Integumentary System

1. Integumentary System • Epidermis and dermis • Hypodermis • Thick and thin skin • Skin color • Functions of the skin • Hair and nails • Cutaneous glands

2. Overview of the Skin • Largest organ of the body (16% of body weight) • Two layers • epidermis • Keratinized __________________________ epithelium • contains ______________ • dermis • connective tissue layer • Rests on subcutaneous layer or hypodermis • Normal thickness of 0.5 mm, up to 5 mm

3. Cell Types & Layers of the Epidermis Stratum basale

4. Dermis • Thicker than epidermis • Composition • collagen, elastic & reticular fibers, fibroblasts & accessory structures such as hair follicles and glands • Dermal papillae • Layers • papillary layer • reticular layer

5. Layers of the Dermis

6. Hypodermis • Known as subcutaneous tissue or superficial fascia • Has more adipose than dermis • Functions • ______________________ • ______________________ Hypodermis

7. Skin Colors (Pigmentation) • ________________ is red pigment of red blood cells • visible through dermal collagen fibers • ________ is yellow pigment of vegetables & egg yolks • concentrates in stratum corneum & subcutaneous fat • Melanin pigment produced by ___________________ • pigment synthesis stimulated by UV radiation from sunlight • produces yellow, brown, black and reddish hues

8. Abnormal Skin Colors • Cyanosis - blueness from lack of ____________ • Erythema - redness from dilated cutaneous vessels • Jaundice - yellowing of skin & sclera - bilirubin • Bronzing - golden-brown color of Addison disease (deficiency of glucocorticoid hormone) • Pallor - pale color from lack of blood flow • Albinism - a genetic lack of melanin • Hematoma - a bruise (visible clotted blood)

9. Skin Markings • Birthmarks • Hemangiomas (strawberry marks) • Port-wine marks • (discolored skin, malformations of dermal blood capillaries) • Café au lait spots • Freckles & moles = aggregations of melanocytes • freckles are flat; moles are elevated • Epidermal ridges - leave oily fingerprints

10. Functions of the Skin • Barrier = tough, dry, acid mantle, water barrier, UV barrier • Vitamin D synthesis • UV light converts 7-dehydrocholesterol in dermal vessels to vitamin D3 • Cutaneous absorption • 1-2 % oxygen absorption by diffusion through skin • fat-soluble vitamins (A, D, E & K) easily absorbed • Sensory functions • receptors for heat, cold, touch, pressure, vibration & pain • Thermoregulation • cutaneous vasodilation & constriction and sweating • Psychological and social functions • appearance & social acceptance • facial expression and nonverbal communication

11. Characteristics of Human Hair • S. corneum of the skin contains soft keratin • Hair and nails are composed of hard keratin • toughened by disulfide bridges between molecules • Hair found almost everywhere on the body • 3 different body hair types • lanugo -- fine, unpigmented fetal hair • vellus -- fine, unpigmented hair • terminal hair -- coarse, long, pigmented hair

12. Structure of Hair and Follicle • Hair is a filament of keratinized cells • Shaft: parts above skin • Root: parts below within follicle • Follicle: epidermal invagination into dermis • Cross section layers: medulla, cortex and cuticle • Bulb: swelling in base where hair originates • Papilla: vascular tissue in bulb • Hair color is due to melanin pigments • eumelanin • pheomelanin (agouti signaling protein)

13. Structure of Hair Follicle • Epithelial root sheath is an extension of the epidermis • Connective tissue root sheath is derived from the dermis • Hair receptors entwine each follicle • Arrector pili muscle

14. Growth of Hair • Mitosis in stratum basale of epithelial root sheath • as cells become keratinized they are pushed upward • Grow 1 mm every 3 days • Anagen (growth) phase lasts 6-8 years (scalp) • Catagen (degenerative) phase , growth stops, club hair, 2-3 wks • Telogen (resting) phase, 1-3 months • Anagen in eyelashes and eyebrows lasts about a month • Alopecia • Hirsutism • Pattern baldness (sex influenced trait)

15. Functions of Hair • Body hair too thin to provide warmth • Sensory functions • alert us to parasites crawling on skin • Scalp hair provides heat retention & sunburn cover • Sex and individual recognition • Beard, pubic & axillary hair indicate sexual maturity & help distribute sexual scents • Guard hairs & eyelashes prevent foreign objects from getting into nostrils, ear canals or eyes • Expression of emotions with eyebrows

16. Nails • Clear, hard derivative of stratum corneum • densely packed cells filled with hard keratin • Flat nails allow for fleshy, sensitive fingertips • Growth rate is 1 mm per week • new cells added by mitosis in the nail matrix • nail plate is visible part of nail

18. Cutaneous Glands • Sweat glands • _______________ • _______________ • Sebaceous glands • Ceruminous glands • Mammary glands

19. Sweat Glands • Filtrate of plasma • 500 ml of perspiration/day • Merocrine gland - simpletubular gland • millions of them • cool the body • Apocrine glands • found only near hair follicles & respond to stress & sex • body odor produced by _______________ action on fatty acids

20. Sebaceous Glands • Oily secretion called ______________ that contains broken-down cells • Flask-shaped gland with duct that may open into hair follicle

21. Ceruminous Glands • Modified sweat gland • Found only in external ear canal • Their secretion combines with sebum to produce earwax • waterproof keeps eardrum flexible

22. Breasts and Mammary Glands • Breasts of both sexes rarely contain glands • Secondary sexual characteristic of females • Glandular tissue - only during lactation and pregnancy • modified apocrine sweat gland • Mammary ridges or milk lines

23. Diseases of the Skin • Most vulnerable organ to injury & disease • skin diseases common in old age • Skin cancer • induced by UV rays of the sun • most common in fair-skinned and elderly • basal cell carcinoma • arises from cells of the stratum basale • treated by surgical removal & radiation? • squamous cell carcinoma • arises from keratinocytes in the stratum spinosum • if neglected, metastasis to the lymph nodes can be lethal • malignant melanoma (most deadly cancer) • arises from melanocytes of a preexisting mole • ABCDE--asymmetry, border irregular, color mixed, diameter over 6 mm, & evolving

24. Some Skin Disorders • See Table 6.3 • Acne • Dermatitis • Eczema • Psoriasis • Rosacea • Seborrhea • Tinea

25. Burns • Causes of burns -- hot water, sunlight, radiation, electric shock or acids and bases • Causes of deaths • fluid loss, infection, & effects of dead tissue • Degrees of burns • 1st-degree = only the epidermis (red, painful & edema) • 2nd-degree = epidermis & part of dermis (blistered) • epidermis regenerates from hair follicles & sweat glands • 3rd-degree = epidermis, dermis & more is destroyed • often requires grafts & fibrosis may occur • Treatment -- fluid replacement & infection control

26. Wound Healing of a Laceration • Damaged vessels leak blood • Damaged cells & mast cells leak histamine • dilates blood vessels • increases blood flow • increases capillary permeability • Plasma seeps into wound carrying antibodies, clotting factors & WBCs

27. Wound Healing of a Laceration • Clot forms • Scab forms on surface • Macrophages start to clean up debris

28. Wound Healing of a Laceration • New capillaries grow • Fibroblasts deposit new collagen • Fibroblastic phase begins in 3-4 days & lasts up to 2 weeks Formation of granulation tissue.

29. Wound Healing of a Laceration • Surface epithelial cells multiply & spread beneath scab • Scab falls off • Epithelium regenerates • Connective tissue forms only scar tissue (fibrosis) • Remodeling phase may last 2 years Epithelial regeneration & connective tissue fibrosis.