Glandular epithelium is the membranous tissue made up of cells that covers all the glands in the body. The main function of glandular epithelium is the secretion of fluids into ducts or fluids of the body. Secretion types depend on the location and function of the gland.
Epithelium is a tissue that is made up of different types of cells. It forms the inner lining of body cavities and hollow organs, and it covers the body and organs as well. Epithelial tissue is also referred to as avascular tissue because it has no direct supply of blood. Due to the fact that it covers the whole body and lines organs, the epithelium always has a surface that is either exposed externally, as in skin, or internally to an organ, such as the large intestine, or another open space.
The types of cells that make up epithelium are quite varied. They are classified by how thick they are and their shape. Generally speaking, epithelium cells are tightly packed together and have no space, or very little space, between them. Glandular epithelium has a variety of cells types in its structure, but they are usually columnar or cuboidal in shape.
Functions of the glandular epithelium depend on the type of gland that it covers. There are two types of glands, endocrine and exocrine. Endocrine glands secrete into tissue fluid or blood, such as the thyroid gland. Exocrine glands secrete through ducts onto surfaces, such as the sebaceous glands of the skin, or the glands of the digestive tract lining.
In addition to types of glands, there are also different types of secretion methods that glandular epithelium cells utilize. The exocrine glands have several methods. Most exocrine cells are merocrine glands, which means they release their fluids through exocytosis, a process of guided secretion through the cell. Exocrine cells also secrete by means of partially releasing part of the cells, which happens in apocrine glands, or by totally destroying itself to become part of the fluid, which is the case in a holocrine gland.
Merocrine cells are either serous or mucous. Serous cells release a watery, enzyme filled fluid called serous fluid. Mucuos cells produce mucus, which is a protective fluid.
Glandular epithelium has numerous and complex functions in the body. It is a vital part of the digestive, protective, and hormonal systems. Often times, problems in the glandular epithelium are the source of problems with an organ or gland.