Chapter 5 The Integumentary System PDF

ANATOMY & PHYSIOLOGY Chapter 5 THE INTEGUMENTARY SYSTEM Dr. Karen V. Goodwin, D.C. FIGURE 5.1 Your skin is a vital part of your life and appearance (a–d). Some people choose to embellish it with tattoos (a), makeup (b), and even piercings (c). (credit a: Steve Teo; credit b: “spaceodiss...

ANATOMY & PHYSIOLOGY Chapter 5 THE INTEGUMENTARY SYSTEM Dr. Karen V. Goodwin, D.C. FIGURE 5.1 Your skin is a vital part of your life and appearance (a–d). Some people choose to embellish it with tattoos (a), makeup (b), and even piercings (c). (credit a: Steve Teo; credit b: “spaceodissey”/flickr; credit c: Mark/flickr; credit d: Lisa Schaffer) THE INTEGUMENTARY SYSTEM The Integumentary System: The skin and its accessory structures 16% of body weight 1.5 to 2 m2 The largest organ system Protects the body, provides immune defense, synthesizes hormones, maintains fluid content, modulates body temperature Needs daily maintenance to maintain health THE INTEGUMENTARY SYSTEM The Integumentary System: The skin and its accessory structures Epidermis Dermis Hypodermis Accessory Structures FIGURE 5.2 GOAL: Understand everything in this figure. Layers of Skin The skin is composed of two main layers: the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Beneath the dermis lies the hypodermis, which is composed mainly of loose connective and fatty tissues. THE EPIDERMIS Characteristics of the Epidermis: Keratinized, stratified squamous epithelium Four (sometimes five) layers: Thin skin: most of the skin of the body—has four layers Thick skin: palms of hands or soles of feet-–five layers Avascular Cells are called “keratinocytes”: Manufacture and store keratin, a fibrous structural protein Keratin makes hair, nails and skin hard/tough Outer layers of keratinocytes are dead and slough off regularly FIGURE 5.3 Thin Skin versus Thick Skin These slides show cross-sections of the epidermis and dermis of (a) thin and (b) thick skin. Note the significant difference in the thickness of the epithelial layer of the thick skin. From top, LM × 40, LM × 40. (Micrograph of thin skin provided by the Regents of University of Michigan Medical School © 2012. Micrograph of thick skin taken by Karen V. Goodwin, Texas Woman’s University, © 2020.) THE EPIDERMIS Layers of the Epidermis: Stratum Basale—”base” Stratum Spinosum—”spiny” Stratum Granulosum—”grainy” Stratum Lucidum—”translucent” Stratum Corneum—(Latin: cornu=horn) “has horns” “Be Still…Granny Looks Crazy!” FIGURE 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. THE EPIDERMIS Stratum Basale: Bottom layer; more cuboidal in shape Constantly undergoing mitosis New daughter cells push older cells upward toward the apical surface Closest to the nutrients obtained from the dermis All keratinocytes come from this cell Two other special cells found in this layer: Melanocyte: covers the basal cells with its armlike extensions, like an umbrella. It’s melanin protein protects the basal cells from UV damage and determines the skin tone. Merkel cell (aka tactile cell): detects “light touch”. Most abundant in hands and feet. FIGURE 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. THE EPIDERMIS Stratum Spinosum: Appears spiny when stained due to the desmosomes connecting the cells 8-10 cell rows thick Some cell division may still be occurring These cells begin synthesizing keratin protein These cells also secrete glycolipids that make the epidermis “waterproof” Other special cells found in this layer: Langerhans (aka Dendritic) Cells: Immune system cells that capture pathogens and debris similar to macrophages FIGURE 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. THE EPIDERMIS Stratum Granulosum: 3-5 cell rows thick Cells are tightly interlocked, no longer divide, and become flatter and thicker as they near end of life cycle. Strictly producing: Keratin protein Keratohyalin – connects keratins together making this layer appear “grainy” Nuclei and organelles disintegrate once the proteins are made FIGURE 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. THE EPIDERMIS Stratum Lucidum: ONLY FOUND IN THICK SKIN: PALMS AND SOLES “Cells” are dead; sacs of protein wrapped in membrane is all that is left. Stratum Lucidum cells contain high amounts of eleidin protein which doesn’t stain, making it “translucent” (clear). Stratum Corneum: “Cells” are dead; sacs of protein wrapped in membrane