Epithelial Tissue

Functions

Protects, secretes, absorbs, excretes

Protects

Provides barrier

Secretes

Produce and release products

Absorbs

To take in a substance

Excrete

Remove waste

Types of Epithelium

Covering and lining, glandular

Covering and Lining Epithelium

Outer layer of skin and organs, lines blood vessels, and body cavities

Glandular Epithelium

Type of Epithelial Tissue - has cells that produce and discharged substances (secretion)

General Features

Closely packed cells with little extracellular material

Cell Layers

Single or multiple layers of cells

Apical Surface

Free surface of epithelial cells

Basal Surface

Surface adhering to the basement membrane

Avascular

Without blood vessels

Diffusion

Exchange of wastes and nutrients with connective tissues

Connective Tissue

Holds epithelium in place

Nerve Supply

Epithelial tissue has a nerve supply

High Mitotic Rates

Repairs wear and tear

Simple Epithelium

Single layer of cells

Stratified Epithelium

Several layers of cells

Pseudostratified

One layer of cells where not all reach the apical surface

Cell Shapes

Squamous, cuboidal, columnar, transitional

Squamous

Flat; scale-like cells

Cuboidal

Cube-shaped cells with round nucleus

Columnar

Tall and rectangular cells

Transitional

Cells that change shape

Gland

One cell or a group of cells that produce and discharge substances

Exocrine Glands

Secretes into ducts that open into surfaces

Endocrine Glands

Ductless, secretes hormones into blood

Holocrine Glands

Whole cell is discharged (e.g., sebaceous gland)

Merocrine Glands

Product leaves via exocytosis (e.g., salivary gland)

Apocrine Glands

Apical surface pinches off (e.g., mammary gland)