Simple squamous epithelium

Simple squamous epithelium is a type of epithelium that consists of a single layer of squamous cells. Squamous cells are flat and scale-like cells. The squamous cells are in contact with the basement membrane that lies beneath it. Simple squamous epithelium is permeable and present in the areas where small-molecule needs to pass through the membrane. The movement of a molecule across the membrane occurs through filtration and diffusion. These types of epithelia are found in the capillaries, alveoli, glomeruli, and other areas of the body where rapid diffusion occurs.

Diffusion is the movement of molecules from a high concentration gradient to a low concentration gradient. The nuclei of squamous cells are flat. Simple squamous epithelium is also called pavement epithelium and it is because of its tile-like appearance.

The main functions with which the simple squamous epitheliums are associated are filtration and diffusion. Simple squamous epithelial tissues are very thin due to which it forms a very delicate lining and offers very little protection.



Functions of simple squamous epithelium

The simple squamous epithelium ate most commonly found in the areas where absorption and transport of material take place. These types of epitheliums play a major role in the process of diffusion, and filtration. Due to this, they are found in the kidneys, alveoli, and capillaries.

The cells of simple squamous epitheliums are tightly packed but they make a thin layer due to which it becomes a suitable environment for selective transmembrane transport.

The squamous cells are held through tight junctions that are made by membrane proteins and these proteins ensure that only ions, gases, and Water molecules pass through the cells.

Simple squamous epithelium does not allow diffusion through interstitial spaces.




Simple squamous epithelium is found in the air sacs of the lungs, and the lining of the heart and blood vessels.




Many pathologists and anatomists consider endothelium as a specialized epithelial cell however some make a distinction between them. In this article, we will consider it as a specialized form of epithelium. Endothelium-derived from the mesoderm that limes the inner surface of blood and lymphatic vessels. Endothelium is a single layer of thin, squamous cells.  The endothelial cells that come in contact with the blood are called vascular endothelial cells while those with lymphatics are called lymphatic endothelial cells.

The vascular type line the entire circulatory system and performs many functions such as fluid filtration, hemostasis, and hormones trafficking. Endothelial cells actively send signals to the immune cells during inflammation to act.


The mesothelium is derived from the mesoderm that consists of a single layer of squamous cells. The mesothelium line several body cavities. For example thoracic cavity, abdominal cavity, and the heart sac. Visceral mesothelium covers the internal reproductive organs.

Mesothelium is made of specialized cells that line the body cavities and produces and releases a lubricating fluid between the layers.

Cancer of mesothelium is called mesothelioma. This is a condition in which the mesothelium becomes abnormal and divide abnormally without any control. This condition can damage nearby organs. Mostly mesothelioma begins in pleurae and in the peritoneum.




Example of simple squamous epithelium

These epitheliums are found in many locations such as alveoli, kidneys, etc. Most of the squamous cells arise from the ectoderm but some arise from the mesoderm such as endothelium and mesothelium. Endothelium and mesothelium are specialized types of epithelial tissues.

1. Alveoli
Air enters the body and lastly reached the alveoli that are a highly vascularized bulbous structure. Alveoli are made of a single layer of squamous cells and are surrounded by capillaries. Capillaries also consists of simple squamous cells. The alveoli and capillaries allow the exchange of gases.

2. Bowman capsule
Nitrogenous wastes produced from the metabolism f proteins and nucleic acids are very harmful to the body and they must be removed from the body. These wastes are removed from the blood by a structure called glomeruli. Glomeruli are tuft of capillaries that interacts with the bowman’s capsule. The outer layer of the bowman capsule and the capillaries are made of squamous cells that assist the process of diffusion and filtration.



Squamous cell carcinoma of skin

Squamous cell carcinoma of the skin is a condition in which cancer develops in the middle and outer layers of the skin. This condition may become aggressive and can grow or spreads to other parts causing serious complications.  The cause of the squamous cell carcinoma is prolonged exposure to ultraviolet radiation.

1. Red nodule
2. Flat sore
3. Rough scaly patch on your lip
4. Red sore inside your mouth
5. Red sores on your genitals




Terms used in this article


Basement membrane

The basement membrane is a thin extracellular matrix that separates the epithelium from the underlying connective tissues. When the basement membrane is seen with the electron microscope its shows that it consists of two layers that are the basal lamina and reticular connective tissue layer. The basal lamina layer is further classified into two layers that are lamina Lucida and lamina densa. Lamina Lucida is a clear layer and lies closer to the epithelium while the lamina densa is a dense layer that lies close to the connective tissue.


Capillaries are small blood vessels which diameter ranges from 5 to 10 micrometers. Capillaries carry blood between venules and arteries. There are three types of capillaries that are continuous capillaries, fenestrated capillaries, and sinusoidal capillaries.


Alveoli are the tiny air sacs present in the lungs that allow the exchange of gases.


Diffusion is the process in which substances move from a high concentration area goes to the low concentration gradient area.


The peritoneum is a serous membrane that lines the abdominal cavity and abdominal viscera.

Abdominal cavity

It is a large cavity that is present between the thoracic cavity and the pelvic cavity.

Thoracic cavity

It is also called a chest cavity that is protected by ribs, skin, muscles, an facia.


Glomerulus is a tuff of small blood vessels that interact with the first portion of a nephron called bowman capsule.  Bloods come to the glomerulus from where it filters into the bowman capsule and then the process of urine formation begins.