The Skin

Skin as an organizing model:

• What is it?   * Skin is made up of three layers: epidermis, dermis, hypodermis (fatty later)   * Skin is a vital organ     * Covers the outside of the body     * Protective barrier against pathogens and injuries   * The largest organ at 2mm thick, 6 lbs   * There are 2 general types of skin:     * Thin and Hairy     * Thick and Hairless
• What does it do?   * Protection     * Air = Desiccation     * Water = Bloating / Pruning     * Sun/U-V = Burns     * Cold/heat = frostbite/heatstroke   * Structural Integrity     * The integrity of the body
• How does it do it?   * Protection (mostly epidermis)     * Desiccation - keratin, lipid layer     * Water - keratin, lipid layer     * Sun/U-V - role of pigment / melanin     * Cold/heat - surface blood vessels   * Structural (mostly dermis)     * Integrity - dermal layer has a network of tough collagen fibers in connective tissue   * What else does skin do?   * Regulated body temperature   * Gathers sensory information from the environment   * Stores water, and fat, and synthesizes vitamin D
• What is it made of?   * Layers of Skin     * Epidermis = epithelium     * Dermis = connective tissue   * Specialized Cells and Structures     * Basket cells: surround the base of hair follicles and can sense pressure. Evaluated when assessing nerve health.     * Blood Vessels: can carry nutrients and oxygen-rich blood to the cells that make up layers of skin     * Hair Erector Muscle (Arrector Pili Muscle): Tiny muscle connected to each hair follicle and the skin. When it contracts, the hair stands erect     * Hair Follicle: a tube-shaped sheath that surrounds the part of the hair that is under the skin and nourishes the hair     * Hair Shaft: the part of the hair that is above the skin     * Langerhans Cells: Attach themselves to antigens that invade damaged skin and alert the immune system to their presence     * Melanocyte: a cell that produces melanin, and is located in the basal layer of the epidermis. touch sensitive     * Pacinian corpuscle: a nerve receptor located in the subcutaneous fatty tissue that responds to pressure and vibration     * Sensory Nerves: skin is innervated with these       * sense and transmit heat, pain, and other sensations     * Stratum Corneum       * the outermost layer of the epidermis   * Glands     * Sebaceous Gland - empties oily secretion into the hair follicle     * Sweat gland - small tubular structures within the subcutaneous     * Ceruminous gland - specialized sudoriferous glands located in the EAC. Mixes with sebaceous to form cerumen

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