The epithelium can be defined as a complex of highly organised cells organised into sheets without the presence of significant intercellular material that covers the body’s interior and external surfaces, as well as the secreting organs, to name a few examples. In layman’s words, epithelial definition refers to a layer of cells that covers the surface of the body or the lines of a body cavity. Plants and animals both have epithelium, which is a type of cell wall. Epithelial cells, on the other hand, can be cuboidal, flat, or cylindrical in shape, and they can be stacked in one or several layers, depending on their function. Epithelial tissue can be divided into two types: covering and lining epithelium, which covers both the exterior and inner body surfaces of most organs, and glandular epithelium, which is responsible for the formation of the majority of the body’s glands.
What are the Epithelium’s Layers and How Do They Work?
Simple epithelia and stratified epithelia are the two most important layers of the epithelium, respectively.
Simple epithelia are made up of a single layer of cells that are in direct contact with the basement membrane of the surrounding tissue. Simple epithelial tissue is made up of columnar cells that are elongated in shape.
These cells are frequently found in regions where absorption and filtration are required, such as the lining of most of the body’s cavities, such as the lining of the female ovary and the walls of the blood arteries.
Stratified epithelia are made up of numerous layers of cells that are present on the basal surface and that remain linked to the basement membrane throughout their life cycle. They do not, on the other hand, come into contact with the basement membrane. These cells provide higher protection against external hazards, such as hazardous poisons, than their counterparts. It is common to find stratified tissues in places where protection is required, such as the lining of the oesophagus or the lining of the urethra and bladder.
In what ways does the epithelium differ from other parts of the body?
The epithelium is divided into three segments based on the morphology of the cells:
Cells of the Squamous Epithelium:
The squamous epithelium is formed of flat, scale-like irregular cells with disc-shaped nuclei that are centrally situated in the epithelium. Squamous epithelia are classified into two types: basic squamous epithelium and stratified squamous epithelium.
Simply put, the squamous epithelium is a barrier that permits things to flow through by diffusion or filtration, as well as secreting mucus. This epithelium’s major job is to protect the body’s interior organs from abrasion and abrasion-induced injury.
Cuboidal Cells:
Cuboidal Epithelium is made up of cube-shaped cells with spherical nuclei that are positioned in the centre of the cell. Simple cuboidal epithelium and stratified cuboidal epithelium are the two forms of cuboidal epithelium that can be found in the body. Simple cuboidal cells have the major role of secretion and absorption, whereas stratified cuboidal epithelium has the primary purpose of protecting the body.
Columnar Cells:
Columnar cells are made up of cells that are both taller and thinner, forming a column-like structure. Columnar cells have nuclei that are typically oval in shape, extended from top to bottom, and positioned close to the basal surface. There are three basic forms of columnar epithelia: simple columnar epithelium, pseudostratified columnar epithelium, and stratified columnar epithelium. Simple columnar epithelium is the most common variety. Pseudostratified columnar cells secrete mucus and enzymes, and they also absorb nutrients, whereas simple columnar cells secrete mucus and transport mucus. Abrasion protection and mucus secretion are the fundamental functions of stratified columnar epithelium, which is found throughout the body.
Epithelial Tissue Has a Variety of Functions
In accordance with the definition, epithelial tissue is a layer of cells that are tightly connected to one another to form continuous sheets that cover sites that have been exposed to external substances. Therefore, the following are some of the activities of epithelial tissue-
1.Protection of the tissues beneath the skin
2.Secretion is the process through which chemicals are released from cells.
3.Absorption occurs by the introduction of tiny molecules into cells.
As a result of the migration of molecules down their concentration gradient, diffusion occurs.
4.A sievelike membrane is used to filter out tiny molecules, and this process is called filtration.
5.Reception through the senses
The Cellularity of Epithelial Tissue Exhibits the Following Interesting Characteristics:
In the epithelium, cells are separated by a small quantity of extracellular materials, primarily projections of their integral membrane proteins into the tiny spaces between the cells, which serve to maintain the integrity of the epithelium.
1.Support Provided by Connective Tissue: All epithelial sheets in the body are supported by an underlying connective tissue layer.
2.This trait states that the adjacent epithelial cells immediately link at a number of sites through specific cell junctions, which are seen in many epithelial cells.
3..Regeneration: Another distinguishing property of epithelial tissues is their remarkable ability to regenerate after being damaged. As a result, while some epithelia are killed by friction, others are damaged by harmful elements present in the external environment, such as germs and acids, as well as smoke. Their surface cells are prone to rubbing off. However, if the epithelium receives sufficient nutrients, it will be able to quickly replace the cells that have been lost through cell division, which is accomplished through mitosis (cell division).
4.A free apical surface is present on all epithelia, which is linked to the basal surface by a polarity. The function and structure of the apical and basal surfaces, on the other hand, are distinguished by a property known as polarity. The apical surface of the epithelia is adjacent to an open space such as a gland, tube, cavity, or hollow organ. The basal surface, on the other hand, is supported by a thin supporting sheet of the basal lamina, which is a component of the foundation membrane.
Conclusion
The most significant distinction between epithelial and connective tissue is found in the cells that make up each type of tissue, as well as their roles. Squamous, cuboidal, and columnar epithelial tissue are the three types of cells that make up epithelial tissue. Cells in connective tissue, as well as cartilaginous, collagenous, elastic, and fatty tissues, are immersed in an indeterminate matrix that surrounds them. Fibroblasts are the most frequent type of cell, although there are also macrophages, mast cells, adipocytes, plasma cells, leukocytes, and other types. Body cavities, blood arteries, the digestive system, and other sensitive internal organs are lined with epithelial tissue, which aids in excretion, transportation, absorption, protection, and secretion by performing a variety of functions. Connective tissue, on the other hand, is responsible for the formation of connections, the support of other tissues, and the binding of other tissues.