SKIN• Outer Covering of the Body

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

Components

• Three Primary Layers– Epidermis– Dermis– Hypodermis (Subcutaneous Adipose

Layer)

• Pigmentation or Melanin

Layers of the Skin

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

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

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

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

Skin with Layers of the Epidermis

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

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

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

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

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

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

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

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