Adipose Tissue: White and Brown

• Adipose tissue is a type of connective tissue.

Adipose Tissue

• Large cells are found isolated or in small groups with loose or dense irregular connective tissue.
• Occurs in large aggregates.
• It is a connective tissue in which fat-storing cells or adipocytes predominate.
• Adipose tissue represents 15%-20% of body weight in men and more in women, but this is not a fixed percentage and can be much less in an athlete.
• Adipose tissue stores neutral fats, chiefly triglycerides.
• White and brown adipose tissues differ in color, location, function, and structure.

White Adipose Tissue

• White adipose tissue is more common than brown adipose tissue in adults.
• Cells each contain one large cytoplasmic droplet.
• It is used for long-term energy storage.
• A completely developed white adipocyte ranges between 50 and 150 umm in diameter and is unilocular, meaning each fat cell contains only one fat vacuole.
• White adipose tissue has a signet-ring appearance because the nucleus is pushed to the periphery as the cytoplasm is full of fat, giving it a ring shape under a microscope because the fat is washed out.
• The distribution of white adipose tissue changes significantly through childhood and adult life, appearing evenly distributed throughout the body in newborns and babies, but differing after puberty.
• Adipocytes develop from mesenchymal stem cells so liposuction can be used to get fat tissue in order to have mesenchymal stem cells.
• In females, white adipose tissue is found around the belly, buttock, and breast areas; in males, it is usually around the abdomen.

Brown Adipose Tissue

• Brown adipose is usually found in newborns, and decreases with time, but small amounts are in adults.
• Brown adipose constitutes 2%-5% of the newborn body weight.
• It is mainly located in the back, neck, and shoulders of newborns, and only in scattered areas around the kidneys, adrenal glands, aorta, and mediastinum of adults.
• It is also found in relatively small amounts in the neck of adults.
• The color of brown fat comes from the abundant mitochondria and large number of blood capillaries.
• Brown adipocytes contain many small lipid inclusions and are multilocular.
• Brown adipose tissue functions primarily in heat production and warming the blood, or thermogenesis.
• The cells of brown fat are smaller than white adipocytes and the nucleus is more centrally located.
• Brown fat is utilized to maintain temperature and can also be observed in hibernating animals.