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The hypodermis, sometimes also known as the subcutaneous tissues, is the most interior layer of human skin. Skin is a more complex organ than most people realize, and it has several important parts; all work together, but they each tend to have a distinct identity, too. The main role of the subcutaneous tissues is to store fat. This fat can act as an energy reserve, and also provides a layer of insulation and protection. Together with the other layers, it also provides strength, elasticity, and helps anchor the skin to muscles and bones. Depending on how thick a person’s fat reserves are, this layer is sometimes very noticeable, though it does tend to be more prominent in certain body parts and anatomical areas than others. A lot depends on individual body shape, as well as things like diet and exercise. The term “hypodermis” has a related but different meaning in botany, the study of plant science; in these settings, it describes a layer of cells that covers and protects an outside plant element, including but not limited to seeds, roots, leaves, and stems.
Human skin is typically composed of three distinct layers. All are composed of various cells and each has a specific purpose, though they all work together to help skin function as it should. The epidermis is the outermost layer, and is what people see and feel. It supports hair growth and is the first line of defense against outside elements. Next comes the dermis, which is typically the thickest layer; it does things like produce sweat and natural skin oils, and also helps facilitate nerve sensations.
The subcutaneous level is the deepest. Its primary function is fat storage, and it acts as something of a reserve, keeping fatty tissues readily available for energy conversion in case of famine or other major energy shortage. In starvation scenarios, the body usually depends on fat stores to provide emergency energy to keep all systems running. Fat also provides insulation, which can help people stay warm and can also help regulate body temperature. When these fatty cells are spread evenly across a person’s skin, they can provide a fairly even distribution.
Being the innermost layer also means that this part of the skin has an important role to play when it comes to anchoring the organ as a whole to the bones and tissues beneath. The epidermis, dermis, and subcutaneous layer are all connected to each other through a network of fibers and linked cells, and then are affixed to the more interior aspects of the body through this innermost subcutaneous level.
There are certain places anatomically where the hypodermis is more obvious. Although subcutaneous tissue is distributed over the whole body, it typically accumulates in the shoulders and abdomen in men. In women, the tissue accumulates around the buttocks, hips, and thighs. It mostly contains hair follicle roots, blood vessels, and nerves, as well as adipose tissue, which is the tissue commonly associated with obesity or being overweight.
Not all parts of the body have this sort of fatty tissue, though. Areas without it include the eyelids, genitals, and nipples. These have skin generally, but it’s much thinner and usually doesn’t connect to the bones or denser muscles.
The subcutaneous layer is generally dense and firm, and as such can help the skin as a whole stay tight and elastic. However, all of this begins to change as the body ages. The fat stores tend to get looser over time, which can lead to wrinkles, bags and folds that impact the outermost layers and are visible on the outside. People often try to avoid this with a number of creams and lotions, as well as certain surgical and medical interventions.
The term “hypodermis” can also be used in relation to plants. In botany, the term is used to describe the cells that cover the stem, leaf, flower, fruit, root, and seed parts of the plant. This layer serves as a barrier that protects the plant from infection, injury, and dehydration. It may also be called an “exodermis” in these settings.
Because of the amount of vascular development subcutaneous tissue is the main route of administration for some injections. Insulin, a drug used by diabetics to control glucose levels in the blood, is given in these areas.
Human Growth Hormones are often given in this method as well. Just like with fat, subcutaneous tissue can store drugs for a gradual release over time in these areas.