The subcutaneous layer is made up of fat cells. It is composed of irregular, loose connective tissue that forms the deepest layer of the skin.
The subcutaneous layer, also known as the superficial fascia, consists of tissue in the innermost layer of skin that lies between the outer skin and deeper inner muscle tissue, according to the University of Michigan Health System. Its fat cells help to insulate the body from cold temperatures. Lymph vessels, superficial veins and cutaneous nerves pass through the subcutaneous layer.
The layer is a depot of fat storage that also provides shock absorption that cushions the internal organs and deep tissues, protecting them from blunt trauma from the exterior environment, according to Dartmouth College. The fat in the subcutaneous layer can also provide the body with a reserve source of fuel.
The subcutaneous layer varies in thickness according to where it is located on the body. For example, the layer is thin on the area around the eyelids and thick on the waist and abdomen, as stated by Dr. Daniel Kapp. It thins out across the body as people age.
Medical professionals treat the subcutaneous layer during surgical procedures such as an abdominoplasty, which involves removing excess fatty tissue and skin from the abdomen, and liposuction, which involves suctioning fatty tissue from various parts of the body, according to Kapp.