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The Integumentary System, but Shares Some of Skin’S Properties

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The Integumentary System, but Shares Some of Skin’S Properties PowerPoint® Lecture Slides The Skin and the Hypodermis prepared by Leslie Hendon University of Alabama, Birmingham • Skin—our largest organ • Accounts for 7% of body weight • Varies in thickness from 1.5–4.4mm C H A P T E R 5 • Divided into two distinct layers • Epidermis The • Dermis Integumentary • Hypodermis—lies deep to the dermis • Composed of areolar and adipose tissues System • Not part of the integumentary system, but shares some of skin’s properties Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Skin Structure The Skin and Hypodermis • Functions 1. Protection—cushions organs and protects from Hair shaft bumps, chemicals, water loss, UV radiation Dermal papillae Epidermis Subpapillary vascular 2. Regulation of body temperature---Capillary Papillary plexus network and sweat glands regulate heat loss layer Pore Appendages of skin 3. Excretion—urea, salts, and water lost through Dermis Reticular Eccrine sweat gland sweat layer Arrector pili muscle Sebaceous (oil) gland Hair follicle 4. Production of vitamin D---Epidermal cells use Hair root UV radiation to synthesize vitamin D Hypodermis (superficial fascia) 5. Sensory reception—Contains sense organs Nervous structures Sensory nerve fiber Dermal vascular plexus associated with nerve endings Lamellar (Pacinian) corpuscle Adipose tissue Hair follicle receptor (root hair plexus) Copyright © 2011 Pearson Education, Inc. Figure 5.1 Copyright © 2011 Pearson Education, Inc. Figure 5.2 Gross structure of skin and underlying tissues. Epidermis • Is composed of keratinized stratified squamous epithelium • Contains four main cell types • Keratinocytes • Location—stratum spinosum; produce keratin a fibrous protein Epidermis • Melanocytes • Location—basal layer; manufacture and secrete the pigment melanin Dermis • Tactile epithelial cells (Merkel cells) Hypodermis • Location—basal layer; attached to sensory nerve endings Deep fascia • Dendritic cells (Langerhans cells) • Location—stratum spinosum; part of immune system; Muscle macrophage-like Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. 1 Epidermis Layers of the Epidermis • Keratinocytes—most abundant cell type in • Stratum basale (stratum geminativum) epidermis • Stratum spinosum • Arise from deepest layer of epidermis • Stratum granulosum • Produce keratin, a tough fibrous protein • Stratum lucidum (only in thick skin) Produce antibodies and enzymes • • Stratum corneum • Keratinocytes are dead at skin's surface Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 5.3a Epidermal cells and layers of the epidermis. Stratum corneum Epidermal Cells and Layers of the Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs Epidermis filled with keratin. Glycolipids in extracellular space. Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum corneum Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled Stratum spinosum with keratin. Glycolipids in extracellular space. Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Desmosomes Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Stratum basale Stratum spinosum Deepest epidermal layer; one row Several layers of keratinocytes unified by of actively mitotic stem cells; desmosomes. Cells contain thick bundles of some newly formed cells become intermediate filaments made of pre-keratin. part of the more superficial Stratum basale layers. See occasional Deepest epidermal layer; one row of actively mitotic melanocytes and dendritic cells. stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and dendritic cells. Dermis (a) Dermis Copyright © 2011 Pearson Education, Inc. Figure 5.3a Copyright © 2011 Pearson Education, Inc. Figure 5.3b Epidermal cells and layers of the epidermis. Stratum corneum Most superficial layer; 20–30 Keratinocytes Epidermal Cells and Layers of the layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in Epidermis extracellular space. Keratinocytes Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum corneum Most superficial layer; 20–30 layers of dead cells Stratum spinosum represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Desmosomes Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. Stratum