The skin is the largest organ of the integumentary system and protects the body from damage. It has three main layers - the epidermis, dermis, and hypodermis. The epidermis is the outermost layer and provides a protective barrier. It contains melanocytes that produce melanin and give skin its color. The dermis lies below the epidermis and contains connective tissue, nerves, and blood vessels. The deepest layer is the hypodermis, which contains fat and connects the skin to underlying muscles and bones. The skin protects the body, helps regulate temperature and fluid levels, and allows for sensation and vitamin D production.

1. SKIN Outer Covering of the Body

2. Integument and Cutaneous Membrane - Alternative Names for Skin Major Organ of the Integumentary System Accounts for about 15 percent of the Body’s Weight Self-Repairing Protective Boundary Between the Body and the External Environment

3. Components Three Primary Layers Epidermis Dermis Hypodermis (Subcutaneous Adipose Layer) Pigmentation or Melanin

4. Layers of the Skin

5. Epidermis Outermost Layer of the Skin Forms Waterproof, Protective Wrap Over Body’s Surface Made Up of Stratified Squamous Epithelium With Underlying Basal Lamina Has Five Layers

6. Layers of the Epidermis and Their Charcteristics Stratum basale - Deepest Layer; Site of Continuous Cellular Reproduction; Contains the Only Cells of the Epidermis that Receive Nutrition; Cells Are Constantly Undergoing Division and Pushing Up to the Body Surface Stratum Spinosum - Many Keratinocytes with Spiny Appearance; Some Keratin

7. Layers of the Epidermis (Con’t) Stratum Granulosum - Three to Five Rows of Flat Cells; Site of Keratohyalin and Keratin Formation Stratum lucidum - Only in the Thick Sking of the Palms and Soles; Consists of Clear, Flat, Dead Cells; Cells Contain Eleidin Stratum Corneum - Outermost Layer of Epidermis; 25 to 30 Rows Flat, Dead Cells Filled with Keratin; Continuously Shed and Replaced

8. Two Important Items Found in the Epidermis Keratin Hard Protein Gives Skin Rigidity and Water-Repellent Features Melanocytes Produces Black Pigment Called Melanin Responsible for Color of the Skin Protects Against Damage from Ultraviolet Rays

9. Skin with Layers of the Epidermis

10. Dermis Lies Beneath the Epidermis Consists of Connective Tissue Cushions the Body from Stress and Strain Structurally Divided into Two Areas: Papillary Region Reticular Region

11. Papillary Region of the Dermis Composed of Loose Areolar Connective Tissue Named for Its Fingerlike Projections Called papillae Extend Toward the Epidermis Provide Dermis with “Bumpy” Surface Forms Contours in the Skin’s Surface Called Friction Ridges In Palms, Fingers, Soles and Toes Help Hand or Foot Grasp By Increasing Friction Occur in Patterns - Genetically and Epigenetically Determined and Therefore Unique to the Individual

12. Reticular Region of the Dermis Lies Deep in the Papillary Region Much Thicker Composed of Dense Irregular Connective Tissue Gives The Dermis Its Protective Strength, Extensibility, and Elasticity

13. Hypodermis Also Called the Subcutaneous Layer Third and Deepest Layer Composed of Fat Cells Called Lipocytes Purposes: Attach the Skin to Underlying Bones and Muscles Protects Deepe Tissues of the Body Acts as Insulation for Heat and Cold

15. Functions of the Skin Protection: Acts as Barrier from Pathogens and Damage Between Internal and External In Bodily Defense Sensation: Contains Variety of Nerve Endings that React to Heat and Cold, Pressure, Vibration and Tissue Injury Heat Regulation: Contains Blood Supply Far Greater than Its Requirement, Allowing Precise Control of Energy Loss by Radiation, Convection and Radiation Control of Evaporation: The Skin Provides a Relatively Dry and Semi-Permeable Barrier to Fluid Loss

16. Functions of the Skin Aesthetics and Communication: Others See Our Skin and Assess Our Mood, Physical State and Attractiveness Storage and Synthesis: Acts as Storage Center for Lipidsn and Water. As Well as a Means of Synthesis of Vitamin D by Action of UV on Certain Parts of the Skin Excretion: Sweat, Released from Skin Contains Urea, a Waste Product Absorption: Oxygen, Nitrogen and Carbon Dioxide Can Diffuse Into the Epidermis in Small Amounts. Additionally, Medicine Can Be Administered Through the Skin by Ointments or Adhesive Patch Water Resistance: Acts as Barrier So Essential Nutrients Are Not Washed Out of the Body

17. Possible Diseases and Injuries to the Skin Rash: Change of the Skin which Affects Color, Appearance or Texture. It Can Be Localized in One Area or Affect All Skin Sunburn: Burn to Living Tissue Caused by Over Exposure to Ultraviolet Radiation Commonly From Sun’s Rays. It Is Leading Cause of Non-Malignant Skin Tumors Skin Cancer - Malignant Growth On the Skin. Most Common Types Are: Basal Cell, Squamous Cell and Melanoma - Which All Trace Back to Mutation of Melanin Cells Albinism: Form of Hypopigmentary Congenital Disorder, Characterized by Partial or Total Lack of Melanin Pigmen in Eyes, Skin and Hair Acne: Most Common in Adolescence and Characterized by Lesions, Most Commonly Called Pimples Cold Sores - Infection by Herpes Simplex Virus and Causes Small Blister or Sores Around the Mouth

18. References Fremgen, Bonnie F and Frucht Suzanne S. Medical Terminology, A Living Language (4th Ed).Upper Saddle River, New Jersey: Pearson Prentic Hall. Pp. 50-52. Wikipedia.com Images From Wikipedia.com, skin-care.net