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Block D - Digestion and Metabolism > Human Body Composition > Flashcards

Human Body Composition Flashcards

1
Q

2 major fluid compartments of the body

A 
Intracellular fluid (ICF)
Extracellular fluid (ECF)
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2
Q

2 subcompartments of the ECF

A

Intravascular

Interstitial (extravascular)

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3
Q

Percent of body weight occupied by water in an average man

A

60%

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4
Q

Percent body weight occupied by ICF

A

40%

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5
Q

Percent body weight occupied by ECF

A

20%

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6
Q

Percent body weight occupied by water in old age

A

50%

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7
Q

Percentage of ECF water in the interstitial compartment

A

75 - 80%

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8
Q

Percentage of ECF water in the vascular compartment

A

20 - 25%

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9
Q

Name of fluid in the intravascular compartment

A

Plasma

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10
Q

Via which compartment does water enter and leave the body?

A

Intravascular compartment

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11
Q

What determines the volume of water that ends up in a given compartment?

A 
Osmotic pressure (the number of osmotically active particles within)
Intravascular hydrostatic pressure
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12
Q

Define an osmole

A

The number of osmotically active particles in a solution

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13
Q

Define an osmotically active particle

A

A dissolved molecule (solute) that cannot penetrate through a water-permeable membrae

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14
Q

Semi-permeable membrane separating the ECF and ICF

A

Cell membrane

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15
Q

4 naturally occurring molecules that can freely penetrate cell membranes

A

Oxygen
Carbon dioxide
Water
Urea

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16
Q

Solute composition of the ICF

A

Sodium and chloride = very low
Potassium, magnesium and phosphate = very high
Protein = very high (approx. 200 g/L)

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17
Q

Solute composition of the ECF

A 
Sodium = high (140 mmol/L)
Chloride = high (105 mmol/L)
Potassium = very low (4 mmol/L)
Protein = very low (relative to ICF)
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18
Q

Semi-permeable membrane separating the interstitial and intravascular compartments of the ECF

A

Capillary wall

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19
Q

2 components of the bloodstream

A

Fluid (plasma)

Cells (blood cells)

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20
Q

What do the capillaries retain in their lumen (despite being porous)

A

Blood cells

High molecular weight proteins

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21
Q

One of the main reasons why capillaries retain high molecular weight proteins

A

To create an osmotic pressure to counter-balance the hydrostatic pressure that would otherwise force plasma water out of them into the interstitial compartment and deplete the intravascular compartment

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22
Q

Approximate hydrostatic pressure inside the capillaries relative to the arterial pressure

A

Considerably less than half (but far from zero)

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23
Q

Pressure in the interstitial compartment

A

Approximately zero

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24
Q

Define colloid oncotic pressure

A

Inward directed osmotic pressure (in the capillaries)

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25
Q

WHat exerts the colloid oncotic pressure?

A

The concentration difference of high molecular weight proteins across the capillary wall

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26
Q

Main high molecular weight protein in the capillary responsible for the colloid oncotic pressure

A

Albumin

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27
Q

Define the hematocrit

A

Content of blood occupied by red blood cells (40% normally)

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28
Q

Percentage of blood occupied by plasma

A

60%

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29
Q

Most acutely critical body compartment

A

Intravascular compartment

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30
Q

Purpose of the interstitial compartment in terms of water balance

A

Buffer to minimize volume fluctuations in the intravascular compartment (since it is a zero pressure system)

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31
Q

Speed of equalization between the ECF sub-compartments’ osmolarity and why

A

Rapid (minutes) because the ECF’s main osmoles (sodium and chloride) permeate easily through the capillary wall

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32
Q

Speed of equalization between the ECF and ICF osmolarity and why

A

Long (hours) because it occurs as a result of water shifts alone

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33
Q

Standard osmolarity of all fluid compartments at equilibrium

A

300 mOsm/L

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34
Q

Normal serum sodium concentration

A

140 mmol/L

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35
Q

Importance of serum sodium concentration measurement

A

Indication of osmolarity in all of the fluid compartments

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36
Q

What fluid does the intracellular compartment contain

A

Water inside the body’s cells (mostly skeletal muscle cells)

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37
Q

Anatomic correspondence of the intracellular compartment

A

Body cell mass (BCM)

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38
Q

Reason why the volume of the ICF compartment is large

A

1) A lot of cells in the body

2) These cells exert a strong osmotic pressure

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39
Q

Why do the cells of the body exert a strong osmotic pressure?

