● Body Fluids and Solutes
○ Body Fluids Compartments
■ Interstitial fluid
● Extracellular Fluid (ECF)
● Surrounds tissue cells and includes lymph
■ Intravascular fluid
● ECF
● Plasma - liquid component of blood
■ Transcellular fluid
● ECF - minor part
● Sweat, digestive secretions, cerebrospinal, pericardial, synovial,
intraocular, and pleural fluids
■ **Capillary walls and cell membranes separate the intracellular and
extracellular compartments
● Movement of Body Fluids and Electrolytes
○ Osmosis
■ Major method of transporting body fluids
■ Process stops when the concentration of solutes has been equalized on
both sides of the cell membrane
■ Osmolarity - concentration of particles in a solution, or its pulling power
■ Isotonic solution - a solution that has about the same osmolarity as
plasma
● Remains in the intravascular compartment without any net flow
across the semipermeable membrane
■ Hypertonic solution - greater osmolarity than plasma
● Water moves out of the cells and is drawn into the intravascular
compartment, causing the cells to shrink
■ Hypotonic solution - less osmolarity than plasma
● Hypotonic solution in the intravascular space moves out of the
intravascular space and into ICF, causing cells to swell and
possibly burst
○ Diffusion
■ Diffusion - tendency of solutes to move freely throughout a solvent
■ Solute moves from an area of higher concentration to an area of lower
concentration until equilibrium is reached
■ O2 and carbon dioxide exchange in the lung’s alveoli and capillaries
occurs by diffusion
○ Filtration
■ Passage of fluid through a permeable membrane
■ From high pressure to low
■ Capillary filtration results from the force of blood <pushing= against the
walls of the capillaries
■ <Pushing= force is referred to as hydrostatic pressure
● When hydrostatic pressure inside capillary exceeds the
surrounding interstitial space, fluids and solute are forced out of
the capillary wall into the interstitial space
■ Reabsorption is the process that acts to prevent too much fluid from
leaving the capillaries no matter how high the hydrostatic pressure
■ Colloid osmotic pressure - when plasma proteins (albumin) facilitate
reabsorption process by <pulling= the fluid back into the capillaries
○ Active Transport
, ■ Requires energy for movement of substances through a cell membrane,
against the concentration gradient, from an area of lesser solute
concentration to an area of higher solute concentration
● Regulations of Acid-Base Balance
○ Buffers
■ Prevents body fluids from becoming overly acidic or alkaline
■ Can function as a base or like an acid
■ Carbonic Acid-Sodium Bicarbonate Buffer System
● Most important system of the body bc carbonic acid is the most
common acid in body and bicarbonate is the body's most common
base
● 20:1 ratio!!! (20 bicarbonate to 1 part carbonic acid)
● pH will change if ratio is out of order
● Lungs help by regulating the production of carbonic acid
● Kidneys assist the bicarbonate system by regulating production of
bicarbonate
■ Phosphate Buffer System
● Active in ICFs, especially in renal tubules
● Converts alkaline sodium phosphate, a weak base, to acid-sodium
phosphate in the kidneys
■ Protein Buffer System
● Mixture of plasma proteins and the globin portion of hemoglobin in
red blood cells
● Minimize changes in pH and serve as excellent buffering agents
over a wide range of pH values working both inside and outside
the cells
○ Respiratory Mechanisms
■ Lungs are primary controller of the body’s carbonic acid supply
■ When there are lots of CO2 in blood, sensitive chemoreceptors in the
respiratory center in the medulla are stimulated to increase the rate and
depth of respirations to eliminate more CO2. And then the opposite can
occur
■ Response is short term, and the response of the kidneys is needed for
long-term adjustments
○ Renal Mechanisms
■ Kidneys excrete or retain hydrogen ions and form or excrete bicarbonate
ions in response to the pH of the blood
■ In presence of acidosis - kidneys excrete hydrogen ions and form and
conserve bicarbonate ions, thus raising the pH to the normal range
■ In the presence of alkalosis - kidneys retain hydrogen ions and excrete
bicarbonate ions in an effort to return to a balanced state
■ Concentration of bicarbonate in the plasma is regulated by the kidneys
■ Regulation occurs more slowly in the kidneys
● May take as long as 3 days
● Fluid and Electrolyte Balance Disorders
○ Hypovolemia - Fluid volume deficit (FVD) is caused by loss of both water and
solutes in the same proportion from the ECF space
■ 5% weight loss is considered a pronounced fluid deficit; an 8% loss or
more is considered severe. 15% weight loss is usually life threatening
■ Tachycardia is the earliest sign
■ A decrease in BP may indicate
