What Is Subcutaneous Tissue?

압구정피부과 The subcutaneous tissue, also called the hypodermis, superficial fascia or tela subcutanea, is the deep layer of your skin. It stores fat and helps your body regulate its temperature.


Hematomas of the subcutaneous tissue are seen as mottled hyperechoic lesions with posterior acoustic shadowing. Mild subcutaneous edema is shown as fluid distended anechoic connective tissue septa among fat lobules.


In many parts of the body the subcutaneous fat layer, also called deep fascia or adipose tissue provides insulation for your muscle and organs. Like a layer of insulation in your home, it protects the muscles and tissues underneath it from changes in temperature. It also absorbs shock from movements.

The fat layer helps us maintain a normal body temperature and also serves to absorb medicines that we inject. If the fat layer thins, it can lead to hypothermia in cold weather and reduce the effectiveness of some medicines.

Unlike visceral fat that accumulates around our internal organs, the fat in the subcutaneous layer is located under your skin and can be thick or thin depending on your overall body fat percentage. It is thickest in the buttocks and abdomen and thinner on the arms and thighs. The thickness of the subcutaneous fat layer also varies between men and women. In the 3D head model study, needle insulation had a maximum effect when the conductive part of the needle reached the high impedance fat layer.

Shock Absorption압구정피부과

The subcutaneous layer consists of fat, and the body stores extra fat in this tissue as an energy reserve. It helps protect the deeper tissues and muscles from shock, changes in temperature, and other stresses. The fat also serves as a buffer, absorbing impact from falls or other traumas.

This layer of skin is also important for regulating the temperature and producing sweat to keep the body cool. Damage to the subcutaneous tissue can cause third or fourth degree burns, which may leave charred and white wounds that require medical attention. The layer can also be damaged by conditions such as abscesses, pressure ulcers (bed sores), tumors, and panniculitis, a group of painful bumps under the skin.

Medicines injected into the subcutaneous layer are absorbed more slowly than when they are injected into muscle. This is because the layer has far fewer blood vessels than muscle does. This can be a disadvantage for people who need frequent injections. They can avoid this problem by varying the injection site. The subcutaneous layer may also store excess fat, which can lead to lipohypertrophy.

Structural Support

Besides providing insulation, regulating temperature and storing fat, the subcutaneous tissue acts as a gliding plane between skin and fascia and protects deeper structures like bones and muscles from acute trauma. It is composed of a network of connective septa and fat lobules (Fig. 1a-c). The size of adipocytes varies with nutrition habits, resulting in thicker or thinner layers.

Inflammation of the subcutaneous tissue progressing to cellulitis or abscess may be visualized on US by diffusely increased echogenicity of the fat layer (Fig. 2a-b). US also demonstrates fluid accumulation within the fatty lobules due to dilation of lymphatic channels. Depending on the level of edema, the fat lobules appear hypoanechoic (Fig. 2c-e).

Twisting of injection ports surgically inserted into the subcutaneous tissue is associated with failure of the injection procedure and fluid accumulation (Fig. 3). US demonstrates the twisting by showing a linear hyperechoic appearance of the metallic base tilted toward the skin replacing the normal concave superior face of the soft silicone component. US can also detect the presence of suture material forming granulomas after therapeutic interventions with nonabsorbable stitches (Fig. 4a-b).

Energy Storage

The large proportion of fat in subcutaneous tissue acts as an insulation layer, protecting the bones, muscles and organs under it from shock, and provides the body with a reserve source of energy. It also helps regulate the internal body temperature, preventing it from getting too hot or too cold (thermoregulation).

The fat stored in subcutaneous tissue is composed of adipocytes, or fat cells. It varies throughout the body, but is thickest in areas such as the buttocks, palms of hands and soles of feet. The fat is arranged in lobules separated by connective tissue septa. US demonstrates that the lobules become hyperechoic as fluid accumulates in dilated lymphatic channels.

Subcutaneous tissue is a good location to inject medications because of its limited network of blood vessels, making it easy for drugs to be absorbed. However, if foreign bodies are injected into the subcutaneous tissue, they may not be removed, resulting in complications such as granuloma formation, secondary soft-tissue infection and septic arthritis. US can accurately demonstrate twisting of injection ports surgically inserted into the subcutaneous tissue, a common cause of fluid accumulation and asymptomatic foreign-body-related abscesses (Kohler et al, 2005).

Medicine Injections

Injections administered subcutaneously can deliver medications that need to be administered over a long period of time, such as insulin for diabetes. They can also be used to administer drugs for autoimmune diseases and arthritis. Subcutaneous injections deliver medication more slowly than intramuscular (into the muscle) injections.

Medications administered by subcutaneous injection can cause local pain or discomfort, but this can be minimized. Various factors affect the amount of pain felt, including the needle’s size and type, the injection site, the amount injected and the patient’s pain sensitivity.

Before giving a subcutaneous injection, wash your hands and clean the injection site. A dry, taut skin surface allows for easy entrance of the needle. Ensure the syringe is labeled correctly and not expired or foamy, cloudy or has crystals.

Pinch a fold of skin that includes fatty tissue in the arm, upper thigh or abdomen (depending on the location of the medication). Use short, thin needles that are conveniently lubricated to minimize pain. Be sure to insert the needle at a 90 degree angle and remove it quickly. Discard the needle in a sharps container and perform hand hygiene afterward.