Sometimes the doctor uses a hand-held The skin has three layers. Beneath the surface of the skin are nerves, nerve endings, glands, hair follicles, and blood vessels. Sweat is produced by glands in the dermis and reaches the surface of the skin through tiny ducts. The epidermis is the relatively thin, tough, outer layer of the skin. Most of the cells in the epidermis are keratinocytes. They originate from cells in the deepest layer of the epidermis called the basal layer.
New keratinocytes slowly migrate up toward the surface of the epidermis. Once the keratinocytes reach the skin surface, they are gradually shed and are replaced by newer cells pushed up from below. The outermost portion of the epidermis, known as the stratum corneum, is relatively waterproof and, when undamaged, prevents most bacteria, viruses, and other foreign substances from entering the body.
The epidermis along with other layers of the skin also protects the internal organs, muscles, nerves, and blood vessels from injury. In certain areas of the body that require greater protection, such as the palms of the hands and the soles of the feet, the stratum corneum is much thicker. Scattered throughout the basal layer of the epidermis are cells called melanocytes, which produce the pigment melanin, one of the main contributors to skin color.
Melanin's primary function, however, is to filter out ultraviolet radiation from sunlight see Overview of Sunlight and Skin Damage Overview of Sunlight and Skin Damage Sunlight stimulates vitamin D production, helps control some chronic skin diseases such as psoriasis , and causes a sense of well-being.
However, sunlight can cause skin damage. Damage includes Skin cancer is most common among people who work or play sports outside and among sunbathers.
Fair-skinned people are particularly susceptible The epidermis also contains Langerhans cells, which are part of the skin's immune system. It provides a barrier between your vital, life-sustaining organs and the influence of outside elements that could potentially damage them. For any form of armor, a breach in the protective barrier poses a danger. The skin can be breached when a child skins a knee or an adult has blood drawn—one is accidental and the other medically necessary.
Because the needles involved in producing body art and piercings must penetrate the skin, there are dangers associated with the practice. These include allergic reactions; skin infections; blood-borne diseases, such as tetanus, hepatitis C, and hepatitis D; and the growth of scar tissue. Despite the risk, the practice of piercing the skin for decorative purposes has become increasingly popular. According to the American Academy of Dermatology, 24 percent of people from ages 18 to 50 have a tattoo.
Tattooing has a long history, dating back thousands of years ago. The dyes used in tattooing typically derive from metals. A person with tattoos should be cautious when having a magnetic resonance imaging MRI scan because an MRI machine uses powerful magnets to create images of the soft tissues of the body, which could react with the metals contained in the tattoo dyes.
Watch this video to learn more about tattooing. The fact that you can feel an ant crawling on your skin, allowing you to flick it off before it bites, is because the skin, and especially the hairs projecting from hair follicles in the skin, can sense changes in the environment.
The hair root plexus surrounding the base of the hair follicle senses a disturbance, and then transmits the information to the central nervous system brain and spinal cord , which can then respond by activating the skeletal muscles of your eyes to see the ant and the skeletal muscles of the body to act against the ant.
The skin acts as a sense organ because the epidermis, dermis, and the hypodermis contain specialized sensory nerve structures that detect touch, surface temperature, and pain.
These receptors are more concentrated on the tips of the fingers, which are most sensitive to touch, especially the Meissner corpuscle tactile corpuscle Figure , which responds to light touch, and the Pacinian corpuscle lamellated corpuscle , which responds to vibration. Merkel cells, seen scattered in the stratum basale, are also touch receptors.
In addition to these specialized receptors, there are sensory nerves connected to each hair follicle, pain and temperature receptors scattered throughout the skin, and motor nerves innervate the arrector pili muscles and glands. This rich innervation helps us sense our environment and react accordingly.
Thermoregulation The integumentary system helps regulate body temperature through its tight association with the sympathetic nervous system, the division of the nervous system involved in our fight-or-flight responses. The sympathetic nervous system is continuously monitoring body temperature and initiating appropriate motor responses. Recall that sweat glands, accessory structures to the skin, secrete water, salt, and other substances to cool the body when it becomes warm.
Even when the body does not appear to be noticeably sweating, approximately mL of sweat insensible perspiration are secreted a day. If the body becomes excessively warm due to high temperatures, vigorous activity Figure ac , or a combination of the two, sweat glands will be stimulated by the sympathetic nervous system to produce large amounts of sweat, as much as 0.
