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Definition epithelial tissue and parts
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DEFINITION
Epithelial tissues are thin tissues that cover all the exposed surfaces of the body. They form the external skin, the inner lining of the mouth, digestive tract, secretory glands, the lining of hollow parts of every organ such as the heart, lungs, eyes, ears, the urogenital tract, as well as the ventricular system of the brain and central canals of the spinal cord.
The cells making up epithelia are often closely bound to one another through specialized structures called tight junctions. They are also free from blood vessels and nerves and are supported by a connective tissue called the basement membrane. They have polarity with a distinct basal domain facing the basement membrane and the other apical surface facing the lumen of an organ or the external environment.
PARTS
There are different types of epithelial tissue depending on their function in a particular location. The simplest classification of these tissues is based on the number of cell layers.
simple epithelia and stratified epithelia
When the epithelium is composed of a single layer of cells, it is called simple epithelial tissue and those containing two or more layers of cells are called stratified epithelial tissues. One particular type is called pseudostratified because a single layer of cells having varying heights gives the appearance of being stratified.
Epithelia can also be classified based on the shape of the cells, giving rise to three types:
- Squamous epithelial tissue: consists of extremely thin cells that resemble the scales of a fish
- Cuboidal epithelial tissue: contains cells that appear square in cross-section but are marginally longer than they are wide
- Columnar epithelial tissue: consists of elongated cell involved in absorption of materials
The number of cell layers and cell types together give rise to 6 different types of epithelial tissue.
- Simple squamous epithelia
- Simple cuboidal epithelia
- Simple columnar epithelia
- Stratified squamous epithelia
- Stratified cuboidal epithelia
- Stratified columnar epithelia
Epithelial tissues are thin tissues that cover all the exposed surfaces of the body. They form the external skin, the inner lining of the mouth, digestive tract, secretory glands, the lining of hollow parts of every organ such as the heart, lungs, eyes, ears, the urogenital tract, as well as the ventricular system of the brain and central canals of the spinal cord.
The cells making up epithelia are often closely bound to one another through specialized structures called tight junctions. They are also free from blood vessels and nerves and are supported by a connective tissue called the basement membrane. They have polarity with a distinct basal domain facing the basement membrane and the other apical surface facing the lumen of an organ or the external environment.
PARTS
There are different types of epithelial tissue depending on their function in a particular location. The simplest classification of these tissues is based on the number of cell layers.
simple epithelia and stratified epithelia
When the epithelium is composed of a single layer of cells, it is called simple epithelial tissue and those containing two or more layers of cells are called stratified epithelial tissues. One particular type is called pseudostratified because a single layer of cells having varying heights gives the appearance of being stratified.
Epithelia can also be classified based on the shape of the cells, giving rise to three types:
- Squamous epithelial tissue: consists of extremely thin cells that resemble the scales of a fish
- Cuboidal epithelial tissue: contains cells that appear square in cross-section but are marginally longer than they are wide
- Columnar epithelial tissue: consists of elongated cell involved in absorption of materials
The number of cell layers and cell types together give rise to 6 different types of epithelial tissue.
- Simple squamous epithelia
- Simple cuboidal epithelia
- Simple columnar epithelia
- Stratified squamous epithelia
- Stratified cuboidal epithelia
- Stratified columnar epithelia
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