EPITHELIAL TISSUE

1.     SIMPLE CUBOIDAL EPITHELIAL TISSUE

Description: one layer of adjacent cuboidal cells standing on the basement membrane. The distinguishable feature is the nucleus which is central, full rounded and dark while the cytoplasm is distributed evenly around the nucleus taking the light pink or purple color.

Location: lining the renal tubules and ducts of the glands.

Function: secretion

Slide #4: a section from mammal thyroid gland follicles or kidney tubules. Notice the circular ribbons, which represent simple cuboidal epithelium. Notice that the nuclei are fully rounded and separated by almost even distance and the nuclei are centrally located within the edges of the ribbon.

2.     SIMPLE COLUMNAR EPITHELIAL TISSUE

Description: one layer of adjacent cylindrical cells with dark, oval and basal nuclei. The cytoplasm is concentrated at the top of cell having very light color.

Location and Function: protection mainly and:

*absorption when the apical surface has microvilli as in the gastrointestinal tract.

*movement when apical surface has cilia as in oviduct.

Slide #5: a section from mammal small intestine, which is lined by simple columnar epithelium. Notice the columnar cells, oval and basal nuclei, and the dark pinkish line on the apical surface representing the microvilli.

3.     STRATIFIED SQUAMOUS EPITHELIAL TISSUE

Function: high level of protection against mechanical, thermal and chemical hazards.

*KERATINIZED STRATIFIED SQUQMOUS EPITHELIUM Description: many layers of flat cells with central small nuclei.

The apical layers of the tissue lost their nuclei and appear as very dark layers covered by a fibrous protein =keratin.

Location :  the epidermis of the skin.

Slide #6: A section from human skin, sectioned through epidermis, dermis, and hypodermis stained with hematoxylin & eosin. The epidermis (apical part of the skin) represents the keratinized stratified squamous epithelium. Notice the multi layers of keratin apically, which don’t have nuclei.

*NON-KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM

Description: many layers of flat cells with central small nuclei. The apical layers of the tissue still having their own small nuclei with dark stain while the cytoplasm is light and concentrated at the periphery.

Location : lining of the oral cavity, esophagus and vagina

Slide #7: A section of human esophagus stained with hematoxylin & eosin. The lining of the esophagus represent the non- keratinized stratified squamous epithelium. Notice the layers of cells and the flat cells, with nuclei, on the apical surface.