Squamous epithelia is a kind of epithelium that is present in the outermost layer of the body. It is made up of flat cells that have a scale-like appearance. Squamous epithelia can be present as a single layer of cells or it can also be present as multiple layers of cells stacked one above the other. Single layered or multi-layered squamous epithelia have different physical structures and functions. The cytoplasm that is present in these cells consists of a small round nucleus. Squamous epithelial cells have a smooth texture and it is present in a variety of locations in the human body. They perform an array of functions. 

Simple squamous epithelia

Simple squamous epithelia is a category of squamous epithelial cells that are found attached to the basement membrane, the bottom-most layer of the cell. 

• These cells are in direct contact with each other and they do not have spaces in between them. 
• They are tightly packed together. 
• Their shape is irregular and they are flat in structure. Since the surface of these cells is so flat, they can easily cause the exchange of gases and other substances by simple diffusion. 
• Most of these cells can be found in the lining of the body structures and organs. They make up several blood vessels and capillaries as well. 
• They are important because they help in the reduction of friction.
• They also help in the easy exchange of gases from the external surface of the cell to inside the cell. 

Stratified squamous epithelia

Stratified squamous epithelial cells are the type of epithelial cells that are found in the form of layers of cells stacked on top of each other. The bottom-most layer of this cell stack is in direct contact with the basement membrane. The remaining layers are attached to one other. This property helps in maintaining the structural integrity of the cells. 

This type of epithelium is most suitable for the areas that undergo continuous abrasion. This is because even if the cells disintegrate due to external friction, there would still be a layer of cells present below it. 

Depending on the presence or absence of keratin in these cells, their location is decided. This is because the cells that contain keratin need to be kept wet with the help of body secretions. On the other hand, if the cell does not contain keratin then it does not require any form of lubrication from the bodily secretions. 

Location and structure of squamous epithelia

The squamous epithelial cells are present in various parts of the human body. 

• In the respiratory system, the simple squamous epithelium is found in the lungs and the alveoli. Since the simple squamous epithelium is very thin, it helps the lungs and the alveoli in the exchange of gases. 
• They are also present in the human blood vessels and capillaries. 
• Stratified squamous epithelia are found in several organs such as the lining of the mouth, skin and the vaginal orifice. Their shape is polygonal and they are smooth. This also helps in the smooth flow of liquids without any type of friction. 

Functions of squamous epithelial cells

• One of the major functions of squamous epithelial cells is that it protects the underlying organs. 
• It also helps in providing a smooth and frictionless surface in case secretion is taking place. 
• It also protects the underlying cells from any kind of physical trauma. 
• Some of these cells also help in the production of mucous that acts as a lubricating agent. The cells that help in the production of mucus are called the goblet cells. 
• Another function of these cells is the transportation and absorption of materials in the body. 
• These cells help in checking the passage of particles throughout the different cavities of the body. 
• Various processes such as diffusion of nutrients, gases and functioning of the bowman’s capsule take place with these cells. 

Conclusion

It can be concluded that squamous epithelial cells are the simplest type of epithelial cells. They can be further divided into two types, depending upon the layer of cells. The single-layered squamous epithelia are called simple squamous epithelia and the multi-layered squamous is known as the stratified squamous epithelia. Squamous epithelial cells are present in various locations in the human body such as the skin, blood vessels and body cavities. It also serves various functions such as secretion, absorption and transportation of materials.