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Adipose tissue is primarily located beneath the skin, but is also found around internal organs. In the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold. Around organs, it provides protective padding. It also functions as a reserve of nutrients.
In a severely obese person, excess adipose tissue hanging downward from the abdomen is referred to as a panniculus (or pannus). A panniculus complicates surgery of the morbidly obese, and may remain as a literal "apron of skin" if a severely obese person loses most of the excess weight (as after a bypass).
Adipose tissue has an "intracellular matrix," rather than an extracellular one. Adipose tissue is divided into lobes by small blood vessels. The cellstained for keratin The cell is the structural and functional unit of all living organisms. Some organisms, such as bacteria, are unicellular, consisting of a single cell. Other organisms, such as humans, are multicellular, (humans have an estimated 100,0s of this layer are adipocytes.
Fat cells have an important physiologicalPhysiology is the study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided into plant physiology and animal physiology but the principles of physiology are universal, no matter what partic role in maintaining triglycerideTriglycerides or triacylglycerols are natural fats and oils, composed of glycerin (chemically, "glycerol") and fatty acid chains. Chemical structure The fatty acids are linked to the glycerol so as to form 3 ester functional groups: : CH COOR CH COOR' CH and free fatty acid levels, as well as determining insulin resistance. Abdominal fat has a different metabolic profile—being more prone to induce insulin resistance. This explains to a large degree why central obesity is a marker of impaired glucose tolerance and is an independent risk factor for cardiovascular disease (even in the absence of diabetes mellitus and hypertension).
Hormones secreted by adipose tissue include:
A specialised form of adipose tissue in human infants, and some animals, is brown fat or brown adipose tissue. It is located mainly around the neck and large blood vessels of the thorax. This specialised tissue can generate heat by "uncoupling" the respiratory chain of oxidative phosphorylation within mitochondria, leading to the breakdown of fatty acids. This thermogenic process may be vital in neonates exposed to the cold, who then require this thermogenesis to keep warm as they are unable to shiver, or take other actions to keep themselves warm.
Attempts to stimulate this process pharmacologically have so far been unsuccessful, but might in the future be a target of weight loss therapy.