Cell Layers:

• Simple epithelium: Single layer of cells
• Stratified epithelium: Multiple layers of cells
• Pseudostratified epithelium: Appears to have multiple layers due to the varying positions of nuclei, but all cells are in contact with the basement membrane

Cell Shapes:

• Squamous: Flat, scale-like cells
• Cuboidal: Cube-shaped cells
• Columnar: Tall, column-shaped cells

Protection:

Epithelial tissue acts as a protective barrier against mechanical injury, pathogens, and fluid loss.

Absorption:

Some epithelial cells are specialized for absorbing substances, such as nutrients in the intestines or ions in the kidneys.

Secretion:

Glandular epithelial cells secrete substances such as hormones, enzymes, and mucus.

Simple Squamous Epithelium:

This type of epithelium is thin and allows for the exchange of substances. It is found in the alveoli of the lungs and the lining of blood vessels.

Stratified Squamous Epithelium:

It provides protection and is found in the outer layer of the skin, the lining of the mouth, throat, and esophagus.

Simple Cuboidal Epithelium:

These cells are involved in secretion and absorption and are found in the kidney tubules and glands.

Simple Columnar Epithelium:

These cells are specialized for absorption and secretion. They line the digestive tract and the uterus.