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| Subcutaneous tissue | |
|---|---|
 The hypodermis is the lower layer of skin shown in the diagram above. | |
| Details | |
| System | Integumentary |
| Identifiers | |
| Latin | tela subcutanea[1] |
| MeSH | D040521 |
| TA98 | A16.0.03.001 |
| TA2 | 7083 |
| TH | H3.12.00.2.00001 |
| FMA | 9630 |
| Anatomical terminology | |
Thesubcutaneous tissue (from Latin subcutaneous 'beneath the skin'), also called thehypodermis,hypoderm (from Greek 'beneath the skin'),subcutis, orsuperficial fascia,[2] is the lowermost layer of theintegumentary system invertebrates.[3] The types of cells found in the layer arefibroblasts,adipose cells, andmacrophages. The subcutaneous tissue is derived from themesoderm, but unlike thedermis, it is not derived from the mesoderm'sdermatome region. It consists primarily ofloose connective tissue and contains larger blood vessels and nerves than those found in the dermis. It is a major site of fat storage in the body.
Inarthropods, a hypodermis can refer to an epidermal layer of cells that secretes thechitinouscuticle. The term also refers to a layer of cells lying immediately below theepidermis of plants.
The hypodermis forms an important insulating layer and/or food store in some animals, such as whales and hibernating mammals.
In some plants, the hypodermis is a layer of cells immediately below the epidermis of leaves. It is often mechanically strengthened, for example, in pine leaves, forming an extra protective layer or a water storage tissue.
Subcutaneous fat is the most widely distributed subcutaneous tissue layer.[1] It is composed of adipocytes, which are grouped together inlobules separated byconnective tissue.[5] The number of adipocytes varies among different body areas, while their size varies according to the body's nutritional state.[12] It acts as padding and as an energy reserve, as well as providing some minorthermoregulation via insulation.[10][5] Subcutaneous fat is found just beneath the skin, as opposed tovisceral fat, which is found in theperitoneal cavity,[13] and can be measured usingbody fatcalipers to give a rough estimate of total bodyadiposity.[14]
Injection into the subcutaneous tissue is aroute of administration used for drugs such asinsulin: because it possesses few blood vessels, the tissue absorbs drugs slowly.[10]: 135 Subcutaneous injection is believed to be the most effective manner to administer some drugs, such as human growth hormones. Just as the subcutaneous tissue can store fat, it can also provide good storage space for drugs that need to be released gradually because of limited blood flow. "Skin popping" is a slang term that includes this method of administration and is usually used in association withrecreational drugs.