is all that is left. 15-30 rows of squamous (flat) cells Dry, dead cells protect from the environment, microbes, etc. Prevents dehydration of underlying cells and tissues Prevents mechanical damage and resists abrasion; outer cells slough off FIGURE 5.5 Layers of the Epidermis The epidermis of thick skin has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. THE DERMIS Structures of the Dermis: Layers: Papillary Dermis Reticular Dermis Nerve Receptors: Meissner's (aka tactile) Corpuscles Pacinian (aka lamellar) Corpuscles Ruffini’s (aka bulbous) Corpuscles Free nerve endings Root hair plexus Hair Follicle and arrector pili muscles Glands: Eccrine sweat glands Apocrine sweat glands Sebaceous sweat glands THE DERMIS Structures of the Dermis: Layers: Papillary Dermis: Loose Areolar connective tissue Free nerve endings and Meissner's corpuscles Very vascular and has lots of macrophages Dermal papillae: fingerlike projections Your pattern of dermal papillae makes your fingerprint Reticular Dermis: Dense irregular connective tissue Collagens extend up into papillary layer and down into hypodermis Collagens bind water for skin hydration Rich nerve supply, both sensory and sympathetic Very vascular Hair follicles and sweat glands found here FIGURE 5.2 GOAL: Understand everything in this figure. Layers of Skin The skin is composed of two main layers: the epidermis, made of closely packed epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Beneath the dermis lies the hypodermis, which is composed mainly of loose connective and fatty tissues. THE DERMIS Sensory Nerve Receptors: Free Nerve Endings: Pain and temperature Meissner's/tactile corpuscles: Discriminative touch Ruffini’s/bulbous: Stretch, grip, and slippage Pacinian/lamellar corpuscles: Deep pressure and vibration Root Hair Plexus: senses movement of the hair Other Nerves: Sympathetic fibers: vasoconstrict (or reduced stimulus relaxes) blood vessels to change flow; stimulate arrector pili muscles for goosebumps/chills FIGURE 5.15 Light Micrograph of a Meissner’s Corpuscle In this micrograph of a skin cross-section, you can see a Meissner corpuscle (arrow), a type of touch receptor located in a dermal papilla adjacent to the basement membrane and stratum basale of the overlying epidermis. LM × 100. (credit: “Wbensmith”/Wikimedia Commons) THE DERMIS Light Micrograph of a Pacinian Corpuscle In this micrograph of a skin cross-section, you can see a Pacinian corpuscle (arrow), a type of pressure receptor located deep in the dermis. (Pacinian corpuscles, light micrograph - Stock Image - C024/8140 - Science Photo Library) FIGURE 5.7 Layers of the Dermis This stained slide shows the two components of the dermis—the papillary layer and the reticular layer. Both are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct. The dermal papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen fiber bundles below belong to the reticular layer. LM × 10. (credit: modification of work by “kilbad”/Wikimedia Commons) THE HYPODERMIS The Hypodermis is the “subcutaneous layer”, underneath the skin. Primarily made of adipose tissue and loose areolar connective tissue. Considered the “superficial fascia” Thermal insulation, cushioning, and lipid storage SKIN PIGMENTATION Melanocytes produce melanin to protect the DNA of skin cells from UV radiation. More melanin = darker skin; less melanin = lighter skin Any skin tone may sun burn Sun and tanning bed exposure causes breakdown of folic acid in the skin; keratinocytes secret chemical signals for “help” which stimulate melanocytes to create excess melanin. When the cells with excess melanin die and are lost, tan fades. The buildup of UV damaged obtained in efforts to tan can permanently affect the skin (wrinkles; age spots) However, sunlight is needed to prompt Vitamin D production. BALANCE is the key. FIGURE 5.8 Skin Pigmentation The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes. SKIN PIGMENTATION NORMAL VARIANTS: Freckles: Accumulations of melanin Nevus (pl. “Nevi”): moles; concentrated areas of melanocytes. Should be monitored for any changes indicating cancerous overgrowth Poliosis: A white patch of hair that lacks melanin DISORDERS: Albinism: a lack of melanin production due to double recessive gene Vitiligo: autoimmune damage to melanocytes causing them to cease producing melanin. This condition tends to progress over time. Melanoma: Skin cancer of