Term “epithelium” was used by Ruysch. This tissues cover the body organs on the outside & inside. In epithelial tissue, the cells remain closely situated. Hence, due to absence of inter cellular space the inter cellular fluid is absent or very less. They have an inter cellular cementing material which is a glycoprotein containing hyaluronic acid. The epithelial tissues have one or more layers of the cells. The height of the cells is variable such as squamous, flat, cuboidal & columnar.
In epithelial tissues, the cells are based on a basement membrane
Following cellular connections are found in between the cells of the epithelial tissues –
- Tight Junction – They are mainly formed in the cells of columnar epithelium.
- Intercellular bridges – They are mainly found in the transitional epithelium.
- Desmosome or Macula adharence – They are button¬like structures in between the plasma membranes of adjacent cells. They have inter cellular spaces & tonofibrils. They are mainly found in stratified epithelium.
The free (outer) surface of the epithelium may be smooth and it may have microvilli (protoplasmic processes which increase surface for absorption in ileum) or cilia (Example – trachea, oviduct) or stereocilia (Example – epididymis, vas deferens).
