Epithelial tissue (Semester 2: Biomedical Revision Notes)

Information taken from the text book 'Life'. 

There are four 4 classes of tissue:

Tissue = A collection of cells performing a similar function.







We'll start talking about the Epithelial tissue. Epithelial tissue are sheets of densely packed, tightly connected epithelial cells (as shown in the image above).
Epithelial cells have many functions, 

• They create boundaries between the inside and the outside of the body and between body compartments. 
• They line the blood vessels and make up various ducts and tubules.

Filtration and transportation are important functions of the epithelial cells because

• They both act as barriers and provide transport across those barriers. 
• They control what molecules and ions can move between the blood and interstitial fluid. 
• They can selectively transport ions and molecules from one side of an epithelial membrane to the other.

Absorption of nutrients molecules from your gut and the secretion of acid into your stomach.

Photo taken from http://www.news.leiden.edu/

Some epithelial cells are, like those in the lungs or at the skins surface, are extremely thin (squamous) to facilitate movement of substances across them.

The skin is epithelial tissue that receives much wear and tear. Accordingly, epithelial cells in the deepest layer of the skin have a high rate of cell division. Producing new cells that move progressively to the skin surface. die, and are shed.
A cross section of the skin reveals layering of the cells, from the newly formed ones to the innermost germinal layer to the dead ones on the surface.

Due to this appearance, the skin is called a stratified epithelium.
In contrast, the gut epithelium consists of a single layer of tall, closely packed cells called a simple columnar epithelium. The epithelial cells of your gut are replaced about every 5 days; those in your skin are removed every 1 to 2 months.

A single layer of cuboidal epithelial cells form a tubule in the kidney. These cells have many molecular transport functions.