Lect 5 intergumentary


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Lect 5 intergumentary

  1. 1. Chapter 5 The Integumentary System Lecture Outline
  2. 2. INTRODUCTION <ul><li>The skin and its accessory structures make up the integumentary system. </li></ul><ul><li>The integumentary system functions to guard the body’s physical and biochemical integrity, maintain a constant body temperature, and provide sensory information about the surrounding environment. </li></ul><ul><li>Skin and its accessory structures </li></ul><ul><ul><li>structure </li></ul></ul><ul><ul><li>function </li></ul></ul><ul><ul><li>growth and repair </li></ul></ul><ul><ul><li>development </li></ul></ul><ul><ul><li>aging </li></ul></ul>
  3. 3. STRUCTURE OF THE SKIN (Figure 5.1) <ul><li>The superficial portion of the skin is the epidermis and is composed of epithelial tissue. </li></ul><ul><li>The deeper layer of the skin is the dermis and is primarily composed of connective tissue. </li></ul><ul><li>Deep to the dermis is the subcutaneous layer or hypodermis. ( not a part of the skin) </li></ul><ul><ul><li>It consists of areolar and adipose tissue. </li></ul></ul><ul><ul><li>fat storage, an area for blood vessel passage, and an area of pressure-sensing nerve endings. </li></ul></ul>
  4. 4. Overview of Epidermis <ul><li>Stratified squamous epithelium </li></ul><ul><li>avascular (contains no blood vessels) </li></ul>
  5. 5. Four Principle Cells of the Epidermis – Figure 5.2 <ul><li>keratinocytes </li></ul><ul><ul><li>produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant </li></ul></ul><ul><li>melanocytes </li></ul><ul><ul><li>produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light </li></ul></ul><ul><li>Langerhans cells </li></ul><ul><ul><li>derived from bone marrow </li></ul></ul><ul><ul><li>participate in immune response </li></ul></ul><ul><li>Merkel cells </li></ul><ul><ul><li>contact a sensory structure called a tactile (Merkel) disc and function in the sensation of touch </li></ul></ul>
  6. 6. Layers (Strata) of the Epidermis <ul><li>Stratum corneum </li></ul><ul><li>Stratum lucidum </li></ul><ul><li>Stratum granulosum </li></ul><ul><li>Stratum spinosum </li></ul><ul><li>Stratum basale </li></ul>
  7. 7. Stratum Basale ( stratum germinativum) <ul><li>Stratum corneum </li></ul><ul><ul><li>Barrier to light, heat, water, chemicals & bacteria </li></ul></ul><ul><ul><li>Lamellar granules in this layer make it water-repellent. </li></ul></ul><ul><li>Stratum lucidum </li></ul><ul><ul><li>Contains precursor of keratin </li></ul></ul><ul><li>Stratum granulosum </li></ul><ul><ul><li>transition between the deeper, metabolically active strata and the dead cells of the more superficial strata </li></ul></ul><ul><li>Stratum spinosum </li></ul><ul><ul><li>provides strength and flexibility to the skin </li></ul></ul><ul><li>Stratum basale </li></ul><ul><ul><li>Deepest single layer of epidermis </li></ul></ul>
  8. 8. Dermis (Figure 5.1) <ul><li>Connective tissue layer composed of collagen & elastic fibers, fibroblasts, macrophages & fat cells </li></ul><ul><li>Contains hair follicles, glands, nerves & blood vessels </li></ul><ul><li>Two major regions of dermis </li></ul><ul><ul><li>papillary region </li></ul></ul><ul><ul><li>reticular region </li></ul></ul>
  9. 9. Dermis - Papillary Region <ul><li>Top 20% of dermis </li></ul><ul><li>areolar connective tissue containing fine elastic fibers, corpuscles of touch (Meissner’s corpuscles), adipose cells, hair follicles, sebaceous glands, sudoriferous glands </li></ul><ul><ul><li>The collagen and elastic fibers provide strength, extensibility (ability to stretch), and elasticity (ability to return to original shape after stretching) to skin. </li></ul></ul><ul><li>Finger like projections are called dermal papillae </li></ul><ul><ul><li>anchors epidermis to dermis </li></ul></ul><ul><ul><li>contains capillaries that feed epidermis </li></ul></ul><ul><ul><li>contains Meissner’s corpuscles (touch) & free nerve endings for sensations of heat, cold, pain, tickle, and itch </li></ul></ul>
