Functions of the Integumentary System Protection Body temperature

Protection • Three types of barriers – Chemical barriers – Physical barriers – Biological

Chemical Barriers • Skin secretions – Low p. H retards bacterial multiplication – Sebum

Physical Barriers • Flat, dead cells of stratum corneum surrounded by lipids • Keratin and glycolipids block most water and water- soluble substances • Limited penetration of skin – – – Lipid-soluble substances Plant oleoresins (e. g. , Poison ivy) Organic solvents Salts of heavy metals Some drugs Drug agents © 2013 Pearson Education, Inc.

Biological Barriers • Biological barriers – Dendritic cells of epidermis • Present foreign antigens to white blood cells – Macrophages of dermis • Present foreign antigens to white blood cells – DNA • Its electrons absorb UV radiation • Radiation converted to heat © 2013 Pearson Education, Inc.

Functions of the Integumentary System • Body temperature regulation – If body temperature normal ~500 ml/day of routine insensible perspiration (if environmental temperature below 31 -32° C) – If body temperature rises, dilation of dermal vessels and increased sweat gland activity (sensible perspiration) cool the body – Cold external environment • Dermal blood vessels constrict • Skin temperature drops to slow passive heat loss © 2013 Pearson Education, Inc.

Functions of the Integumentary System • Cutaneous sensations – Cutaneous sensory receptors – part of nervous system – detect temperature, touch, and pain – See figure 5. 1 • Metabolic functions – Synthesis of vitamin D precursor and collagenase – Chemical conversion of carcinogens and activate some hormones • Blood reservoir—up to 5% of body's blood volume • Excretion—nitrogenous wastes and salt in sweat © 2013 Pearson Education, Inc.

Skin (Integument) • Consists of two distinct regions – Epidermis—superficial region • Epithelial tissue – Dermis—underlies epidermis • Mostly fibrous connective tissue • Hypodermis (superficial fascia) – – Subcutaneous layer deep to skin Not part of skin but shares some functions Mostly adipose tissue that absorbs shock & insulates Anchors skin to underlying structures – mostly muscles © 2013 Pearson Education, Inc.

Figure 5. 1 Skin structure. Hair shaft Dermal papillae Epidermis Subpapillary plexus Papillary layer Sweat pore Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Dermis Reticular layer Hypodermis (subcutaneous tissue; not part of skin) Nervous structures Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) © 2013 Pearson Education, Inc. Cutaneous plexus Adipose tissue

Introduction • Integumentary system – Consists of the skin and accessory organs; hair, nails, and cutaneous glands • Inspection of the skin, hair, and nails is significant part of a physical exam • Skin is the most vulnerable organ – Exposed to radiation, trauma, infection, and injurious chemicals • Receives more medical treatment than any other organ system • Dermatology—scientific study and medical treatment of the integumentary system 6 -10

Functions of the Skin • Resistance to trauma and infection – Keratin – Dermacidin and defensins – Acid mantle • Other barrier functions – Water – UV radiation – Harmful chemicals • Vitamin D synthesis – Skin carries out first step – Liver and kidneys complete process Figure 6. 2 a 6 -11

Functions of the Skin • Sensation – Skin is an extensive sense organ – Receptors for temperature, touch, pain, and more • Thermoregulation – Thermoreceptors – Vasoconstriction/vasodilation – Perspiration • Nonverbal communication – Facial expression – Importance in social acceptance and self image Figure 6. 2 b 6 -12

The Epidermis Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Sweat pore Stratum corneum Stratum lucidum Exfoliating keratinocytes Stratum granulosum Dead keratinocytes Sweat duct Living keratinocytes Dendritic cell Stratum spinosum Tactile cell Melanocyte Stem cell Stratum basale Dermal papilla Tactile nerve fiber Dermis Dermal blood vessels Figure 6. 3 6 -13

Cells of the Epidermis • Keratinocytes – Produce fibrous protein keratin – Most cells of epidermis – Tightly connected by desmosomes • Melanocytes – 10– 25% of cells in deepest epidermis – Produce pigment melanin – packaged into melanosomes • Protect apical surface of keratinocyte nucleus from UV damage • Dendritic (Langerhans) cells – Macrophages – key activators of immune system • Tactile (Merkel) cells – Sensory touch receptors © 2013 Pearson Education, Inc.