the melanocytes FIGURE 5.9 Moles Moles range from benign accumulations of melanocytes to melanomas. These structures populate the landscape of our skin. (credit: the National Cancer Institute) FIGURE 5.10 Vitiligo Individuals with vitiligo experience depigmentation that results in lighter colored patches of skin. The condition is especially noticeable on darker skin. (b) A photograph of the model Winnie Harlow, who has patches of unpigmented skin around her mouth and face. (credit: (a) Klaus D. Peter (b) Owl Bridge Media / Wikimedia.) SKIN PIGMENTATION OTHER VARIANTS ON COLORATION: Carotene contributes yellowish tint Pheomelanin is responsible for red hair and “ruddy” skin color Flushing/Blushing occurs with the vessels of skin dilate and bring a surge of blood flow Cyanosis: skin takes on a blueish tint when the body is oxygen deprived. Most easily noticed around lips and finger tips Jaundice: a toxic buildup of unconjugated bile salts from the liver will cause skin and eye scleras to take on a yellowish tint. Eyes and anterior wrists are early indicators Palor: Cold, extreme fright, anemia, and other situations where there is lower blood flow or less oxygenation of the skin resulting in pale tone Addison’s disease: Adrenal insufficiency (low cortisol/aldosterone) leads to “bronzing” hyperpigmentation EXAMPLES Abnormalities of skin color Top Left: Cyanosis. Top Right: Jaundice. All bottom images: Addison’s disease. Image credits: Cyanosis Jaundice Addison’s (1) Addison’s (2) SKIN PIGMENTATION Fun Facts: Melanin in the Iris Melanin is also responsible for eye color The more melanin, the darker the eye color The iris has two layers: stroma in front, pigmented epithelium in back Brown eyes have melanin in both layers Blue eyes lack pigment in the front layer; stroma scatters light Green/hazel eyes have light brown pigmentation in both layers also causing light scatter. Can appear different colors in different situations/lighting A complete lack of pigment in the eyes, such as in many forms of albinism, means you will only see the color of the cells and blood vessels and the eyes appear pink/red ACCESSORY STRUCTURES OF THE SKIN Hair Nails Glands FIGURE 5.11 Hair Hair follicles originate in the epidermis and have many different parts. Hair shaft: unanchored portion; mostly visible Hair root bulb: anchored in the dermis Hair matrix: Mitotically active basal cells Medulla: middle Cortex: compressed keratinized cells Cuticle: VERY hard keratinized cells Dermal hair papilla: vessels and nerves Arrector pili muscle: moves the hair (ex: chill bumps) FIGURE 5.12 Hair Follicle The slide shows a cross-section of a hair follicle. Basal cells of the hair matrix in the center differentiate into cells of the inner root sheath. Basal cells at the base of the hair root form the outer root sheath. LM ✕ 4. (credit: modification of work by “kilbad”/Wikimedia Commons) FIGURE 5.13 Nails The nail is an accessory structure of the integumentary system. Interesting Nail Abnormalities: LINK to American Academy of Family Physicians ACCESSORY STRUCTURES OF THE SKIN Sweat Glands: Eccrine sweat glands—use merocrine secretion Regular sweat: water, salts, antibodies, urea and other wastes Abundant on palms, soles and forehead Apocrine sweat glands—axilla and groin Poorly understood human pheromone system Sweat plus other organic compounds that bacteria consume Under nervous system (sympathetic) and hormonal control Sebaceous glands—use holocrine secretion Sebum is a mixture of lipids that keep hair healthy Inactive until puberty FIGURE 5.14 Sebaceous Gland Glands of the Skin Eccrine glands are coiled glands in the dermis that release sweat directly to the surface. Apocrine glands appear similar, but they release their product into a hair follicle. Sebaceous glands belong to the hair follicle and release a lipid-rich sebum to protect hair. (Image credit: Mayo Clinic) FUNCTIONS OF THE INTEGUMENT Protection: Wind, water, UV light, grit, dirt, abrasions, water loss, microbes Sensory input: Gather important information about the world around us Nerves as previously discussed Thermoregulation: The skin releases or conserves heat as the body needs Heat release methods: Radiation Evaporation Convection Conduction Heat conservation methods: Vasoconstriction Vitamin D Syntesis FUNCTIONS OF THE INTEGUMENT Thermoregulation: As the body creates heat, the vessels of the skin vasodilate (open