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Integumentary System. Epidermis and dermis Hypodermis Thick and thin skin Skin color Functions of the skin Hair and nails Cutaneous glands. Overview of the Skin. Largest organ of the body (16% of body weight) Two layers epidermis Keratinized __________________________ epithelium
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Integumentary System • Epidermis and dermis • Hypodermis • Thick and thin skin • Skin color • Functions of the skin • Hair and nails • Cutaneous glands
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
Cell Types & Layers of the Epidermis Stratum basale
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
Hypodermis • Known as subcutaneous tissue or superficial fascia • Has more adipose than dermis • Functions • ______________________ • ______________________ Hypodermis
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
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)
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
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
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
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)
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
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)
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
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
Cutaneous Glands • Sweat glands • _______________ • _______________ • Sebaceous glands • Ceruminous glands • Mammary glands
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
Sebaceous Glands • Oily secretion called ______________ that contains broken-down cells • Flask-shaped gland with duct that may open into hair follicle
Ceruminous Glands • Modified sweat gland • Found only in external ear canal • Their secretion combines with sebum to produce earwax • waterproof keeps eardrum flexible
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
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
Some Skin Disorders • See Table 6.3 • Acne • Dermatitis • Eczema • Psoriasis • Rosacea • Seborrhea • Tinea
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
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
Wound Healing of a Laceration • Clot forms • Scab forms on surface • Macrophages start to clean up debris
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.
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.