A

High concentrations of potassium, magnesium, phosphate and soluble proteins

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40
Q

Define a hypotonic solution

A

Solution that has a relatively low osmolarity

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41
Q

Define a hypertonic solution

A

Solution that has a relatively high osmolarity

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42
Q

Effect of putting a cell in a hypotonic environment

A

Unequal osmotic pressures will drive water into the cell –> swell to a larger volume

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43
Q

Effect of putting a cell in a hypertonic environment

A

Unequal osmotic pressures will drive water out of the cell –> shrink in size

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44
Q

Define simple dehydration

A

A medical condition accompanying hypertonicity of the body’s fluid compartments

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45
Q

Define relative dehydration

A

A disproportionately large amount of sodium in relation to the volume of water in the ECF (hyperosmolarity)

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46
Q

Define hypernatremia

A

Abnormally high serum sodium concentration

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47
Q

Most frequent cause of simple dehydration

A

Failure or inability of the patient to drink enough water to compensate for body losses of water

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48
Q

Key symptom pointing to relative dehydration

A

Thirst

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49
Q

2 clinical symptoms and signs of moderate dehydration (thirst aside)

A

Lethargy

Uneasiness

50
Q

Cause of symptoms in severe dehydration

A

Shift of water out of brain cells –> shrink them enough to depress consciousness and cause coma and death

51
Q

Water buffer for the ECF compartment

A

ICF

52
Q

Effect of simple dehydration on ECF osmolarity

A

Hyperosmolarity

53
Q

Effect of ECF hyperosmolarity on fluid distribution

A

Shift water from the ICF into the ECF –> protect from drastic depletion

54
Q

Define simple (ECF) volume depletion

A

A roughly iso-osmolar loss of electrolytes and water from the ECF

55
Q

2 common causes of volume depletion

A

Severe diarrhea

Protracted vomiting

56
Q

Intravascular compartment effects of a lowered ECF volume (acutely)

A

Reduced volume

Lowered arterial blood pressure

57
Q

Compensatory response to reduced intravascular volume

A

Increased HR to maintain the rate of blood flow through the circulation

58
Q

Describe the compensatory response in SUBTLE forms of ECF depletion and the importance of this

A

HR accelerates only upon assuming an upright position. Measurement of BP and HR, first on lying, then upright posture = important diagnostic maneuver

59
Q

Describe the physical manifestation of low venous pressure

A

Veins that are normally visible, such as jugular veins, become undetectable

60
Q

Describe the contribution to ECF depletion by each of its compartments

A

Interstitial fluid volume and intravascular volumes decrease together, but most decrease occurs in the interstitial

61
Q

Place in the body to examine the interstitial compartment

A

Skin

62
Q

Describe the skin of a patient with normal interstitial fluid volume

A

Juicy

63
Q

Medical term for skin juiciness

A

Turgor

64
Q

Describe decreased skin turgor

A

If you pinch up the skin over the deltoid muscle or sternum or a patient who is volume depleted, the pinched up skin will remain tented, like putty, for a few moments

65
Q

Describe the mouth of a person with volume depletion

A

Small pool of saliva normally present under the tongue disappears

66
Q

Urine excretion under volume depletion

A

Decreased (compensatory mechanism)

67
Q

2 signs and symptoms of a baby experiencing volume depletion

A

Dry diaper

Crying without tears

68
Q

Consequence of blood volume falling >50%

A

Inability to perfuse organs adequately

69
Q

Define hypovolemic shock

A

Inability to perfuse organs adequately

70
Q

Earlier stage of shock

A

Pre-shock

71
Q

Define pre-shock

A

An important and dangerous intravascular volume depletion (>15% of blood volume)

72
Q

5 symptoms and signs of pre-shock

A 
BP very low
HR very fast
Collapsed veins
Reduced (or zero) urine output
Patient feels terrible
73
Q

Body’s response to severe toxic-inflammatory states

A

Cytokines and hormones are released from certain cells to make the capillary wall much more permeable to large molecular weight proteins

74
Q

Consequence on serum albumin in the event of toxic-inflammatory states

A

Albumin can diffuse out of the vascular compartment –> interstitial compartment –> patient’s serum albumin concentration decreases dramatically (NOTE: total albumin unchanged in ECF, just redistributed)

75
Q

Reliable indicator of tissue damage and systemic inflammation

A

Hyperalbuminemia

76
Q

Define over-hydration

A

Decreased serum sodium per L of plasma

77
Q

When can over-hydration AND hypovolemia occur together?

A

In a patient who has been experiencing ECF depletion for a long enough time for their body to sense their low ECF volume and respond by sending a thirst signal to induce them to drink more water. Kidney also reabsorbs more free water.

78
Q

Why does the body allow over-hydration to occur in the setting of hypovolemia?

