Introduction to Physiology and Body Fluid Compartments

Flashcards reviewing introductory physiology concepts, body levels of organization, total body water metrics, fluid compartment distribution, and ionic compositions.

Physiology

The study of normal body functions that explains the purpose and mechanism of body processes.

Cell

The functional living unit of the body.

Chemical Level

The structural level of organization where atoms combine to form molecules.

Cellular Level

The structural level of organization where cells are constructed from molecules.

Tissue Level

The structural level of organization consisting of similar types of cells working together.

Organ Level

The structural level of organization where structures are composed of different types of tissues.

Organ System Level

The structural level of organization consisting of different organs that work closely together.

Total Body Water (TBW)

The total volume of water in the body, accounting for $40\%$ to $80\%$ of total body weight (average $60\%$), equal to $42\,L$ in an adult weighing $70\,kg$.

Lean Body Tissue

Fat-free tissue composed of $73\%$ water ($71\text{ to }72\,ml/100\,g$ of tissue).

Gray Matter of Brain (Water Content)

The body tissue containing the highest water concentration at $85\%$.

Dentin of Teeth (Water Content)

The body tissue containing the lowest water concentration at $10\%$.

Intracellular Fluid (ICF)

The fluid contained inside cells, separated from ECF by plasma membranes, making up $40\%$ of body weight ($28\,L$ in a $70\,kg$ adult) or $2/3$ of total body water.

Extracellular Fluid (ECF)

The fluid outside cells, separated from ICF by cell membranes, making up $20\%$ of body weight ($14\,L$ in a $70\,kg$ adult) or $1/3$ of total body water.

Plasma

The fluid portion of ECF present inside the vascular system, constituting $5\%$ of body weight ($3.5\,L$ in a $70\,kg$ adult) or $1/4$ of ECF.

Interstitial Fluid (ISF)

The tissue fluid portion of ECF located outside the vascular system in microscopic spaces between cells, accounting for $15\%$ of body weight ($10.5\,L$ in a $70\,kg$ adult) or $3/4$ of ECF.

Transcellular Fluid

A small fraction of extracellular fluid contained within epithelial-lined spaces (such as CSF, intra-ocular fluid, pleural fluid, and synovial fluid) that normally does not affect body fluid balance.

Extracellular Fluid Main Ions

Sodium ($\text{Na}^+$ at $142\,meq/l$) is the primary cation, while Chloride ($\text{Cl}^-$ at $104\,meq/l$) and Bicarbonate ($\text{HCO}_3^-$ at $28\,meq/l$) are the main anions.

Intracellular Fluid Main Ions

Potassium ($\text{K}^+$ at $140\,meq/l$) is the primary cation, while Phosphates ($75\,meq/l$) and Proteins ($16\,g\%$) are the main anions.

Capillary Filtration

The movement that pushes water out of capillaries into tissue fluid driven by a hydrostatic pressure difference.

Osmosis (Fluid Transport)

The force that pulls water across membranes into fluid compartments containing higher solute concentration.

Body Fluid Distribution

Anatomical division of total body water into intracellular fluid, interstitial fluid, and intravascular fluid.