Lecture 5 PP w/ Notes
Lecture 5 PP w/ Notes BIOL 2500
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This 47 page Class Notes was uploaded by Kelsey on Sunday September 11, 2016. The Class Notes belongs to BIOL 2500 at Auburn University taught by Dr. Shobnom Ferdous in Spring 2016. Since its upload, it has received 4 views. For similar materials see Human Anatomy & Physiology I in Biology at Auburn University.
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Date Created: 09/11/16
Chapter 5 The Integumentary System PowerPoint Lecture Slides prepared by © Annie Leibovitz/Contact Press ImagIvy Tech Community College Why This Matters • Understanding the integumentary system will help you evaluate and treat injuries to the skin such as burns 2 Regions of the skin • Largest organ in the body • Makes up 16% of the body weight • Covers an area of 2 square meters • Skin and accessory structures are the largest organ system in the human body • Skin is made of multiple layers of cells and tissues • The deeper layer of skin is well vascularized – Blood vessels, sensory and autonomic and sympathetic nerve fibers ensuring communication to and from the brain • Composed of 2 regions: – Epidermis and – Dermis 3 Figure: Skin structure Hair shaft Dermal papillae Epidermis Papillary Subpapillary layer plexus Sweat pore Dermis • Eccrine sweat gland Reticular • Arrector pili muscle layer • Sebaceous (oil) gland • Hair follicle • Hair root Hypodermis (subcutaneous tissue; not part of skin) Cutaneous plexus Nervous structures • Sensory nerve fiber Adipose tissue with free nerve endings • Lamellar corpuscle • Hair follicle receptor (root hair plexus) Practice Drawing and labeling this figure 4 Epidermis • Outermost layer • Avascular • Keratinized, stratified squamous epithelium • 4-5 layers of epithelial cells • Most cells produce keratin (fibrous protein that provides protection) • Thick skin is on palms of the hands and soles of the feet : fifth layer staratum lucidum located between stratum corneum and stratum granulosum • Cells in all these layers except Stratum Basale are called Keratinocytes. 5 Epidermis • New cell production occurs by mitosis in the deeper layers, older cells are at the surface and eventually desquamate (slough off) – new skin every 25-45 days (10 lbs a year) • Keratinocytes at stratum comeum are dead 6 Epidermis 4 cell types: 1. Keratinocytes 2. Melanocytes 3. Langerhans' cells 4. Merkel cells 7 Epidermis 1. Keratinocytes •produce keratin •Keratin is an intracellular fibrous protein that gives hair, nails and skin their hardness and water- resistant properties. •produced at the basal layer of skin and migrate (get pushed) upward •when they reach the free surface of the skin they are dead (membrane bound bags of keratin) •Tightly connected by desmosomes •Millions slough off everyday 8 Epidermis 2. Melanocytes • synthesize melanin (pigment) • found in the deepest layer of the epidermis • Melanin made and accumulated in melanosomes- intercellular vesicles • melanin moves into spidery arms of melanocytes and taken up (passed to) by keratinocytes • shade the kertinocyte nucleus – UV protections, production is stimulated by UV . • Important because UV has enough energy to break chemical bonds 9 Epidermis 3. Merkel cells • found in epidermal/dermal junction • associated with nerve endings, remember epithelial tissue does not have nerves • Merkel cell + nerve = touch receptor 10 Epidermis 4. Langerhans’cell • arise from bone marrow and migrate to epidermis • Function as macrophages engulfing bacteria, foreign particle and damaged cells that occurs in the layer • macrophages that activate immune system • form a network (layer) in the epidermis – an immune barrier. 2 line of defense 11 Layers of the Epidermis • Epidermis is made up of four or five distinct layers – Thick skin contains five layers (strata) and is found in high-abrasion areas (hands, feet) – Thin skin contains only four strata • Five layers of skin 1. Stratum basale 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum (only in thick skin) (like sole of foot or palm of hand) 5. Stratum corneum 13 Stratum corneum (horny layer) • outer most stratum, superficial layer and exposed to the outside environment • 20-30 cells thick keratin and thickened plasma membranes protect against abrasion and penetration •Also prevents dehydration of underlying tissues •glycolipid between cells waterproof •The