Ch. 25: Body Fluid, Extracellular, Intracellular Fluids

How does severe anemia effect hematocrit?

It can fall as low as 0.10, which is barely sufficient to sustain life

How do the compositions of the plasma and the interstitial fluid compare?

They are pretty much the same, except that there is a higher concentration of proteins in the plasma.

How does a hypertonic solution affect cell volume?

cell shrinks

What amounts can urine volume be?

0.5 L/day if dehydrated to 20 L/day if drinking tremendous amounts of water

How is blood volume measured?

total blood volume = plasma volume / (1 - hematocrit)

About how much water is lost by insensible water loss through the respiratory tract each day?

~300-400 ml/day

What percentage of the total body weight does intracellular fluid constitute?

~40%

What is the average total body water for women?

~50% of body weight

How much of the blood is made up of plasma or red blood cells?

~60% of blood is plasma and ~40% of blood is RBCs but this varies considerably based on gender, weight, and other factors.

What is the total body water in the average 70 kg adult man?

~60% of body weight or ~42 L

What is the average blood volume of adults?

~7% of body weight or ~5 L

About how much is insensible water loss per day?

~700 ml

How would you find the unknown volume of chamber B if 1 ml of solution containing 10 mg/ml dye is dispersed in the chamber and final conc. is 0.01 mg/ml?

(1 ml x 10 mg/ml) / 0.01 mg/ml = 1000 ml

What are the criteria for using "indicator-dilution" method to measure unknown volume?

(1) indicator disperses evenly throughout the compartment (2) indicator disperses only in compartment being measured (3) indicator is not metabolized or excreted

How is water added to the body?

(1) ingested in the form of liquids or water in the food ~2100 ml/day (2) synthesized as a result of oxidation of carbohydrates ~200 ml/day

What values do you need to know to use the equation to calculate an unknown volume with "indicator-dilution" method?

(1) total amnt of substance injected into the chamber (numerator of the equation) (2) conc. of the fluid in the chamber after the substance has been dispersed (denominator of equation)

What is the osmotic pressure (or pi in van't Hoff's osmosis equation)?

(atm) amount of pressure required to stop the process of osmosis (in your experimental setup

What is the standard osmotic pressure (amnt of pressure needed to stop movement of osmosis)?

1 mosm/L = 19.3 mmHg

1 mol / L of glucose = how many osmoles?

1 osm/L

What is the volume of the transcellular fluid?

1-2 L

For each milliosmole conc. gradient of an impermeant solute how much osmotic pressure is generated across the cell membrane?

19.3 mm Hg

1 mol/L of NaCl = how many osmoles?

2 osm/L

What are examples of the amount of sodium intake?

20 mEq/day to 300-500 mEq/day

If plasma volume = 3 L and hematocrit = 0.40, what is total blood volume?

3 L / (1 - 0.40) = 5 L

1 mol/L Na2SO4 = how many osmoles?

3 osm/L

What separates the intracellular fluid and the extracellular fluid?

A cell membrane that is highly permeable to water but not to most of the electrolytes in the body

What is one of the reasons that percentage of total body weight that is fluid decreases with age?

Aging is usually associated with an increased percentage of body weight being fat, which decreases the percentage of water in the body.

How does the amount of anions compare in plasma and interstitial fluid?

Anions have a higher concentration in the interstitial fluid than in the plasma bc they are repelled by the negative charges of the proteins in the plasma.

How is water lost through the respiratory tract?

As air enters the resp. tract, it becomes saturated with moisture, to a vapor pressure of about 47 mm Hg, before it is expelled. Bc the vapor pressure of the inspired air is usually less than 47 mm Hg, water is continuously lost through the lungs with respiration.

Does blood contain extracellular fluid or intracellular fluid?

Both. It contains the fluid in the plasma (ECF) and the fluid in the RBCs (ICF). But blood is considered to be a separate fluid compartment bc it is contained in its own chamber - the circulatory system.

How is hematocrit measured?

By centrifuging blood in a "hematocrit tube" until the cells are tightly packed in the bottom of the tube.

How does a hypotonic solution affect cell volume?

