In humans, adipose tissue is located: beneath the skin (subcutaneous fat), around internal organs (visceral fat), in bone marrow (yellow bone marrow), intermuscular (Muscular system) and in the breast tissue. Adipose tissue is found in specific locations, which are referred to as adipose depots. Apart from adipocytes, which comprise the highest percentage of cells within adipose tissue, other cell types are present, collectively termed stromal vascular fraction (SVF) of cells. SVF includes preadipocytes, fibroblasts, adipose tissue macrophages, and endothelial cells. Adipose tissue contains many small blood vessels.
In the integumentary system, which includes the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold. Around organs, it provides protective padding. However, its main function is to be a reserve of lipids, which can be oxidised to meet the energy needs of the body and to protect it from excess glucose by storing triglycerides produced by the liver from sugars, although some evidence suggests that most lipid synthesis from carbohydrates occurs in the adipose tissue itself. Adipose depots in different parts of the body have different biochemical profiles. Under normal conditions, it provides feedback for hunger and diet to the brain.
The two superficial depots are the paired inguinal depots, which are found anterior to the upper segment of the hind limbs (underneath the skin) and the subscapular depots, paired medial mixtures of brown adipose tissue adjacent to regions of white adipose tissue, which are found under the skin between the dorsal crests of the scapulae. The layer of brown adipose tissue in this depot is often covered by a “frosting” of white adipose tissue; sometimes these two types of fat (brown and white) are hard to distinguish.
The inguinal depots enclose the inguinal group of lymph nodes. Minor depots include the pericardial, which surrounds the heart, and the paired popliteal depots, between the major muscles behind the knees, each containing one large lymph node. Of all the depots in the mouse, the gonadal depots are the largest and the most easily dissected, comprising about 30% of dissectible fat.