Lecture 10 Biology
In this lecture we will provides an introduction to the concept of how cells, the fundamental building blocks of the body, are assembled into tissues and how tissues assemble into organs in order to perform complex functions necessary for the operation of the body. There are four basic tissue types in the body : 1-Epithelial tissue 2-Connective tissue 3- Muscle tissue 4- Nervous tissue. They are represented in most organs.
Epithelial tissues are composed of closely aggregated polyhedral cells with very little extracellular substance. These cells have strong adhesion and form cellular sheets that cover the surface of the body and line its cavities. The principal functions of epithelial tissues are: 1- Covering, lining, and protecting surfaces (eg, skin)
2-Absorption (eg, the intestines)
3- Secretion (eg, the epithelial cells of glands)
4-Contractility (eg, myoepithelial cells)