CHAPTER 5 Two major components of the integumentary system is the skin which is the largest organ of the body and accesory structures associated with the skin. Functions of the Skin: - Protection from mechanical abrasion/injuries. It serves as a barrier to microbial invasion. - Regulation of body temperature through glands. We can radiate heat away from our body by increasing our perspiration rate (letting water with a high heat capacity leave our body) or by bringing blood vessels close to the surface of the body. - Secretion – the skin has various glands responsible for secreting things onto the surface of the skin. - Absorption of UV rays to activate cells responsible for making melanin and to make Vitamin D in our skin. - Sensation – afferent sensory information ( Ex: temperature, pain, vibration) bring sensory information to the brain and spinal cord. An efferent command is then sent out in response to the afferent sensory information received. Accesory Structures associated with the Skin: - Hair Shafts go deep into the dermis to structures that make the hair shafts called hair follicles. - Sebaceous Glands ( ecorine glands ) are always associated with hair follicles. These glands open up into the hair follicle where oil is released. The oil released follows the hair shaft out and onto the surface of the skin - Sweat glands open onto the surface of the skin. They have a secretory portion and a duct portion (which opens up to a pore on the surface of the skin). - Various sensory structures which include: • Pacinian Corpuscle – deep touch and is found in the reticular layer . • Meissner Corpuscle – light touch and is found in the dermal papillae & the Rete Apparatus . - Nerve Fibers connected to sensory afferent structures help bring sensory information to the brain and spinal cord. - Smooth muscles that connect to the bottom hair follicles and to the bottom of the epidermis. When the smooth muscle contracts it causes the hair shaft to become erect. The two major components of skin: 1. Epidermis – outermost lining of the skin and parietal to the dermis. The epidermis is a keratinized (cornified) stratified squamous epithelium and is avascular (does not contain blood vessels). - Contains stem cells which differentiate into keratinocytes (cells that make keratin) located at the most basale region of the epidermis. We want to protect keratinocytes from UV radiation. If these stem cells are hit with radiation, they will lose control of their ability to regulate division which leads to cancer. We protect these stem cells from UV with melanin .
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