Describe the structure and function of different types of epithelial tissues. Draw a diagram of each type of epithelial tissue.

(N/A) Epithelial tissues are the covering or protective tissues in the animal body. Epithelium covers most organs and cavities within the body and keeps different body systems separate. The skin,the lining of the mouth,the lining of blood vessels,lung alveoli,and kidney tubules are all made of epithelial tissue.
Epithelial tissue cells are tightly packed and form a continuous sheet. They have only a small amount of cementing material between them and almost no intercellular spaces. The permeability of the cells of various epithelia plays an important role in regulating the exchange of materials between the body and the external environment and also between different parts of the body. Regardless of the type,all epithelia are usually separated from the underlying tissue by an extracellular fibrous basement membrane.
Epithelial tissues are of the following types:
$(1)$ Simple squamous epithelium: Extremely thin and flat,forming a delicate lining. Found in blood vessels and lung alveoli where transportation occurs.
$(2)$ Stratified squamous epithelium: Arranged in many layers to prevent wear and tear. Found in the skin and lining of the mouth.
$(3)$ Columnar epithelium: Tall epithelial cells present where absorption and secretion occur,such as the inner lining of the intestine. If they have cilia,they are called ciliated columnar epithelium,which helps in moving mucus.
$(4)$ Cuboidal epithelium: Cube-shaped cells forming the lining of kidney tubules and ducts of salivary glands,providing mechanical support.
Additionally,some epithelial tissue folds inward to form a multicellular gland,known as glandular epithelium.