Epithelial Tissue Characteristics and Functions

Flashcards covering the characteristics, functions, and structures of epithelial tissue, as well as details on types of epithelial tissue and glandular epithelium.

Epithelial tissue

Consists of closely packed cells with little extracellular matrix, forming sheets that cover body surfaces and line cavities.

Avascular

Lacking blood vessels.

Highly innervated

Supplied with nerves.

Basement membrane

Structure that attaches epithelium to connective tissue and acts as a semipermeable filter.

Basal lamina

The layer of the basement membrane produced by the epithelium.

Reticular lamina

The layer of the basement membrane produced by the connective tissue.

Cellular junctions

Provide adhesion and communication between cells.

Tight junctions

Also known as zonulae occludens; inhibits paracellular movements by forming a seal between adjacent cells.

Adherens junctions

Also known as zonula adherens; firmly anchors a cell to its neighbor.

Desmosomes

Also called macula adherens; functions like a 'spot weld' to attach neighboring cells.

Hemidesmosome

A junction that attaches a cell to the basal lamina of the basement membrane.

Gap junction

A communicating junction that allows the exchange of small molecules between cells.

Connexons

The small tunnels that comprise gap junctions.

Simple epithelium

One layer of cells.

Stratified epithelium

Two or more layers of cells.

Simple squamous epithelium

Single layer of flat, thin cells involved in diffusion, found in kidneys and alveoli.

Endothelium

Simple squamous epithelium that lines blood vessels.

Mesothelium

Simple squamous epithelium that lines large body cavities.

Simple cuboidal epithelium

Single layer of cube-shaped cells involved in secretion and absorption, found in the kidneys and thyroid gland.

Simple columnar epithelium

Single layer of tall cells involved in secretion and absorption, found in the gastrointestinal tract.

Pseudostratified columnar epithelium

Composed of tall, irregular cells that appear stratified; found in the respiratory tract and male reproductive tract.

Keratinized stratified squamous epithelium

Multiple layers of flat cells packed with keratin, involved in protection, found in the skin.

Non-keratinized stratified squamous epithelium

Multiple layers of cells not packed with keratin, found in moist cavities.

Transitional epithelium

Lines most of the urinary tract; allows stretching and protects underlying tissue.

Microvilli

Increase surface area for absorption; folds of the cell membrane containing actin filaments.

Stereocilia

Longer, less motile than microvilli; found in the male reproductive system and inner ear.

Cilia

Composed of microtubules; move fluid and suspended matter along the epithelial surface.

Glandular epithelium

Specialized epithelium that produces and secretes various macromolecules.

Exocrine glands

Glands that develop from covering epithelium and remain connected to the surface via ducts.

Endocrine glands

Ductless glands that release their products into the bloodstream.

Serous secretion

Watery secretion from exocrine glands.

Mucous secretion

Thick secretion from exocrine glands.

Myoepithelial cells

Contractile cells that help propel secretory products out of exocrine glands.

Follicular arrangement

Arrangement of endocrine glands where cells form follicles that store products, surrounded by capillaries.

Anastomosing cords

Arrangement of endocrine glands where cells are arranged in cords, each in contact with capillaries.