entire layer is replaced during a period of about 4 weeks 14 Stratum lucidium •2-3 layers of dead cells filled with keratin •this layer appears clear when viewed under a microscope •smooth and seemingly translucent layer of the epidermis •the cells are densely packed with eleiden, a clear protein rich in lipids, derieved from keratohyalin, which gives the transparent appearance and provides a barrier to water •only present in thick skin (palms, fingertips, soles of feet) •lies superficial to the stratum granulosum 15 Stratum granulosum •3-5 layers of cells that are alive but organelles are beginning to disintegrate •2 populations of granules in the cells •keratohyline granules– which forms keratin •lamellated granules - which forms waterproofing glycolipids 16 Stratum spinosum – Several cell layers thick (5-7) – Cells contain weblike system of intermediate prekeratin filaments attached to desmosomes • Allows them to resist tension and pulling – Keratinocytes in this layer appear spikey, so they are called prickle cells – Scattered among keratinocytes are abundant melanosomes and dendritic cells (produced by underlying melanocytes) •Contains melanin granules produced by underlying melanocytes •Langerhan’s cell network in this layer…immune cells 17 Stratum Basale • Deepest epidermal layer • Attaches epidermis to basal lamina, below which lie the layers of the dermis (Layer that is firmly attached to dermis) – Consists of a single row of stem cells that actively divide (mitotic), producing two daughter cells each time • One daughter cell journeys from basal layer to surface, taking 25–45 da– Cell dies as it moves toward surface • Other daughter cell remains in stratum basale as stem cell – Layer also known as stratum germinativum because of active mitosis – 10–25% of layer also composed of melanocytes – Melanin produced here is transported up to the Stratum Spinosum – Small percentage of merkell cells – These are part of nerve receptor, associated with nerve fibers in the underlying connective tissue 18 Dermis • The dermis might be considered the “core” of the integumentary system • Innermost layer • Made of dense irregular connective tissue • It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. • The dermis is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts 19 Dermis: 2 layers • Papillary layer • just below stratum basal of epidermis • made of areolar connective tissue with collagen and elastic fibers very vascularized • projections called dermal papillae extend superiorly and indent the epidermis • on palms and soles they are larger and the dermal papillae lay on top of dermal ridges, together they form an epidermal ridge (fingerprints) – Dermal papillae can contain capillary loops, free nerve endings (meissners corpusles- touch receptors) 20 micrograph of the dermis. Epidermis Papillary layer Dermis Reticular layer © 2016 Pearson Education, Inc. Reticular layer •80% of dermis, thicker layer •dense irregular connective tissue with large bundles of collagen and elastin •elastin fibers provide some elasticity to the skin •collagen binds water to keep the skin hydrated •most fibers run parallel with skin •separation of less dense regions between bundles form cleavage or tension lines - hard to see—can see them on your arms •flexor lines – folds that occur near joints where skin can’t move freely, palm lines 22 Dermal modifications result in characteristic skin markings. Flexure lines on digit Flexure lines on the palm Flexure lines of the © 2016 Pearson Education, Inc. Hypodermis • Beneath the dermis, deep dermal layer • Not considered true integumentary layer, but has important functions • stores fat for insulation and shock absorption • anchors skin to underlying bone and muscle • Pathway for blood vessels, nerves, to reach skins upper layers 24 Skin color : Pigmentation – Only thing that is different in different races, not even a difference in anatomy, physiological difference – 3 pigments, melanin, carotene, hemoglobin determine color Melanin is the major player made of tyrosin (AA) range in color from yellow to reddish brown to black color depends on enzyme in melanocytes tyrosinase, cuts the amino acid chain at different lengths passed to melanosomes in keratinocytes • ***Skin color depends on amount of GET THE REST OF THIS BULLET 25 Skin color – Freckles and moles are local accumulations of melanosomes – Light stimulates melanocytes to make melanin – tan • helps protect DNAby absorbing the light • remember that UV has the ability to break bonds – Another protein, Carotene is a yellow to orange pigment- usually found in plants (carrots) • only provides a small amount of color • accumulates in stratum corneum and in fatty tissue of hypodermis • most obvious in thickened skin (palms and soles) 26 Accessory structure of skin • Three anatomical features of skin that are important (Hair, nails and glands) • Glands: important physiological features of skin • 4 types: sweat glands Sudoriferous- Two main types – Eccrine(merocrine) sweat glands – Apocrine sweat glands – Merocrine/eccrine (exocytosis) – Apocrine (pinching) 27 28 Accessory structure of skin • Sudoriferous glands produce sweat to cool the body • Sweat glands develop from epidermal projections • The secretions are excreted by exocytosis through a duct without affecting the cells of the gland • Two types of sweat glands, each produce slightly different products 29 Merocrine/ eccrine (exocytosis) –most common (2.5 million) –Produce hypotonic sweat for thermoregulation –has a deep coiled secretory portion in the dermis with a releasing duct that extends to the surface of the epidermis to a pore –secretion is sweat = water and salt, blood filtrate, also contains vit C and a microbialcide called dermicidin, some nitrogenous waste (urine) –prevents over heating of the body through evaporative heat loss, maintains homeostasis –glands located every where except nipples and genitalia most common on hands and forehead 30 Apocrine sweat glands(pinching) –less abundant (rare) but larger than eccrine –coiled secretory portion has a duct that opens in to hair follicles (different) –found in the axillary (arm pit) and pubic regions -Secrete viscous milky or yellowish sweat that contains fatty substances and proteins –odorless when first released, bacteria break down sweat, leading to body odor –sticky and viscous, causes yellow pits –not active until puberty, secretion under nervous and hormonal control –though to be analogous to sexual scent glands of lower mammals (pheromones) 31 Ceruminous glands- ear wax • Modified apocrine glands found in the lining of the ear • Secrete a sticky bitter substance called cerumen • Insect deterrent, block foreign objects from entering ear 32 Mammary glands –specialized sweat glands (modified apocirne gland) that secrete milk- in one tribe the man lactates too bc they put hormones on their nipples Sebaceous Glands (oil) – alveolar gland - present everywhere except palms and soles of feet - particularly numerous on face neck and chest - secrete sebum -made of oily lipid and cell fragments, Oily holocrine secretion -bactericidal properties - softens and lubricates hair and skin - when a gland becomes blocked by excess sebum, forms a pimple -if excess oxidizes and dries = blackhead -if not, infected=whitehead -become active during puberty 33 Hair – Hair is a karatinous filamentous growing out of the epidermis – Made of dead keratinized cells – every where accept, palms, soles, lips, nipples, external genitalia – used to sense things touching us, head hair guards against heat loss, physical trauma (cushion), light (sunblock), filter things (nose, ears –dirt, bugs, eyelashes, eyebrows-sweat) – hair growth: 2.5 mm per week grows in cycles – anagen – growing- phase, – catagen – regressive phase – cells that produce hair die and the bulb of the hair shrivels – telegen resting phase, after rest the hair cells proliferate again to form a new hair, the old one falls out – head hair follicles remain active (in anagen) for 6-10 yrs, lose 90 hairs a day, eyebrows 3-4 mo • longer they are active, longer you can grow your hair. 34 Hair follicle •Hair matrix is the actively dividing area of the bulb that makes hair •Associated with each hair follicle are smooth muscle cells called arrector pili muscles •Contracts in response to cold temps or a frightening situation, pulling follicle upright (hair stands on end) •Shape of follicle determine texture of hair flat=curly round = straight 35 – Baldness • hair follicles have limited cells, if hair is not replaced as quickly as it falls out, thinning results or baldness (alopecia) • terminal hair is replaced by thin whispy vellus hair (infant hair) • male pattern baldness is the most common, genetically determined • a gene in the follicle changes its sensitivity to DHT(Dehydrotestoterone) in adulthood, shortens