The dermis is a tough but elastic support structure that houses nerves, blood vessels, lymphatics, and cutaneous appendages pilosebaceous units, eccrine and apocrine sweat glands. It is thicker averages 1 to 4 mm than the epidermis which is about as thin as piece of paper. The dermis varies in thickness.
It is very thick on the back almost 1 cm ; it is very thin on the eyelid. The dermis has two main zones, the papillary dermis and the reticular dermis. It contains many collagen cells as well as fat. Fat, in particular, helps insulate our body from the cold and act as a cushion for our internal structures such as muscles and organs when something hits us.
Fat can also be called upon by the body in times of great need as an energy source. Given the alternative names for this layer, it should come as no surprise that this is the layer where subcutaneous injections are given into via a hypodermic needle. Skin sensory receptors: Those nearest the surface of the skin include receptors that detect gentle pressure, temperature, and vibrations, as well as naked nerve endings dendrites that detect pain.
Deeper in the dermis are naked dendrites that wind around the bases of hair follicles and detect motions of the hairs, as well as receptors such as Pacinian corpuscles that respond to strong pressure and vibrations. Skin color is determined largely by the amount of melanin pigment produced by melanocytes in the skin. Skin color is largely determined by a pigment called melanin but other things are involved.
Your skin is made up of three main layers, and the most superficial of these is called the epidermis. The epidermis itself is made up of several different layers.
Melanocyte: Cross-section of skin showing melanin in melanocytes. The deepest of the epidermal layers is called the stratum basale or stratum germinativum. In this layer lie important cells called melanocytes. Their name is derived from two parts: melano-, which means black or darkness, and -cyte, which means cell. Melanocytes are irregularly shaped cells that produce and store a pigment called melanin.
The most abundant type of melanin is called eumelanin. This pigment is stored in organelles called melanosomes. Eumelanin is responsible for the brown and black pigmentation of human skin or the lack thereof if little of it is produced. The production of melanin is called melanogenesis—genesis means formation or development. Regardless of background, every person has largely the same number of melanocytes, but the genetics of each person is what determines how much melanin is produced and how it is distributed throughout the skin.
For example, light skinned individuals may have darker places like nipples and moles. Conversely, dark skinned individuals have a lighter tone to the palms of their hands. Another critical factor, exposure to sunlight, triggers the production of melanin as well.
This is what gives us a tan. People with darker skin have more active melanocytes compared to people with lighter skin. However, the pigment of our skin also involves the most abundant cells of our epidermis, the keratinocytes. While melanocytes produce, store, and release melanin, keratinocytes are the largest recipients of this pigment. The transfer of melanin from melanocytes to keratinocytes occurs thanks to the long tentacles each melanocyte extends to upwards of 40 keratinocytes.
Tanned Skin: Exposure to UV radiation through tanning causes changes in the pigmentation of the skin by increasing melanin production. Privacy Policy.
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The dermis is located beneath the epidermis and is the thickest of the three layers of the skin 1. The main functions of the dermis are to regulate temperature and to supply the epidermis with nutrient -saturated blood. Much of the body's water supply is stored within the dermis. This layer contains most of the skins' specialized cells and structures, including:. The upper, papillary layer, contains a thin arrangement of collagen fibers. The papillary layer supplies nutrients to select layers of the epidermis and regulates temperature.
Both of these functions are accomplished with a thin, extensive vascular system that operates similarly to other vascular systems in the body. Constriction and expansion control the amount of blood that flows through the skin and dictate whether body heat is dispelled when the skin is hot or conserved when it is cold. The lower, reticular layer, is thicker and made of thick collagen fibers that are arranged in parallel to the surface of the skin.
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