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Chapter 5

Chapter 5. Structure of the skin. Inte- whole Gument – body Made up of Epithelial and Connective Tissues Is the largest and thinnest organ in the body appendages : hair, nails, glands one square inch of skin contains more structures than some entire organs

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Chapter 5

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  1. Chapter 5

  2. Structure of the skin • Inte- whole • Gument – body • Made up of Epithelial and Connective Tissues • Is the largest and thinnest organ in the body • appendages: hair, nails, glands • one square inch of skin contains more structures than some entire organs • thick skin produces prints and has no hair • cutaneous membrane referred to as the integument

  3. cutaneous membrane referred to as the integument • Cutaneous Membrane : covers the external body surfaces • Adult skin is about 17-20 sq. ft and 10-11 lbs. • thick skin produces prints and has no hair • Ex. Eyelids 1/50” thickness • Ex. Heels 1/8” thickness

  4. Structure of the skin • Layers of the skin: • epidermis: outermost, made of a thin sheet of stratified squamous epithelium • Epi: above • Has hair • dermis: deepest layer, thicker, made mostly of connective tissue • Lacks hair • subcutaneous layer (hypodermis): lies beneath the dermis • made mostly of loose areolar and adipose tissue • insulates, stores energy, shock absorber • Injections are quick and relatively pain free vs. muscle injections • Fat: up to 10 cm in obese individuals

  5. Epidermis • Contain keratin: a tough fibrous protein • strata = layers • melanocytes: cells that produce pigment • cells of the epidermis are held together by desmosomes (cell junctions) • Most of the body is covered by thin skin • Ex. Back, arms, etc (hairy skin) • Thick skin • Palms and feet (no hair)

  6. Cell layers of the epidermis • 1. Stratum corneum; outer most layer of skin • cells continually flake off • Average person sheds about 40 lbs of dead skin cells during their life • 25-30 dead cell layers (flat keratinocytes) • millions of epithelial cells reproduce daily to replace the ones shed • Contains keratin and is our bodies 1st line of defense • 2. Stratum lucidum: clear layer • found in thick skin • Gel substance “eleidin” that will turn into keratin

  7. Cell layers of the epidermis • 3. Stratum granulosum: keratinization begins • Process of cells moving layers – gain keratin as they move up! • Cells begin to regenerate • 4. Stratum spinosum: • Spiny layer (contains RNA) • 5. Stratum basale: base layer (single layer of columnar cells) • only layer where mitosis occurs • new cells move toward surface • Contains keratinocytes (Keratin cells and some stem cells produce new keratinocytes • Stratum Spinosum and Stratum basale make up the growth layer

  8. Epidermal growth and repair • Takes about 35 days to regenerate skin • About 5 weeks • this process will speed up if skin is damaged • Constantly replacing itself all of the time • calluses form when mitotic activity increases due to friction • Causes a thick stratum corneum

  9. Dermis • Deeper of the two layers and much thicker • Called the “true skin” • contains a specialized network of nerves to process sensory info: pain, pressure, touch, and temp • Also includes sweat, oil (subcutaneous gland), blood vessels, and hair follicles.

  10. Layers of the dermis • 1. Papillary layer: made of collagenous and elastic fibers • when elastic fibers decrease wrinkles develop • dermal papillae: parallel rows of projections • binds skin layers together • form ridges and grooves for prints • ridges develop before birth and never change • allow us to walk upright and grip things • Ridges produce friction which give us traction

  11. Layers of the dermis • 2. Reticular layer: dense irregular Connective Tissue with collagen & Elastic Fibers • Serves as part of attachments for many muscles • arrector pili muscles: muscle that contracts only when you are frightened or cold (goosebumps)

  12. Dermal growth and repair • Doesn’t continually regenerate as epidermis does, only during the healing process • Langer’s lines (cleavage lines): patterns formed by the white collagenous fibers • incisions made parallel to cleavage lines will heal better • elastic fibers that are stretched will weaken and tear (stretch marks) • Pregnancy, growth, and weight • Bluish furrows with jagged edges • Heal and lose color (white) • Scars = Dense mass of Connective Tissue • Blisters – separation in epidermis and dermis layers

  13. Skin color • Melanin: determines skin color • number of melanocytes is the same, but the amount of pigment produced varies from person to person • Melanocytes = melanin producing cells • The hormone tyrosinase regulates the release of melanin • Albinism – enzyme tyrosinase is absent at birth

  14. Factors that determine Skin color • Heredity • Inherited from parents • Sunlight – prolonged exposure increase melanin • People that live near the equator • Hormones produced by the pituitary gland • ACTH and MSH • Age • Lower tyrosinase activity = gray hair • carotene: yellow pigment that also contributes to skin color

  15. Skin color • Skin can change color depending on blood flow and oxygen • Hemoglobin • Oxygen carrying pigment in RBCs • cyanosis: decrease in blood flow causes the skin to turn bluish gray • Not enough oxygen in the blood • Vessels constrict = pale • Vessels dilate = pinker

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