The Epidermis • Epidermis—keratinized stratified squamous epithelium – Includes dead cells at skin surface packed with tough keratin protein – Lacks blood vessels • Depends on the diffusion of nutrients from underlying connective tissue – Contains sparse nerve endings for touch and pain 6 -15

Figure 5. 2 b The main structural features of the skin epidermis. Keratinocytes Stratum corneum Most superficial layer; 20– 30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Typically five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum spinosum Dendritic Several layers of keratinocytes unified by desmosomes. cell Cells contain thick bundles of intermediate filaments made of pre-keratin. Sensory Stratum basale nerve Dermis Deepest epidermal layer; one row of actively ending mitotic stem cells; some newly formed cells Melanin Tactile become part of the more superficial layers. granule (Merkel) cell See occasional melanocytes and dendritic Melanocyte Desmosomes cells. © 2013 Pearson Education, Inc.

Come, Let’s Get Sun Burned © 2013 Pearson Education, Inc.

Layers of the Epidermis: Stratum Corneum (Horny Layer) • 20– 30 rows of dead, flat, anucleate keratinized membranous sacs • Three-quarters of epidermal thickness • Though dead, its cells have functions – Protect deeper cells from environment and water loss – Protect from abrasion and penetration – Barrier against biological, chemical, and physical assaults © 2013 Pearson Education, Inc.

Layers of the Epidermis: Stratum Lucidum (Clear Layer) • Only in thick skin • Thin, translucent band superficial to the stratum granulosum • A few rows of flat, dead keratinocytes © 2013 Pearson Education, Inc.

Layers of the Epidermis: Stratum Granulosum (Granular Layer) • Thin - four to six cell layers • Cell appearance changes – Cells flatten – Nuclei and organelles disintegrate – Keratinization begins • Cells accumulate keratohyaline granules – Help form keratin in upper layers – Cell accumulate lamellar granules • Their water-resistant glycolipid slows water loss • Cells above this layer die – Too far from dermal capillaries © 2013 Pearson Education, Inc.

Layers of the Epidermis: Stratum Spinosum (Prickly Layer) • Several layers thick • Cells contain web-like system of intermediate prekeratin filaments attached to desmosomes • Abundant melanosomes and dendritic cells © 2013 Pearson Education, Inc.

Layers of the Epidermis: Stratum Basale (Basal Layer) • • Deepest epidermal layer Also called stratum germinativum Firmly attached to dermis Single row of stem cells – Actively mitotic – Produces two daughter cells • One cell journeys from basal layer to surface – Takes 25– 45 days – Dies as moves toward surface • One cell remains in stratum basale as stem cell • Melanocytes compose 10 – 25% of this layer © 2013 Pearson Education, Inc.

Cell Differentiation in Epidermis • Cells change from stratum basale to stratum corneum • Accomplished by specialized form of apoptosis – Controlled cellular suicide – Nucleus and organelles break down – Plasma membrane thickens – Allows cells to slough off as dandruff and dander – Shed ~ 50, 000 cells every minute © 2013 Pearson Education, Inc.

Dermis • Strong, flexible connective tissue • Cells – Fibroblasts, macrophages, and occasionally mast cells and white blood cells • Fibers in matrix bind body together – "Hide" used to make leather • Contains nerve fibers; blood and lymphatic vessels • Contains epidermal hair follicles; oil and sweat glands • Two layers – Papillary – Reticular © 2013 Pearson Education, Inc.

Layers of the Dermis: Papillary Layer • Areolar connective tissue with collagen and elastic fibers and blood vessels • Loose tissue – Phagocytes can patrol for microorganisms • Dermal papillae – Superficial peglike projections © 2013 Pearson Education, Inc.