Cell swells

How is interstitial fluid volume measured?

ECF volume - plasma volume

What is polycythemia?

Excessive production of RBCs which can cause hematocrit to rise to 0.65

Why does the increase in sweat bc of heat or exercise not rapidly deplete the body fluids?

Fluid intake is also increased by activating the thirst mechanism

How does adding more of a solute to water effect water conc. ?

Higher solute concentration, lower water concentration

What is another way to measure blood volume without using the hematocrit?

Inject RBCs labeled w radioactive chromium into circulation and let them mix in. Then measure the radioactivity of a mixed blood sample and calculate total blood volume using "indicator-dilution" principle.

What happens to the percentage of total body weight that is fluid as a person grows older?

It gradually decreases

Why is blood considered a separate fluid compartment than ECF and ICF?

It is contained in its own chamber - the circulatory system

Why is there more sodium in the extracellular fluid?

It is drawn out by Na/K ATPase

Why can antipyrene also be used to measure TBW?

It is very lipid soluble and can rapidly penetrate cell membranes and distribute itself uniformly throughout the intracellular and extracellular compartments.

How does hematocrit compare in women and men?

Men have a higher hematocrit than women. (Men usually 0.40, women usually 0.36)

How does the osmotic coefficient relate to NaCl osmotic pressure?

NaCl doesn't always stay separated, so osmolarity is less than 2. So once you get osmolarity multiply by 0.93 = 286 mOsm/L

How does an isotonic solution affect cell volume?

No change

Is the measurement of hematocrit completely accurate?

No. It is impossible to completely pack the RBCs together so ~3-4% of the plasma remains trapped among the cells and the true hematocrit is ~96% of the measured hematocrit.

What is the difference between plasma and interstitial fluid?

Plasma has a higher concentration of protein

What does the intracellular fluid contain?

Small amounts of sodium and chloride, almost no calcium, large amounts of potassium and phosphate, moderate amounts of magnesium and sulfate, and large amounts of protein

What is the sodium space or the inulin space?

Some of the substances (such as radioactive Na) used to measure ECF may diffuse into the cells in small amounts, so it is referred to as sodium or inulin space instead of true ECF volume.

How is intracellular volume measured?

TBW - ECF volume.

Why is the protein concentration higher in plasma than interstitial fluid?

The capillaries have a low permeability to the plasma proteins so only small amounts of proteins leak in to the interstitial spaces in most tissues.

Why is the intracellular fluid of all the different cells together considered one large fluid compartment?

The concentrations of different substances are similar from one cell to another.

What is the "indicator-dilution" method based on?

The conservation of mass principle; the total mass of a substance after dispersion in the fluid compartment will be the same as the total mass injected into the fluid compartment.

What is hematocrit?

The fraction of the total blood volume composed of cell

How does the Donnan effect determine the amount of cations in the plasma and interstitial fluid?

The proteins are negative and they draw in cations, so there are more cations in the plasma than the interstitial fluid.

What happens when the cornified layer of skin becomes denuded (as with extensive burns)?

The rate of evaporation can increase as much as 10-fold, to 3 to 5 L/day. This is why burn victims must be given large amounts of fluid, usually intravenously, to balance fluid loss.

Why can severe diarrhea be life threatening?

The water loss through feces can increase to several liters per day.

How does the plasma and interstitial fluid exchange substances?

There are pores in the capillary membranes which are highly permeable to almost all solutes in ECF except proteins. So the extracellular fluids constantly mix and the plasma and interstitial fluid have about the same composition except for proteins which are higher in plasma.

What happens to respiratory fluid loss as the temperature decreases?

There is a greater loss of water from the lungs bc the atmospheric vapor pressure decreases to nearly 0 in colder weather (i.e. the dry feeling in resp. passages in cold weather)

How does the amount of protein compare in intracellular fluid and plasma?

There is about 4 times the amount of protein in intracellular fluid than in plasma.

How is plasma volume measured?

Using a substance that does not readily penetrate the capillary membranes but remains in the vascular system after injection (albumin labeled w radioactive iodine or Evans blue dye)

How can you measure total body water (TBW)?

