animal cells and tissues: Epithelia

They are tissues that cover the surface of internal and external organ.
They give protection, secretion, absorption, gaseous diffusion, excretion etc.
connective tissue= basement membrane

Simple epithelia: Single layer of epithelial cell, e.g. Squamous, ciliated epithelium
compound epithelia: more than one layer, e.g. stratified epithelium

Squamous epithelium
Consist of flattened, plate-like cells with disc shape nucleus and wavy boundary.

features:
The thinness of the epithelium allows rapid diffusion/filtration of materials

Place found:
alveolar membrane, bowman's capsule

Ciliated epithelium
Consist of columnar cells with numerous cilia on the free surface. Goblet cells interspersed among columnar cells.
Columnar cells: tall and narrow shape, containing elongated nucleus.
Goblet cells: specialized epithelial cell that secret mucus

features:
Coordinated beating action produced facilitate movement of material(dust/ cell)

Place found:
inner surface of the oviduct, inner lining of trachea

Stratified epithelium:
Consist of basement membrane--germinative layer and layers of old cells

• Germinative layer is a site where active cell division takes place.
• Newly divided cells are pushed upwards to replace the old ones,while the old cells become gradually flattened near the surface.
• The outermost cells are usually dead, flattened and gradually sloughed off because they are kept away from the nutrient supply

features:
Protect the underlying tissues against abrasion.

Place found:
inner lining of virgina
epidermis of skin

• the outer cells are keratinized (layer of keratin)
• horny and waterproof layer provides excellent protection from mechanical injury and dehydration