The Skin and Subcutaneous Tissue • Skin is body’s largest and heaviest organ – Covers 1. 5 to 2. 0 m 2 ; composes 15% of body weight • Layers – Epidermis: stratified squamous epithelium – Dermis: deeper connective tissue layer – Hypodermis—connective tissue layer below dermis (not part of skin, but associated with it) • Skin thickness ranges from 0. 5 to 6 mm – Thick skin covers front of hands, bottoms of feet • Has sweat glands, but no hair follicles or sebaceous (oil) glands • Epidermis 0. 5 mm thick – Thin skin covers rest of the body • Possesses hair follicles, sebaceous glands, and sweat glands • Epidermis about 0. 1 mm thick 6 -26

The Hypodermis • Hypodermis Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display – Subcutaneous tissue – Has more areolar and adipose than dermis has – Pads body and binds skin to underlying tissues – Common site of drug injection since it has many blood vessels • Subcutaneous fat Figure 6. 1 – – Energy reservoir Thermal insulation Thicker in women Thinner in infants, elderly 6 -27

The Dermis Figure 6. 5 6 -28

The Dermis • Dermis—connective tissue layer beneath epidermis – Ranges from 0. 2 mm (eyelids) to 4 mm (palms, soles) – Composed mainly of collagen – Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings – Houses hair follicles and nail roots – Is the tissue of the facial skin to which skeletal muscles attach and cause facial expressions of emotion – Has a wavy, conspicuous boundary with the superficial epidermis • Dermal papillae are upward, finger-like extensions of dermis • Epidermal ridges are downward waves of epidermis • Prominent waves on fingers produce friction ridges of fingerprints 6 -29

The Dermis • Papillary layer—superficial zone of dermis – Thin zone of areolar tissue in and near the dermal papilla – Allows for mobility of leukocytes and other defense cells – Rich in small blood vessels • Reticular layer—deeper and thicker layer of dermis – Consists of dense, irregular connective tissue – Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity 6 -30

Dermal Papillae • Most contain capillary loops • Some contain Meissner's corpuscles (touch receptors) • Some contain free nerve endings (pain receptors) • In thick skin lie atop dermal ridges that cause epidermal ridges – Collectively ridges called friction ridges • Enhance gripping ability • Contribute to sense of touch • Pattern is fingerprints © 2013 Pearson Education, Inc.

Figure 5. 4 a Dermal modifications result in characteristic skin markings. Openings of Friction

Layers of the Dermis: Reticular Layer • • ~80% of dermal thickness Dense fibrous connective tissue Elastic fibers provide stretch-recoil properties Collagen fibers – Provide strength and resiliency – Bind water – Cleavage lines because most collagen fibers parallel to skin surface • Externally invisible • Important to surgeons • Incisions parallel to cleavage lines gap less and heal more readily © 2013 Pearson Education, Inc.

Figure 5. 4 b Dermal modifications result in characteristic skin markings. Cleavage lines in

Skin Markings • Flexure lines – Dermal folds at or near joints – Dermis tightly secured to deeper structures – Skin cannot slide easily for joint movement causing deep creases – Visible on hands, wrists, fingers, soles, toes © 2013 Pearson Education, Inc.

Skin Markings • Freckles and moles—tan to black aggregations of melanocytes – Freckles—flat, melanized patches – Moles (nevi)—elevated, melanized patches often with hair • Moles should be watched for changes in color, diameter, or contour that may suggest cancer • Hemangiomas (birthmarks)—patches of discolored skin caused by benign tumors of dermal capillaries – Some disappear in childhood, others last for life – Capillary hemangiomas, cavernous hemangiomas, portwine stain 6 -36

Figure 5. 4 c Dermal modifications result in characteristic skin markings. Flexure lines on

Skin Markings • Friction ridges—markings on the fingertips that leave oily fingerprints on surfaces we touch – Everyone has a unique pattern formed during fetal development that remains unchanged throughout life – Not even identical twins have identical fingerprints – Allow manipulation of small objects • Flexion lines (flexion creases)—lines on the flexor surfaces of the digits, palms, wrists, elbows – Mark sites where skin folds during flexion of joints – Skin bound to deeper tissues along these lines 6 -39

Other Skin Markings • Striae – Silvery-white scars – "Stretch marks" – Extreme stretching causes dermal tears • Blister – From acute, short-term trauma – Fluid-filled pocket that separates epidermal and dermal layers © 2013 Pearson Education, Inc.

