Transcript Skin Cancer
Chapter 5 c Functions, Homeostatic Imbalances, Burns, Cancer, Development Functions of the Integumentary System • Protection • Body Temperature Regulation • Cutaneous Sensation • Metabolic Functions • Blood Reservoir • Excretion Protection • The skin has three types of barriers: – Chemical – Physical/Mechanical – Biological Protection • Chemical Barriers • Melanin - pigment that forms a shield to prevent UV damage • Skin secretions – low (acidic) pH secretions in sweat called Acid Mantle inhibits bacterial growth • Skin secretions – sebaceous glands secrete sebum with substances that kill bacteria Protection • Mechanical Barriers – Keratinized cells – • hardness – Continuity of skin • Glycolipids waterproof – block diffusion of water and water soluble substances – Preventing their loss from and entry into the body Substances that do penetrate: • Lipid soluble substances like oxygen, carbon dioxide, vitamins A, D, E, & K, and steroids • Oleoresins of certain plants like poison ivy and poison oak Substances that do penetrate: • Organic solvents such as acetone, drycleaning fluid, and paint thinner (which dissolves the cell lipids) • Salts of heavy metals such as lead, mercury, and nickel Homeostatic imbalance • Organic solvents and heavy metals can be lethal • Passage of organic solvents through the skin into blood can cause the kidneys to shut down or cause brain damage • Absorption of lead results in anemia and neurological defects Never Handle Organic solvents or heavy metals with your bare hands Protection • Biological Barriers • Langerhans’ cells of the epidermis – Active elements of the immune system. They present antigens (foreign substances) to specialized white blood cells Protection • Biological Barriers • Macrophages in the dermis – If bacteria or viruses get past the Langerhan’s cells in the epidermis, the dermal macrophages will get rid of them Protection • Biological Barriers • DNA – Usually shielded by melanin but electrons in DNA can absorb UV rays and transfer as heat to water molecules Body Temperature Regulation • Our bodies must maintain its temperature within homeostatic limits. • As long as the external air temperature is lower than our body temperature, the skin surface will lose heat to the air Body Temperature Regulation • Body temperature regulation is accomplished by the – Dilation of dermal vessels (to cool) – Constriction of dermal vessels (to warm) – Increasing sweat gland secretions (to cool) Body Temperature Regulation • When at rest in an environment below 31oC (88oF) sweat glands secretions unnoticeable • – ½ Liter per day Body Temperature Regulation • When body temperature rises, sweating becomes noticeable – loss of fluid up to 12 liters in one day! Cutaneous Sensation • Cutaneous sensory receptors – Part of nervous system – Classified as exteroceptors (because the respond to stimuli outside the body) – Sense touch and pain – Meissner’s corpuscles (in dermal papillae) – Merkel discs Metabolic Functions • Synthesis of vitamin D – When sunlight hits the skin, modified cholesterol molecules in dermal blood vessels are converted to vitamin D – Need vitamin D for Calcium metabolism (calcium cannot be absorbed from digestive tract without vitamin D) Metabolic Functions • Also several other Chemical conversions such as – the disarming of many cancercausing chemicals that penetrate the epidermis – Conversion of some harmless chemicals into carcinogens Metabolic Functions • Also several other Chemical conversions such as – Activation of some steroid hormones – cortisone cream into hydrocortisone (an antiinflammatory steroid) – Production of proteins such as collagenase, an enzyme that aids in detering wrinkles Blood Reservoir • Can hold 5% of the body’s entire blood volume • When other body organs need a greater blood supply, nervous system constricts dermal blood vessels, pushing more blood into circulation, making more available to those organs Excretion of Wastes • Limited amounts of ammonia, urea, and uric acid is eliminated from the body in sweat • Most of these wastes are eliminated in urine Chapter 5 c Part 2 Functions, Homeostatic Imbalances, Burns, Cancer, Development Homeostatic Imbalances of Skin • Skin can develop more than 1000 different conditions and ailments • Most common skin disorders are bacterial, viral or fungal infections • Less common, but more damaging are skin cancer and burns Skin Homeostatic Imbalances Infections • Athletes foot • Caused by fungal infection Skin Homeostatic Imbalances Infections • Boils and Carbuncles • Caused by bacterial infection Skin Homeostatic Imbalances Infections • Cold sores • Caused by virus Skin Homeostatic Imbalances Allergies • Contact dermatitis • Exposure causes allergic reactions Poison Ivy Skin Homeostatic Imbalances Infections • Impetigo • Caused by bacterial infection Skin Homeostatic Imbalances • Psoriasis • Caused is unknown • Triggered by trauma, infection, stress Skin Homeostatic