Kin 290 Chapter 4 Week 4
Kin 290 Chapter 4 Week 4 Kin 290
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This 8 page Class Notes was uploaded by Leonard Carey on Monday April 11, 2016. The Class Notes belongs to Kin 290 at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months taught by Dr. Satern in Spring 2016. Since its upload, it has received 9 views. For similar materials see Anatomy & Physiology in Kinesiology at 1 MDSS-SGSLM-Langley AFB Advanced Education in General Dentistry 12 Months.
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Date Created: 04/11/16
Chapter 5 Chapter 5 The Integumentary System Why This Matters • Understanding the integumentary system will help you evaluate and treat injuries to the skin such as burns Integumentary System • Integumentary system consists of: • Skin • Hair • Nails • Sweat glands • Sebaceous (oil) glands 5.1 Structure of skin (Figure 5.1 – p. 151) • Skin consists of two distinct regions: • Epidermis: superficial region (the outer most region) • Consists of epithelial tissue and is avascular • Dermis: underlies epidermis • Mostly fibrous connective tissue, vascular • Hypodermis (superficial fascia) • Subcutaneous layer deep to skin • Not part of skin but shares some functions • Mostly adipose tissue that absorbs shock and insulates • Anchors skin to underlying structures: mostly muscles 5.2 Epidermis Cells of the Epidermis • Epidermis consists mostly of keratinized stratified squamous epithelium • Four cell types found in epidermis: 1. Keratinocytes • Produce fibrous keratin (protein that gives skin its protective properties) • Major cells of epidermis • Tightly connected by desmosomes • Millions slough off every day Cells of the Epidermis (cont.) 2. Melanocytes • Spidershaped cells located in deepest epidermis • Produce pigment melanin, which is packaged into melanosomes • Melanosomes are transferred to keratinocytes, where they protect nucleus © 2016 Pearson Education, Inc. 1 Chapter 5 from UV damage 3. Dendritic (Langerhans) cells • Starshaped macrophages that patrol deep epidermis • Are key activators of immune system 4. Tactile (Merkel) cells • Sensory receptors that sense touch Layers of the Epidermis (Figure 5.2 – p. 152) • Epidermis is made up of four or five distinct layers • Thick skin contains five layers (strata) and is found in highabrasion areas (hands, feet) • Thin skin contains only four strata Layers of the Epidermis (cont.) • Cells change by going through apoptosis (controlled cell death) • Dead cells slough off as dandruff and dander • Humans can shed ~50,000 cells every minute 5.3 Dermis (Figure 5.3 – p. 154) • Strong, flexible connective tissue • Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells • Fibers in matrix bind body together • Makes up the “hide” that is used to make leather • Contains nerves, blood vessels, and lymphatic vessels • Contains epidermal hair follicles, oil glands, and sweat glands • Two layers • Papillary • Reticular Papillary Layer • Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels • Loose fibers allow phagocytes to patrol for microorganisms • Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis • Projections contains capillary loops, free nerve endings, and touch receptors (tactile corpuscles, also called Meissner’s corpuscles) Papillary Layer (cont.) (Figure 5.4a – p. 155) • In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges © 2016 Pearson Education, Inc. 2 Chapter 5 • Collectively ridges are called friction ridges • Enhance gripping ability • Contribute to sense of touch • Sweat pores in ridges leave unique fingerprint pattern 5.4 Skin Color • Three pigments contribute to skin color 1. Melanin • Only pigment made in skin; made by melanocytes • Packaged into melanosomes that are sent to keratinocytes to shield DNA from sunlight • Sun exposure stimulates melanin production • Two forms: reddish yellow to brownish black • All humans have same number of keratinocytes, so color differences are due to amount and form of melanin • Freckles and pigmented moles are local accumulations of melanin Skin Color (cont.) 2. 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 3. Hemoglobin • Pinkish hue of fair skin is due to lower levels of melanin • Skin of Caucasians is more transparent, so color of hemoglobin shows through Quiz tuesday 5.5 Hair • Consists of dead keratinized cells • None located on palms, soles, lips, nipples, and portions of external genitalia • Functions: • Warn of insects on skin • Hair on head guards against physical trauma • Protect from heat loss • Shield skin from sunlight Structure of a Hair • Hairs (also called pili): flexible strands of dead, keratinized cells • Produced by hair follicles © 2016 Pearson Education, Inc. 3 Chapter 5 • Contains hard keratin, not like soft keratin found in skin • Hard keratin is tougher and more durable, and cells do not flake off • Regions: • Shaft: area that extends above scalp, where keratinization is complete • Root: area within scalp, where keratinization is still going on Structure of a Hair (cont.) • Three parts of hair shaft: • Medulla: central core of large cells and air spaces • Cortex: several layers of flattened cells surrounding medulla • Cuticle: outer layer consisting of overlapping layers of single cells Structure of a Hair (cont.) (Figure 5.6a & b – p. 158) • Hair pigments are made by melanocytes in hair follicles • Combinations of different melanins (yellow, rust, brown, black) create all the hair colors • Red hair has additional pheomelanin pigment • Gray/white hair results when melanin