A

The body permits its fluid compartments to become hypo-osmolar because its survival priority is preservation of the intravascular volume

79
Q

Amount of water that the skin can soak up and release without visible change

A

2 - 3 kg (10 pounds)

80
Q

The most sensitive way to detect small changes in the ECF volume

A

Record and follow the patient’s weight

81
Q

Characteristic and specific sign of ECF excess

A

Palpable and usually visible accumulation of fluid within and under the skin (edema)

82
Q

Most dangerous consequence of over-expansion of the total ECF compartment

A

Intolerable over-expansion of the intravascular compartment

83
Q

4 signs and symptoms of over-expansion of the intravascular compartment

A

Feeling of distress
Normal (or above-normal) BP
Swollen veins (high venous pressure)
Expanded interstitial compartment (edema)

84
Q

2 commonest settings for ever-expansion of the intravascular compartment

A 
Acute RHF
Acute LHF (--> pulmonary edema)
85
Q

Define effusion

A

Abnormal accumulation of fluid in potential spaces of the body (i.e. pleural space or pericardium)

86
Q

Define ascites

A

Excessive ECF accumulation in the abdomen (peritoneum)

87
Q

Define transudate

A

An effusion with the chemical composition of normal interstitial fluid (same electrolyte pattern and a LOW protein concentration)

88
Q

Cause of transudates

A

Pathological expansion of the ECF compartment, developing from an increased outward hydrostatic P, negative interstitial tissue P, and decreased plasma oncotic P

89
Q

Define exudate

A

Protein-rich and often cell-rich outpouring of inflammatory fluid

90
Q

Cause of exudate

A

Infection or tissue damage

91
Q

4 anatomic compartments of the human body

A

Fat
Non-fat soft tissues (body cell mass)
Extracellular fluids
Structural compartment (skeleton and associated connective tissue)

92
Q

Define the body cell mass

A

Hydrated, metabolically active protein tissues of the body

93
Q

Approximate percent body weight occupied by bones and supporting extracellular ligaments and structural protein

A

20%

94
Q

Ideal percent of body weight occupied by fat

A

20% in men

30% in women

95
Q

Most variable compartment

A

Fat

96
Q

Two techniques to determine contribution of pure fat to total body weight

A

Densitometry

Measuring total body water (isotope dilution or bioelectrical impedance analysis)

97
Q

Describe densitometry

A

Measurement of total body fat by relying on different densities of pure fat (0.900 kg/L) and the rest of the body (1.100 kg/L). Every density in between these boundaries corresponds to a unique fraction of fat/total body weight

98
Q

Differentiate between pure fat and the fat seen and felt on a person

A

Adipose tissue = physical fat, comprised of 85% pure fat and 15% water

99
Q

For precise calculations of body fat loss, what must one consider?

A

The 15% of body water that accompanies any important change in pure fat

100
Q

Equation for BMI

A

Weight (kg) / height^2 (m)

101
Q

Conversion from kg to lbs

A

1 kg = 2.2 lbs

102
Q

Conversion from inches to cm

A

1 inch = 2.54 cm

103
Q

2 exceptions to BMI

A

1) Professional athletes and body builders may have an abnormally high muscle mass and low fat, but high BMI
2) ECF compartment expansion or depletion under pathological conditions

104
Q

Define BMI >25

A

Implies that the body’s fat content is greater than normal

105
Q

Define BMI <18 - 20

A

Implies the body’s fat content is below normal

106
Q

Define BMI >30

A

Association with increasing health risk that increases in rough proportion to the increase in BMI

107
Q

Approximate percent of BCM occupied by skeletal muscle

A

80%

108
Q

Define the peripheral protein store

A

Portion of the BCM containing skeletal muscle

109
Q

Approximate percent of BCM occupied by all other non-adipocyte cels of the body (i.e. organs, bone marrow, blood cells)

A

20%

110
Q

Define the central/visceral protein store

A

Proteins from the portion of the BCM containing organs, blood cells and bone marrow (non-adipocyte cells that are non-skeletal muscle)

111
Q

When does BCM decrease

A

Muscle mass loss

112
Q

Define BCM loss of >10 - 15%

A

Association with reduced strength and a variety of physiological derangements

113
Q

Define BCM loss of >25%

A

Association with severe disability and an increased risk of death from several possible complications

114
Q

Define BCM loss of >45%

A

Commonly incompatible with survival

115
Q

Most important way to assess a patient’s BCM

A

Examine their muscle groups

116
Q

Method to measure the rate of change of BCM

A

Calculate changes in body nitrogen content

117
Q

Percent weight of protein occupied by nitrogen

A

16%

118
Q

1 g of N lost corresponds to what mass of protein lost?

A

6.25 g of protein

119
Q

1 g of protein lost corresponds to what mass of normally hydrated lean tissue lost?

A

5 g

120
Q

Equation for the estimation of daily N output

A

Urinary urea N excretion : 2 g N (urinary non-urea N) + 2 g fecal N

121
Q

Define sarcopenia

A

The decrease of muscle mass with age (old people’s fat mass tend to increase)

Block D - Digestion and Metabolism (29 decks)

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