Imbalances Skin Cancer Cancer – abnormal cell mass Skin cancer is the most common type of cancer Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 4.29 Cancer • Two types – Benign •Does not spread (encapsulated) – Malignant •Metastasized (moves) to other parts of the body Skin Cancer • The three major types of skin cancer are: Basal cell carcinoma Squamous cell carcinoma Melanoma Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 4.30 Basal Cell Carcinoma • Least malignant • Most common type (90% of all skin cancer) • Arises from the Basal layer • Stratum basale cells proliferate and invade the dermis and hypodermis Basal Cell Carcinoma • Slow growing and often does not metastasize • Can be cured by surgical excision in 99% of the cases Squamous Cell Carcinoma • Arises from keratinocytes of the stratum spinosum • Arise most often on scalp, ears, and lower • Grows rapidly & lip metastasizes if not removed • Metastasizes to lymph nodes Squamous Cell Carcinoma • Early removal allows a good chance of cure • Prognosis is good if treated by radiation therapy or removed surgically Malignant melanoma • Most deadly of skin cancers – because it is highly metastatic and resistant to chemotherapy Malignant melanoma • Cancer of melanocytes • Metastasizes rapidly to lymph and blood vessels • Detection uses ABCD rule ABCD(E) Rule A = Asymmetry Two sides of pigmented mole do not match B = Border irregularity Borders of mole are not smooth, it is irregular and exhibits indentations C = Color Different colors in pigmented area, black, brown, tan, and sometimes red or blue Slide 4.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings ABCD(E) Rule • D = Diameter – Spot is larger than 6 mm in diameter (size of a pencil eraser) • E = Elevation – Spot is elevated above the skin surface. Melanoma • Treated by wide surgical excision accompanied by immunotherapy • Chance of survival is poor if the lesion is over 4 mm thick Skin Cancer • Most skin tumors are benign and do not metastasize • A crucial risk factor for nonmelanoma skin cancers is the disabling of the p53 gene (tumor suppressor gene) by overexposure to UV radiation in sunlight Skin Homeostatic Imbalances Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Dehydration Electrolyte imbalance Circulatory shock Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 4.25 Rule of Nines • Way to determine the extent of burns • Body is divided into 11 areas for quick estimation • Each area represents about 9% Figure 5.8a Severity of Burns • First-degree burns • Only epidermis is damaged • Skin is red and swollen • Pain Severity of Burns • Second-degree burns • Epidermis and upper dermis are damaged • Skin is red and swollen with blisters • Pain Severity of Burns • Third-degree burns • Entire thickness of the skin is damaged • Burn area appears gray-white, cherry red, or black • No initial edema or pain since nerve endings are destroyed Severity of Burns • Fourthdegree burns • Burns extend through the skin to injure muscle, ligaments , tendons , nerves, blood vessels, and bones. Critical Burns Burns are considered critical if: Over 25% of body has second degree burns Over 10% of the body has third degree burns There are third degree burns of the face, hands, or feet Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 4.28 Developmental Aspects of the Integument: Fetal • Epidermis develops from ectoderm • Dermis and hypodermis develop from mesoderm Developmental Aspects of the Integument: Fetal • Lanugo – downy coat of delicate hairs covering the fetus during 5th and 6th months Shed by 7th month when vellus hairs start to appear Developmental Aspects of the Integument: Fetal • Vernix caseosa – a white, cheesy looking substance produced by sebaceous glands that protects the skin of the fetus in the amnion (babies are born with it) Developmental Aspects of the Integument: Fetal • Milia – small white spots on forehead and nose caused by accumulations in sebaceous glands Disappears by third week after birth Developmental Aspects of the Integument: Adolescent to Adult • Skin and hair become oilier and acne may appear in adolescence • Skin shows the effects of cumulative environmental assaults around age 30 • Scaling and dermatitis become more common as we age Developmental Aspects of the Integument: Old Age • Epidermal replacement of cells slows and skin becomes thinner • Skin becomes dry and itchy • Subcutaneous fat layer diminishes, leading to intolerance of cold Developmental Aspects of the Integument: Old Age • Decreased elasticity and loss of subcutaneous tissue leads to wrinkles • Decreased numbers of melanocytes and Langerhans’ cells increase the risk of skin cancer Developmental Aspects of the Integument: Old Age • By 50 the number of active hair follicles is less, and hair thins. • Hair loses its luster • Delayed-action genes responsible for graying and male pattern baldness become active Quiz Next time! 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