CHAPTER 5- The integumentary System Integumentary System= looking at a bunch of tissues composed together to work toward the common function of working toward covering the surface of the body for protection and other functions. The organs of the integumentary system include the skin and its accessory structures including hair, nails, and glands, as well as blood vessels, muscles, and nerves. The integumentary system: – Maintains the body’s integrity- covering surface of body and protecting it – Maintains temperature- by sweating, kinetic energy making hair stand up when cold, thermoreceptors, provides subcutaneous layer insulation, dilation of blood vessels (to release heat, why face turns red when hot) – Converts inactive vitamin D to its active form – Provides sensory information – Maintains homeostasis. Layers of Skin • The skin has 3 major layers: – The superficial layer is called the epidermis. – The layer just deep to the epidermis is called the dermis. – The subcutaneous (subQ) layer (also called the hypodermis) is located deep to the dermis.
Papillary region- area of connective tissue between papillae in the dermis. Divided out because it is mostly areolar connective tissue. Reticular region of the dermis is dense irregular CT. The Epidermis Contains four major types of cells: Keratinocytes- produce keratin - a tough fibrous protein that provides protection. Melanocytes- run through the epidermis, produce the pigment melanin. The amino acid tyrosine along with the enzyme tyrosinase makes melanin. U.V. Light activates tyrosinase and increases the production of melanin The amount of melanin produced varies from light to dark skin, but the number of melanocytes is consistent in all skin colors. There is a genetic trigger that triggers a lot or little amount of melanin production which is why there are variations in skin tones. Intraepidermal macrophages (Langerhans cells)- are involved in the immune responses, important for cell protection, derived from white blood cells that help to protect the body against bacteria (microbes) Tactile epithelial (Merkel) cells- function in the sensation of touch, associated with the tactile neurons involved in touch, still unsure of the function. Epidermis of the skin is stratified squamous keratinized. These cells are the keratinocytes.
Skin Pigments Melanin is produced by melanocytes in the stratum basale. Melanin is a class of compounds found in plants and animals where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acid, and their reduced forms. Another common form of melanin is pheomelanin, a red-brown polymer of benzothiazine units largely responsible for red hair and freckles Extensions from the melanocytes move all around the epidermis.
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