The Evolution of Skin Color • Variations in skin color result from multiple evolutionary selection pressures, especially differences in exposure to UV light (UV accounts for up to 77% of skin tone variation) • UV light has both harmful and beneficial effects – Adversely: it causes skin cancer, breaks down folic acid – Beneficially: it stimulates vitamin D synthesis • Populations that evolved in the tropics have wellmelanized skin to protect against excessive UV 6 -41

The Evolution of Skin Color • Populations that evolved in far northern and southern latitudes (weak sun) have light skin to allow adequate UV • Populations that evolved at high altitudes or dry climates (less UV filtering) also are darker skinned • Importance of vitamin D for calcium (crucial for pregnancy, lactation) might explain why women are lighter skinned than men 6 -42

The Evolution of Skin Color • Other factors complicate the association between UV exposure and skin tone – Migration, cultural differences in clothing, and shelter – Intermarriage of people of different geographic ancestries – Sexual selection: a preference in mate choice for partners of light or dark complexion 6 -43

Skin Color Figure 6. 6 a, b 6 -44

Skin Color • Exposure to UV light stimulates melanin secretion and darkens skin – This color fades as melanin is degraded and old cells are exfoliated • Other pigments can influence skin color – Hemoglobin—pigment in red blood cells • Adds reddish to pinkish hue to skin – Carotene—yellow pigment acquired from egg yolks and yellow/orange vegetables • Concentrates in stratum corneum and subcutaneous fat 6 -45

Skin Color • Melanin—most significant factor in skin color – Produced by melanocytes, accumulates in keratinocytes – Two forms of the pigment: • Eumelanin—brownish black • Pheomelanin—reddish yellow (sulfur-containing) • People of different skin colors have the same number of melanocytes – Darker skinned people • • Produce greater quantities of melanin Melanin breaks down more slowly Melanin granules more spread out in keratinocytes Melanized cells seen throughout the epidermis – Lighter skinned people • Melanin clumped near keratinocyte nucleus • Little melanin seen beyond stratum basale 6 -46

Skin Color • Three pigments contribute to skin color – Melanin • Only pigment

Melanin • Two forms – Reddish-yellow to brownish-black • Color differences due to amount and form • Produced in melanocytes – Same relative number in all people • Migrates to keratinocytes to form "pigment shields" for nuclei • Freckles and pigmented moles – Local accumulations of melanin • Sun exposure stimulates melanin production • Sunspots (tinea versicolor) are fungal infection; not related to melanin © 2013 Pearson Education, Inc.

Carotene and Hemoglobin • Carotene – Yellow to orange pigment • Most obvious in palms and soles – Accumulates in stratum corneum and hypodermis – Can be converted to vitamin A for vision and epidermal health • Yellowish-tinge of some asians – carotene and melanin variations • Hemoglobin – Pinkish hue of fair skin © 2013 Pearson Education, Inc.

Skin Color in Diagnosis • Cyanosis – Blue skin color - low oxygenation of hemoglobin • Erythema (redness) – Fever, hypertension, inflammation, allergy • Pallor (blanching) – Anemia, low blood pressure, fear, anger • Jaundice (yellow cast) – Liver disorder • Bronzing – Inadequate steroid hormones in Addison's disease • Bruises – Clotted blood beneath skin © 2013 Pearson Education, Inc.

Skin Color • Colors of diagnostic value – – Cyanosis—blueness due to oxygen deficiency Erythema—redness due to increased blood flow to skin Pallor—paleness due to decreased blood flow to skin Albinism—milky white skin and blue-gray eyes due to genetic lack of melanin synthesizing enzyme – Jaundice—yellowing due to bilirubin in blood (can be caused by compromised liver function) – Hematoma—bruising (clotted blood under skin) 6 -51