Using radioactive water (titrium 3H2O or heavy water, deuterium 2H2O) that will mix with TBW a few hrs. after injection to blood and dilution principle can be used to calculate TBW

How can you estimate the volume of extracellular fluid?

Using substances that disperse in the plasma and interstitial fluid but do not readily permeate the cell membrane (radioactive Na, Cl, iothalamate, thiosulfate, and inulin)

What is the equation to find the unknown volume of chamber B using "indicator-dilution" method, where A is the indicator?

Volume B = (Volume A x Concentration A) / Concentration B

How do you calculate osmotic pressure of 0.9% NaCl?

conc. NaCl = 9 g/L molarity = 9 g/L / 58.5 g/mol (MW) = 0.154 mol/L 2 osmoles = osmolarity = 2 x 0.154 = 0.308 = 308 mOsm/L 308 x 19.3 = 5944 mmHg

What is insensible water loss?

continuous loss of water by evaporation from the resp. tract and diffusion through skin (called this bc we are not consciously aware of it, but it occurs continually in humans)

Is there more sodium in the intracellular or extracellular domain?

extracellular domain

What are the two main compartments that total body fluid is distributed in?

extracellular fluid and intracellular fluid

In premature and newborn babies what is the total body water like?

from 70-75% of body weight

What does the extracellular fluid (including plasma and interstitial fluid) contain?

high sodium and chloride, pretty high bicarbonate ions, small amount of potassium, calcium, magnesium, phosphate, and organic acid ions

What separates the plasma and interstitial fluid?

highly permeable capillary membranes

What is the extracellular fluid divided into?

interstitial fluid and blood plasma

What are the two largest compartments of extracellular fluid?

interstitial fluid and plasma

Is there more protein in the intracellular domain or extracellular domain?

intracellular domain

What is osmosis?

net diffusion of water across a selectively permeable membrane from a region of high water conc. to one that has a lower water conc.

What are the units of osmolarity?

osmoles / L of solution

What are the units of osmolality?

osmoles / kg H2O

Using Van't Hoff's law what is the osmosis equation?

pi = iMRT pi = osmotic pressure i = van Hoff's factor M = molarity/molality R = gas constant (changes) T = temp (K)

What is the noncellular part of the blood?

plasma

How can the volume of a fluid compartment in the body be measured?

the "indicator-dilution" method; placing an indicator substance in the compartment, allowing it to disperse evenly throughout compartment's fluid, + analyzing the extent to which the substance is diluted.

What determines the relative amounts of extracellular fluid distributed between the plasma and interstitial spaces?

the balance of hydrostatic and colloid osmotic forces across the capillary membranes

What minimizes the water loss by diffusion through the skin?

the cholesterol-filled cornified skin layer of the skin, which provides a barrier against excessive loss.

What is hematocrit?

the fraction of blood composed of RBCs

What regulates the extracellular components?

the kidneys

What determines the distribution of fluid btwn intracellular and extracellular compartments?

the osmotic effect of the smaller solutes (Na, Cl, other electrolytes) acting across the cell membrane

What is the rate of osmosis?

the rate of diffusion of water

What is the specialized type of extracellular fluid that is a small compartment including fluid in synovial, peritoneal, pericardial, and intraocular spaces, as well as the cerebrospinal fluid?

transcellular fluid

Do women or men usually have more fat?

women

Is there insensible water loss in people born without sweat glands?

yes

What can the amount of sweat loss increase to on a very hot day or during heavy exercise?

~1-2 L/hour

What portion of the extracellular fluid is plasma?

~1/4

About how much water is normally lost in the feces?

~100 ml/day

What is the normal volume of sweat lost per day?

~100 ml/day

What is the volume of the interstitial fluid?

~11 L

What is the volume of extracellular fluid in a normal 70 kg man?

~14 L

What percentage of the total body weight does extracellular fluid constitute?

~20%

About how much is the total water intake per day?

~2300 ml/day

What is the volume of the intracellular fluid?

~28 L

What is the volume of the plasma

~3 L

What portion of the extracellular fluid is interstitial fluid?

~3/4

What is the average water loss by diffusion through the skin?

~300 - 400 ml/day