Structural Organisation in Animals – Notes

Epithelial Tissues
Animal tissues are broadly classified into four types, namely epithelial connective, muscular and neural.
Epithelial cells are compactly arranged with little intercellular matrix.
The epithelium and other tissues have three types of specialised junctions, namely tight, adhering and gap junctions.
Simple epithelium consists of a single layer of cells and serves as a lining for body cavities, ducts and tubes.
Compound epithelium consists of two or more layers and its chief function is protection against mechanical and chemical stress.
Simple epithelium is categorised into squamous, cuboidal and columnar.
Some cuboidal and columnar cells have cilia on their free surface and therefore called ciliated epithelium.
Some cuboidal and columnar cells are also specialised for secretion and are therefore called glandular epithelium.

Connective Tissues
Connective tissues are the most abundant and widely distributed tissues in animals.