Question

Write about the special features of simple epithelium, its location, and its different types. Draw suitable diagrams also.

Answer 1

1. Simple epithelium is composed of a single layer of cells. They are found in the organs of absorption, secretion and filtration. Simple epithelial tissue is further classified into squamous epithelium, cuboidal epithelium, columnar epithelium, ciliated epithelium and pseudostratified epithelium. The squamous epithelium is made of a single thin layer of flattened cells with irregular boundaries. They are found in the kidney glomeruli, air sacs of lungs, lining of heart, blood vessels and lymphatic vessels and are involved in functions like forming a diffusion boundary and filtration in sites where protection is not important.
2. The cuboidal epithelium is made of a single layer of cube-like cells. This tissue is commonly found in the kidney tubules, ducts and secretory portions of small glands and the surface of the ovary. Its main functions are secretion and absorption.
3. The columnar epithelium is composed of a single layer of tall cells with round to oval nuclei at the base. It lines the digestive tract from the stomach to the rectum.
4. The functions of this epithelium include absorption, secretion of mucus, enzymes and other substances.
5. This ciliated type propels mucus by ciliary actions and it lines the small bronchioles, fallopian tubes and uterus. Non-ciliated type lines most of the digestive tract, gall bladder and secretory ducts of glands.
6. Pseudo-stratified epithelial cells are columnar but unequal in size. Although the epithelium is single-layered yet it appears to be multi-layered because the nuclei lie at different levels in different cells. Hence, it is also called pseudostratified epithelium and its functions are protection, secretion and absorption. Ciliated forms line the trachea and the upper respiratory tract. The non-ciliated forms line the epididymis, large ducts of glands and tracts of the male urethra.