Human Anatomy: Chapters 1-6

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Anatomy

The study of body structure and relationships among structures; provides the physical framework for physiological processes.

Physiology

The study of how body structures function; explains the chemical and physical mechanisms that sustain life.

Homeostasis

The maintenance of a relatively stable internal environment; ensures cellular survival despite external changes.

Anatomical Position

Standard reference position where the body is upright, facing forward, arms at sides, and palms forward; provides a consistent basis for directional terms.

Sagittal Plane

A vertical plane dividing the body into right and left sections; used to observe bilateral symmetry and lateral structures.

Frontal Plane

A vertical plane dividing the body into anterior and posterior portions; used to evaluate front-to-back spatial orientation.

Transverse Plane

A horizontal plane dividing the body into superior and inferior portions; used to view cross-sectional internal anatomy.

Anterior

Nearer to or at the front of the body; describes the ventral positioning of structures.

Posterior

Nearer to or at the back of the body; describes the dorsal positioning of structures.

Proximal

Nearer to the attachment of a limb to the trunk; defines relative proximity along an extremity.

Distal

Farther from the attachment of a limb to the trunk; defines relative distance along an extremity.

Epithelial Tissue

A cellular, avascular tissue covering body surfaces and lining cavities; serves to protect, absorb, secrete, and filtrate.

Apical Surface

The free, unattached surface of epithelial tissue facing an open space or lumen; specialized for absorption, secretion, or fluid movement.

Basement Membrane

An extracellular layer anchoring epithelial tissue to underlying connective tissue; regulates molecular diffusion and structural support.

Simple Squamous Epithelium

A single layer of flat, scale-like cells; facilitates rapid diffusion and filtration in lungs and blood vessels.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells; specialized for secretion and absorption in kidney tubules and glands.

Simple Columnar Epithelium

A single layer of tall, column-shaped cells; functions primarily in active absorption and mucus secretion in the digestive tract.

Stratified Squamous Epithelium

Multiple cell layers with flattened apical cells; protects underlying tissues from mechanical abrasion and chemical wear.

Pseudostratified Ciliated Columnar Epithelium

A single layer of cells appearing multilayered due to varying nuclear heights; secretes and propels mucus across airways.

Transitional Epithelium

Stratified tissue whose cell shape changes with stretching; accommodates volume fluctuations in the urinary bladder.

Endocrine Gland

A ductless gland that secretes hormones directly into interstitial fluid and blood; coordinates body-wide physiological regulation.

Exocrine Gland

A gland that secretes products into ducts leading to epithelial surfaces; delivers enzymes, sweat, or saliva to target sites.

Tight Junction

A web of transmembrane proteins sealing adjacent epithelial cell membranes; prevents leakage of materials between cells.

Desmosome

A plaque-anchored cell junction with intermediate filaments; resists mechanical tearing and sheer stress in epithelial sheets.

Gap Junction

A channel formed by connexins connecting neighboring cells; allows rapid passage of ions and electrical signaling.

Skeletal Muscle Tissue

Striated, multinucleated, voluntary muscle tissue attached to bones; generates body locomotion and maintains posture.

Cardiac Muscle Tissue

Striated, branched, involuntary muscle tissue found in heart walls; pumps blood rhythmically throughout the circulatory system.

Smooth Muscle Tissue

Non-striated, involuntary, spindle-shaped muscle tissue in organ walls; propels substances through internal lumens.

Sarcomere

The functional contractile unit of a myofibril bounded by Z-discs; shortens during muscle contraction.

Intercalated Disc

A specialized intercellular junction in cardiac muscle containing desmosomes and gap junctions; synchronizes contraction across heart tissue.

Integumentary System

Organ system composed of skin, hair, nails, and glands; provides physical protection, thermoregulation, and sensation.

Epidermis

The superficial, avascular layer of keratinized stratified squamous epithelium; acts as the primary barrier against pathogens and fluid loss.

Stratum Basale

The deepest epidermal layer containing dividing stem cells; continuously generates new keratinocytes.

Stratum Spinosum

An epidermal layer with spiny desmosome-connected cells; provides strength and resistance to mechanical tension.

Stratum Granulosum

An epidermal layer where keratinocytes undergo apoptosis and form keratohyalin; serves as a critical water-retention barrier.

Stratum Lucidum

A clear, thin layer of dead keratinocytes found only in thick skin; provides extra toughness to palms and soles.

Stratum Corneum

The outermost epidermal layer of dead, keratin-filled cells; shields underlying living tissues from abrasion and infection.

Keratinocyte

The predominant cell type of the epidermis; produces tough keratin protein to waterproof and protect the skin.

Melanocyte

A specialized dendritic cell in the stratum basale; synthesizes melanin pigment to protect DNA from ultraviolet radiation.

Dendritic Cell

An immune cell residing in the epidermis; detects pathogens and activates adaptive immune responses.

Tactile Epithelial Cell

A receptor cell in the stratum basale associated with a sensory nerve ending; detects light touch sensations.

Dermis

The vascular layer of connective tissue beneath the epidermis; provides structural tensile strength and nourishes epithelial cells.

Papillary Dermis

The superficial dermal layer of areolar tissue with dermal papillae; anchors the epidermis and supplies it with nutrients via capillaries.

Reticular Dermis

The deep dermal layer of dense irregular connective tissue; provides elasticity, tensile strength, and structural support.

Hypodermis

The subcutaneous layer of adipose and areolar tissue deep to the dermis; anchors skin to muscles, insulates, and stores energy.

Sebaceous Gland

An exocrine gland associated with hair follicles; secretes oily sebum to lubricate and waterproof skin and hair.

Eccrine Sweat Gland

A coiled tubular skin gland open to pores; secretes watery sweat for evaporative thermoregulation.

Apocrine Sweat Gland

A sweat gland in axillary and anogenital regions producing viscous secretions; functions in scent production and emotional sweating.

Hair Follicle

A tubelike epidermal invagination extending into the dermis; produces hair fibers for touch sensation and physical protection.

Arrector Pili

A smooth muscle bundle attached to a hair follicle; contracts in response to cold or fear to pull hairs upright.