wider) to allow more blood to flow through the skin. Heat from the blood stream is released into the environment by the skin. Heat release methods: Radiation – heat leaves the skin as infrared waves Evaporation -- when the skin becomes dry, sweat glands are triggered to release sweat (water) to the surface. As the water evaporates, heat leaves with it. Convection – heat is transferred by air that passes by Conduction -- heat is transferred to items we touch (clothing, chairs, etc.) Heat conservation methods: Vasoconstriction – when we are cold, our skin vessels constrict so that less blood flows past the surface and less heat is lost FIGURE 5.16 Thermoregulation During strenuous physical activities, such as skiing (a) or running (c), the dermal blood vessels dilate and sweat secretion increases (b). These mechanisms prevent the body from overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low temperatures (b). (credit a: “Trysil”/flickr; credit c: Ralph Daily) FUNCTIONS OF THE INTEGUMENT Vitamin D Synthesis: Cholesterol in the skin exposed to UV light is synthesized into cholecalciferol The liver converts cholecalciferol to calcidiol The kidneys convert calcidiol to calcitriol, active Vitamin D3 Vitamin D3: Technically a hormone rather than a vitamin Prompts the intestine to absorb calcium Essential to healthy immune function Insufficiency has been linked to higher cancer and disease risks Rickets: childhood lack of calcium; soft bones deform to be “bow-legged” Osteomalacia: soft bones due to lack of calcium Darker skin individuals have more protection against UV light, but increased risk of low Vitamin D levels RICKETS Rickets Rickets is the childhood form of osteomalacia, soft bones, due to a lack of Vitamin D and/or a lack of dietary calcium. (Image credits: Diagram on left. Image college, right.)  DISORDERS AND DISEASES OF SKIN Cancers of skin: Basal Cell Carcinoma: Stratum Basale Squamous Cell Carcinoma: Stratum Spinosum Melanoma: Melanocytes Basal Cell Carcinoma Squamous Cell Carcinoma Melanoma (credit: John Hendrix, MD) (credit: the National Cancer (credit: the National Cancer Institute) Institute, Centers for Disease Control) FIGURE 5.21 Eczema Eczema is a common skin disorder that presents as a red, flaky rash. (credit: “Jambula”/Wikimedia Commons, Centers for Disease Control) FIGURE 5.22 Acne Acne is a result of over-productive sebaceous glands, which leads to formation of blackheads and inflammation of the skin. DISORDERS AND DISEASES OF SKIN Injuries: Contusion: “bruise”: damaged blood vessels in the dermis bleed. The lost blood changes colors as it breaks down and must be removed by macrophages Petechiae: superficial capillaries are broken leaving small red dots. (Ex: ripping off medical tape or a bandaid, suction injuries, etc) Laceration: “cut”: Even though the dermis is dense irregular tissue, there are still discernable patterns in the arrangement of the collagen called “lines of cleavage”. A laceration parallel to a line of cleavage heals with less scarring than a laceration across lines of cleavage. INJURIES OF THE SKIN Lines of Cleavage: Patterns of collagen are shown at right, which help us resist tension in the most common directions of body motion. Petechiae: Shown below, petechiae occur with the breakage of capillaries, or with serious clotting disorders. Image credit DISORDERS AND DISEASES OF SKIN Injuries: Burns: measured in degrees First degree — epidermis only Second degree — involves the dermis Third degree — extends completely through the whole dermis Fourth degree – involves muscle and/or bone ”Full thickness burns” (3rd and 4th degree) cannot heal on their own because all of the origin tissues and cells for healing are destroyed Rule of Palm/Rule of Nines: The size of a burn is quickly estimated by using the “rule of palm” where the palm = 1% of the body surface, -OR- the “rule of nines” where each extremity = 9% of the body surface FIGURE 5.23 Calculating the Size of a Burn The size of a burn will guide decisions made about the need for specialized treatment. Specific parts of the body are associated with a percentage of body area. (Image Credit ) LEGAL CASE: 1994 Liebeck vs MacDonald’s Restaurants This OpenStax ancillary resource is © Rice University under a CC-BY 4.0 International license; it may be reproduced or modified but must be attributed to OpenStax, Rice University and any changes must be noted.