○ Body Fluids Compartments
■ Interstitial fluid
● Extracellular Fluid (ECF)
● Surrounds tissue cells and includes lymph
■ Intravascular fluid
● ECF
● Plasma - liquid component of blood
■ Transcellular fluid
● ECF - minor part
● Sweat, digestive secretions, cerebrospinal, pericardial, synovial,
intraocular, and pleural fluids
■ **Capillary walls and cell membranes separate the intracellular and
extracellular compartments
● Movement of Body Fluids and Electrolytes
○ Osmosis
■ Major method of transporting body fluids
■ Process stops when the concentration of solutes has been equalized on
both sides of the cell membrane
■ Osmolarity - concentration of particles in a solution, or its pulling power
■ Isotonic solution - a solution that has about the same osmolarity as
plasma
● Remains in the intravascular compartment without any net flow
across the semipermeable membrane
■ Hypertonic solution - greater osmolarity than plasma
● Water moves out of the cells and is drawn into the intravascular
compartment, causing the cells to shrink
■ Hypotonic solution - less osmolarity than plasma
● Hypotonic solution in the intravascular space moves out of the
intravascular space and into ICF, causing cells to swell and
possibly burst
○ Diffusion
■ Diffusion - tendency of solutes to move freely throughout a solvent
■ Solute moves from an area of higher concentration to an area of lower
concentration until equilibrium is reached
■ O2 and carbon dioxide exchange in the lung’s alveoli and capillaries
occurs by diffusion
○ Filtration
■ Passage of fluid through a permeable membrane
■ From high pressure to low
■ Capillary filtration results from the force of blood <pushing= against the
walls of the capillaries
■ <Pushing= force is referred to as hydrostatic pressure
● When hydrostatic pressure inside capillary exceeds the
surrounding interstitial space, fluids and solute are forced out of
the capillary wall into the interstitial space
■ Reabsorption is the process that acts to prevent too much fluid from
leaving the capillaries no matter how high the hydrostatic pressure
■ Colloid osmotic pressure - when plasma proteins (albumin) facilitate
reabsorption process by <pulling= the fluid back into the capillaries
○ Active Transport
, ■ Requires energy for movement of substances through a cell membrane,
against the concentration gradient, from an area of lesser solute
concentration to an area of higher solute concentration
● Regulations of Acid-Base Balance
○ Buffers
■ Prevents body fluids from becoming overly acidic or alkaline
■ Can function as a base or like an acid
■ Carbonic Acid-Sodium Bicarbonate Buffer System
● Most important system of the body bc carbonic acid is the most
common acid in body and bicarbonate is the body's most common
base
● 20:1 ratio!!! (20 bicarbonate to 1 part carbonic acid)
● pH will change if ratio is out of order
● Lungs help by regulating the production of carbonic acid
● Kidneys assist the bicarbonate system by regulating production of
bicarbonate
■ Phosphate Buffer System
● Active in ICFs, especially in renal tubules
● Converts alkaline sodium phosphate, a weak base, to acid-sodium
phosphate in the kidneys
■ Protein Buffer System
● Mixture of plasma proteins and the globin portion of hemoglobin in
red blood cells
● Minimize changes in pH and serve as excellent buffering agents
over a wide range of pH values working both inside and outside
the cells
○ Respiratory Mechanisms
■ Lungs are primary controller of the body’s carbonic acid supply
■ When there are lots of CO2 in blood, sensitive chemoreceptors in the
respiratory center in the medulla are stimulated to increase the rate and
depth of respirations to eliminate more CO2. And then the opposite can
occur
■ Response is short term, and the response of the kidneys is needed for
long-term adjustments
○ Renal Mechanisms
■ Kidneys excrete or retain hydrogen ions and form or excrete bicarbonate
ions in response to the pH of the blood
■ In presence of acidosis - kidneys excrete hydrogen ions and form and
conserve bicarbonate ions, thus raising the pH to the normal range
■ In the presence of alkalosis - kidneys retain hydrogen ions and excrete
bicarbonate ions in an effort to return to a balanced state
■ Concentration of bicarbonate in the plasma is regulated by the kidneys
■ Regulation occurs more slowly in the kidneys
● May take as long as 3 days
● Fluid and Electrolyte Balance Disorders
○ Hypovolemia - Fluid volume deficit (FVD) is caused by loss of both water and
solutes in the same proportion from the ECF space
■ 5% weight loss is considered a pronounced fluid deficit; an 8% loss or
more is considered severe. 15% weight loss is usually life threatening
■ Tachycardia is the earliest sign
■ A decrease in BP may indicate
