Most Things Biology

Photomicrograph of simple squamous epithelium in lung tissue. Alveolar sacs, appearing as open, balloon-like spaces, are surrounded by thin, dark-staining walls of cells. Overall, the texture is airy with branching cellular boundaries of pink and purple hues. — **Figure 1:** Lung tissue under microscope, alveoli and cell structure visible.

Simple squamous epithelium is a type of epithelial tissue characterized by a single layer of flat, scale-like cellsThe basic structural and functional units of life.. These cells are thin and closely packed, allowing for efficient diffusionPassive movement of molecules from areas of high to low concentration. and filtrationThe process by which fluid moves out of capillaries into surrounding tissues due to hydrostatic pre across the epithelial barrier. Simple squamous epithelium is found in areas where rapid diffusion or filtration is necessary.

Cell Shape

The cell shape of squamous cells looks quite different when cut on alternating axes. When you think of squamous cells, imagine a fried egg. It’s like the one you just cracked into the pan and let cook. Look at the egg top-down while it’s in the frying pan. It looks like a circle, with another circle in the center of it. But, if you put that fried egg on a sandwich and take a bite, the side view looks very different. Squamous cells, when scraped from the cheek, looks like the fried-egg view. Most histological pictures of squamous cells cut in the other direction can be difficult to recognize.

Layering

This type of epithelia has only one layer of these cells. The tips of the cells in this layer overlap ever so slightly. To extend the breakfast foods analogy, think of a stack of pancakes that pushed (not tipped, pushed) to one side.

Function

Simple squamous epithelium is well-suited for gas, liquid, and small molecule diffusion. The thin shape of these cells allows for easy diffusion. It lines structures where chemicals and substances need to be exchanged quickly. As blood pulses through capillariesThe smallest blood vessels where gas, nutrient, and waste exchange occurs between blood and tissues., oxygen and carbon dioxide need to disembark into the interstitial fluidThe fluid surrounding cells within tissues.. The simple squamous cells lining blood vessels, collectively called the endotheliumThe innermost layer of blood vessels, composed of simple squamous epithelial cells, which reduces f, facilitate quick exchange of these gases. In lungs, they function similarly. They line millions of open spaces in the lungs. This provides a short distance for gases to move to enter and exit the blood.

Locations

Simple squamous cells are found lining the open spaces of the lungs. All the simple squamous cells lining the blood vessels are referred to as the endothelium. This layer is continuous with the simple squamous cells of the endocardium. The endocardium is the lining of the heart.

Specializations

Simple squamous epithelial cells may have specialized structures such as microvilliTiny projections on the surface of epithelial cells that increase surface area for absorption. or ciliaHair-like projections on the surface of some cells that move fluids or particles. depending on their location and function. For example, endothelial cells lining blood vessels may be fenestrated. They contain small pores to facilitate the exchange of substances between blood and surrounding tissues.