Epithelium

Histology

The study of tissues.

Simple epithelium

1. Simple squamous 2. Simple cuboidal 3. Simple columnar 4. Pseudostratified columnar

Stratified epithelium

1. Stratified squamous 2. Stratified cuboidal 3. Stratified columnar 4. Transitional

Glands

1. Exocrine 2. Endocrine

Epithelium

Tissue that covers outer body surface OR lines a body cavity. (Often forms glands.)

Characteristics of epithelia

1. Cellularity, composed almost entirely of cells. 2. Cell junctions. 3. Polarity (the two sides are different.) Ex: Goblet cell-secrets mucus 4. Basement membrane (anchors epithelium to the underlying connective tissue.) 5. Ability to regenerate quickly

Apical

Toward space

Basal

Toward attachment

Avascular

Not associated with blood vessels

Innervated

Associated with nerve cell processes

Absorption

Active uptake of molecules (Active: USES CELL ENERGY)

Secretion

Active release of molecules (Active: USES CELL ENERGY)

Microvilli

Extensions to increase surface area

Diffusion

Molecules move down concentration gradient (Passive: NO ENERGY USED)

Filtration

Plasma (fluid component blood) leaks across capillary walls (Passive: NO ENERGY USED.)

Propulsion

Cillia drive fluid along surface of epithelium

Sliding

Protection

Sensory reception

Epithelial cell generates sensory signal

Classification: Simple

Each cell is attached to basement membrane

Classification: Stratified

Multiple layers; only the basal layer directly attached to basement membrane

Simple

Stratified

Squamous

Cuboidal

Columnar

Simple squamous

(Thinnest kind) No surface projections

Alveoli

Lining of air sacs in lungs

Mesothelium

Lining of closed body cavities

Endothelium

Inner lining of heart & blood vessels

Glomerular

Capsule in kidney where filtration occurs.

Simple cuboidal

Glands (most), kidney tubules

Simple columnar