the follicular growth cycle so that hairs are shed before they even grow long enough to exit the follicle 36 • Nails – scale like modification of the epidermis, hard keratin • Integument system function- – Protection – forms a barrier 3 ways • chemical barrier –skin secretions are slightly acidic which slows bacterial growth – acid mantle –bactericidal substances in sebum, human defensin in skin – protective peptides, –melanin protects again UV rays bc UV can break down your DNAand when DNAis mutated can lead to problems 37 • Physical barrier –continuity of skin and hardness of keratinized cells limits entry of foreign substances –glycolipids make skin water proof, but some things can pass through mehg –hair »on the head for insulation » eyebrows slow flow of sweat into the eyes »in hose and ear trap airborne particles –Biological barriers »Langerhan’s ells help activate immune system »dermal macrophages are phagocytic cells that defend again micro organisms »DNAabsorbs UV radiation and transfers it to atomic nuclei as heat which dissipates in water 38 • Body temperature regulation –increase in temperature stimulates sweat glands to begin secretory activity –evaporation of sweat pulls heat away from the body and cools us (500 ml to 12 L a day) –in cold weather blood vessels constrict so warm blood bypasses the skin, allowing skin temp to drop and conserve heat in the body core – cold hands • Sensation – cutaneous receptors (exteroceptors) – Important for sexual arousal so we will keep reproducing 39 –Epidermis touch receptors meissner’s corpuscles –Dermis touch receptors – associated with merkel cells in epidermis pain receptors – nociceptors temp receptors – thermoreceptors pressure receptors hair follicle receptors – hair movement 40 • Metabolism –when the skin is exposed to sunlight, cholesterol in the blood is converted to vitamin D precursor –transported to the liver and kidneys to be metabolized into vitamin D –vit D aids in Ca absorption in the small intestine –skin cells produce some important proteins, i.e. collagenase • Blood reservior –holds 5% of blood volume, when organs need more blood, shunted from skin-shock=pale • Excretion –limited amounts of nitrogenous waste via sweat glands 41 Burns • causes tissue damage resulting from excessive heat or exposure to chemicals • catastrophic loss of body fluids containing proteins and electrolytes-this leads to dehydration and electrolyte imbalance and then renal failure (kidney shut down) and circulatory shock (inadequate blood circulation due to reduced blood volume) 42 Burns • example of 1st degree burn • most sunburns • 2nd degree burn (deep partial thickness burn) • damages the epidermis and upper layer of the dermis • symptoms of 2nd degree burn • mimic 1st degree burn but with blisters • healing of 2nd degree: burned area is red and painful but skin regeneration occurs with little or no scarring within 3 to 4 weeks if skin is taken care of properly 43 Burns • to save a patient suffering from severe burns • the lost fluids must be replaced immediately via intravenous (IV) route • examples of 3rd degree burn • burned area appear, gray-white, cheery red, or blackened but little or no edema • treatment of 3rd degree • nerve endings destroyed so no pain, skin grafting is advised • burns are considered critical if (3) 44 Burns rule of nines : a method used to estimate the extent and severity of burns rule of nines divides body into 11 areas, each accounting for 9% of the total body area plus 1% for the genitals sections of rule of nines (5) 1. head and neck- 9% 2. upper limbs- 18% 3. trunk-36% 4. perineum-1% 5. lower limbs- 36% 45 Developmental Aspects of the Integumentary System • Infancy to adulthood: skin thickens and accumulates more subcutaneous fat; sweat and sebaceous gland activity increases, leading to acne – Optimal appearance during 20s and 30s – After age 30, effects of cumulative environmental assaults start to show – Scaling and dermatitis become more common Developmental Aspects of the Integumentary System • Aging skin – Epidermal replacement slows; skin becomes thin, dry, and itchy (decreased sebaceous gland activity) – Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles – Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells – Hair thinning • Ways to delay aging: – UV protection, good nutrition, lots of fluids, good hygiene
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