Anatomy and physiology advice to clients An introduction epithelial cells

Epithelial Cells Epithelial cells are the first type of tissue that we are going to investigate. They line all our organs and come in several different types. They have different functions. Some are involved in absorption of nutrients such as those in the digestive system. Some deliver important products such as those in glands. Some are involved in protecting such as those in skin and some have multiple roles. We will come across quite a few of them in these learning sessions. All epithelial cell layers sit on a basement membrane. This keeps them in place. If epithelial cells ever change and become new types of cells then this is called a carcinoma. If this new growth breaks through the basement membrane then the carcinoma is said to be malignant because it has spread.

Simple squamous epithelial cells The first type of epithelial cell is called a simple squamous epithelial cell. These are arranged like paving stones resting on a basement membrane. There is only one layer of cells in a simple epithelial tissue. Generally the nucleus of the cell is thicker than the cytoplasm in squamous epithelial cells, so it tends to bulge out when you look at it under a microscope and magnify it about 1000 times.

Simple squamous A single layer of squamous epithelium forms a mesothelium. These line the heart (pericardium), lung (pleural cavity) and gastrointestinal tract (peritoneal cavity). This slide shows gut squamous epithelial cells underlined by smooth muscle. The squamous epithelial cells have the thin blue nuclei at the top. The mesothelium provides reduced friction surfaces and lets organs move freely. Throughout our lessons we will come across the mesothelium.

Simple cuboidal In cuboidal cells the cell width is the same as the cell height. Cuboidal cells are very important cells where absorption and secretion occur. You can see in this slide the cuboidal cells lining these kidney tubules. Note the darker cell nucleus

Simple columnar Columnar epithelial cells look just like columns. The cells are usually the same height and the nuclei are nearly always at the same level

Simple columnar Columnar epithelial cells are also involved in absorption and secretion These columnar epithelia line the surface of the gall bladder and you can see the features that we have just described. Sometimes they have cilia attached

Ciliated columnar epithelia Some cells have very fine cilia attached to them. The cilia are very fine hairs attached to the surface of the cell and have specialised functions themselves. These cells are ciliated columnar epithelia found in the gut

Simple columnar with goblet cells Very often the epithelial cells are associated with other cells such as Goblet cells. Goblet cells secrete mucus for lubrication Can you see the goblet cells sandwiched between columnar epithelial cells?

Pseudostratified Pseudostratified look like they have several layers. They look this way because the cell nuclei are at different levels All cells rest on basement membrane but only columnar type reach the surface The cells in this slide are ciliated pseudostratified columnar epithelia

Stratified squamous Some epithelial tissue is made up of more than one layer and these are called stratified This is a section of skin showing keratinised stratified squamous epithelia cells Can you see the stratified epithelial layers and the keratin layer at the top? These cells produce keratin to help weatherproof your skin.

Stratified columnar Stratified columnar epithelial cells mainly line large ducts such as salivary glands, the pancreas, sweat glands and parts of the urethra Can you see two layers of columnar epithelial cells in this slide?

Transitional epithelial cells Transitional epithelial cells change from one shape to another as the organ shape changes A good example of this is found in the bladder where cells are cuboidal when the bladder is empty and change to squamous when the bladder is full

Learning tools In your scrap book draw each of the cells illustrated in this presentation