The subcutaneous tissue or subcutis is the layer of tissue directly underlying the cutis. It is mainly composed of adipose tissue. Its physiological function includes insulation and storage of nutrients. Injections Subcutaneous injections are given by injecting a fluid or a solid pellet into the subcutis. It is used to administer a variety of medical treatments. Subcutaneous injections of fluid are used to administer vaccines and medications. A pellet may be injected to deliver long-lasting dos… (More on Subcutaneous)