The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the
integumentary system in
vertebrates.
The types of cells found in the layer are
fibroblasts,
adipose cells
Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adipocytes are derived from mesenchymal stem cells which give rise to adipocytes through adipogenesis. I ...
, and
macrophages. The subcutaneous tissue is derived from the
mesoderm, but unlike the
dermis, it is not derived from the mesoderm's
dermatome region. It consists primarily of
loose 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.
In
arthropods, a hypodermis can refer to an epidermal layer of cells that secretes the
chitinous
cuticle. The term also refers to a layer of cells lying immediately below the
epidermis of plants.
Structure
* Fibrous bands anchoring the skin to the
deep fascia
Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments.
This fibrous connective tissue interpenetrates and surrounds the ...
*
Collagen and
elastin fibers attaching it to the dermis
* Fat is absent from the eyelids, clitoris, penis, much of
pinna, and scrotum
* Blood vessels on route to the dermis
* Lymphatic vessels on route from the dermis
* The glandular part of some
sweat gland
Sweat glands, also known as sudoriferous or sudoriparous glands, , are small tubular structures of the skin that produce sweat. Sweat glands are a type of exocrine gland, which are glands that produce and secrete substances onto an epithelial ...
s;
mammary glands lie entirely within the subcutaneous tissue
(which are modified
apocrine sweat glands)
* Cutaneous nerves
and free endings
* Hair follicle roots
*
Ruffini and
Pacinian corpuscles
Pacinian corpuscle or lamellar corpuscle or Vater-Pacini corpuscle; is one of the four major types of mechanoreceptors (specialized nerve ending with adventitious tissue for mechanical sensation) found in mammalian skin. This type of mechanorece ...
*
Mast cells
A mast cell (also known as a mastocyte or a labrocyte) is a resident cell of connective tissue that contains many granules rich in histamine and heparin. Specifically, it is a type of granulocyte derived from the myeloid stem cell that is a p ...
* Bursae, in the space overlying joints in order to facilitate smooth passage of overlying skin
* Fine, flat sheets of muscle, in certain locations, including the scalp, face, hand, nipple, and scrotum, called the
panniculus carnosus
The panniculus carnosus is a part of the subcutaneous tissues in vertebrates. It is a layer of striated muscle deep to the panniculus adiposus.McGrath, J.A.; Eady, R.A.; Pope, F.M. (2004). ''Rook's Textbook of Dermatology'' (Seventh Edition). Black ...
In some animals, such as whales and hibernating mammals, the hypodermis forms an important insulating layer and/or food store.
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
Subcutaneous fat is the layer of subcutaneous tissue that is most widely distributed.
[ It is composed of adipocytes, which are grouped together in ]lobules
In anatomy, a lobe is a clear anatomical division or extension of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to t ...
separated by connective tissue. The number of adipocytes varies among different areas of the body, while their size varies according to the body's nutritional state. It acts as padding and as an energy reserve, as well as providing some minor thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperatur ...
via insulation. Subcutaneous fat is found just beneath the skin, as opposed to visceral fat, which is found in the peritoneal cavity, and can be measured using body fat calipers to give a rough estimate of total body adiposity.
Clinical significance
Injection
Injection into the subcutaneous tissue is a route of administration used for drugs such as insulin: because it is highly vascular, the tissue absorbs drugs quickly. 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 there is limited blood flow. " Skin popping" is a slang term that includes this method of administration, and is usually used in association with recreational drugs.
Disease
* Subcutaneous abscess A subcutaneous abscess is an abscess located in the subcutaneous tissue (also hypodermis). The abscess is formed due to a hypodermal infection by a bacterium, a fungus or a parasite. Typically, this kind of abscess needs drainage, usually for a mi ...
* Subcutaneous tumor Subcutaneous may refer to:
* Subcutaneous injection
* Subcutaneous tissue
The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The ...
See also
* Dermis
* Epidermis
References
{{DEFAULTSORT:Subcutaneous Tissue
Skin anatomy