Epithelium | Anatomy, Structure & Function (2024)



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Paneth’s cell
argentaffin cell
stratified epithelium
transitional epithelium
stratified ciliated epithelium

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epithelium, in anatomy, layer of cells closely bound to one another to form continuous sheets covering surfaces that may come into contact with foreign substances. Epithelium occurs in both plants and animals.

In animals, outgrowths or ingrowths from these surfaces form structures consisting largely or entirely of cells derived from the surface epithelium. In this way the central nervous system, the sensitive surfaces of special sense organs, glands, hair, nails, and other structures all originate. The epithelial cells possess typical microscopical characteristics: the cell outline is clearly marked, and the nucleus large and spherical or ellipsoidal. The cytoplasm of the cell is usually large in amount and often contains large numbers of granules.

Epithelium may be protective, absorptive, or secretory. It may produce special outgrowths (hairs, nails, horns on animals), and manufacture chemical material (e.g., keratin), in which case the whole cell becomes modified. In other instances it contains fat droplets, granules of various kinds, protein, mucin, watery granules, or glycogen. In a typical absorbing cell, granules of material are absorbed. A secreting cell forming specific substances stores them until they are utilized—e.g., fat, in sebaceous and mammary glands; enzymes in salivary and gastric glands; and various excretory substances in the renal epithelium of the kidney.

The cells forming an epithelial membrane are of various types: columnar, cubical, squamous (flattened), irregular, or ciliated (i.e., with hairlike projections). The membranes formed by these cells may be only one cell thick, as in the major part of the gastrointestinal tract, or consist of several layers, as in the epidermis of the skin. Columnar epithelium covers the intestinal tract from the end of the esophagus to the beginning of the rectum. It also lines the ducts of many glands. A typical form covers the villi (nipple-like projections) of the small intestine. Cubical epithelium is found in many glands and ducts (e.g., the kidney), the middle ear, and the brain. Squamous, or flattened, epithelial cells, very thin and irregular in outline, occur as the covering epithelium of the alveoli of the lung and of the glomeruli and capsule of the kidney. Ciliated epithelium lines the trachea, bronchi of the lungs, parts of the nasal cavities, the uterus and oviduct of the female, and the vas deferens and epididymis of the male. A single projection from the exposed surface of a cell, usually large and long, is called a flagellum. Flagellated cells are common on the surface of many simple animals.

When the cells of an epithelial surface are several layers deep, various epithelial types can be distinguished: stratified, stratified ciliated, and transitional epithelium. In stratified epithelium, which is found in the epithelium of the skin and of many mucous membranes (e.g., mouth, esophagus, rectum, conjunctiva, vagin*), the surface cells are flattened, those of the middle layer are polyhedral, and those of the lowest layer are cubical or columnar. This type of epithelium covers surfaces exposed to friction. The surface cells are constantly being rubbed off and are replaced by new cells growing up from below. Hence, the deepest layer is formative, and successive stages upward reveal a gradual transformation into scaly cells that no longer show any sign of being alive.

In stratified ciliated epithelium the superficial cells are ciliated and columnar. This epithelium lines parts of the respiratory passages, the vas deferens, and the epididymis. Transitional epithelium lines the urinary bladder; its appearance depends upon whether the bladder is contracted or distended.

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Epithelium | Anatomy, Structure & Function (2024)


What is epithelial tissue answer key? ›

Epithelial tissues are widespread throughout the body. They form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.

What is the structure and function of the epithelial tissue answer? ›

Epithelial tissue or epithelium forms the outer covering of the skin and also lines the body cavity. It forms the lining of respiratory, digestive, reproductive and excretory tracts. They perform various functions such as absorption, protection, sensation and secretion.

What is the structure and function of the simple epithelium? ›

Simple epithelium has only one cell layer where every cell is in direct contact with the underlying basem*nt membrane. Generally, this type of epithelium is found inside the body probably due to the fragile nature and forms the lining of the body cavities, blood and lymph vessels, heart and respiratory system.

What does it mean when you have epithelial cells in your urine? ›

If there are squamous epithelial cells in your urine, it may mean your sample was contaminated. This means that the sample contains cells from another part of the body. This can happen if you do not clean your genital area well enough when collecting your urine sample with the clean catch method.

What is the main role of epithelial tissue in the body? ›

There are three primary functions of epithelial tissue: serving as a protective barrier, secreting substances, and absorbing substances. The main function of specific tissues varies by the specific location and type of cell. Protective barriers are typically formed by stratified epithelium and goblet cells.

What is epithelial tissue pdf? ›

✓Epithelium (epithelial tissue) covers body surfaces, lines body cavities, and forms glands. ✓Connective tissue underlies or supports the other three basic tissues, both structurally and functionally. ✓Muscle tissue is made up of contractile cells and is responsible for movement.

How does the structure of epithelial cells relate to their function? ›

Epithelial tissue structure is directly related to its function. Single layers of squamous epithelial cells create thin membranes that allow the transfer of nutrients quickly through the barrier. This is found lining the capillaries of the blood, the glomerulus of the kidneys, and the alveoli of the lungs.

What is the function of the epithelium quizlet? ›

Function of epithelial cells is to form linings or covering membranes - reflected in the arrangement of fitting closely together to form intact sheets of cells.

What are the types of tissue structure and function? ›

There are 4 basic types of tissue: connective tissue, epithelial tissue, muscle tissue, and nervous tissue. Connective tissue supports other tissues and binds them together (bone, blood, and lymph tissues). Epithelial tissue provides a covering (skin, the linings of the various passages inside the body).

What is the structure of the epithelium? ›

Epithelial tissue is made up of epithelial cells. The cells can be different shapes and can be arranged in a single layer or multiple layers depending on where they are in your body and what kind of functions they have. In biology, a cell is the smallest unit that can live on its own.

What is epithelium? ›

The term "epithelium" refers to layers of cells that line hollow organs and glands. It is also those cells that make up the outer surface of the body.

What is the function of the tissue? ›

Tissues: A group of cells that have similar structure and function together as one unit is known as tissue. Tissues provide shape to the body and help body to conserve heat and store energy. There are four types of tissues: Connective tissue, Epithelial tissue, Muscle tissue and Nervous tissue.

Should I be worried about squamous epithelial cells in urine? ›

A moderate amount of squamous epithelial cells in the urine is not necessarily a cause for concern. However, if the number of these cells is consistently high or there are other signs of a urinary tract infection, further investigation and treatment may be necessary.

What cancers cause epithelial cells in urine? ›

Bladder Cancer or Other Urologic Cancers: Cancerous growths in the urinary tract can disrupt normal cell turnover, resulting in epithelial cells in urine.

How to reduce epithelial cells in urine naturally? ›

If your epithelial cells are high then you are recommended to drink plenty of water and take antibiotic medications. However, if you have any kidney diseases then you are recommended to make lifestyle changes, exercise regularly and consult with a nephrologist to prevent further damage.

What is epithelial tissue tissue? ›

Epithelium or epithelial tissue is a thin, continuous, protective layer of compactly packed cells with little extracellular matrix. Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs.

What is an epithelial tissue defined as? ›

A thin layer of tissue that covers organs, glands, and other structures within the body.

What is the epithelial tissue quizlet? ›

Epithelium covers the body surface, lines body cavities, forms the external and internal linings of many organs, and constitutes most gland tissue. The functions of epithelial tissue include protection, secretion, excretion, absorption, filtration, and sensation. Each cell contains a nucleus.

What is the definition of epithelial? ›

Listen to pronunciation. (eh-pih-THEE-lee-ul) Refers to the cells that line the internal and external surfaces of the body.

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