  10. 10. Dermis - Reticular Region <ul><li>Dense irregular connective tissue </li></ul><ul><li>Contains interlacing collagen and elastic fibers </li></ul><ul><li>Packed with oil glands, sweat gland ducts, fat & hair follicles </li></ul><ul><li>Provides strength, extensibility & elasticity to skin </li></ul><ul><ul><li>stretch marks are dermal tears from extreme stretching </li></ul></ul><ul><li>Epidermal ridges form in fetus as epidermis conforms to dermal papillae </li></ul><ul><ul><li>fingerprints are left by sweat glands open on ridges </li></ul></ul><ul><ul><li>increase grip of hand </li></ul></ul>
  11. 11. Dermis -- Structure <ul><li>Epidermal ridges increase friction for better grasping ability and provide the basis for fingerprints and footprints. The ridges typically reflect contours of the underlying dermis. </li></ul><ul><li>Lines of cleavage in the skin indicate the predominant direction of the underlying collagen fibers. Knowledge of these lines is especially important to plastic surgeons. </li></ul>
  12. 12. Basis of Skin Color <ul><li>The color of skin and mucous membranes can provide clues for diagnosing certain problems, such as </li></ul><ul><ul><li>Jaundice </li></ul></ul><ul><ul><ul><li>yellowish color to skin and whites of eyes </li></ul></ul></ul><ul><ul><ul><li>buildup of yellow bilirubin in blood from liver disease </li></ul></ul></ul><ul><ul><li>Cyanosis </li></ul></ul><ul><ul><ul><li>bluish color to nail beds and skin </li></ul></ul></ul><ul><ul><ul><li>hemoglobin depleted of oxygen looks purple-blue </li></ul></ul></ul><ul><ul><li>Erythema </li></ul></ul><ul><ul><ul><li>redness of skin due to enlargement of capillaries in dermis </li></ul></ul></ul><ul><ul><ul><li>during inflammation, infection, allergy or burns </li></ul></ul></ul>
  13. 13. Skin Color Pigments <ul><li>Melanin produced in epidermis by melanocytes </li></ul><ul><ul><li>melanocytes convert tyrosine to melanin </li></ul></ul><ul><ul><ul><li>UV in sunlight increases melanin production </li></ul></ul></ul><ul><li>The wide variety of colors in skin is due to three pigments - melanin, carotene, and hemoglobin (in blood in capillaries) - in the dermis. </li></ul><ul><li>Carotene in dermis </li></ul><ul><ul><li>yellow-orange pigment (precursor of vitamin A) </li></ul></ul><ul><ul><li>found in stratum corneum & dermis </li></ul></ul><ul><li>Hemoglobin </li></ul><ul><ul><li>red, oxygen-carrying pigment in blood cells </li></ul></ul><ul><ul><li>if other pigments are not present, epidermis is translucent so pinkness will be evident </li></ul></ul>
  14. 14. Accessory Structures of Skin <ul><li>develop from the embryonic epidermis </li></ul><ul><li>Cells sink inward during development to form: </li></ul><ul><ul><li>hair </li></ul></ul><ul><ul><li>oil glands </li></ul></ul><ul><ul><li>sweat glands </li></ul></ul><ul><ul><li>nails </li></ul></ul>
  15. 15. Structure of Hair <ul><li>Shaft -- visible </li></ul><ul><li>Root -- below the surface </li></ul><ul><li>Follicle surrounds root </li></ul><ul><li>Functions of Hair </li></ul><ul><ul><li>P revents heat loss </li></ul></ul><ul><ul><li>Decreases sunburn </li></ul></ul><ul><ul><li>Eyelashes help protect eyes </li></ul></ul><ul><ul><li>Touch receptors (hair root plexus) senses light touch </li></ul></ul>
  16. 16. Glands of the Skin <ul><li>Specialized exocrine glands found in dermis </li></ul><ul><li>Sebaceous (oil) glands </li></ul><ul><li>Sudiferous (sweat) glands </li></ul><ul><li>Ceruminous (wax) glands </li></ul><ul><li>Mammary (milk) glands </li></ul>
