M04.01.011 Epithelial cells

Epithelial cells are a type of tissue found in various organs and structures throughout the body. They line the surfaces of organs, cavities, and vessels, serving as protective barriers and participating in various physiological functions. Epithelial cells can be classified into different types based on their structure, function, and location. Here are some common types of epithelial cells and their features:

1. Squamous Epithelial Cells:
   • Structure: Squamous epithelial cells are thin, flat, and scale-like in shape. They have a flattened nucleus and a thin cytoplasm.
   • Function: Squamous cells provide a protective barrier and are involved in facilitating diffusion and filtration processes. They are found in structures like the alveoli of the lungs and the lining of blood vessels.
2. Cuboidal Epithelial Cells:
   • Structure: Cuboidal epithelial cells are cube-shaped with a centrally located nucleus. They have a more rounded appearance compared to squamous cells.
   • Function: Cuboidal cells are involved in absorption, secretion, and transport processes. They are found in organs such as the kidneys, thyroid gland, and salivary glands.
3. Columnar Epithelial Cells:
   • Structure: Columnar epithelial cells are tall and cylindrical in shape. They have elongated nuclei located near the basal side of the cell.
   • Function: Columnar cells are specialized for secretion, absorption, and protection. They are found in structures like the lining of the digestive tract and the respiratory tract.
4. Transitional Epithelial Cells:
   • Structure: Transitional epithelial cells have a unique appearance, varying in shape from squamous to cuboidal depending on the degree of stretching of the tissue. They can appear rounded or plump when the tissue is relaxed.
   • Function: Transitional cells are highly specialized for stretching and distensibility. They line structures like the urinary bladder, allowing it to expand and accommodate urine.
5. Pseudostratified Epithelial Cells:
   • Structure: Pseudostratified epithelial cells appear layered or stratified but are actually a single layer of cells of varying heights. They have nuclei at different levels, giving the false impression of stratification.
   • Function: Pseudostratified cells are primarily found in the respiratory tract, where they play a role in mucus secretion and the movement of mucus by cilia.

It’s important to note that these epithelial cell types can exist as different subtypes in various organs and tissues, each with specific adaptations and functions based on their location and physiological requirements. Epithelial cells form the interface between the external and internal environments, and their features contribute to their protective and functional roles in the body.