Structure of the Hair and Follicle • Follicle—diagonal tube that extends into dermis and possibly hypodermis – Epithelial root sheath • Extension of the epidermis lying adjacent to hair root • Widens at deep end into bulge—source of stem cells for follicle growth – Connective tissue root sheath • Derived from dermis but a bit denser • Surrounds epithelial root sheath • Hair receptors—sensory nerve fibers entwining follicles • Piloerector muscle (arrector pili)—smooth muscle attaching follicle to dermis – Contracts to make hair stand on end (goose bumps) 6 -52

Structure of the Hair and Follicle Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Hair shaft Sebaceous gland Piloerector muscle Hair receptor Bulge Hair root Hair matrix Hair bulb Apocrine sweat gland Dermal papilla Blood capillaries in dermal papilla (a) • Hair is divisible into three zones along its length – Bulb: a swelling at the base where hair originates in dermis or hypodermis • Only living hair cells are in or near bulb – Root: the remainder of the hair in the follicle – Shaft: the portion above the skin surface Figure 6. 7 a 6 -53

Sweat Glands • Two kinds of sweat (sudoriferous) glands: apocrine and merocrine – Apocrine sweat glands • Locations: groin, anal region, axilla, areola, beard area in men – Inactive until puberty • Ducts lead to nearby hair follicles • Produce sweat that is milky and contains fatty acids • Respond to stress and sexual stimulation – Believed to secrete pheromones—chemicals that can influence behavior of others • Bromhidrosis—disagreeable body odor produced by bacterial action on sweat from apocrine glands 6 -54

Sweat Glands • Also called sudoriferous glands • All skin surfaces except nipples and parts of external genitalia • ~3 million person • Two main types – Eccrine (merocrine) sweat glands – Apocrine sweat glands • Contain myoepithelial cells – Contract upon nervous system stimulation to force sweat into ducts © 2013 Pearson Education, Inc.

Apocrine Sweat Glands • Confined to axillary and anogenital areas • Sweat + fatty substances + proteins – Viscous; milky or yellowish – Odorless until bacterial interaction body odor • Larger than eccrine sweat glands • Ducts empty into hair follicles • Begin functioning at puberty – Function unknown but may act as sexual scent gland • Modified apocrine glands – Ceruminous glands—lining of external ear canal; secrete cerumen (earwax) – Mammary glands – secrete milk © 2013 Pearson Education, Inc.

Eccrine Sweat Glands • • Most numerous Abundant on palms, soles, and forehead Ducts connect to pores Function in thermoregulation – Regulated by sympathetic nervous system • Their secretion is sweat – 99% water, salts, vitamin c, antibodies, dermcidin (microbe-killing peptide), metabolic wastes © 2013 Pearson Education, Inc.

Figure 5. 7 b Photomicrograph of a sectioned eccrine gland (140 x). Sebaceous gland Sweat pore Eccrine gland Duct Dermal connective tissue Secretory cells Photomicrograph of a sectioned eccrine gland (140 x) © 2013 Pearson Education, Inc.

Cutaneous Glands 6 -59

Cutaneous Glands Figure 6. 11 a Figure 6. 11 b Figure 6. 11 c • The skin has five types of glands: merocrine sweat glands, apocrine sweat glands, sebaceous glands, ceruminous glands, and mammary glands 6 -60

Sweat Glands (Continued) – Merocrine (eccrine) sweat glands • Most numerous skin glands— 3 to 4 million in adult skin – Especially dense on palms, soles, and forehead • Simple tubular glands • Watery perspiration that helps cool the body – Myoepithelial cells—contract in response to stimulation by sympathetic nervous system and squeeze perspiration up the duct • Found in both apocrine and merocrine glands 6 -61

Sweat Glands • Sweat—begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland – Some sodium chloride and other small solutes remain in the sweat • Some sodium chloride reabsorbed by duct – Some drugs are excreted in sweat – On average, 99% water, with p. H range of 4 to 6 • Acid mantle—inhibits bacterial growth – Insensible perspiration— 500 m. L/day • Does not produce visible wetness of skin – Diaphoresis—sweating with wetness of the skin • Exercise—may lose 1 L sweat per hour 6 -62

Sebaceous (Oil) Glands • Widely distributed – Not in thick skin of palms and soles • Most develop from hair follicles and secrete into hair follicles • Relatively inactive until puberty – Stimulated by hormones, especially androgens • Secrete sebum – Oily holocrine secretion – Bactericidal – Softens hair and skin © 2013 Pearson Education, Inc.

