Tissues and Epithelial Tissue - Key Terms

A comprehensive set of vocabulary flashcards covering tissues, epithelial classifications, glands and secretions, junctions, basal structures, connective tissue components, and related connective tissue disorders.

Tissues

Groups of structurally similar cells with related functions; four major tissue types: muscle, nervous, epithelial, connective.

Muscle tissue

Contractile tissue derived from mesoderm; includes skeletal, cardiac, and smooth muscle; functions to produce force and motion.

Skeletal muscle

Striated, usually attached to the skeleton; contracts to produce voluntary movement.

Cardiac muscle

Involuntary, branched striated muscle found in the heart; pumps blood.

Smooth muscle

Non-striated, spindle-shaped cells with a single nucleus; located in walls of hollow organs; involuntary; propels substances along internal passageways.

Nervous tissue

Tissue specialized to react to stimuli and conduct impulses; composed of neurons.

Neuron

Nerve cell that transmits impulses; highly excitable.

Epineurium

Dense connective tissue sheath surrounding a nerve.

Perineurium

Sheath surrounding bundles of nerve fibers within a nerve.

Endoneurium

Thin layer of loose connective tissue surrounding individual nerve fibers.

Epithelial tissue

Sheets of cells covering body surfaces and cavities; functions include protection, sensation, secretion, absorption, excretion, diffusion, cleaning, and reducing friction; also forms glands.

Gland

Organ that secretes substances; exocrine glands have ducts; endocrine glands are ductless.

Simple squamous epithelium

Single layer of flat cells; facilitates diffusion and reduces friction; lines alveoli, capillaries, and body cavities.

Simple cuboidal epithelium

Single layer of cube-shaped cells; functions in secretion and absorption; found in glands, kidney tubules, and certain ducts; includes germinal epithelium.

Germinal epithelium

Epithelium involved in production of gametes: egg cells in the ovary and sperm cells in the testes.

Simple columnar epithelium

Elongated column-shaped cells; lines stomach and intestines; goblet cells secrete mucus.

Goblet cell

Unicellular gland that secretes mucus; interspersed among columnar epithelium.

Pseudostratified columnar epithelium

Single layer with nuclei at varying levels; often ciliated; secretes mucus; lines trachea and upper respiratory tract, also vas deferens.

Stratified cuboidal epithelium

Multi-layered epithelium; protects ducts of sweat glands and the male urethra.

Stratified columnar epithelium

Several cell layers; provides protection and some secretion; limited locations (e.g., male urethra, large ducts of glands).

Stratified squamous epithelium

Multiple cell layers; protects underlying tissues; common in vagina and skin.

Transitional epithelium

Epithelium that resembles both stratified squamous and stratified cuboidal; surface cells dome-shaped; stretches readily to distend urinary organs.

Basal lamina

Protein-rich layer underlying epithelial cells; acts as a filter and a base for regeneration.

Basement membrane

Thick barrier formed by the basal lamina plus underlying reticular fibers; supports epithelia.

Exocrine gland

Gland that secretes onto body surfaces or cavities via ducts (e.g., goblet cells, sweat glands).

Endocrine gland

Ductless gland that secretes hormones into the bloodstream for transport to target tissues.

Merocrine secretion

Secretory products released via membrane-bound vesicles by exocytosis; gland remains intact.

Apocrine secretion

Apical portion of the cell is pinched off during secretion; secretions may contain membrane fragments (e.g., mammary glands).

Holocrine secretion

Secretory cell dies; its entire contents become the secretion (e.g., sebaceous glands; some sweat glands).

Tight junctions (zonula occludens)

Junctions formed by claudin/occludin that seal adjacent cells and prevent paracellular passage; maintain apical-basal polarity.

Desmosomes

Adhesive junctions with cadherins; plaques connect cells and anchor intermediate filaments for mechanical strength.

Gap junctions

Intercellular channels formed by connexons that allow small molecules to pass directly between neighboring cells.

Basal lamina (revisited)

Protein sheet beneath epithelial cells; part of the basal lamina limiting regeneration and filtration.

Connective tissue

Tissue that supports and binds other tissues; cells scattered in an extracellular matrix; derived from mesoderm.

Loose connective tissue

Areolar tissue with collagenous, elastic, and reticular fibers; surrounds and supports organs.

Collagenous fibers

Thick white fibers of collagen providing tensile strength.

Elastic fibers

Fibers that provide elasticity and resilience to tissues.

Reticular fibers

Thin supportive fibers forming networks in organs.

Adipose tissue

Specialized connective tissue for fat storage; insulation and energy reserve.

Cartilage

Semi-rigid connective tissue with chondrocytes in lacunae; avascular and flexible.

Bone

Rigid connective tissue; osteocytes in lacunae; mineralized matrix providing support and protection.

Marfan syndrome

Autosomal dominant connective tissue disorder with tall stature, long limbs, and cardiovascular abnormalities; linked to defects in fibrillin-1.

Fibrillin-1

Glycoprotein essential for elastic fiber formation; gene located on chromosome 15.

Ehlers-Danlos syndrome

Group of genetic disorders involving defective collagen synthesis (types I and III), causing hyperflexible joints and fragile skin.