The dermis is separated from the epidermis by the epidermal-dermal junction, a basement membrane. Compared to the epidermis, the dermis is much thicker, housing with it blood vessels, nerves, lymphatic capillaries and sensory receptors. It is being held together by a pool of fibrous connective tissues that offers support to various accessory structures. The dermis is the one to thank for because it gives the skin elasticity, strength and firmness. A layer called the papillary layer exists as the superficial layer of the dermis and is notable for being vascular and made up of loose connective tissues. Pegs of the papillary layer push through to the epidermis and is called dermal papillae. The dermal papillae brings with it nerve endings, axons and vessels among the elastic fibers and collagen.
The hair shaft ascends from the epidermal follicle and pushes down to reach the vascular dermal papillae during development. With its limited capability to push down, hair shafts are not found in people with thick skin. The visible skin hair that we see is only the part that which starts to leave the epidermis of the skin and at the other end of the visible hair is a bulb which is the root of the hair. Layers of keratin enveloped by layers of follicular cells compose the hair shafts. A bundle of smooth muscles ensure the attachment of the hair shaft to the dermal papillae which gives it nutrition and other supply vital to its survival and nourishment. This bundle of smooth muscles is the arrector pili. When the muscle contracts, the hair which is embedded in it also reacts that’s why sometimes we notice our hair to be perpendicular with the skin or what we call Goosebumps.
Sebaceous glands surround the hair follicles and are referred to as an oil-producing, grape-shape collection of cells. This gland is responsible for keeping the hair and skin moisturized. The oil produced by the sebaceous glands is called sebum and it is the number one enemy of adolescents. During the peak of hormonal activity in adolescents, some of the sebum cannot escape the sebaceous glands and gets trapped, which later becomes acne. There are also instances when the sebaceous glands secrete too much sebum and the skin appears oily; on the other hand when there is low production of sebum the skin appears dry. To understand how this sebum is produced, we need to look at the base of each gland. The base of the sebaceous glands is mitotically active, which means it is performing active division and the newly produced daughter cells converge in the center of the gland and is filled with lipids. The cell debris and the secretory product make up the sebum. The sebum then travels to the skin or coats the hair. When sebum reaches the skin, it provides a certain degree of waterproofing.
Sweat glands are found in the deep dermis and appear to be coiled, tubular glands. Sweating is a mechanism of the hypothalamus to induce a certain degree of cooling by evaporation. If someone is to taste sweat, there is a characteristic saltiness to it. That’s due to the reason that sweat is largely salt water with a little mix of urea and other molecules. The glandular cells located at the base of the sweat glands lies closely to an area of rich capillaries. Not known to all, the cells actually produce sweat. This sweat that the cells produce is a filtrate of plasma. There are 2 characterized sweat glands, referred to as the apocrine and the eccrine glands. To say it simply, apocrine sweat glands respond to emotional stress and the eccrine glands are the more common sweat glands.
The vast activity happening in the skin reflects how important the structure is to our survival. For medical professionals, an in-depth understanding in the roles and functions of the skin and the structures contained within it offers a peek into the window of the engineering of the human body.