Figure 5. 7 a Photomicrograph of a sectioned sebaceous gland (90 x). Sebaceous gland Dermal Hair in connective hair follicle tissue Sebaceous gland duct Sweat pore Eccrine gland Secretory cells Photomicrograph of a sectioned sebaceous gland (90 x) © 2013 Pearson Education, Inc.

Sebaceous Glands • Sebaceous glands are flask-shaped and have short ducts opening into hair follicles • Holocrine secretion style • Sebum—oily secretion of sebaceous glands – Keeps skin and hair from becoming dry, brittle, and cracked – Lanolin—sheep sebum 6 -65

Ceruminous Glands • Ceruminous glands are simple, coiled, tubular glands in external ear canal • Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen) – – Keeps eardrum pliable Waterproofs the canal Kills bacteria Makes guard hairs of ear sticky to help block foreign particles from entering auditory canal 6 -66

Mammary Glands • Mammary glands—milk-producing glands that develop only during pregnancy and lactation – Modified apocrine sweat glands – Rich secretion released through ducts opening at nipple • Mammary ridges or milk lines – Two rows of mammary glands in most mammals – Primates kept only two glands, but a few people have additional nipples along the milk line (polythelia) 6 -67

Skin Cancer • Skin cancer—most cases caused by UV rays of the sun damaging skin cell DNA – – Most often on the head, neck, and hands Most common in fair-skinned people and the elderly One of the most common, easily treated cancers Has one of the highest survival rates if detected and treated early • Three types of skin cancer named for the epidermal cells in which they originate – Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma 6 -68

Skin Cancer Figure 6. 12 c • Malignant melanoma - Skin cancer that arises from melanocytes - Less than 5% of skin cancers, but most deadly form - Can be successfully removed if caught early, but if it metastasizes it is usually fatal - Greatest risk factor: familial history of malignant melanoma - Highest incidence in men, redheads, and people who had severe sunburn as a child 6 -69

UV Rays and Sunscreen • UVA and UVB are improperly called “tanning rays” and “burning rays” – Both thought to initiate skin cancer – No such thing as a “healthy tan” • Sunscreens protect you from sunburn but unsure if they provide protection against cancer – High SPF numbers can give false sense of security – Chemical in sunscreen damage DNA and generate harmful free radicals 6 -70

Skin Grafts and Artificial Skin • Third-degree burns often require skin grafts • Graft options – Autograft: tissue taken from another location on the same person’s body • Split-skin graft—taking epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area – Isograft: skin from identical twin • Temporary grafts (immune system rejection) – – Homograft (allograft): from unrelated person Heterograft (xenograft): from another species Amnion from afterbirth Artificial skin from silicone and collagen 6 -71

Skin Cancer Figure 6. 12 b • Squamous cell carcinoma - Arises from keratinocytes of stratum spinosum - Lesions usually on scalp, ears, lower lip, or back of the hand - Have raised, reddened, scaly appearance later forming a concave ulcer - Chance of recovery good with early detection and surgical removal - Tends to metastasize to lymph nodes and may become lethal 6 -72

Skin Cancer • Basal cell carcinoma Figure 6. 12 a - Most common type - Least dangerous because it seldom metastasizes - Forms from cells in stratum basale - Lesion is small, shiny bump with central depression and beaded edges 6 -73

Skin Cancer • Most skin tumors are benign (not cancerous) and do not metastasize (spread) • Risk factors – Overexposure to UV radiation – Frequent irritation of skin • Some skin lotions contain enzymes that can repair damaged DNA • Three major types of skin cancer – Basal cell carcinoma – Squamous cell carcinoma – Melanoma © 2013 Pearson Education, Inc.

Basal Cell Carcinoma • Least malignant; most common • Stratum basale cells proliferate and slowly invade dermis and hypodermis • Cured by surgical excision in 99% of cases © 2013 Pearson Education, Inc.

