Human Integumentary System PDF

HUMAN INTEGUMENTARY SYSTEM  OUTLINE III. HUMAN INTEGUMENTARY SYSTEM 1. Structure of the Skin 2. Accessory Structures of the Skin 3. Types of Skin 4. Functions of the Skin 5. Maintaining Homeostasis: Wound Healing  HUMAN INTEGUMENTARY SYSTEM ❑ Integu...

HUMAN INTEGUMENTARY SYSTEM  OUTLINE III. HUMAN INTEGUMENTARY SYSTEM 1. Structure of the Skin 2. Accessory Structures of the Skin 3. Types of Skin 4. Functions of the Skin 5. Maintaining Homeostasis: Wound Healing  HUMAN INTEGUMENTARY SYSTEM ❑ Integumentary system ✓ Components: a. Skin b. Hair c. Oil and sweat glands d. Nails e. Sensory receptors  HUMAN INTEGUMENTARY SYSTEM ❑ Integumentary System ✓ General Functions: a. Helps maintain a constant body temperature b. Protects the body c. Provides sensory information about the surrounding environment  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin ▪ Skin (Cutaneous membrane) covers the external surface of the body and is the largest organ in weight. ✓Parts of the Skin: 1. Epidermis ✓ Superficial, thinner portion, composed of epithelial tissue. 2. Dermis ✓ Deeper, thicker connective tissue. ▪ Subcutaneous layer (hypodermis) ✓ consists of areolar, adipose tissue, large blood vessels, and nerve ending (lamellated corpuscles).  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin 1. Epidermis ✓ thin, simple, keratinized stratified squamous epithelium and it gives rise to most derivatives of the integument ✓ Principal Types of Cells: 1. Keratinocytes 2. Melanocytes 3. Intraepidermal macrophages 4. Tactile epithelial  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin ✓ Principal Types of Cells 1. Keratinocytes (90%) a. Keratin is a tough and fibrous protein accumulates in the interior of the cell’s cytoplasm. b. Lamellar granules releases a water repellent sealant. 2. Melanocytes (8%) ✓ Their long, slender projections extend between the keratinocytes and transfer melanin granules. a. Melanin is a yellow-red or brown-black pigment absorbing damaging UV radiation.  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin ✓ Principal Types of Cells 3. Intraepidermal macrophages (Langerhans cells) ✓ Immune response against microbes. 4. Tactile epithelial cells (Merkel cells) ✓ In contact to sensory neuron (tactile disc) to detect touch sensations.  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin ✓ Types Skin: 1. Thin skin ✓ Four layers: Stratum, basale, spinosum, granulosom, and corneum. 2. Thick skin ✓ Exposure to skin is the greatest such as the fingertips, palms, and soles. ✓ Five layers: Stratum, basale, spinosum, granulosom, lucidum and corneum.  HUMAN INTEGUMENTARY SYSTEM ❑ Keratinization and Growth of the Epidermis  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin 2. DERMIS ✓The second, deepest part of the skin which is composed of dense irregular connective tissue containing collagen and elastic fibers. ✓Fibroblasts, macrophages, adipocytes, blood vessels, nerves, glands, hair follicles are embedded in the epidermal layer.  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin 2. DERMIS ▪ Regions of the Dermis 1. Papillary Region a. Dermal papillae are small, nipple-shaped structures that project into the undersurface of the epidermis. b. Capillary loops; blood vessels c. Corpuscles of touch or Meissner corpuscles, nerve endings that are sensitive to touch. d. Free nerve endings that initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching.  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin 2. DERMIS ▪ Regions of the Dermis 2. Reticular Region ✓ Attached to the subcutaneous layer ✓ Large collagen fibers helps the skin resist stretching. ✓ Blood vessels, nerves, hair follicles, sebaceous (oil) glands, and sudoriferous (sweat) glands occupy the spaces between fibers.  HUMAN INTEGUMENTARY SYSTEM ❑ Structures of the Skin ▪ Epidermal ridges appear as straight lines or as a pattern of loops and whorls, as on the tips of the digits. ▪ Functions 1. create a strong bond between the epidermis and dermis in a region of high mechanical stress. 2. increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction 3. increase surface area, which increases the number of corpuscles of touch and thus increases tactile sensitivity.  