chap06_powerpoint_le2.ppt integumentary system
- 1. 6-1 Chapter 6 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
- 2. 6-2 The Integumentary System • Functions of the skin and subcutaneous tissue – epidermis and dermis – hypodermis – thick and thin skin – skin color – skin markings • Hair and nails • Cutaneous glands • Skin disorders
- 3. 6-3 Overview • Largest organ (15% of body weight) • Epidermis – keratinized stratified squamous epithelium • Dermis – connective tissue layer • Hypodermis • Thickness variable, normally 1-2 mm – dermis may thicken, up to 6 mm – stratum corneum layer increased • calluses on hands and feet
- 4. 6-4 Structure of the Skin
- 5. 6-5 Functions of the Skin • Resistance to trauma and infection – packed with keratin and linked by desmosomes – acid mantle (pH 4-6) • Barrier to ultraviolet light • Vitamin D synthesis • Sensory receptors • Thermoreceptors through sweating • Nonverbal communication
- 6. 6-6 Cells of the Epidermis • Stem cells – undifferentiated cells in deepest layers • Keratinocytes – most of the skin cells • Melanocytes – synthesize pigment that shield UV • Tactile (merkel) cells – receptor cells associated with nerve fibers • Dendritic (langerhans) cells – macrophages guard against pathogens
- 7. 6-7 Cell and Layers of the Epidermis
- 8. 6-8 Stratum Basale • Single layer cells on basement membrane • Cell types in this layer – keratinocytes • undergo mitosis to replace epidermis – melanocytes • distribute melanin through cell processes • melanin picked up by keratinocytes – merkel cells are touch receptors • form Merkel disc
- 9. 6-9 Stratum Spinosum • Several layers of keratinocytes – appear spiny due to shrinkage during histological preparation • Contains dendritic (Langerhans) cells – macrophages from bone marrow that migrate to the epidermis – 800 cells/millimeter2 – help protect body against pathogens by “presenting” them to the immune system
- 10. 6-10 Stratum Granulosum • 3 to 5 layers Flat keratinocytes • Contain keratinohyalin granules – combine with filaments of cytoskeleton to form keratin • Produces lipid-filled vesicles that release a glycolipid by exocytosis to waterproof the skin – forms a barrier between surface cells and deeper layers of the epidermis – cuts off surface strata from nutrient supply
- 11. 6-11 Stratum Lucidum • Thin translucent zone seen only in thick skin • Keratinocytes are packed with eleidin, a precursor to keratin – does not stain well • Cells have no nucleus or organelles
- 12. 6-12 Stratum Corneum • Up to 30 layers of dead, scaly, keratinized cells – surface cells flake off (exfoliate)