Adipose tissue develops from mesenchymaL cells and is classified as a type of connective tissue.
The main cells of this tissue are adipocytes, also known as adipose cells or fat cells.
Adipocytes are specialized for storing lipids within their cytoplasm. The stored lipid occur as several small droplets or one large drop. These drops are not surrounded by a membrane. Therefore they are considered as cell inclusions rather than organelles. Triglycerides (neutral fats) are the main component the lipid.
There are two varieties of adipose tissue: unilocular tissue also called yellow or white fat and multilocular adipose tissue also called brown fat. They present significant differences in their morphology, functions, and distribution in the body.
Early in adipocyte development, the cytoplasm contains many small lipid droplets. As the adipocytes mature the lipid droplets develop differently depending on the type of adipose tissue being formed.
During the development of unilocular adipose tissue the droplets merge into one large drop while during the development of multilocular adipose tissue the small droplet remain.
Adipocytes are found scattered singly within the connective tissue or more commonly organized as clusters of varying sizes. Neighboring cells in a cluster are separated by a small amount of extracellular matrix. Part of this matrix consists of a network of thin reticular fibers formed primarily by type III collagen that provide an structural support for the cells, but they usually not seen with a light microscope in routine stained sections.
In addition to adipocytes, the adipose tissue also contains blood vessels, nerves and a small number of resident and transient connective tissue cells.
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