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Chapter 5 Outline

Chapter 5 Outline - Vandan Desai BIOL 251Anatomy Physiology...

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Vandan Desai BIOL 251—Anatomy & Physiology I 1 Chapter 5—The Integumentary System I. The Skin (pp. 149–155; Figs. 5.1–5.4) A. The hypodermis, also called the superficial fascia, is subcutaneous tissue beneath the skin consisting mostly of adipose tissue that anchors the skin to underlying muscle, allows skin to slide over muscle, and acts as a shock absorber and insulator (p. 149; Fig. 5.1). B. Epidermis (pp. 150–152; Fig. 5.2) 1. The epidermis is a keratinized stratified squamous epithelium. 2. Cells of the Epidermis a. The majority of epidermal cells are keratinocytes that produce a fibrous protective protein called keratin. b. Melanocytes are epithelial cells that synthesize the pigment melanin. c. Epidermal dendritic cells or Langerhans cells, are macrophages that help activate the immune system. d. Tactile cells are associated with sensory nerve endings. 3. Layers of the Epidermis a. The stratum basale (basal layer) is the deepest epidermal layer and is the site of mitosis. b. The stratum spinosum (prickly layer) is several cell layers thick and contains keratinocytes, melanin granules, and the highest concentration of epidermal dendritic cells. c. The stratum granulosum (granular layer) contains keratinocytes that are undergoing a great deal of physical changes, turning them into the tough outer cells of the epidermis. d. The stratum lucidum (clear layer) is found only in thick skin and is composed of dead keratinocytes. e. The stratum corneum (horny layer) is the outermost protective layer of the epidermis composed of a thick layer of dead keratinocytes. C. Dermis (pp. 152–153; Figs. 5.3–5.4) 1. The dermis is composed of strong, flexible connective tissue. 2. The dermis is made up of two layers: the thin, superficial papillary layer is highly vascularized areolar connective tissue containing a woven mat of collagen and elastin fibers; and the reticular layer, accounting for 80% of the thickness of the dermis, is dense irregular connective tissue.
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