HUMAN INTEGUMENTARY SYSTEM ❑ Structural Basis of Skin Color ▪ Three pigments: 1. Melanin 2. Hemoglobin 3. Carotene  HUMAN INTEGUMENTARY SYSTEM ❑ Structural Basis of Skin Color ▪ Three pigments: 1. Melanin. ✓ Two Forms: 1. Pheomelanin – yellow to red 2. Eumelanin – brown to black ✓ Melanocytes synthesizes melanin from the amino acid tyrosine in the presence of an enzyme tyrosinase in an organelle called melanosome. ✓ Freckles, age spot, and nevus or mole. ✓ Melanin serves a protective function  HUMAN INTEGUMENTARY SYSTEM ❑ Structural Basis of Skin Color 2. Hemoglobin ✓ Skin color ranges from pink to red depending on the oxygen content of blood moving through capillaries in the dermis. ✓ Blood vessels dilate from heat, skin reddens ✓ Blood flow decreases, skin pales  HUMAN INTEGUMENTARY SYSTEM ❑ Structural Basis of Skin Color 3. Carotene ✓ A yellow-orange pigment that gives egg yolks and carrots their color. ✓ The precursor of vit. A in the synthesis of pigments needed for vision is stored in stratum corneum, fatty areas of the dermis and subcutaneous layer.  HUMAN INTEGUMENTARY SYSTEM ❑ Accessory Structures 1. Hair (pili) 2. Skin glands 3. Nails  HUMAN INTEGUMENTARY SYSTEM ❑ Accessory Structures 1. Hair (pili) ✓Are present on most skin surfaces except the palms, palmar surfaces of the fingers, soles, and plantar surfaces of the feet. ✓Functions: a. Hair on the head guards the scalp from injury and the sun’s rays b. Decreases heat loss from the scalp c. Eyebrows and eyelashes protect the eyes from foreign particles d. Sensing light touch; Touch receptors (hair root plexus)  HUMAN INTEGUMENTARY SYSTEM ❑ Accessory Structures ▪ Anatomy of the Hair: 1.Shaft – the superficial portion of the hair. 2.Root – the portion of the hair deep to the shaft that penetrates into the dermis. 3. Hair follicle – surrounds the root of the hair by epithelial root sheath. 4. Dermal root sheath – the dense dermis surrounding the hair follicle. 5. Bulb – an onion-shaped structure at the base of each hair follicle surrounding the dermal root sheath.  HUMAN INTEGUMENTARY SYSTEM ❑ Accessory Structures ▪ Three concentric layers of cells of the shaft and the root: a. Medulla –contain large amounts of pigment granules. b. Cortex – forms the major part of the shaft and consists of elongated cells. c. Cuticle of the hair –consists of single layer of thin, flat cells that are heavily keratinized.  HUMAN INTEGUMENTARY SYSTEM ❑ Accessory Structures 6. Papilla of the hair – housed by the bulb containing areolar connective tissue and blood vessels nourishing the growing hair follicle and hair matrix. 7. Hair matrix – contains a germinal layer of cells arise from stratum basale, the site of cell division. 8. Arrector pili – smooth muscle, autonomic nerve endings stimulate this to contract during cold or fright. 9. Hair root plexus – dendrites of neurons, sensitive to touch.  HUMAN INTEGUMENTARY SYSTEM ❑ Hair Growth 1. Growth Stage ✓ Cells of the matrix divide and are added to the base of the hair root, existing cells are pushed upward and hair grows longer. 2. Regression Stage ✓ Cells of the hair matrix stops dividing. The hair follicle shrinks, and the hair stops growing. 3. Resting Stage ✓ A new growth cycle begins, the old hair root falls out or is pushed out of the hair follicle, and a new hair begins to grow.  HUMAN INTEGUMENTARY SYSTEM ❑ Types of Hair 1. Lanugo ✓ Very fine, nonpigmented, downy hairs that cover the body of the fetus. 2. Terminal hairs ✓ Long, coarse, heavily pigmented hairs of the eyebrows, eyelashes, and scalp. 3. Vellus hairs ✓ Short, fine, pale hairs of the rest of the body that are barely visible to the naked eye.  HUMAN INTEGUMENTARY SYSTEM ❑ Hair Color: 1. Dark-colored hair ✓ Eumelanin (brown to black) 2. Blond and red hair ✓ Pheomelanin (yellow to red) 3. Gray hair ✓ Few melanin granules 4. White hair ✓ Lack of melanin and the accumulation of air bubbles in the shaft.  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Glands  HUMAN INTEGUMENTARY SYSTEM ❑ ACCESSORY STRUCTURE: Nail ✓ Nails are plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid covering over the dorsal surfaces.  HUMAN INTEGUMENTARY SYSTEM ❑ Nail ▪ Functions: 1. They protect the distal end of the digits. 2. They provide support and counter pressure to the palmar surface of the fingers to enhance touch perception and manipulation. 3. They allow us to grasp and manipulate small objects, and they can be used to scratch and groom the body in various ways.  