Cytology, General Histology and Embryology - V. K. Napkhanyuk 2002

Tissues
Epithelial Tissues

Epithelial Tissues (textus epithelialis) cover the body surface, line the mucous and serous membranes of Internal Organs, and form the majority of glands.

Phylogenetically, these are the oldest tissues, having first emerged at the dawn of multicellular Organism evolution. A characteristic feature of these tissues is that they consist exclusively of epithelial Cells interconnected by various types of junctions, forming a continuous sheet resting on a basement membrane.

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Fig. 30. Classification of epithelium by its origin

Fig. 31. Morphofunctional classification of epithelium

Sources of Epithelial Tissue development. Epithelia develop from all three germ layers, starting from the 3rd to 4th week of Human embryonic development. Depending on the developmental source, ectodermal, mesodermal, and entodermal epithelia are distinguished.

Classification of epithelium. Today, several classifications of epithelial tissues exist, based on various criteria: origin, Structure, and Functions (Fig. 30, 31).



Last update: 10/08/2026

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