier of glomeruli

A

3 layers

  1. capillary wall
    - fenestrated, freely permeable to small molecules
    - negatively charged glycoproteins in surface
  2. basement membrane
    - porous matrix of extracellular proteins including type IV collagen, laminin, fibronectin and other negatively charged proteins
  3. podocytes (with processes and slit pores-40x140 Å)
    - long finger like processes with negatively charged proteins

SO the filtration barrier is…
-size-selective: more permeable to small molecules
-charge-selective: more permeable to positively charged molecules (proteins
generally are negatively charged)

50
Q

two need to know proteins of the glomerular molecular lattice

A

main reason for size selectivity (albumin cant get through cause the slit is too small for it)

  1. nephrin (N)
  2. P-cadherin (P-C)
    - some genetic diseases dont have these which can cause proteinuria
51
Q

Filtration Fraction (ff)

A

FF = Flomerular filtration rate / Renal blood flow

52
Q

where do you have a higher concentration of hematocrit?

A

at the efferent end of the capillary

53
Q

how does postglomerular resistance influence changes in RR, GFR, and RBF

A

increase in postglomerular resistance causes:
RBF- decreases
GFR and FF- increase

decrease in postglomerular resistance causes:
RBF- increases
GFR and FF- decrease

54
Q

Pathophysio. causes of decreased glomerular filtration rate

A
  • renal disease
  • diabetes
  • hypertension
  • urinary tract obstruction (kidney stones)
  • increased plasma protein
55
Q

what happens when things are filtered out of the blood and into bowmens capsule?

A

increases GFR

Physiology Block 3 (2 decks)

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