ANATOMY AND HISTOLOGY

Objectives:

·        Identify the epithelial tissue.

·        Differentiate between the different types of epithelial tissue.

·        Identify the contents and structures of each type of the epithelial tissue.

General location: faces a free surface:*covering externally

                                                                *lining cavity

General characteristics :

*Very adjacent cells

*The basement membrane

*Avascularized tissue

*Cellular communication

*High rate of cell division

Classification: 1*No. of layers: * 1 layer------------------------SIMPLE

                                             * multiple layers------------STRATIFIED

                       2*Shape of the cell:* flattened, rounded nucleus, peripheral thin cytoplasm-------------------------------------SQUAMOUS

                                     *cuboidal, full rounded and central nucleus, evenly distributed cytoplasm---------------------------CUBOIDAL

                                      *cylindrical, oval and basal nucleus, apical cytoplasm--------------------------------------------------COLUMNAR

There are 2 exceptional cases for the previous classification:

·        Pseudostratified epithelial tissue: the tissue seems to have more than one layer, but actually each cell reaches the basement membrane.

·        Transitional epithelial tissue: the cells take different shapes, flattened in stressed state while dome shaped in relaxed state.

TYPES OF EPITHELIAL TISSUE:

1.     SIMPLE SQUAMOUS EPITHELIAL TISSUE

Description: one layer of adjacent flattened cells. The nucleus occupies the majority of the cell at the center, staining darkly under the microscope while the cytoplasm is lighter in color and appears peripherally, looks as thin line connecting between two nuclei.

Location: lining of blood vessels, heart, lung alveoli, and kidney glomeruleous.

Function:  filtration and exchange.

Slide #1: a smear of Human Cheek Cells stained with hematoxylin & eosin. Notice the irregular shape and round, centrally located nuclei in the squamous isolated cells.

Slide #2: a whole mount Mammal Mesothelium stained with silver and hematoxylin. Notice the irregular shape of the cells and the arrangement of the cells together in the simple squamous epithelium.

Slide #3: a section from mammal Kidney stained with hematoxylin & eosin. Look for the lining of Bowman's capsule, which is simple squamous epithelium; it looks as thin lines (cytoplasm) connecting round, darkly stained nuclei.