Figure 5. 8 Photographs of skin cancers. Basal cell carcinoma © 2013 Pearson Education,

Squamous Cell Carcinoma • Second most common type • Involves keratinocytes of stratum spinosum • Usually scaly reddened papule on scalp, ears, lower lip, and hands • Does metastasize • Good prognosis if treated by radiation therapy or removed surgically © 2013 Pearson Education, Inc.

Melanoma • Cancer of melanocytes • Most dangerous – Highly metastatic and resistant to chemotherapy • Treated by wide surgical excision accompanied by immunotherapy • Key to survival is early detection – ABCD rule – A: asymmetry; the two sides of the pigmented area do not match – B: border irregularity; exhibits indentations – C: color; contains several (black, brown, tan, sometimes red or blue) – D: diameter; larger than 6 mm (size of pencil eraser) © 2013 Pearson Education, Inc.

Burns • Burns—leading cause of accidental death – Fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock – Deaths result primarily from fluid loss, infection, and toxic effects of eschar (burned, dead tissue) – Debridement: removal of eschar • Classified according to depth of tissue involvement – First-degree burn: involves only epidermis • Redness, slight edema, and pain • Heals in days – Second-degree burn: partial-thickness burn; involves part of dermis • May appear red, tan, or white; blistered and painful • Two weeks to several months to heal and may leave scars – Third-degree burn: full-thickness burn; involves epidermis, all of dermis, and often some deeper tissues • Often requires skin grafts • Needs fluid replacement, infection control, supplemental nutrition 6 -79

Degrees of Burn Injuries Figure 6. 13 6 -80

Burns • Tissue damage caused by heat, electricity, radiation, certain chemicals – Denatures proteins – Kills cells • Immediate threat: – Dehydration and electrolyte imbalance • Leads to renal shutdown and circulatory shock • To evaluate burns – Rule of nines – Used to estimate volume of fluid loss © 2013 Pearson Education, Inc.

Figure 5. 9 Estimating the extent and severity of burns using the rule of nines. Totals 41/2% Anterior and posterior head and neck, 9% Anterior and posterior upper limbs, 18% 41/2% Anterior 41/2% trunk, 18% 9% 9% Anterior and posterior trunk, 36% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% © 2013 Pearson Education, Inc.

Burns Classified by Severity • Partial-thickness burns – First degree • Epidermal damage only – Localized redness, edema (swelling), and pain – Second degree • Epidermal and upper dermal damage – Blisters appear • Full-thickness burns – Third degree • • Entire thickness of skin involved Skin gray-white, cherry red, or blackened Not painful (nerve endings destroyed) or swollen Skin grafting usually necessary © 2013 Pearson Education, Inc.

Severity and Treatment of Burns • Critical if – >25% of body has second-degree burns – >10% of body has third-degree burns – Face, hands, or feet bear third-degree burns • Treatment includes – Debridement (removal) of burned skin – Antibiotics – Temporary covering – Skin grafts © 2013 Pearson Education, Inc.

Figure 5. 10 Partial thickness and full thickness burns. 1 st-degree burn 3 rd-degree burn 2 nd-degree burn Skin bearing partial thickness burn (1 st- and 2 nd-degree burns) © 2013 Pearson Education, Inc. Skin bearing full thickness burn (3 rd-degree burn)

Developmental Aspects • Fetal – Ectoderm epidermis; Mesoderm dermis and hypodermis – Lanugo coat: delicate hairs in 5 th and 6 th month – Vernix caseosa: sebaceous gland secretion; protects skin of fetus • Infancy to adulthood – Skin thickens; accumulates more subcutaneous fat – Sweat and sebaceous gland activity increases – Effects of cumulative environmental assaults show after age 30 – Scaling and dermatitis become more common © 2013 Pearson Education, Inc.

Developmental Aspects • Aging skin – Epidermal replacement slows, skin becomes thin, dry and itchy (decreased sebaceous gland activity) – Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles – Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells – Hair thinning • To delay – UV protection, good nutrition, lots of fluids, good hygiene © 2013 Pearson Education, Inc.