Biophysics - Unit 3: Biological Fluids

Vocabulary flashcards covering the biophysics of biological fluids, including mechanics, pressures in the human body, intermolecular forces, and cellular fluid distribution.

Biological Fluid Biophysics

The study of the physical behavior, movement, and transport of liquids (blood, plasma, urine) and gases within living systems using principles of fluid statics and dynamics.

Fluids

Substances (liquids or gases) whose molecules have little cohesion, allowing them to deform continuously and flow under external forces, adapting to the shape of their container.

Viscosity

The internal resistance to flow or "stickiness" within a fluid.

Density ($\rho$)

The mass per unit volume of a substance, expressed as $\rho = \frac{m}{V}$.

Compressibility

The ability of a substance to reduce its volume when subjected to pressure.

Newtonian Fluids

Fluids that maintain a constant viscosity regardless of the forces applied, such as water.

Non-Newtonian Fluids

Fluids with variable viscosity, such as blood or honey.

Ideal Fluids

Theoretical fluids characterized by having zero viscosity.

Laminar Flow

A smooth and orderly regime of fluid flow.

Turbulent Flow

A chaotic fluid flow regime characterized by the presence of eddies or whirlpools.

Fluid Statics

The branch of fluid mechanics that studies fluids at rest.

Fluid Dynamics

The branch of fluid mechanics that studies fluids in motion.

Specific Weight ($\gamma$)

The force of gravity per unit volume, calculated as $\gamma = \frac{mg}{V} = \rho g$.

Pressure ($P$)

The force exerted per unit area, defined by the formula $P = \frac{F}{A}$.

Hydrocephalus

The excessive accumulation of cerebrospinal fluid in the cerebral ventricles, which increases intracranial pressure and can damage brain tissue.

Glaucoma

A disease that damages the optic nerve due to high intraocular pressure in the aqueous humor, typically exceeding $22\,mmHg$.

Receptive Relaxation

The process by which the stomach expands to accommodate food without a sharp increase in intragastric pressure.

Peristalsis

Pressure waves that advance food through the digestive tract using a high-pressure gradient behind the bolus and low pressure in front of it.

Cohesion Forces

The attraction between molecules of the same substance, which generates surface tension and droplet formation.

Adhesion Forces

The attraction between molecules of different substances, which enables humectation or wetting.

Surface Tension ($\sigma$)

The membrane-like force at the surface of a liquid caused by unequal molecular attraction, calculated using $F = 2 L \sigma$ or $P = \frac{2\sigma}{r}$.

Capillarity

The phenomenon where a liquid's surface rises or falls in a small-diameter tube, governed by the formula $h = \frac{2\sigma \cos(\theta)}{\gamma r}$.

Osmosis

The diffusion of water molecules through a porous or semipermeable membrane, defined by the osmotic pressure formula $P_{os} = C R T$.

Intracellular Fluid

The fluid inside cells (cytosol) that accounts for $60\%$ of total body water and is rich in potassium, magnesium, and phosphorus.

Extracellular Fluid

Fluid outside cells (interstitial fluid and plasma) comprising one-third of total body water ($20\%$ of body weight), rich in sodium, chlorine, and bicarbonate.