Epiteelikudoksia

Epiteelikudoksia, or epithelial tissue, is one of the four basic types of animal tissue. It forms a protective covering for the body's surfaces, lines internal cavities and organs, and forms glands. Epithelial tissue is characterized by cells that are tightly packed together with very little extracellular space. The cells are arranged in one or more layers, depending on the function.

Epithelial tissues have several key functions. They provide protection against mechanical injury, harmful chemicals, and invasion by microorganisms. They also play a role in absorption, where substances are taken into the body, and secretion, where substances are released from the body or into cavities. Another important function is excretion, the removal of waste products. Epithelial cells can also form sensory surfaces, detecting stimuli from the environment.

There are several classifications of epithelial tissue based on the number of cell layers and the shape of the cells. Simple epithelium consists of a single layer of cells, while stratified epithelium has multiple layers. Epithelial cells can be squamous (flat), cuboidal (cube-shaped), or columnar (taller than they are wide). These classifications are often combined, such as simple squamous epithelium or stratified cuboidal epithelium. The specific structure of an epithelial tissue is directly related to its function in a particular location in the body. For example, simple squamous epithelium in the lungs facilitates rapid diffusion of gases, while stratified squamous epithelium in the skin provides robust protection.