Body Fluids Flashcards

1
Q

What is osmolarity?

A

mOsm (milliosmoles)/L =

concentration of particles per liter of solution.

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2
Q

What is osmolality?

A

mOsm/kg = concentration of

particles per kg solvent (water in biological systems)

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3
Q

What is an effective osmole?

A

Refers to a solute that does not easily cross a membrane.

It is an effective osmole because it creates an osmotic force for water.

Proteins are effective osmoles for the vascular compartment

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4
Q

What is the average daily intake of water breakdown?

A
• Ingestion (fluids or food):
      • 2100 ml/day
• Metabolism:
      • 200 ml/day
Total Daily Intake: 2300 ml/day
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5
Q

What is the average daily loss of water breakdown?

A

• Insensible evaporation:
• 350 ml/day through skin (3-5 liters/day for severe burns)
• 350 ml/day via lungs
• Sweat:
• 100 ml/day (5000 ml/day during exercise)
• Feces:
• 100 ml/day
• Urine:
• 1400 ml/day (500 ml/day during exercise)
Total Daily Loss: 2300 ml/day

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6
Q

What is the total body water?

A

42 liters (70 kg male)
• 50% body weight in females because of more body fat
• 70-75% body weight in premature and newborn

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7
Q

What is the osmolar gap?

A

(helps to narrow the differential diagnosis)
• Difference between the measured osmolality and the estimated osmolality (Normal ≤ 15)
• ECF Effective osmolality = 2(Na+) mEq/L + (glucose mg%/18) + (urea mg%/2.8)

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8
Q

What are some common things that can elevate the osmolar gap?

A
  • Ethanol
  • Methanol
  • Ethylene glycol
  • Acetone
  • Mannitol
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9
Q

What is the intracellular fluid composition?

A
  • Small amounts of sodium and chloride ions
  • Almost no calcium ions
  • Large amounts of potassium and phosphate ions
  • Moderate amounts of magnesium and sulphate ions
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10
Q

True or false plasma has a higher concentration of proteins because capillaries have a low permeability to plasma proteins.

A

True

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11
Q

True or false, ionic composition of plasma and interstitial fluid is similar.

A

True, because they are separated by highly permeable capillary membranes.

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12
Q

Indicator-Dilution Principle

A

• Applies to measurement of fluid volumes in body
fluid compartments.
• Requirements for an indicator:
• Disperses evenly throughout compartment
• Disperses only in compartment being measured
• Not metabolized or excreted
• Not toxic
Vol B = Vol A x conc. A / conc. B

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13
Q

What are the relative amounts of extracellular fluids in interstitial spaces and plasma determined primarily by?

A

the balance of hydrostatic and colloid forces across

capillary membranes

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14
Q

What is the distribution of fluid between intracellular and

extracellular compartments determined mostly by?

A

osmotic effects primarily of sodium and chloride

ions.

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15
Q

How much osmotic pressure is exerted across the cell membrane for each mOsm concentration gradient of an
impermeant solute?

A

about 19.3 mm Hg

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16
Q

What is the percentage of the total osmolarity of the interstitial fluid and plasma due to sodium and chloride ions?

A

About 80%

17
Q

How much of the osmolarity is due to potassium ion for the intracellular fluid?

A

about half

18
Q

If the cell membrane is exposed to pure water and the
osmolarity of intracellular fluid is 282 mOsm/L, what is the potential osmotic pressure that develop across the cell membrane?

A

more than 5400 mm Hg

19
Q

What happens in an isotonic solution to the extracellular fluid compartment?

A
  • Extracellular osmolarity does not change
  • Extracellular volume increases

solutes having an osmolarity of 282 mOsm/L is isotonic

  • Water cannot enter or leave the cell
  • Examples: 0.9% NaCl or 5% Glucose
20
Q

What happens in an hypertonic solution to the extracellular fluid compartment?

A

• Intracellular volume decreases
• Extracellular volume increases
• Osmolarity in both compartments increases
• A solution of impermeant solutes having an osmolarity >
282 mOsm/L = hypertonic
• Water will diffuse out of the cell

21
Q

What happens in an hypotonic solution to the extracellular fluid compartment?

A
  • Volume of both compartments increases
  • Osmolarity in both compartments decreases
  • A solution of impermeant solutes having an osmolarity
22
Q

What are the causes and consequences of hyponatremia?

A

Causes:

  • primary loss of NaCl
  • diarrhea
  • vomitting
  • overuse of diuretics
  • Addison’s disease

Consequences:

- brain cell edema
- headache, nausea, lethargy, disorientation    - seizures, coma, permanent brain damage/injury, death
23
Q

What are the causes and consequences of hypernatremia?

A

Causes:

  • loss of water
  • excess sodium in extracellular fluid
  • excess NaCl added to the extracellular fluid

Consequences:
- intense thirst and secretion of ADH

24
Q

intracellular edema

A

causes:

- hyponatremia    - depression of the metabolic systems of the tissues    - lack of adequate nutrition to the cells

can also occur in inflammed tissues

25
Q

extracellular edema

A

causes:

- abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries    - failure to the lymphatics to return fluid from the interstitium back into the blood (lymphedema)    - excessive capillary fluid filtration
26
Q

True or false, when interstitial fluid pressure is below 0, little fluid accumulates in tissues.

A

true

27
Q

What is the safety factor against edema?

A

3 mm Hg

28
Q

True or false, when interstitial fluid pressure rises above 0, free fluid (as opposed to gel fluid) rapidly begins to accumulate in tissues.

A

true

29
Q

What is the anatomical organization of the kidneys?

A
  • Capsule
  • Renal cortex:
    • Bowman’s capsule
    • Proximal and distal convoluted tubules
  • Renal medulla:
    • Renal pyramids
  • Renal pelvis:
    • Major and minor calyces
30
Q

Describe the structure of the nephron.

A

• 800,000 – 1,000,000 nephrons/kidney
• Decrease by 10% every year after the age of 40
• Each large collecting duct (≈ 250/kidney) receives urine from 4000 nephrons
• Cortical nephrons have glomeruli located in outer cortex and have short loops of Henle
• Juxtaglomerular nephrons (20-30% of total) have glomeruli deep in renal cortex near medulla and have long loops of Henle.
• Juxtaglomerular nephrons have long efferent arterioles
associated with peritubular capillaries (vasa recta).

31
Q

What is the pathway of blood flow to the kidneys?

A
Renal artery 
Interlobar arteries 
Arcuate arteries 
Interlobular arteries 
Afferent arterioles 
Glomerular capillaries 
Efferent arterioles
32
Q

What is the pathway of blood flow from the kidneys?

A
Peritubular capillaries
Interlobular veins
Arcuate veins
Interlobar veins 
Renal veins
33
Q

True or false, efferent arterioles help regulate hydrostatic pressure in both sets of capillaries.

A

true

34
Q

What percent/amount of the total cardiac output do the kidneys receive?

A

22% , 1100 ml/min

35
Q

What does high hydrostatic pressure in glomerular capillaries cause?

A

rapid fluid filtration

36
Q

What does low hydrostatic pressure in peritubular capillaries permit?

A

rapid fluid reabsorption

37
Q

What is considered high hydrostatic pressure in glomerular capillaries?

A

~ 60 mmHg

38
Q

What is considered low hydrostatic pressure in peritubular capillaries?

A

~ 13 mmHg