Biochemistry: Body and Biological Fluids

A set of vocabulary flashcards covering human body composition models, fluid compartments, and specific biological fluids based on biochemistry lecture notes.

Body Composition Models

Conceptual models used to classify body mass into compartments (such as 2-, 3-, and 4-compartment models), where measuring more compartments reduces the error in body composition estimates.

Adult Male Body Composition

The average mass breakdown for an adult male, consisting of $60\%$ body water and $40\%$ solids ($20\%$ fat, $15\%$ protein, and $5\%$ minerals).

Adult Female Body Composition

The average mass breakdown for an adult female, consisting of around $50\%$ body water and around $50\%$ solids (around $30\%$ fat, $15\%$ protein, and $5\%$ minerals).

Body Fluids

Various aqueous solutions within the body comprising water and dissolved substances like electrolytes and proteins, essential for nutrient transport, waste removal, and homeostasis.

Intracellular Fluid (ICF)

The fluid compartment contained inside cells by their plasma membranes, accounting for about $\frac{2}{3}$ of total body water ($40\%$ of total body weight) and composed primarily of potassium, organic anions, and proteins.

Extracellular Fluid (ECF)

The fluid compartment located outside cells, accounting for the remaining $\frac{1}{3}$ of total body water ($20\%$ of total body weight), composed primarily of a $NaCl$ and $NaHCO_3$ solution.

Interstitial Fluid (ISF)

The main component of extracellular fluid that surrounds tissue cells but does not circulate, making up about $\frac{3}{4}$ of the ECF.

Blood Plasma

The yellow, intravascular liquid portion of circulating blood in which blood cells are suspended, representing $55\%$ of total blood volume and about $\frac{1}{4}$ of the ECF.

Transcellular Fluid

The portion of total body water contained within epithelial-lined spaces, representing the smallest fluid compartment at about $2.5\%$ of total body water.

Amniotic Fluid

A clear, slightly yellowish liquid contained in the amniotic sac that surrounds the fetus during pregnancy.

Aqueous Humor

Fluid produced by the eye that provides nourishment to ocular tissues and maintains internal intraocular pressure.

Bile

A digestive fluid produced by the liver and stored in the gallbladder that aids in digestion, fat absorption via emulsification, and waste excretion.

Cerebrospinal Fluid (CSF)

A clear fluid surrounding the brain and spinal cord in the subarachnoid space that cushions against mechanical injury, provides buoyancy, and enables nutrient delivery and waste removal.

Cerumen

The medical term for earwax; a waxy substance secreted in the human ear canal that varies in color from brown, orange, red, yellowish, to gray.

Chyle

A milky fluid composed of lymph and emulsified free fatty acids formed in the small intestine during digestion and absorbed by lymphatic lacteals.

Exudate

Fluid consisting of cells, proteins, and solid material that leaks out of blood vessels into surrounding tissue during infection, inflammation, or wound healing.

Gastric Juice

A highly acidic, enzyme-rich mixture of water, hydrochloric acid, electrolytes, and organic substances secreted by the stomach to digest food.

Lymph

The fluid flowing through the lymphatic system that returns fluid from tissue spaces back into central venous circulation.

Mucus

A slippery, stringy protective fluid produced by epithelial tissue linings to moisturize organ surfaces and trap irritants like dust, smoke, or microbes.

Pericardial Fluid

A lubricating fluid produced by pericardial membranes that sits between the layers surrounding the heart to reduce friction during cardiac contractions.

Peritoneal Fluid

A lubricating liquid found in small amounts ($5\text{--}20\,\text{mL}$) between the layers of the peritoneum lining the abdominal cavity.

Pleural Effusion

The accumulation of excess fluid between the layers of the pleura surrounding the lungs.

Pus

A thick inflammatory fluid containing dead tissue, white blood cells, and bacteria produced by the body while combatting infection.

Saliva

A thick, colorless fluid in the mouth containing water, mucus, proteins, mineral salts, and amylase that aids in digestion and clears cellular debris.

Sebum

An oily, waxy substance secreted by cutaneous sebaceous glands that coats, moisturizes, and protects the skin.

Serous Fluid

A watery fluid resembling blood serum that originates from the liquid portion of blood and fills various body cavities.

Synovial Fluid

A viscous fluid located in joint cavities that cushions the ends of bones and reduces friction during joint movement.

Sweat

An aqueous fluid containing dissolved salts secreted by dermal sweat glands that cools the skin surface via evaporation for thermoregulation.

Tears

Clear liquid secreted by lacrimal glands to lubricate the eyes, clean away irritants, and support ocular immune defense.

Urine

A liquid metabolic waste product formed by the kidneys that travels through the ureters to the urinary bladder prior to excretion.