Epithelial Tissue Basics Epithelial tissue covers the whole

Epithelial Tissue

Basics. Epithelial tissue covers the whole surface of the body. It’s made up of closely packed tissue that usually are in one or more layers. The Epithelial tissue that covers or lines the surface of the interior of the body is known as endothelium. They are tightly packed together with almost no intercellular space and is usually separated from the underlying tissue by another thin sheet of tissue called the basement membrane. It provides support for the epithelium and binds neighboring structures.

Functions of Epithelial Tissue Protection: Epithelial cells from the skin protect underlying tissue from mechanical injury, harmful chemicals, invading bacteria and from excessive loss of water. Absorption: Certain epithelial cells lining the small intestine absorb nutrients from the digestion of food. Ø Excretion: Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine. Sweat is also excreted Sensation: from the body by epithelial cells in the sweat Sensory stimuli penetrate specialized epithelial cells. glands. Specialized epithelial tissue containing sensory nerve endings is found in the skin, eyes, ears, nose Ø Diffusion: and on the tongue. Simple epithelium promotes the diffusion of Secretion: gases, liquids and nutrients. Because they form In glands, epithelial tissue is specialized to secrete such a thin lining, they are ideal for the diffusion specific chemical substances such as enzymes, of gases (ex. walls of capillaries and lungs). hormones and lubricating fluids. Ø Cleaning: Ciliated epithelium assists in removing dust particles and foreign bodies which have entered the air passages.

Types of Epithelial Tissue There are two groups, depending on the number of layers. Epithelial tissue is only one cell thick, also known as simple epithelim. It it is two or more cells thick-(example: our skin)-its known as stratified epithelium.

Squamous (pavement) epithelium Squamous cells have the appearance of thin, flat plates. The shape of the nucleus usually corresponds to the cell form and help to identify the type of epithelium. Example: Squamous cells tend to have horizontal flattened, elliptical nuclei because of the thin flattened form of the cell. They form the lining of cavities such as the mouth, blood vessels, heart and lungs and make up the outer layers of the skin.

Simple Cuboidal Epithelium. They are square and cuboidal in shape. Each cell has a spherical nucleus in the center. Cuboidal epithelium is found in glands and in the lining of the kidney tubules as well as in the ducts of the glands. They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes.

Simple Columnar Epithelium One or more layers and elongated and column-shape sine the nuclei are elongated and are usually located near the base of the cells. Columnar epithelium forms the lining of the stomach and intestines. Some columnar cells are specialized for sensory reception such as in the nose, ears and the taste buds of the tongue. Goblet cells (unicellular glands) are found between the columnar epithelial cells of the duodenum. They secrete mucus or slime.

Ciliated Columnar Epithelium Just like Simple columnar epithelial cells but they possess fine hair-like outgrowths which are also called Cilia on their free surface. They produce rapid, rhythmic, and wavelike beatings in certain directions that causes mucus to move, flow, or stream in that specific direction. Can be found in air passages like the nose. Also found in uterus and Fallopian tubes of females.

Glandular Epithelium Columnar epithelium with goblet cells is called glandular epithelium. Columnar and cuboidal epithelial cells often become specialized as gland cells which are capable of synthesizing and secreting certain substances such as enzymes, hormones, milk, mucus, sweat, wax and saliva

Stratified Epithelium. This epithelia is composed of several layers of cells. The top of the cells are flat and scaly. The mouth cavity is an example of unkeratinisied, stratified epithelium.