basale Stratum spinosum Deepest epidermal layer; one row Several layers of keratinocytes unified by of actively mitotic stem cells; desmosomes. Cells contain thick bundles of Dermis intermediate filaments made of pre-keratin. some newly formed cells become Stratum basale part of the more superficial Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells Dendritic cell layers. See occasional become part of the more superficial layers. See Dermis melanocytes and dendritic cells. occasional melanocytes and dendritic cells. Tactile epithelial cell Dendritic cell Melanin Sensory Sensory Melanocyte granule Melanocyte nerve nerve Melanin ending (b) Desmosomes ending Tactile granule epithelial cell Copyright © 2011 Pearson Education, Inc. Figure 5.3b Copyright © 2011 Pearson Education, Inc. 2 Layers of the Epidermis Layers of the Epidermis • Stratum basale • Stratum granulosum • Deepest layer of epidermis • Consists of keratinocytes and tonofilaments • Attached to underlying dermis • Tonofilaments contain: Cells actively divide • • Keratohyaline granules—help form keratin • Stratum basale contains • Tactile epith. Cells/Merkel cells—associated with sensory nerve • Lamellated granules—contain a waterproofing glycolipid ending • Stratum lucidum (clear layer) • Melanocytes—secrete the pigment melanin • Occurs only in thick skin • Stratum spinosum (spiny layer) • Locations of thick skin—palms and soles • “Spiny” appearance caused by: • Composed of a few rows of flat, dead keratinocytes • Artifacts of histological preparation • Stratum corneum (horny layer) • Contains thick bundles of intermediate filaments (tonofilaments) • Thick layer of dead keratinocytes and thickened plasma • Resist tension membranes • Contain protein prekeratin • Contains star-shaped dendritic cells • Protects skin against abrasion and penetration • A type of macrophage • Function in immune system Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 5.4 Thick skin. Epidermis Dermis Stratum corneum • Second major layer of the skin Stratum lucidum • Strong, flexible connective tissue Stratum granulosum • Richly supplied with blood vessels (important role in temperature control) and nerves Stratum spinosum Stratum basale Dermis • Has two layers • Papillary layer—includes dermal papillae Papillary dermis • Reticular layer Dermal • Deeper layer—80% of thickness of dermis papilla • Flexure lines Reticular • Creases on palms Collagen dermis fibers Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. The Two Regions of the Dermis Dermal Modifications Friction ridges Openings of sweat gland ducts Dermis (b) Papillary layer of dermis, SEM (570×) (a) Light micrograph of thick skin identifying the extent of the Flexion dermis, (100×) 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 (c) Reticular layer of dermis, SEM (430×) reticular dermis the hand Copyright © 2011 Pearson Education, Inc. Figure 5.5 Copyright © 2011 Pearson Education, Inc. Figure 5.6 3 Hypodermis Skin Color • Deep to the skin—also called superficial • Three pigments contribute to skin color fascia or subcutaneous layer • Melanin • Contains areolar and adipose CT • Most important pigment—made from tyrosine • Anchors skin to underlying structures • Carotene • Helps insulate the body • Yellowish pigment from carrots and • Has different distribution in males and tomatoes females • Hemoglobin • Caucasian skin contains little melanin • Allows crimson color of blood to show through Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Nails Structure of a Nail Lunule Lateral nail fold • Nails—scalelike modification of epidermis • Made of hard keratin • Parts of the nail • Free edge (a) Body Free edge Body Eponychium • of nail of nail (cuticle) Root of nail Proximal Nail • Root nail fold matrix • Nail folds • Eponychium—cuticle (b) Nail bed Phalanx (bone of fingertip) Copyright © 2011 Pearson Education, Inc. Copyright © 2011 Pearson Education, Inc. Figure 5.7 Appendages of the Skin Appendages of the Skin • Hair • Hair has three concentric layers of keratinized cells • Medulla—central core • Flexible strand of dead, keratinized cells • Cortex—surrounds medulla • Hard keratin—tough and durable • Cuticle—outermost layer Hair follicles • Chief parts of a hair • • Extend
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