Adipose tissue

Adipose tissue, also known as body fat or simply fat, is a type of connective tissue composed mainly of adipocytes. Adipose tissue is primarily located beneath the skin, but is also found around internal organs. It serves as a storage facility for fat that can be used as energy, provides insulation and protection for organs, and plays a significant role in the endocrine system.

Structure

Adipose tissue is divided into two main types: white adipose tissue (WAT) and brown adipose tissue (BAT). WAT stores energy and is the predominant form in adult humans, while BAT is involved in cold-induced thermogenesis.

White Adipose Tissue

White adipose tissue is found in subcutaneous and visceral fat. Subcutaneous fat is located under the skin and is found all over the body, while visceral fat is located around the internal organs. WAT cells contain a single large fat droplet, which pushes the nucleus to the periphery of the cell.

Brown Adipose Tissue

Brown adipose tissue is primarily located in the neck and large blood vessels of the thorax. BAT cells contain numerous smaller fat droplets and a high number of mitochondria, which gives it its brown color. BAT is responsible for thermogenesis following exposure to cold and diet.

Function

Adipose tissue has a variety of functions. It serves as a major energy storage site, provides insulation and mechanical protection, and plays a significant role in regulating metabolism through the secretion of hormones such as leptin and adiponectin.

Energy Storage

Adipose tissue stores energy in the form of triglycerides. During periods of energy excess, triglycerides are synthesized and stored in adipocytes. During periods of energy deficit, triglycerides are broken down into free fatty acids and glycerol, which can be used as energy.

Insulation and Protection

The location of adipose tissue beneath the skin and around organs provides insulation and mechanical protection. Subcutaneous fat insulates the body from heat loss, while visceral fat provides protection for internal organs.

Endocrine Function

Adipose tissue is considered an endocrine organ as it produces hormones that regulate metabolism. These include leptin, which regulates appetite and energy balance, and adiponectin, which regulates glucose and lipid metabolism.

Health Implications

Excess adipose tissue, particularly visceral fat, is associated with increased risk of metabolic diseases such as type 2 diabetes, heart disease, and certain types of cancer. Conversely, insufficient adipose tissue, as seen in lipodystrophy, can also lead to metabolic complications.