Epithelial Tissues 1

Epithelial Tissues1 ( Practice 2 )
Classification of Tissues
1- Epithelial Tissue: covering and lining; and glands
2- Connective Tissue: protects and supports, binds organs together, stores energy, and provides immunity
3- Muscular Tissue: movement
4- Nervous Tissue: transmits impulses that coordinate body activities
They are sheets of continuous cells that cover surfaces, line cavities of the body and are the major tissues of glands.
* Endothelium: is the lining of circulatory system (blood vessels, lymph vessels and heart).
* Mesothelium: is the lining of major body cavities: peritoneum, pleura and pericardium
1- Simple Squamous Epithelium
- One layer of flat shaped cells.
- Lines body cavities and blood vessels (e.g. in Bowman’s capsule, endothelial lining of blood/lymph vessels, and mesothelium of pleural and peritoneal cavities )
Function :
selective lubricated barrier that allows movement & diffusion ( exchange of gases , nutrients , wastes )
The kidney consists of an outer cortex and an inner medulla. In the cortex there are round structures called glomeruli which are surrounded by the Bowman s capsule.
2- Simple Cuboidal Epithelium
Simple cuboidal epithelium consists of a single layer of cube-shaped cells. Each cell has a spherical nucleus in the center. It is adapted for secretion and absorption

Locations: lining
- kidney tubules
- salivary ducts
- pancreatic ducts
- liver
- thyroid gland
- mammary gland
3-Simple columnar epithelium
Comes into two forms:
* Non ciliated Simple columnar epithelium A single layer of nonciliated rectangular cells. Also functions in secretion and absorption. Specialized cells containing microvilli perform absorption. Goblet cells secrete mucus. Located in stomach and intestine.
* Ciliated Simple columnar epithelium
A single layer of rectangular cells. Functions in movement. Located in oviduct, seminal vesicle and ependymal canal.

4- Pseudostratified Ciliated Columnar Epithelium
-the nuclei are at different levels, giving the false impression of several layers of cells. In fact all the cells touch the basement membrane but not all reach the surface.
-lining the upper respiratory tract (nose, nasopharynx, trachea, bronchi and bronchioles) and is sometimes called “respiratory epithelium.
Function : Because has cilia and goblet cells functions in secretion and movement