MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL BASIS OF HUMAN VITAL ACTIVITY

1.2. CELL. TISSUES. CONCEPT OF AN ORGAN, ORGAN SYSTEM, AND ORGANISM

EPITHELIAL TISSUE

1. Surface epithelium

The morphological Classification of surface epithelium is based on the number of Cell layers and cell shape. Therefore, epithelium is primarily subdivided into simple and stratified types.

In Simple Epithelium, all Cells rest upon the basement membrane. In Stratified Epithelium, only the deepest basal layer of epithelial cells contacts the basement membrane, whereas the overlying cells lose this contact. Simple epithelium is further subdivided into single-layer (monolayered) and pseudostratified. Single-layer epithelium, in turn, is classified by cell shape into squamous, cuboidal, and columnar. In single-layer epithelium, all cells are uniform in shape and size, with their nuclei located at the same level. In pseudostratified epithelium, due to the varied types, sizes, and shapes of the cells, their nuclei lie at different levels, yet all epithelial cells remain in contact with the basement membrane (Fig. 1.4).

Stratified epithelium is subdivided into non-keratinized stratified squamous, keratinized stratified squamous, and transitional epithelium. This classification depends on the Structural Features of the Superficial layer of epithelial cells.

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Fig. 1.4. Schematic diagram of various types of surface epithelium: a - simple squamous; b - simple cuboidal; c - simple columnar brush border epithelium; d - pseudostratified ciliated; e - stratified non-keratinized squamous; f - stratified transitional in a stretched state; g - stratified transitional in a relaxed state.