Lecture 5 Integument System PDF

1 Integumentary System 2 Expected Learning Outcomes 3 Dermatology • Study and treatment of integumentary system: the skin (integument), hair, nails, and cutaneous glands • Skin is body’s largest organ • Two layers within skin plus a nearby layer –Epidermis: epithelium of skin –Dermis: connectiv...

1 Integumentary System 2 Expected Learning Outcomes 3 Dermatology • Study and treatment of integumentary system: the skin (integument), hair, nails, and cutaneous glands • Skin is body’s largest organ • Two layers within skin plus a nearby layer –Epidermis: epithelium of skin –Dermis: connective tissue of skin –Hypodermis: connective tissue just underneath skin Integumentary System: 4 1 Two Divisions • Skin: –Integument –Largest body organ –Two layers •Epidermis •Dermis 2 • Accessory Organs –Hair –Nails –Cutaneous glands 5 Thick versus Thin Skin 1 • Thick skin –Epidermis 400-600μm –Thick stratum corneum –Contains stratum lucidum –Lacks: •Hair •Sebaceous glands –Found: •Palms (palmar) •Soles (plantar) 2 1 •Palms (palmar) •Soles (plantar) •Digits (volar) 2 • Thin skin –Epidermis 75-150μm –Thin stratum corneum –No stratum lucidum –Contains: •Hair •Sweat glands •Sebaceous glands 6 Functions of the Skin • Resistance to trauma and infection • Water retention • Synthesis of Vitamin D • Sensation • Thermoregulation • Nonverbal communication 7 8 Epidermis • Keratinized stratified squamous epithelium –Superficial cells are dead • Avascular –Nutrients must diffuse from deeper connective tissue • Sparse nerve endings • 9 Cells of the Epidermis • Tactile (Merkel) cells –Sense receptors • Dendritic (Langerhans) cells –Macrophage cells • Stem Cells –Produce keratinocytes –Only in deep layer of epidermis • Keratinocyte –Synthesize keratin • Keratinocyte –Synthesize keratin –Majority of visible epidermal cells • Melanocytes –Stratum basale –Brown to black pigment –Same amount in all people 10 Strata and Cell Types of the Epidermis 1 Figure 5.3 2 (a) ©Biophoto Associates/Science Source 11 Layers of Epidermis • Superficial to deep –Stratum corneum •Several layers of dead, scaly cells –Stratum lucidum •Only in thick skin •Cells lack organelles –Stratum granulosum •Cells have dark granules –Stratum spinosum •Several layers of cells –Stratum basale •Only one cell thick •Varied cell types 12 Dermis • Rich in collagen fibers • Large blood supply • Contains cutaneous glands, hair follicles, piloerector muscles, and nail roots • 13 Two Layers of Dermis 1 • Papillary layer –Superficial thin zone –Areolar tissue –Rich in blood –Extends upwards as dermal papillae; epidermis down as friction 2 13 1 –Rich in blood –Extends upwards as dermal papillae; epidermis down as friction ridges –Friction ridges-fingerprints 2 • Reticular layer - Deep, thick layer - Dense, irregular connective tissue - Striae (stretch marks): stretching of the dermal collagen 14 Hypodermis • Not a true layer of the skin • Located below the dermis • Contains adipose (subcutaneous fat) and areolar tissue • Functions –Energy storage –Thermal insulation –Connection to deeper tissue 15 Stratification of the Skin and Hypodermis 1 16 Stratification of the Skin and Hypodermis 2 17 Skin Color • Melanin: produced by melanocytes –Eumelanin: brownish black –Phenomelanin: reddish yellow –Across individuals, skin tones vary due to type and distribution of melanin (not number of melanocytes). • Hemoglobin: red pigment of blood • Carotene –Yellow orange –Concentrates in stratum corneum 18 Variation in Skin Pigmentation 1 Figure 5.5 a, b 2 (a bottom) ©Dennis Strete/McGraw-Hill Education, (a top) ©Lopolo/Shutterstock, (b bottom) ©Dennis Strete/McGraw-Hill Education, (b top) ©Arthur Tilley/Getty Images 19 Diagnostic Skin Colors 1 • Cyanosis –Blueness –Lack of oxygen 19 1 –Blueness –Lack of oxygen • Erythema –Redness –Increased blood flow • Pallor –Pale or ashen –Reduced blood flow • 2 • Albinism –White –Genetic lack of melanin • Jaundice –Yellow –Liver and bilirubin • Hematoma –Bruise 20 21 Skin Markings 1 • Friction ridges –Characteristic of primates –Aid in manipulating objects –Unique pattern for all individuals • Flexion lines (creases) • Freckles –Flat, melanized patches –Vary with heredity and UV exposure • 2 • Moles (nevus) –Elevated patch of melanized skin –“Beauty marks” • Hemangiomas (birthmarks) –Discolored skin –Caused by benign tumors of capillaries Hair • Also called a pilus(singular) or pili (plural) • Hair is an accessory organ of the skin (as are nails, skin glands) • Filament of keratinized cells 21 • • • • 22 Hair is an accessory organ of the skin (as are nails, skin glands) Filament of keratinized cells Grows from oblique tube called a hair follicle Grows almost everywhere, except: –Lips –Nipples –Parts of genitals –Palms and soles –Ventral and lateral surfaces of fingers and toes –Distal segments of fingers – Three Types of Hair 1 Downy hair (lanugo). • Fine, downy, unpigmented hair of fetus. Vellus hair. • Fine, unpigmented. • Two-thirds hair of women. • One-tenth hair of men. • All hair of children except eyebrows, eyelashes, and scalp. 2 Terminal. • Coarse, pigmented. • Eyebrows, eyelashes, and scalp. • After puberty. • Axillary. • Pubic. • Male facial hair. • Some hair on trunk and limbs. 