epitéliumok

Epitheliums are one of the four basic tissue types in the body, alongside connective tissue, muscle tissue, and nervous tissue. Epithelial tissue, or epithelium, forms the covering of all body surfaces, the lining of body cavities, and the hollow organs of internal organs and all glands. It is composed of cells that are tightly packed together with very little intercellular space. These cells are supported by an underlying layer of connective tissue called the basement membrane.

Epithelial cells are specialized for various functions, including protection, secretion, absorption, and excretion. The type of epithelium found in a particular location depends on its specific role. For instance, the skin is covered by stratified squamous epithelium, which provides a tough, protective barrier. The lining of the digestive tract is composed of simple columnar epithelium, which is ideal for absorption of nutrients. Glands, such as sweat glands and salivary glands, are formed from epithelial tissue that is specialized for secretion.

Epitheliums are classified based on two main criteria: the number of cell layers and the shape of the cells. Epitheliums can be simple (one layer of cells) or stratified (multiple layers of cells). The cell shapes can be squamous (flat), cuboidal (cube-shaped), or columnar (taller than they are wide). Combinations of these classifications describe specific types of epithelium, such as simple squamous epithelium, stratified cuboidal epithelium, and pseudostratified columnar epithelium. This tissue also plays a crucial role in sensory perception, as many epithelial tissues contain nerve endings.