Week 2 - Anatomy & Physiology: Energy, Tissues, &

Potential Energy

Stored energy held within chemical bonds or concentration gradients that has the capacity to do work.

Kinetic Energy

The energy of motion or active work (e.g., muscle contraction or movement of molecules).

ATP Hydrolysis

The breaking of ATP's high-energy phosphate bond using water, which releases energy and leaves ADP and inorganic phosphate ($P_i$).

ADP Phosphorylation

The addition of a phosphate group to ADP, which requires energy input from food/cellular respiration to synthesize ATP.

Ionic Bond

A chemical bond formed when one or more electrons are completely transferred from one atom to another, creating charged ions.

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of valence electrons.

Electrolytes

Ionic compounds or salts that dissociate into charged ions in water and are capable of conducting electrical currents in the body.

Nonpolar Covalent Bond

A covalent bond where electrons are shared equally between atoms due to similar electronegativities.

Polar Covalent Bond

A covalent bond where electrons are shared unequally, creating slightly positive ($\delta+$) and slightly negative ($\delta-$) poles.

Simple Diffusion

Passive transport process where small, nonpolar molecules pass directly through the lipid bilayer down their concentration gradient.

Facilitated Diffusion

Passive transport process where charged or polar molecules cross the plasma membrane down their gradient using channel or carrier proteins.

Osmosis

The net movement of water molecules across a selectively permeable membrane toward a higher solute concentration.

Uniporter

A carrier protein that transports only a single type of solute across the plasma membrane.

Symporter

A carrier protein that transports two different solutes across the membrane in the same direction simultaneously.

Antiporter

A carrier protein that transports two different solutes across the membrane in opposite directions.

Primary Active Transport

A cell transport process that directly consumes ATP to pump solutes against their concentration gradient (e.g., $Na^+/K^+$ pump).

Phagocytosis

A type of active vesicular transport ("cell eating") where a cell engulfs large particles or debris into a membrane-bound vesicle.

Epithelial Tissue

Primary tissue type that covers body surfaces, lines cavities, forms glands, and acts as a barrier with high regenerative capacity.

Connective Tissue

Primary tissue type that supports, protects, binds other tissues together, and stores energy (e.g., bone, blood, adipose tissue).

Muscular Tissue

Primary tissue type specialized for contraction and producing physical force or movement.

Nervous Tissue

Primary tissue type specialized for sensing stimuli, processing information, and transmitting electrical signals.

Basement Membrane

An extracellular layer anchor underlying connective tissue to epithelial cells.

Avascularity of Epithelium

The characteristic of epithelial tissue lacking direct blood vessels, relying on diffusion of nutrients from underlying connective tissue.

Tissue Regeneration

The replacement of damaged or destroyed tissue with the exact same cell type, fully restoring original tissue function.

Fibrosis

The replacement of damaged tissue with collagen-rich scar tissue, resulting in permanent structural change and loss of original function.

Keratinocytes

The primary structural cell type of the epidermis that produces protective keratin protein and Vitamin D precursors.

Melanocytes

Epidermal cells located in the stratum basale that synthesize the pigment melanin.

Dendritic Cells (Langerhans Cells)

Star-shaped immune cells residing in the epidermis that engulf pathogens and alert the immune system.

Tactile Cells (Merkel Cells)

Sensory receptors located at the epidermal-dermal junction that detect fine touch sensations.

Stratum Basale

The deepest, single-cell layer of the epidermis containing actively dividing stem cells, melanocytes, and tactile cells.

Stratum Spinosum

Epidermal layer containing several layers of keratinocytes bound by desmosomes, along with immune dendritic cells.

Stratum Granulosum

Epidermal layer where keratinocytes undergo keratinization, flatten, and release lipid-rich waterproofing granules.

Stratum Lucidum

A thin, clear layer of dead keratinocytes found only in thick skin (palms and soles).

Stratum Corneum

The most superficial epidermal layer consisting of multiple layers of dead, fully keratinized, flattened cells.

Melanosome

A membrane-bound organelle inside melanocytes that synthesizes, stores, and transports melanin pigment into neighboring keratinocytes.

Topical Drug Delivery

Application of polar drugs that act locally on the skin surface because they cannot cross the lipid-waterproof barrier of the epidermis.

Transdermal Drug Delivery

Application of nonpolar drugs through the skin surface that pass through the epidermis and enter dermal blood vessels for systemic body distribution.

Thick Skin

Skin found on palms and soles containing 5 epidermal layers (includes stratum lucidum), a thicker stratum corneum, sweat glands, but NO hair or oil glands.

Thin Skin

Skin covering most of the body containing 4 epidermal layers (lacks stratum lucidum), hair follicles, sebaceous glands, and sweat glands.

Papillary Layer of Dermis

Superficial dermal layer composed of loose areolar connective tissue with projections (dermal papillae) that interlock with the epidermis.

Reticular Layer of Dermis

Deep dermal layer composed of dense irregular connective tissue containing dense collagen fibers providing multidirectional strength.

First-Degree Burn

Partial-thickness burn involving damage only to the epidermis, characterized by redness, swelling, and mild pain (e.g., mild sunburn).

Second-Degree Burn

Partial-thickness burn damaging the entire epidermis and upper dermis, characterized by pain, redness, and blister formation.

Third-Degree Burn

Full-thickness burn destroying the entire epidermis and dermis into the hypodermis, usually painless due to destroyed nerve endings and requiring skin grafts.

Arrector Pili Muscle

A small band of smooth muscle attached to a hair follicle that contracts to pull the hair upright, causing "goosebumps".

Anagen Phase

The active growth phase of a hair follicle during which matrix cells actively divide to build the hair strand.

Catagen Phase

The short regressive/transition phase of hair growth where matrix cells die and the follicle detaches from its dermal papilla.

Telogen Phase

The resting phase of hair growth during which the old hair strand falls out and the follicle remains inactive before restarting growth.

Nail Matrix

The actively dividing, thickened proximal portion of the nail bed responsible for continuous nail growth.

Eccrine Sweat Glands

Abundant, simple tubular glands that secrete a watery sweat directly onto the skin surface for evaporative thermoregulation.

Apocrine Sweat Glands

Large sweat glands located in axillary and anogenital regions that secrete a protein and lipid-rich sweat into hair follicles, active starting at puberty.

Ceruminous Glands

Modified apocrine glands located in the external ear canal that secrete cerumen (earwax) for physical protection.

Mammary Glands

Modified apocrine glands located in breast tissue specialized for producing and secreting milk to nourish offspring.

Sebaceous Glands

Exocrine glands usually attached to hair follicles that secrete sebum, an oily substance that lubricates skin/hair and acts as a bactericide.