When the sweat evaporates from the skin surface, the body is cooled as body heat is dissipated. The larger part of the nail, the nail plate , looks pink because of the network of tiny blood vessels in the underlying dermis. The whitish crescent-shaped area at the base of the nail is the lunula LOON-yuh-luh.
Fingernails grow faster than toenails. Like hair, nails grow faster in summer than in winter. A nail that's torn off will regrow if the matrix isn't severely injured. Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Does Skin Do? Skin, our largest organ, has many jobs.
It: protects the network of muscles, bones , nerves, blood vessels, and everything else inside our bodies forms a barrier that prevents harmful substances and germs from entering the body protects body tissues against injury helps control body temperature through sweating when we're hot and by helping keep heat in the body when we're cold Without the nerve cells in skin, people couldn't feel warmth, cold, or other sensations.
What Are the Parts of Skin? In these layers are three special types of cells: Melanocytes meh-LAH-nuh-sites make melanin , the pigment that gives skin its color. All people have roughly the same number of melanocytes; the more melanin made, the darker the skin. Exposure to sunlight increases the production of melanin, which is why people get suntanned or freckled. Keratinocytes ker-uh-TIH-no-sites make keratin , a type of protein that's a basic component of hair, skin, and nails.
Keratin in the skin's outer layer helps create a protective barrier. It can be split into the papillary and reticular layers. The papillary layer is outermost and extends into the epidermis to supply it with vessels. It is composed of loosely arranged fibers. Papillary ridges make up the lines of the hands giving us fingerprints. The reticular layer is more dense and is continuous with the hypodermis. It contains the bulk of the structures such as sweat glands.
The reticular layer is composed of irregularly arranged fibers and resists stretching. 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 supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. Fat serves as padding and insulation for the body. The fingernail is an important structure made of keratin.
The fingernail generally serve two purposes. It serves as a protective plate and enhances sensation of the fingertip. The protection function of the fingernail is commonly known, but the sensation function is equally important.
The fingertip has many nerve endings in it allowing us to receive volumes of information about objects we touch. The nail acts as a counterforce to the fingertip providing even more sensory input when an object is touched.
The structure we know of as the nail is divided into six specific parts: the root, nail bed, nail plate, eponychium cuticle , perionychium, and hyponychium. Root The root of the fingernail is also known as the germinal matrix. This portion of the nail is actually beneath the skin behind the fingernail and extends several millimeters into the finger. The fingernail root produces most of the volume of the nail and the nail bed. This portion of the nail does not have any melanocytes, or melanin producing cells.
The edge of the germinal matrix is seen as a white, crescent shaped structure called the lunula. Nail Bed The nail bed is part of the nail matrix called the sterile matrix. It extends from the edge of the germinal matrix, or lunula, to the hyponychium. The nail bed contains the blood vessels, nerves, and melanocytes, or melanin-producing cells. As the nail is produced by the root, it streams down along the nail bed, which adds material to the undersurface of the nail making it thicker.
It is important for normal nail growth that the nail bed be smooth. If it is not, the nail may split or develop grooves that can be cosmetically unappealing.
Nail Plate The nail plate is the actual fingernail, made of translucent keratin. The pink appearance of the nail comes from the blood vessels underneath the nail. The underneath surface of the nail plate has grooves along the length of the nail that help anchor it to the nail bed.
Eponychium The cuticle of the fingernail is also called the eponychium. The cuticle is situated between the skin of the finger and the nail plate fusing these structures together and providing a waterproof barrier.
Perionychium The perioncyhium is the skin that overlies the nail plate on its sides. It is also known as the paronychial edge. The perionychium is the site of hangnails, ingrown nails, and an infection of the skin called paronychia. Hyponychium The hyponychium is the area between the nail plate and the fingertip. It is the junction between the free edge of the nail and the skin of the fingertip, also providing a waterproof barrier.
Figure 3. Eccrine glands are coiled glands in the dermis that release sweat that is mostly water. In humans, there are two kinds of sweat glands which differ greatly in both the composition of the sweat and its purpose.
Eccrine sweat glands are exocrine glands distributed over the entire body surface but are particularly abundant on the palms of hands, soles of feet, and on the forehead. The primary function is body temperature regulation. Eccrine sweat glands are coiled tubular glands derived leading directly to the most superficial layer of the epidermis out layer of skin but extending into the inner layer of the skin dermis layer.
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