Unformatted text preview: KIN 216 Applied Human Anatomy
Chapter 5 Integumentary System Integument = skin Largest organ in the body is considered an organ because it consists of several kinds of tissues that are structurally arranged to function together Represents ~7% of body weight (>3000 square inches) Variable thickness (1.5 4 mm) 2 regions: dermis, epidermis Integumentary system = skin plus hair, glands, and nails Derm = skin (Greek), cutis = skin (Latin) Dermatitis = ??? Dermabrasion = process to remove tattoo Dermatome = instrument to cut skin Functions of Integumentary System Protection Homeostasis Others Protects against water (keratin), microorganisms (oil glands), UV light damage (melanin) "Same state" Ex: body fluids, temperature Cutaneous absorption Ex: lipids can cross easily (so many toxins and pesticides can cross) Synthesis of vitamin D, which causes maintenance of calcium Touch, pain, temperature Sensory receptors Nonverbal communication Rash, biting fingernails Show emotion w/red face, etc. Epidermis Protective outer covering thin Stratified epithelium (varies in thickness .007.12mm) All layers are dead cells except bottom few (deepest) It takes 68 weeks for bottom layers to reach top, then get sloughed off (millions of them) When cells are alive in bottom layer they secrete keratin (toughens and waterproofs the skin) Increased keratin responsible for cornification of the skin (calluses, corns) Relatively avascular, fairly thin relative to the dermis 5 layers (strata) in thick skin; 4 layers in thin skin Stratum basale Epidermal Layers Stratum spinosum Deepest layer Single row of cells, mostly stem cells Rapid division Merkel cell: associated with touch (sensory nerve ending) Melanocytes: make melanin (dark pigment), shield from UV rays Several cell layers thick Has spines, which don't exist in living cells Langerhans cells: starshaped cell, part of immune system; use endocytosis to engulf foreign proteins and travel to lymph node Epidermal Layers (2) Stratum granulosum 15 layers of flattened keratinocytes Keratohyaline granules: help form keratin in higher strata Lamellated granules: waterproofing In thick skin ONLY Thin, translucent band A few rows of dead keratinocytes Stratum lucidum ("transition zone") Stratum corneum Most external Many cells thick (even thicker in thick skin) Dandruff and skin flakes Thickest of all 3 layers, all living cells; "hide" Contains connective tissue Contains nerves, hair follicles Contains elastin fibers (stretchiness decreases w/age), collagen and reticular fibers as well 2 layers Papillary: superficial 20%, areolar CT, fingerlike projections Reticular: 80%, dense irregular CT, network of collagen Dermis Temperature regulation Integumentary glands (exocrine) arise from glandular epithelial tissue BUT drop down into dermis Hypodermis Binds skin to underlying layers, insulates and cushions SO it's not really part of the skin (just does binding) Loose (areolar) CT, some collagen and elastin Is vascular (larger blood vessels, which feed to capillaries in dermis) Subcutaneous adipose tissue (females have a thicker hypodermis than males ~8%) function of adipose is to insulate, protect, store energy SKINFOLDS here Melanin Skin Pigments Carotene Melan = melancholy dark black bile Made from a single amino acid (tyrosine) Albinos are missing the enzyme tyrosinase Range of color: yellow to reddish brown to black Found in epidermis Function: protects against UV radiation (if cells damaged, results in melanoma cancer) Yelloworange pigment Lipid substance made from cholesterol, found in stratum corneum and fatty tissue of hypodermis In RBCs in vessels Gives skin pink and blue tones PROTEIN with iron, which picks up O2 Hemoglobin Skin Appendages Derive from epidermis and extend into dermis Hair Primary function is to sense touching of skin Flexible strand made of dead, keratinized cells Keratin is hard 3 layers: medulla, cortex, and cuticle Made up of shaft and root Hair pigment is made by melanocytes in hair follicle and transferred into root, produces colors black, brown, red, blond White/gray hair = decreased melanin production Hair Follicles
Extend from epidermis into dermis Deep end forms hair bulb Nerve endings sense touch Hair papilla: portion of dermis with knot of capillaries that nourish, stimulate growth Hair matrix: epithelial cells in hair bulb Each follicle has a bundle of smooth muscle cells (arrector pili) cause hair to stand on end Hair Facts Vellus or terminal Vellus: body hair of children, women (fine, short) Terminal: hair on scalp (longer, coarser) Hair grows ~2 mm per week, but can vary Each follicle undergoes growth cycles With age, hair thins when not replaced as quickly different from pattern baldness, which is genetic Active phase: new hair pushes old out Originate in epidermis BUT are actually located in dermis Exocrine (have ducts, secretions used locally) Two main kinds (sebaceous, sudoriferous) Special kinds = ceruminous (ear wax), mammary Sebaceous (Latin sebum = grease) Occur all over body except palms, soles Simple alveolar, secrete oil onto hair shaft (makes skin and hair oily) Oil (sebum) is waterproof (made of lipids); keeps hair from becoming brittle and epidermis from cracking Glands Sex hormones regulate these glands cause the teenage acne problem when the glands secrete a lot and become infected Latin sudor = sweat (blood filtrate; 99% H2O; salt) Excrete sweat onto skin surface
Most numerous on palms, soles, axillary and pubic regions, and forehead 2 kinds (eccrine and apocrine) Eccrine (more numerous) Sudoriferous Apocrine (larger) Function = evaporative cooling Location = all over body (palms, soles, forehead) Simple tubular gland, coiled releases sweat through pores Location = axillary, pubic regions Special sweat that also contains fat and proteins Function = sexual attractant (smell body odor!) Inactive until puberty Nails Scalelike modification of epidermis made of hard keratin Free edge, body, root, nail bed Pink appearance due to capillary network of dermis underneath Nail matrix: actively growing part Disorders of Integumentary System Burns First degree: epidermis damaged Second degree: epidermis and upper part of dermis damaged Third degree: entire thickness of skin Basal cell carcinoma: least malignant and most common, arises in stratum basale Squamous cell carcinoma: arises from stratum spinosum Melanoma: most dangerous, melanocytes Skin cancer READ on your own p. 119 "Skin throughout life" ...
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- Spring '08
- Stratum Corneum, dermis Deep end