Epithelial Tissues - Types, Structure, Function and Important FAQs (2023)

They are thin tissues that cover all exposed body surfaces. They cover various surfaces of body parts like lining of oral cavity, digestive tract, secretion glands, lining of hollow parts of all organs like heart, lungs, eyes, urogenital tract etc.

Cells that make up epithelial tissue are tightly connected by structures called tight junctions. They lack blood vessels and nerves and are supported by connective tissue called the basement membrane. They exhibit polarity, with distinct basal domains facing the basement membrane and other apical surfaces of the organ lumen or external environment.

Art des Epithelgewebes

The classification of epithelial tissue is based primarily on the number of layers, shape, and function.

  1. Classified by shape:

  1. squamous epithelium:In this type of tissue, the cells are longer than they are tall. They are mainly found in the oral mucosa, esophagus and alveoli (including blood vessels).

  2. Cubic epithelium:Fabrics of this type have a similar width and height, i. H. they are predominantly cuboid.

  3. Columnar epithelium:This type of fabric is taller than it is wide, so it is columnar. They are further divided into two types namely ciliated epithelium and glandular epithelium.

  1. Depending on the number of layers, epithelial tissue is divided into two types. they are:

Simple epithelium/simple epithelium:There is a single layer. They are in direct contact with the basement membrane, which separates them from the underlying connective tissue. They are further divided into different types:

  1. Simple squamous epithelium:Their cells are scaly, flat or round. For example: capillary walls, pericardial cavity, pleural cavity and lining of the peritoneal cavity, alveolar lining.

  2. Simple cubic epithelium:These cell types can have secretory, absorptive or excretory functions. Examples: Collecting ducts of the kidneys, pancreas and salivary glands.

  3. Simple columnar epithelium:These cell types can be secretory, absorptive or excretory in nature. Some of these tissues contain goblet cells and are referred to as simple glandular columnar epithelium. They secrete mucus and are found in the stomach, colon, and rectum.

  4. Pseudostratified epithelium:They can be ciliated or ciliated. An example of cilia is the airway epithelium.

  1. Stratified epithelium:They have two or more cell layers, i.e. they are multilayered. In addition, they are divided into three types:

  1. Stratified squamous epithelium:Above all, they protect against abrasion and water loss. It is mainly found in the mouth, esophagus and throat. Stratified cuboidal epithelium:

  2. Stratified columnar epithelium:Their main functions are secretion and protection. They are located in the covering of the conjunctiva of the eye.

  3. Stratified cuboidal epithelium:Their main function is protection. They are mainly located in the ducts of the sweat glands and the large ducts of the excretory glands.

Structure of the epithelial tissue

They are made up of tightly fitting, connected layers of cells. They are either exposed on external surfaces or in bodily fluids within the body. Special connections exist between epithelial cells. Some of these connection points are as follows:

tight connection:Above all, they prevent the leakage of tissue.

Adhesive connections:They help adjacent tissues stay properly connected.

gap connections:They support the movement of ions and molecules in the tissue.

Epithelial cells have two main membranes:

  1. mucosa:It is also called the mucous membrane cell. Goblet cells have a mucous membrane. Above all, they take on lubricating and protective processes as well as the easy movement of materials in the battery. They are mainly found in the digestive tract.

  2. Serous film:They line up mainly in body cavities, which are usually open to the inside and not to the outside.Example:Pleural cavity, pericardium.

  3. glands:There are mainly two types: exocrine and endocrine. Eccrine glands secrete their secretions into ducts such as goblet cells and sweat glands. The endocrine glands, on the other hand, release their secretions directly into the blood.Example:Hormone.

Function of epithelial cells

Epithelial cells play an important role in various functions of the body. Below are some key features:

  1. secretion process:Most epithelial cells have the ability to produce secretory macromolecules. One of the best examples is the glandular epithelium. Since the endocrine gland is also secretory in nature, it directly releases hormones into the blood including insulin, thyroxine, etc. Eccrine glands are also secretory in nature and release hormones into ducts such as sebum in the skin and digestive enzymes in the small intestine.

  2. Absorption process:The absorption process is mainly carried out through the surface epithelium with the help of microvilli as the microvilli increase the surface area for the absorption process. Another example is the columnar epithelium in the small intestine. Their main function is the absorption of nutrients in the digestive tract.

  3. Transport:There are a variety of pumps powered by epithelial tissue. Example: The kidney's hydrogen ion pump (H+ ion pump) plays a role in urine production.

  4. Protection process:They act as selective and protective barriers. They cause poisoning, lacrimation and infections.

  5. receptor function:Epithelial cells can receive receptors or sensory information and convert it into nerve signals. An example of such epithelial tissue is the mucous membrane of the olfactory nose, which perceives smells from the outside and transmits this information to the central nervous system.

Location of the epithelial tissue

The epithelium has an outer lumen and an inner lumen. In the outer cavity is skin. The radiance of the body is also present. As already said, the outer layer is the human skin, which consists of the following components:

  • keratinocytes

  • epithelial cells

  • stratified squamous cell carcinoma

Nonkeratinizing squamous cell carcinomas are found in the esophagus, mouth, vagina, and rectum. The lungs and gastrointestinal tract are covered by other epithelial cells. There is a special form of epithelium that is also known as vascular endothelium. It is made in the heart and blood vessels. Rapidly growing and regenerating epithelial cells can be seen on the outside of the cornea. The walls of the peritoneum and pericardium are formed by the mesothelium.

development of epithelial cells

These epithelial tissues originate from embryonic germ layers. they are:

  • Ectoderm

  • Mesoderm

  • Endoderm

However, it is a little-known fact that pathologists do not consider endothelium and mesothelium to be true epithelium. Both are now mentioned as being derived from the mesoderm. Students need to know that pathologists refer to mesothelial and endothelial sarcomas as cancers. Carcinoma is cancer in true epithelial cells. However, it is generally accepted that the epithelium originates from all three germ layers.

Epithelial tissue is the main tissue of our body. This is because they cover almost the entire surface of our body. These surfaces include hollow organs and serve to line body cavities. It is the functionality that makes the organization so important. Features are:

  • excretion

  • Secretion

  • absorb

  • Diffusion

  • Filter

About the ciliated epithelium

The ciliated epithelium clears the interior and surroundings of the trachea for passage. It helps move mucus. This is possible due to folds in the membrane. These folds look like hair-like protrusions. This type of tissue is found in the bronchioles in the lungs. Foreign particles trapped inside are transported away as mucus by the local ciliated epithelium.

Students may wonder why epithelial tissue has no blood supply! It is known that the main function of the epithelium is to protect cells. Therefore, there is little possibility of blood loss due to friction and shock at the part containing the epithelial tissue. Therefore, the lack of blood supply to these areas is a gift of nature.


Top Articles
Latest Posts
Article information

Author: Stevie Stamm

Last Updated: 09/09/2023

Views: 5883

Rating: 5 / 5 (60 voted)

Reviews: 83% of readers found this page helpful

Author information

Name: Stevie Stamm

Birthday: 1996-06-22

Address: Apt. 419 4200 Sipes Estate, East Delmerview, WY 05617

Phone: +342332224300

Job: Future Advertising Analyst

Hobby: Leather crafting, Puzzles, Leather crafting, scrapbook, Urban exploration, Cabaret, Skateboarding

Introduction: My name is Stevie Stamm, I am a colorful, sparkling, splendid, vast, open, hilarious, tender person who loves writing and wants to share my knowledge and understanding with you.