  17. 17. Sudoriferous (sweat) glands <ul><li>Eccrine sweat glands have an extensive distribution most areas of skin </li></ul><ul><ul><li>secretory portion is in dermis with duct to surface </li></ul></ul><ul><ul><li>ducts terminate at pores at the surface of the epidermis. </li></ul></ul><ul><ul><li>regulate body temperature through evaporation (perspiration) </li></ul></ul><ul><ul><li>help eliminate wastes such as urea. </li></ul></ul><ul><li>Apocrine sweat glands are limited in distribution to the skin of the axilla, pubis, and areolae; their duct open into hair follicles. </li></ul><ul><ul><li>secretory portion in dermis </li></ul></ul><ul><ul><li>duct that opens onto hair follicle </li></ul></ul><ul><ul><li>secretions are more viscous </li></ul></ul>
  18. 18. Ceruminous Glands <ul><li>Ceruminous glands are modified sudoriferous glands that produce a waxy substance called cerumen. </li></ul><ul><ul><li>found in the external auditory meatus </li></ul></ul><ul><ul><li>contains secretions of oil and wax glands </li></ul></ul><ul><ul><li>barrier for entrance of foreign bodies </li></ul></ul><ul><li>An abnormal amount of cerumen in the external auditory meatus or canal can result in impaction and prevent sound waves from reaching the ear drum (Clinical Application). </li></ul>
  19. 19. Structure of Nails (Figure 5.5) <ul><li>Tightly packed keratinized cells </li></ul><ul><li>Nail body </li></ul><ul><ul><li>visible portion pink due to underlying capillaries </li></ul></ul><ul><ul><li>free edge appears white </li></ul></ul><ul><li>Nail root </li></ul><ul><ul><li>buried under skin layers </li></ul></ul><ul><ul><li>lunula is white due to thickened stratum basale </li></ul></ul><ul><li>Eponychium (cuticle) </li></ul><ul><ul><li>stratum corneum layer </li></ul></ul>
  20. 20. Sebaceous (oil) glands <ul><li>Sebaceous (oil) glands are usually connected to hair follicles; they are absent in the palms and soles </li></ul><ul><li>Secretory portion of gland is located in the dermis </li></ul><ul><ul><li>produce sebum </li></ul></ul><ul><ul><ul><li>contains cholesterol, proteins, fats & salts </li></ul></ul></ul><ul><ul><ul><li>moistens hairs </li></ul></ul></ul><ul><ul><ul><li>waterproofs and softens the skin </li></ul></ul></ul><ul><ul><ul><li>inhibits growth of bacteria & fungi (ringworm) </li></ul></ul></ul><ul><li>Acne </li></ul><ul><ul><li>bacterial inflammation of glands </li></ul></ul><ul><ul><li>secretions are stimulated by hormones at puberty </li></ul></ul>
  21. 21. TYPES OF SKIN <ul><li>Thin skin </li></ul><ul><ul><li>covers all parts of the body except for the palms and palmar surfaces of the digits and toes. </li></ul></ul><ul><ul><li>lacks epidermal ridges </li></ul></ul><ul><ul><li>has a sparser distribution of sensory receptors than thick skin. </li></ul></ul><ul><li>Thick skin (0.6 to 4.5 mm) </li></ul><ul><ul><li>covers the palms, palmar surfaces of the digits, and soles </li></ul></ul><ul><ul><li>features a stratum lucidum and thick epidermal ridges </li></ul></ul><ul><ul><li>lacks hair follicles, arrector pili muscles, and sebaceous glands, and has more sweat glands than thin skin. </li></ul></ul>
  22. 22. FUNCTIONS OF SKIN -- thermoregulation <ul><li>Perspiration & its evaporation </li></ul><ul><ul><li>lowers body temperature </li></ul></ul><ul><ul><li>flow of blood in the dermis is adjusted </li></ul></ul><ul><li>Exercise </li></ul><ul><ul><li>in moderate exercise, more blood brought to surface helps lower temperature </li></ul></ul><ul><ul><li>with extreme exercise, blood is shunted to muscles and body temperature rises </li></ul></ul><ul><li>Shivering and constriction of surface vessels </li></ul><ul><ul><li>raise internal body temperature as needed </li></ul></ul>
  23. 23. FUNCTIONS OF SKIN <ul><li>blood reservoir </li></ul><ul><ul><li>extensive network of blood vessels </li></ul></ul><ul><li>protection - physical, chemical and biological barriers </li></ul><ul><ul><li>tight cell junctions prevent bacterial invasion </li></ul></ul><ul><ul><li>lipids released retard evaporation </li></ul></ul><ul><ul><li>pigment protects somewhat against UV light </li></ul></ul><ul><ul><li>Langerhans cells alert immune system </li></ul></ul><ul><li>cutaneous sensations </li></ul><ul><ul><li>touch, pressure, vibration, tickle, heat, cold, and pain arise in the skin </li></ul></ul>
