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INTEGUMENTARY SYSTEM I Introduction A Integument covering skin largest organ of the body B Integumentary system Skin Exocrine glands Hair Nails associated nerves associated blood vessels II Layers of the Integument A Epidermis epi on derma skin 1 2 3 4 Outer layer Composed of Keratinized Stratified Squamous epithelium Avascular Thick skin 5 layers Thin skin 4 layers B Dermis 1 Middle layer 2 Composed of dense irregular and areolar connective tissues 3 Contains nerve endings hair follicles glands 4 Dermal papillae projections of the dermis into the epidermis Subcutaneous layer hypodermis superficial fascia not considered part of the integument Below dermis Stores fat and anchors upper layers to other tissues Composed of areolar CT and adipose CT III Layers of Epidermis A Stratum Basale single layer of columnar cuboidal cells resting on the basement membrane cells are very mitotic B Stratum Spinosum several layers of polygonal shaped cells with spines Small degree of mitosis here C Stratum Granulosum 3 5 layers of flattened cells with visible granules cells undergo keratinization here keratinization the process by which the nucleus shrivels up cell dies and cell fills up with the protein keratin D Stratum Lucidum 2 3 layers of dead anucleated keratinized clear cells only found in thick skin E Stratum Corneum 20 30 layers of dead keratinized anucleated cells cornified brittle hardened outer cells are constantly shed IV Cells of the Epidermis 1 Keratinocytes most numerous found in all layers produce keratin 2 Melanocytes 2nd most numerous found in the stratum basal with processes extending into the stratum spinous produce melanin 3 Tactile Cells 3rd most numerous found only in the stratum basale provide information regarding tactile light touch sensation 4 Epidermal Dendritic Cells 4th most numerous found primarily in the stratum spinous phagocyte V Layers of the Dermis A Papillary Layer uppermost composed of areolar C T and dermal papillae contains blood vessels