Dermis: The lower or inner layer of the two main layers of cells that make up the skin.The dermis contains blood vessels, lymph vessels, hair follicles, and glands that produce sweat, which helps regulate body temperature, and sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin’s surface through tiny openings in the skin that act as pores.
- The dermis is divided into a papillary region and a reticular region.
- The primary function of the dermis is to cushion the body from stress and strain, provide elasticity to the skin, and a sense of touch, and heat.
- The dermis also contains hair roots, sebaceous glands, sweat glands, receptors, nails, blood vessels, and mechanoreceptors.
- The papillary region is composed of loose areolar connective tissue.
- The reticular region is composed of dense irregular connective tissue.
- The hypodermis lies below the dermis and contains connective tissue, vessels, glands, follicles, hair roots, sensory nerve endings and muscular tissue.
What Does the Dermis Do?
The dermis is the thickest layer of skin and arguably the most important.
It plays several key roles, including:
- Producing sweat. Within the dermis are sweat glands that produce sweat that comes out of the pores. The body sweats as a way to cool itself off, regulate temperature and flush out toxins. There are more than 2.5 million sweat glands on the body, and there are two different types: apocrine and eccrine. Apocrine sweat glands are found in the more odorous parts of the body, including the armpits, scalp and genital region. The sweat glands, which become active during puberty, secrete their substances into the hair follicles. The sweat that is secreted is actually odorless at first; it only starts to smell when it comes in contact with skin bacteria. Eccrine sweat glands are located throughout the rest of the body: on the palms, the soles of feet, armpits and the forehead. These glands emit their substances directly to the surface of the skin.
- Producing oil. The sebaceous glands produce sebum, or oil. Sebum prevents bacterial growth on the skin and conditions the hair and skin. If the follicle in which sebaceous glands are located becomes clogged with excess oil or dead skin cells, a pimple develops.
- Growing hair. Hair follicles are located in the dermis. Every follicle root is attached to tiny muscles, known as arrector pili muscles, that contract when the body becomes cold or scared, causing goosebumps.
- Feeling. The dermis is full of nerve endings that send signals to the brain about how things feel: if something hurts, itches, feels good, etc.
- Distributing blood. Blood vessels are located in the dermis, which feed the skin and remove toxins.
- Protecting the rest of the body. The dermis contains phagocytes, which are cells that consume potentially harmful toxins and impurities, including bacteria. The dermis already protects the body, but the phagocytes provide an additional layer of protection from anything harmful that has penetrated the epidermis.
The hypodermis is not part of the skin and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as to supply it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types found in this area are fibroblasts, macrophages and adipocytes (the hypodermis contains 95% of the body’s fat). Fat serves as padding and insulation for the body.