  24. 24. FUNCTIONS OF SKIN <ul><li>Synthesis of Vitamin D </li></ul><ul><ul><li>activation of a precursor molecule in the skin by UV light </li></ul></ul><ul><ul><li>enzymes in the liver and kidneys modify the activated molecule to produce calcitriol, the most active form of vitamin D. </li></ul></ul><ul><ul><li>necessary vitamin for absorption of calcium from food in the gastrointestinal tract </li></ul></ul><ul><li>excretion </li></ul><ul><ul><li>400 mL of water/day, small amounts salt, CO2, ammonia and urea </li></ul></ul>
  25. 25. Epidermal Wound Healing <ul><li>Abrasion or minor burn </li></ul><ul><li>Basal cells migrate across the wound </li></ul><ul><li>Contact inhibition with other cells stops migration </li></ul><ul><li>Epidermal growth factor stimulates basal cells to divide and replace the ones that have moved into the wound </li></ul><ul><li>Full thickness of epidermis results from further cell division </li></ul>
  26. 26. Deep Wound Healing <ul><li>When an injury extends to tissues deep to the epidermis, the repair process is more complex than epidermal healing, and scar formation results. </li></ul><ul><li>Healing occurs in 4 phases </li></ul><ul><ul><li>inflammatory phase has clot unite wound edges and WBCs arrive from dilated and more permeable blood vessels </li></ul></ul><ul><ul><li>migratory phase begins the regrowth of epithelial cells and the formation of scar tissue by the fibroblasts </li></ul></ul><ul><ul><li>proliferative phase is a completion of tissue formation </li></ul></ul><ul><ul><li>maturation phase sees the scab fall off </li></ul></ul><ul><li>Scar formation </li></ul><ul><ul><li>hypertrophic scar remains within the boundaries of the original wound </li></ul></ul><ul><ul><li>keloid scar extends into previously normal tissue </li></ul></ul><ul><ul><ul><li>collagen fibers are very dense and fewer blood vessels are present so the tissue is lighter in color </li></ul></ul></ul>
  27. 27. Deep Wound Healing <ul><li>Phases of Deep Wound Healing </li></ul><ul><ul><li>During the inflammatory phase , a blood clot unites the wound edges, epithelial cells migrate across the wound, vasodilatation and increased permeability of blood vessels deliver phagocytes, and fibroblasts form </li></ul></ul><ul><ul><li>During the migratory phase , epithelial cells beneath the scab bridge the wound, fibroblasts begin scar tissue, and damaged blood vessels begin to grow. During this phase, tissue filling the wound is called granulation tissue . </li></ul></ul>
  28. 28. Phases of Deep Wound Healing
  29. 29. Deep Wound Healing <ul><li>Phases of Deep Wound Healing </li></ul><ul><ul><li>During the proliferative phase , the events of the migratory phase intensify. </li></ul></ul><ul><ul><li>During the maturation phase , the scab sloughs off, the epidermis is restored to normal thickness, collagen fibers become more organized, fibroblasts begin to disappear, and blood vessels are restored to normal </li></ul></ul><ul><ul><li>Scar tissue formation (fibrosis) can occur in deep wound healing. </li></ul></ul>
  30. 30. Age Related Structural Changes <ul><li>Collagen fibers decrease in number & stiffen </li></ul><ul><li>Elastic fibers become less elastic </li></ul><ul><li>Fibroblasts decrease in number </li></ul><ul><li>decrease in number of melanocytes (gray hair, blotching) </li></ul><ul><li>decrease in Langerhans cells (decreased immune responsiveness) </li></ul><ul><li>reduced number and less-efficient phagocytes </li></ul><ul><li>Most of the changes occur in the dermis </li></ul><ul><ul><li>wrinkling, slower growth of hair and nails </li></ul></ul><ul><ul><li>dryness and cracking due to sebaceous gland atrophy </li></ul></ul><ul><ul><li>Walls of blood vessels in dermis thicken so decreased nutrient availability leads to thinner skin as subcutaneous fat is lost. </li></ul></ul>