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THE INTEGUMENTARY SYSTEM

Explore the complex integumentary system consisting of the skin, its derivatives, and layers like epidermis and dermis, explaining cell types, functions, and protective properties.

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THE INTEGUMENTARY SYSTEM

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  1. THE INTEGUMENTARY SYSTEM • Complex set of organs that includes the skin and its derivatives (sweat and oil glands, hairs, and nails) • Includes: • Nerves • Blood vessels • Muscles • Major function: protection

  2. THE SKIN • Also called the integument, which simply means: covering • Epidermis: • The epidermis is a keratinized stratified squamous epithelium (epi=upon) • Outer most protective shield of the body • Dermis: • Underlying epidermis • Makes up bulk of skin • Composed of: • Fibrous connective tissue • Blood vessels: • Nutrients reach the epidermis by diffusion

  3. SKIN

  4. THE SKIN • Hypodermis: also called superficial fascia • Subcutaneous tissue: • Deep to the skin • Not really part of the skin but it shares some of the skin’s protective functions • Superficial to the tough connective tissue wrapping (fascia) of the skeletal muscles • Consists mostly of adipose tissue: • Stores fat: • Shock absorber • insulation • Anchors the skin to the underlying structures (muscles) • Thickens as one gains weight: • Thighs • Breast • Beer belly

  5. SKIN

  6. Epidermis • A keratinized stratified squamous epithelium consisting of four distinct cell types and four or five distinct layers: • Stratum Corneum • Stratum Lucidum (thick skin) • Stratum Granulosum • Stratum Spinosum • Stratum Basale

  7. Cells of the Epidermis • Include: • Keratinocytes • Melanocytes • Merkel cells • Langerhan’s cells

  8. EPIDERMIS

  9. Cells of the EpidermisKeratinocytes • Produce keratin • Fibrous protein that helps give the epidermis its protective properties • Tightly connected to one another by desmosomes (cell junction composed of thickened plasma membranes joined by filaments) • Arise in the deepest part of the epidermis from a layer of cells (stratum basale) that undergo almost continuous mitosis • Cells pushed upward by the production of new cells beneath them • By the time they reach the free surface of the skin, they are dead, scalelike structures that are little more than keratin-filled plasma membranes • Millions rub off everyday giving us a totally new epidermis every 25 to 45 days • Friction rubs them off (hands, etc) • Persistent friction causes a thickening of the epidermis called a callus

  10. EPIDERMIS

  11. Cells of the EpidermisMelanocytes • Spider shaped cells • Found in the deepest layer of the epidermis • Synthesize the pigment melanin (melan=black) • Made and accumulated in membrane-bound granules (small. grainlike mass) called melanosomes • Moved along actin filaments by motor proteins to the ends of the melanocyte’s processes (spider arms) • From here they are taken up by the keratinocytes • Accumulate on the superficial (sunny side) of the keratinocyte nucleus, forming a pigment shield that protects the nucleus from the damaging effects of ultraviolet (UV) radiation in sunlight

  12. EPIDERMIS

  13. Cells of the EpidermisLangerhan’s Cells • Star-shaped • Arise from bone marrow and migrate to the epidermis • Also called epidermal dendritic cells • Are macrophages (WBC) that help activate our immune system • Their slender processes extend among the surrounding keratinocytes, forming a more or less continuous network

  14. EPIDERMIS

  15. Cells of the EpidermisMerkel Cells • Present at the epidermal-dermal junction • Saped like a spiky hemisphere • Intimately associated with a disclike sensory nerve ending: • This combination is called a Merkel disc • Functions as a sensory receptor for touch

  16. EPIDERMIS

  17. Layers of the Epidermis • Variation in epidermal thickness determines if skin is thick or thin • Thick skin covers: palms, fingertips, and soles of the feet • Five layers: strata (bed sheets) • Deep to superficial: • Stratum basale • Stratum spinosum • Stratum granulosum • Stratum lucidum • Stratum corneum • Thin skin covers the rest of the body • Stratum lucidum is absent and the other layers are thinner

  18. EPIDERMIS

  19. Layers of the EpidermisStratum Basale • Deepest epidermal layer • Attached to the underlying dermis along a wavy borderline • Consists (mostly) of a single row of cells representing the youngest keratinocytes • Many mitotic nuclei • Reflects rapid cell division • Alternate name: stratum germinativum

  20. EPIDERMIS

  21. Layers of the EpidermisStratum Spinosum • Spinosum (prickly) • Several cell layers thick • Cells contain a weblike system of intermediate filaments, which span their cytosol to attach to desmosomes • These intermediate filaments consist mainly of tension-resisting bundles of prekeratin filaments • Keratinocytes appear irregular (spiny) in shape, causing them to be called prickle cells • Spines do not exist in the living cells • They arise during tissue preparation when these cells shrink but their numerous desmosomes hold tight • Scattered among the keratinocytes are: • Melanin granules • Langerhan’s cells (highest concentration)

  22. EPIDERMIS

  23. Layers of the EpidermisStratum Granulosum • Consist of 3-5 layers in which keratinocyte appearance changes drastically • Cells flatten • Nuclei and organelles begin to disintegrate • They accumulate: • Keratohyaline granules: • Help to form keratin in the upper layers • Lamellated granules: • Contain a waterproofing glycolipid that is spewed into the extracellular space and is a major factor in slowing water loss across the epidermis • Cell membranes thicken • Lipids coat the external membrane • Above this layer the epidermal cells are too far from the dermal capillaries, so they die

  24. EPIDERMIS

  25. Layers of the EpidermisStratum Lucidum • Thin translucent band • Few rows of clear, flat, dead keratinocytes with indistinct boundaries • Gummy substance of the keratohyaline granules clings to the keratin filaments in the cells, causing them to aggregate in parallel arrays (regular arrangement) • Visible ONLY in THICK SKIN

