Anatomy

Epithelium

A tissue with a free surface that covers and lines body surfaces, composed of closely packed cells with minimal extracellular material.

Simple Epithelium

A single layer of epithelial cells.

Stratified Epithelium

Multiple layers of epithelial cells.

Avascular

Lacking blood vessels; characteristic of epithelial tissue.

Basal Surface

The surface of epithelial cells that is attached to the basal lamina (basement membrane).

Basal Lamina

A layer that binds epithelial cells to underlying connective tissue, composed of type IV collagen and glycoproteins.

Tight Junctions

Specialized intercellular junctions that prevent diffusion between adjacent epithelial cells.

Desmosomes

Strong spot links between epithelial cells that provide mechanical stability.

Hemidesmosomes

Junctions that anchor epithelial cells to the basal lamina.

Gap Junctions

Intercellular channels that allow communication and the passage of signaling molecules between adjacent cells.

Cilia

Hair-like structures that move mucus and other substances along epithelial surfaces, primarily found in the respiratory tract.

Microvilli

Finger-like projections that increase surface area for absorption, found in intestinal and kidney cells.

Stereocilia

Long microvilli that increase surface area, found in the epididymis and sensory cells of the inner ear.

Simple Squamous Epithelium

A single layer of flat cells that allows for the movement of substances; includes endothelium and mesothelium.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells involved in secretion and absorption.

Simple Columnar Epithelium

A single layer of tall cells that provides protection, secretion, and absorption; can be ciliated or non-ciliated.

Stratified Squamous Epithelium

Multiple layers of flat cells, with superficial layers being flat and deeper layers more cuboidal; can be keratinized or non-keratinized.

Pseudostratified Columnar Epithelium

Appears to have multiple layers but is a single layer with all cells attached to the basement membrane; often ciliated.

Transitional Epithelium

A specialized stratified epithelium that can change shape, found in the urinary tract.

Exocrine Glands

Glands that secrete substances into ducts that lead to the outside of the body.

Endocrine Glands

Ductless glands that secrete hormones directly into the bloodstream.

Goblet Cells

Unicellular exocrine glands that produce mucus, found in the GI and respiratory systems.

Serous Glands

Exocrine glands that secrete a watery fluid.

Mucous Glands

Exocrine glands that secrete a thick, gummy fluid.

Mixed Glands

Exocrine glands that produce both serous and mucous secretions.