Epithelia lines cavities and surfaces of structures throughout the body and they form many glands such as carrying secretions from glands. They may be made up of many layers of cell which are densely packed together which is compound epithelia or just one layer which is a simple epithelia. All the epithelial cells rest on the basement membrane which is where they can grow and repair. Epithelial tissues have to be nourished by the nerve supplies which contain oxygen and nutrients.
Simple epithelia are one cell thick where each cell has contact with the basement membrane. There are 4 different types of simple epithelia which are squamous epithelium, cuboidal epithelium, columnar epithelium and compound epithelia.
These cells look like they are flat and thin where they are close together so this provides the liquids to flow through smoothly. They are usually found in the walls of the lungs alveoli and blood capillaries. The nucleus creates a lump in the centre in each of the cells. These cells cannot protect themselves from any damage so their main function is to allow liquids and materials to pass through smoothly which is through diffusion and osmosis.
These are cube shaped where each of the cells have a nuclei in the centre. Cuboidal epithelium are commonly found secretive tissue where the make secretions. They line ducts and the Kidney tubules to allow materials to pass through and this is where they are most commonly found.
These cells are tall and their nuclei are kind of oval shaped. The columnar epithelium forms the lining of the stomach and intestines. They are associated with microscopic filaments which are known as cilia. Cilia move towards orifices and are commonly affiliated with goblet cells which secrete mucus into the respiratory tracts. Mucus traps particles such as carbon and the cilia transport the mucus to the exterior.