HUMAN INTEGUMENTARY SYSTEM ❑ Functions of the Skin 1. Thermoregulation 2. Storage of blood 3. Protection 4. Cutaneous sensations 5. Excretion and absorption 6. Synthesis of vitamin D  HUMAN INTEGUMENTARY SYSTEM ❑ Functions of the Skin 1. Thermoregulation ✓ The homeostatic regulation of body temperature. ✓ Two ways: 1. Liberating sweat at its surface 2. Adjusting the flow of blood in the dermis through dilation 2. Blood reservoir ✓ Dermis houses an extensive network of blood vessels that carry 8-10% of the total blood flow.  HUMAN INTEGUMENTARY SYSTEM 3. Protection a. Keratin protects tissues from microbes, abrasion heat, and chemicals and resist invasion by microbes. b. Lipids released by lamellar granules inhibit evaporation of water from the skin surface and retard entry of water. c. Oily sebum from sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals. d. Acidic pH of perspiration retards the growth of some microbes. e. Pigmented melanin helps shield against damaging effects of UV light. f. Intraepidermal macrophage alert the immune system and macrophages in the dermis phagocytize bacteria and viruses.  HUMAN INTEGUMENTARY SYSTEM ❑ FUNCTIONS OF THE SKIN 4. Cutaneous sensations ✓ Tactile sensations – touch, pressure, vibration, and tickling. ✓ Thermal sensations – warmth and coolness ✓ Cutaneous sensations – pain as an indication of impending or actual tissue damage 5. Excretion and absorption ✓ Excretion is the elimination of substances from the body. ✓ Absorption is the passage of materials from the external environment into body cells. ✓ Lipid-soluble substances: vit A, D,E, and K, O2 and CO2  HUMAN INTEGUMENTARY SYSTEM ❑ FUNCTIONS OF THE SKIN 6. Synthesis of vitamin D ✓ It requires the activation of a precursor molecule on the skin by UV rays in sunlight. ✓ Calcitol is a hormone that aids in the absorption of calcium from foods in the GI tract into blood. ✓ Vit. D enhance phagocytc activity, increase the production of antimicrobial substances in phagocytes, regulate immune functions, and help reduce inflammation.  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Wound Healing – Skin damage sets in motion a sequence of events that repairs the skin to its normal (or near-normal) structure and function Types: 1. Epidermal wound healing occurs following wounds that affect only the epidermis. 2. Deep wound healing occurs following wounds that penetrate the dermis.  HUMAN INTEGUMENTARY SYSTEM ❑ Wound Healing Processes  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Wound Healing – Four Phases of Deep wound healing 1. Inflammatory phase 2. Migratory phase 3. Proliferative phase 4. Maturation phase  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Wound Healing – Four Phases of Deep wound healing 1. Inflammatory phase - a blood clot forms in the wound and loosely unites the wound edges. ✓ Inflammation, a vascular and cellular response that helps eliminate microbes, foreign material, and dying tissue in preparation for repair. ✓ Vasodilation and increased permeability of blood vessels associated with inflammation enhance delivery of helpful cells. ✓ Phagocytic white blood cells (neutrophils, monocytes, and mesenchymal cells)  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Wound Healing – Four Phases of Deep wound healing 2. Migratory phase - the clot becomes a scab, and epithelial cells migrate beneath the scab to bridge the wound. ✓ Fibroblasts synthesizes scar tissue (collagen fibers and glycoproteins) called granulation tissue. 3. Proliferative phase - extensive growth of epithelial cells beneath the scab, deposition by fibroblasts of collagen fibers in random patterns, and continued growth of blood vessels.  HUMAN INTEGUMENTARY SYSTEM ❑ Skin Wound Healing – Four Phases of Deep wound healing 4. Maturation phase - the scab sloughs off once the epidermis has been restored to normal thickness. ✓ Fibrosis is the process of scar tissue formation. ✓ Types of Scar: 1. Hypertrophic scar is a scar that remains within the boundaries of the original wound. 2. Keloid or cheloid scar if it extends beyond the boundaries into normal surrounding tissues. ✓ Scar tissue differs from normal skin in that its collagen fibers are more densely arranged, it has decreased elasticity, it has fewer blood vessels, and it may or may not contain the same number of hairs, skin glands, or sensory structures as undamaged skin.  HUMAN INTEGUMENTARY SYSTEM ❑ Wound Healing Processes