Chapter 5 (The Integumentary System) PDF

CHAPTER 5 The Integumentary System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation,...

CHAPTER 5 The Integumentary System Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. Integumentary System Skin Sweat/oil glands Hair Nails The Skin and the Hypodermis Skin – our largest organ Accounts for 7% of body weight Varies in thickness from 1.5–4.4mm Divided into two distinct layers Epidermis Dermis Hypodermis – lies deep to the dermis Skin Structure Hair shaft Dermal papillae Epidermis Subpapillary vascular Papillary plexus layer Pore Appendages of skin Dermis Eccrine sweat gland Reticular layer Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Hypodermis (superficial fascia) Nervous structures Sensory nerve fiber Dermal vascular plexus Lamellar (Pacinian) corpuscle Adipose tissue Hair follicle receptor (root hair plexus) The Skin and the Hypodermis Functions Cushions and insulates deeper organs Protects body from bumps, scrapes, and cuts Protects body from chemicals, heat, and cold The Skin and the Hypodermis Acts as a mini-excretory system Production of Vitamin D Contains sensory receptors associated with nerve endings Epidermis Contains four main cell types Keratinocytes Melanocytes Tactile epithelial cells Dendritic cells Epidermis Keratinocytes – most abundant cell type in epidermis Arise from deepest layer of epidermis Produce keratin – a tough fibrous protein Produce antibodies and enzymes Keratinocytes are dead at skin's surface Layers of the Epidermis Stratum basale (stratum germinativum) Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum Epidermal Cells and Layers of the Epidermis Layers of the Epidermis Stratum basale Deepest layer of epidermis Attached to underlying dermis Cells actively divide Stratum basale contains Keratinocytes Merkel cells – associated with sensory nerve ending Melanocytes – secrete the pigment melanin Layers of the Epidermis Stratum spinosum (spiny layer) "Spiny" appearance caused by artifacts of histological preparation Contains keratinocytes Contains star-shaped Dendritic cells Type of macrophage Layers of the Epidermis Stratum granulosum Consists of keratinocytes Keratohyaline granules – help form keratin Lamellated granules – contain a waterproofing glycolipid Layers of the Epidermis Stratum lucidum (clear layer) Occurs only in thick skin Composed of a few rows of flat, dead keratinocytes Stratum corneum (horny layer) Thick layer of dead keratinocytes and thickened plasma membranes Protects skin against abrasion and penetration Dermis Second major layer of the skin Strong, flexible connective tissue Richly supplied with blood vessels and nerves Has two layers Papillary layer – includes dermal papillae Reticular layer – deeper layer – 80% of thickness of dermis Lines and Ridges of the Hand Friction ridges Openings of sweat gland ducts Flexion creases (a) Friction ridges of finger on digit tip (SEM 20) Flexion creases on the palm (b) Cleavage lines in the (c) Flexure lines of reticular dermis the hand Skin Structure Skin Structure Dermis (b) Papillary layer of dermis, SEM (570) (a) Light micrograph of thick skin identifying the extent of the dermis, (100) (c) Reticular layer of dermis, SEM (430) Hypodermis Deep to the skin – also called superficial fascia Contains areolar and adipose connective tissues Anchors skin to underlying structures Helps insulate the body Skin Color Three pigments contribute to skin color Melanin Most important pigment Carotene Yellowish pigment from carrots and tomatoes Hemoglobin Caucasian skin contains little melanin Allows crimson color of blood to show through