production decreases and air bubbles replace melanin in shaft Structure of a Hair Follicle • Extends from epidermal surface to dermis • Hair bulb: expanded area at deep end of follicle (the site where growth takes place) • Hair follicle receptor (or root hair plexus): sensory nerve endings that wrap around bulb • Hair is considered a sensory touch receptor • Wall of follicle composed of: • Peripheral connective tissue sheath • Derived from dermis • Also called fibrous sheath • Glassy membrane: thickened basal lamina • Epithelial root sheath • Derived from epidermis Structure of a Hair Follicle (cont.) (5.6c & d – p. 158) • Hair matrix: actively dividing area of bulb that produces hair cells • As matrix makes new cells, it pushes older ones upward • Arrector pili: small band of smooth muscle attached to follicle • Responsible for “goose bumps” • Hair papilla • Dermal tissue containing a knot of capillaries that supplies nutrients to growing hair © 2016 Pearson Education, Inc. 4 Chapter 5 5.6 Nails (Figure 5.7 – p. 160) • Scalelike modifications of epidermis that contain hard keratin • Act as a protective cover for distal, dorsal surface of fingers and toes • Consist of free edge, nail plate, and root • Nail bed is epidermis underneath keratinized nail plate • Nail matrix: thickened portion of bed responsible for nail growth 5.7 Sweat Glands • Also called sudoriferous glands • All skin surfaces except nipples and parts of external genitalia contain sweat glands • About 3 million per person • Two main types • Eccrine (merocrine) sweat glands • Apocrine sweat glands • Contain myoepithelial cells • Contract upon nervous system stimulation to force sweat into ducts Eccrine (Merocrine) Sweat Glands (Figure 5.8b – p. 161) • Most numerous type • 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 (microbekilling peptide), metabolic wastes Apocrine Sweat Glands • Confined to axillary and anogenital areas • Secrete viscous milky or yellowish sweat that contains fatty substances and proteins • Bacteria break down sweat, leading to body odor • Larger than eccrine sweat glands with ducts emptying into hair follicles • Begin functioning at puberty • Function unknown but may act as sexual scent gland Apocrine Sweat Glands (cont.) • Modified apocrine glands • Ceruminous glands: lining of external ear canal; secrete cerumen (earwax) • Mammary glands: secrete milk Sebaceous (Oil) Glands (Figure 5.8a – p. 161) © 2016 Pearson Education, Inc. 5 Chapter 5 • Widely distributed, except for 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 (bacteriakilling) properties • Softens hair and skin 5.8 Functions of Skin • Skin is first and foremost a barrier • Its main functions include: • Protection • Body temperature regulation • Cutaneous sensations • Metabolic functions • Blood reservoir • Excretion of wastes Protection • Skin is exposed to microorganisms, abrasions, temperature extremes, and harmful chemicals • Constitutes three barriers: • Chemical barrier • Physical barrier • Biological barrier Protection (cont.) • Chemical barrier • Skin secretes many chemicals, such as: • Sweat, which contains antimicrobial proteins • Sebum and defensins, which kill bacteria • Cells also secrete antimicrobial defensin • Acid mantle: low pH of skin retards bacterial multiplication • Melanin provides a chemical barrier against UV radiation damage Protection (cont.) • Physical barrier • Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and watersoluble substances • Some chemicals have limited penetration of skin • Lipidsoluble substances © 2016 Pearson Education, Inc. 6 Chapter 5 • Plant oleoresins (e.g., poison ivy) • Organic solvents (acetone, paint thinner) • Salts of heavy metals (lead, mercury) • Some drugs (nitroglycerin) • Drug agents (enhancers that help carry other drugs across skin) Protection (cont.) • Biological barriers • Epidermis contains phagocytic cells • Dendritic cells of epidermis engulf foreign antigens (invaders) and present to white blood cells, activating the immune response • Dermis contains macrophages • Macrophages also activate immune system by presenting foreign antigens to white blood cells • DNA can absorb harmful UV radiation, converting it to harmless heat Body Temperature Regulation • Under normal, resting body temperature, sweat glands produce about 500 ml/day of unnoticeable sweat • Called insensible perspiration • If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat • Called sensible perspiration; designed to cool body • Cold external environment • Dermal blood vessels constrict • Skin temperature drops to slow passive heat loss Cutaneous Sensations • Cutaneous sensory receptors are part of the nervous system • Exteroreceptors respond to stimuli outside body, such as temperature and touch • Free nerve endings sense painful stimuli Metabolic Functions • Skin can synthesize vitamin D needed for calcium absorption in intestine • Chemicals from keratinocytes can disarm some carcinogens • Keratinocytes can activate some hormones • Example: convert cortisone into hydrocortisone • Skin makes collagenase, which aids in natural turnover of collagen to prevent wrinkles Blood Reservoir • Skin can hold up to 5% of the body’s total blood volume • Skin vessels can be constricted to shunt blood to other organs, such as an © 2016 Pearson Education, Inc. 7 Chapter 5 exercising muscle Excretion • Skin can secrete limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid • Sweating can cause salt and water loss © 2016 Pearson Education, Inc. 8
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