  26. EPIDERMIS

  27. Layers of the EpidermisStratum Corneum • Horny (hard, callous) layer • 23-30 cell layers thick (3/4 of epidermis) • Keratin and the thickened plasma membranes of cells protect the skin against abrasion and penetration • Glycolipid between cells waterproofs this layer • The stratum corneum (horny layer) is the outermost protective layer of the epidermis composed of a thick layer of dead keratinocytes

  28. EPIDERMIS

  29. SKIN

  30. EPIDERMIS

  31. Dermis • Composed of strong, flexible connective tissue • Its cells are typical of those found in any connective tissue proper: • Fibroblasts: cells that form the fibers of connective tissue • Macrophages: protective cell capable of phagocytosis • Mast cells: immune cell that initiates inflammation • White blood cells: protection • Its semifluid matrix is heavily embedded with: • Collagen: strong, fibrous (threadlike) insoluble protein • Elastin: extracellular connective tissue protein • Reticular fibers: supporting framework tissue • The dermis binds the entire body together like a body stocking • It is your hide and corresponds exactly to animal hides used to make leather products • Richly supplied with nerve fibers, blood vessels, and lymphatic vessels • Major portions of hair follicles, as well as oil and sweat glands, are derived from epidermal tissue but reside in the dermis

  32. DermisTwo Layers • 1.The thin, superficial papillary layer is highly vascularized areolar connective tissue containing a woven mat of collagen and elastin fibers • Its superior surface is thrown into peglike projections called dermal papillae (papill=nipple) that indent the overlaying epidermis • Many contain: • Capillary loops • Meissner’s corpuscles: touch receptors • Pain receptors

  33. SKIN

  34. DermisTwo Layers • On the palms of the hands and soles of the feet, these papillae lie atop larger mounds called dermal ridges • Which in turn cause the overlying epidermis to form epidermal ridges that increase friction and enhance the gripping ability of the fingers and feet • Epidermal ridge patterns are genetically determined and unique to each of us • Because sweat pores open along their crest, our fingerprints leave identifying films of sweat called fingerprints on almost anything they touch

  35. SKIN

  36. DermisTwo Layers • Three types of skin markings: • Finger prints • Cleavage lines • Flexure lines

  37. DermisTwo Layers • 2.The reticular layer: • Deeper • Account for 80% of the thickness of the dermis • Extracellular matrix contains thick bundles of interlacing fibers that run in various planes • Most run parallel to the skin surface • Less dense regions, between these bundles form cleavage, or tension lines: • Important to a surgeon: • Incision made parallel to these lines, the skin gapes less and heals more readily than when the incision is made across cleavage lines • Collagen fibers give skin strength and resiliency • Binds water, helping keep the skin hydrated • Elastin fibers provide the stretch-recoil properties of skin

  38. SKIN

  39. DermisTwo Layers • Flexure lines: • Dermal folds that occur at or near joints, where the dermis is tightly secured to deeper structures (notice the deep creases on your palms) • Since the skin cannot slide easily to accommodate joint movement in such regions, the dermis folds and deep skin creases form • Visible on wrists, fingers, soles, and toes

  40. HOMEOSTATIC IMBALANCE • Dermal tearing: • Stretching of the skin during pregnancy • Stretch marks • Blister: • Separation of the epidermal and dermal layers by a fluid-filled pocket

  41. Skin Color • Determined by three pigments: • Melanin • Hemoglobin • Carotene

  42. Melanin • Only pigment made in the skin • Polymer of tyrosine amino acid • Ranges in color from yellow to reddish-brown to black • Synthesis depends on an enzyme in melaocytes called tyrosinase • Passes from melanocytes to the basal keratinocytes

  43. Melanin • All humans have the same relative number of melanocytes • Individual and racial differences in skin coloring reflect the relative kind and amount of melanin made and retained • Melanocytes of black and brown skinned people produce many and darker melanosomes than those of fair-skinned individuals, and their keratinocytes retain it longer • Freckles and pigmented moles are local accumulations of melanin

  44. Melanin • Melanocytes are stimulated by sunlight • Causes substantial melanin buildup, which helps protect the DNA of viable skin cells from UV radiation by absorbing the light and dissipating the energy as heat

  45. HOMEOSTATIC IMBALANCE • Excessive sunlight damages the skin: • Clumping of elastin fibers: results in leathery skin • Depresses the immune system • Alters DNA

  46. Carotene • Yellow to orange pigment found in certain plant products such as carrots • Tends to accumulate in the stratum corneum and in the tissue of the hypodermis • Color most obvious in the palms and soles, where the stratum corneum is thickest (example: the skin of the heel) • Most intense when large amounts of carotene-rich foods are eaten

  47. Hemoglobin • Pinkish hue of fair skin people

  48. Redness: erythema Embarrassment Fever Hypertension Inflammation Allergy Pallor: blanching Fear Anger Emotional stress Anemia Low blood pressure Jaundice: yellow cast Liver disorder (yellow bile pigment accumulates in the blood and deposited in body tissues) Bile normally secreted in the bile pigments (bilirubin) as part of bile Bronzing: Metallic appearance of skin Addison’s disease Hyperfunction of adrenal cortex Black and blue: bruises Blood escaping from the blood vessels and clotting under the skin Skin Color Variations

  49. APPENDAGES OF THE SKIN • Derivatives of the epidermis: • Sweat Glands • Sebaceous Glands • Nails • Hair • Hair Follicles

  50. Sweat (Sudoriferous) Glands • Distributed over the entire skin surface except the nipples and parts of the external genitalia • Two types of sweat glands: • Eccrine • Apocrine

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