The Integumentary System.docx - Anatomy and Physiology – Mrs Verrastro Chapter 6 The Integumentary System I Introduction The skin is one of the

The Integumentary System.docx - Anatomy and Physiology –...

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Anatomy and Physiology – Mrs. Verrastro Chapter 6: The Integumentary System I. Introduction: The skin is one of the largest and heaviest organ of the body. In an average adult, the skin covers about 2 square meters (22 square feet), weighs (10-11 lb) and varies in thickness (1.5 to 4.0 mm) depending on what part of the body it covers. The skin covers all of the exposed surface of the body and is continuous with the mucous membranes lining openings into the body surface, such as those of the digestive, respiratory and urogenital systems. II. Characteristics: The skin consists of 2 layers: 1 - the outer epidermis 2 - the inner dermis The appendages of the skin such as hair, nails, sebaceous glands and sweat glands develop from the embryonic epidermis. Beneath the dermis is the hypodermis (=subcutaneous tissue = superficial fascia) which anchors the skin loosely to underlying tissues (mainly muscles). The hypodermis is NOT part of the skin The skin and its appendages (hair, nails, sebaceous and sweat glands) make up a very complex set of organs that accomplishes several functions: III. Functions: 1 - Protection: barrier against the outside 2 - Protection against dehydration 3 - Body Temperature Regulation 4 - Cutaneous Sensation 5 - Metabolic Functions 6 - Blood Reservoir 7 - Excretion IV. The Epidermal Cells : 1. The Keratinocytes: compose most of the epidermis. They produce a protein: the keratin that helps waterproof the skin and that protects the skin and the underlying tissues from heat, microbes, abrasion and chemicals. 2. The Merkel Cells sensory receptors (touch). They associate with a disclike sensory nerve ending to form the Merkel disc. 3. The Melanocytes synthesize the melanin pigments which protect the skin against ultraviolet damage.
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4. The Langerhan Cells macrophages used in the defense against microorganisms. V. The Epidermal Layers ( From the deepest to the most superficial ) 1. the stratum basale (or stratum germinativum): is the deepest epidermal layer. It consists of one row of cuboidal to columnar shaped cells. Those cells are mostly stem cells that divide rapidly to produce new keratinocytes which push up toward the surface and become part of the more superficial layers (You can understand why this layer is called "germinativum": it "germinates" cells).
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