23 Functions of Hair 24 Structure of Hair and Follicle Three zones along the length of a hair –1. Bulb •Swelling at base where hair originates in dermis •Dermal papillae - provides nutrition •Hair matrix – hair’s growth center –2. Root •Remainder of hair w/in follicle •Dead tissue 25 w/in follicle •Dead tissue –3. Shaft •Portion above the skin’s surface •Dead tissue – 25 Three Layers of a Hair and Follicle • 1. Medulla –Internal layer –Loosely arranged cells –Air spaces – • 2. Cortex –Bulk of hair – • 3. Cuticle –Outer layer –Overlapping scaly cells • 26 Structure of the Hair and Follicle Three layers to a hair: • Medulla. • Internal layer. • Loosely arranged cells and air spaces. • Cortex. • Bulk of hair. • Several layers of long cells. • Cuticle. • Outer layer. • Overlapping scaly cells. 27 Structure of the Hair and Follicle Hair follicle: • Diagonal tube extending in dermis or as deep as hypodermis. • Two layers. • Epithelial root sheath (inner layer). • Connective tissue root sheath (derived from dermis). • Hair receptors. • Nerve fibers that respond to hair’s movement. 28 1 • Hair receptors. • Nerve fibers that respond to hair’s movement. • Arrector muscle (arrector pili). • Smooth muscle that causes “goose bumps.” 28 The Basis of Hair Color and Texture 1 Straight hair is round in cross section, curly hair is flatter. Color depends on pigment within cells of cortex. 2 Figure 5.7 a, b, c, d 3 ©Joe DeGrandis/McGraw-Hill Education 29 Hair Growth and Loss 30 Nails Derivatives of stratum corneum;Composed of very thin, dead, scaly cells w/ parallel rows of keratin; Primates have flat nails, as opposed to claws, for easier manipulation • Nail plate –Free edge –Nail body –Nail root •Nail fold •Nail groove • Nail fold –Nail groove • Nail bed –Hyponychium – epidermis –Nail matrix – growth area –Lunule –Eponychium (cuticle) 31 Cutaneous Glands 32 Sweat (Sudoriferous) Glands • Merocrine (eccrine) –Most numerous –Produce perspiration to cool body •Mainly water •Other waste products also found in urine –Secrete to surface of skin at sweat pore –Abundant on palms, soles, forehead, but found all over body 33 –Secrete to surface of skin at sweat pore –Abundant on palms, soles, forehead, but found all over body –Myoepithelial cells – contractile cells that squeeze sweat up the ducts. Ceruminous Glands 33 Mammary Glands • Found in auditory canal • Cerumen –Earwax –Combination of sebum and dead epidermal cells • Keeps eardrum pliable, waterproofs canal, kills bacteria, and coats guard hairs 34 Prenatal Development of Skin Epidermis – ectoderm. • Two layers. • Periderm. • Basal layer (germative layer). • Intermediate layer produces keratinocytes. Dermis – mesoderm. • Mesenchyme. • Blood vessels – by week 6. • Typical fibrous CT – by week 11. • Dermal papillae – by third month. 35 Prenatal Development of the Epidermis and Dermis Figure 5.11 36 Prenatal Development of Hair Hair follicles. • Month 2: eyebrows, eyelids, upper lip, and chin. • Month 4: elsewhere. • Birth: about 5 million. • No more develop after birth. 37 Prenatal Development of Nails Week 10 – epidermal thickening, ventral fingers. Week 14 – epidermal thickening, ventral toes. Primary nail field – on dorsal surface of digits. Eight months – nail plate to fingertips. Birth – nail plate to tips of toes. 38 1 37 Eight months – nail plate to fingertips. Birth – nail plate to tips of toes. 38 39 40 Prenatal Development of Glands 1 Sebaceous glands. • Present on face at 6 months gestation. Vernix caseosa. • White, greasy skin coating of the fetus. • Protects from abrasion and amniotic fluid. • Aids in passage through vagina. 2 Apocrine sweat glands. • Develop as outgrowths of hair follicle. Eccrine (merocrine) sweat glands. • Develop from embryonic germ layer. Prenatal Development of a Hair Follicle and Cutaneous Glands Figure 5.12 Integumentary System Aging 1 • Senescence – age related degeneration –Hair turns grayer, thinner –Melanocyte stem cells die out –Mitosis slows down –Dead hairs not replaced –Atrophy of sebaceous glands –Skin becomes thinner and more translucent – 2 • Skin and blood supply –Fewer and more fragile vessels –Rosacea •Dilated blood vessels that causes reddened areas –Increased bruising • Thermoregulation –Vulnerability to hypothermia and heat stroke – – 41 Some Disorders of the Integumentary System 1 42 Some Disorders of the Integumentary System 2 Disorders Described Elsewhere. 43 44 41 42 Disorders Described Elsewhere. 43 Skin Cancer • Induced by UV rays (both natural and tanning beds) • Elderly and fair-skinned most common 44 Burns • Leading cause of accidental death • Caused by hyperthermal damage to skin • Death primarily from –Fluid loss –Infection –Toxic effects of eschar (dead tissue) 45 First-Degree Burn (Partial-Thickness Burn) • Only epidermis • Usually localized • Redness, slight edema, and pain • Sunburn • 46 Second-Degree Burn (Partial-Thickness Burn) • Epidermis and part of dermis • Red, tan, or white • Blistered and painful • May cause damage to hair follicles, nerve endings, and cutaneous glands • Sunburns and scalds 47 Third-Degree Burn (Full-Thickness Burn) • Epidermis and dermis are completely destroyed • Contracture and disfigurement can result •