Bio 201 Lecture 1: Integumentary System PDF

The Integumentary System  Introduction Integumentary system – Consists of The skin and its accessory organs; hair, nails, and cutaneous glands (sweat gland and sebaceous glands) 6-2 ...

The Integumentary System  Introduction Integumentary system – Consists of The skin and its accessory organs; hair, nails, and cutaneous glands (sweat gland and sebaceous glands) 6-2  Introduction Integumentary system – We pay more attention to the integumentary system than any other organ system: self image, social acceptance… – Aside from self image and social acceptance, appearance of the skin can give clues about your health; anemia. – Inspection of the skin, hair, and nails is significant part of a physical exam – Skin is the most vulnerable organ Exposed to radiation, trauma, infection, and injurious chemicals – Receives more medical treatment than any other organ system – Dermatology—scientific study and medical treatment of the integumentary system 6-3  Structure of the Skin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hairs Sweat pores Dermal papilla Tactile corpuscle Epidermis (touch receptor) Blood capillaries Hair follicle Dermis Sebaceous gland Hair receptor Apocrine sweat gland Hair bulb Hypodermis (subcutaneous fat) Sensory Merocrine sweat nerve fibers gland Piloerector muscle Cutaneous blood vessels Lamellar (pacinian) corpuscle (pressure receptor) Motor nerve fibers 6-4  Skin structure. Hair shaft Dermal papillae Epidermis Subpapillary Papillary plexus layer Sweat pore Appendages of skin Dermis Reticular Eccrine sweat gland layer Arrector pili muscle 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)  The Skin and Subcutaneous Tissue The body’s largest and heaviest organ – Covers area of 1.5 to 2.0 m2 – 15% of body weight – Most skin is 1 to 2 mm thick Two layers – Epidermis: stratified squamous epithelium – Dermis: connective tissue layer 6-6 Epidermis Dermis The Skin and Subcutaneous Tissue Hypodermis—another connective tissue layer below the dermis. It is not part of the skin but we will study in conjunction with the skin. 6-9 Hypodermis The Skin and Subcutaneous Tissue Skin is normally 1-2 mm thick but thickness of the skin ranges. Thick skin—on palms and sole, and corresponding surfaces on fingers and toes – Has sweat glands, but no hair follicles or sebaceous (oil) glands – Epidermis 0.5 mm thick Thin skin covers rest of the body – Epidermis about 0.1 mm thick – Possesses hair follicles, sebaceous glands, and sweat glands 6-11 Thick Skin Thin Skin  Thick Skin Low Magnification Stratum corneum Epidermis Stratum lucidum Dermis Duct of merocrine sweat gland Stratum granulosum Dermal papillae Stratum basale Stratum  Thick Skin Stratum corneum High Magnification Epidermis Stratum lucidum Stratum granulosum Stratum spinosum Dermis Stratum basale  Thick Skin Histology Epidermis Dermis Corneum Lucidum Granulosum Spinosum Basale Thin Skin  Thin Skin Stratum corneum High Magnification Stratum Epidermis granulosum Stratum spinosum Stratum Dermis basale  Thin Skin Histology Epidermis Dermis Subcutaneous layer Sweat glands Hair follicle Sebaceous gland  Functions of the Skin Resistance to trauma and infection – Keratin (the epidermal cells are packed with though protein: keratin) with strong desmosomes makes skin durable. few infectious organism can penetrate into skin. – Acid mantle (pH 4-6) Other barrier functions – Waterproofing: we don’t absorb water while we swim. – UV radiation – Barrier to Harmful chemicals, exceptions: Mercury, arsenic, lead, acetone, Hydrocortisone ointment (for inflammation), 6-20  Functions of the Skin Vitamin D synthesis – Skin first step – Liver and kidneys complete process Sensation – Skin is our most extensive sense organ contains variety of nerve endings that react to heat, cold, touch, texture, pressure etc. Thermoregulation – Thermoreceptors monitors surface temperature – Vasoconstriction/vasodilation 6-21  Functions of the Skin Nonverbal communication – Face expressions Transdermal absorption – Administration of certain drugs steadily through thin skin via adhesive patches Hydrocortisone ointment (for inflammation) 6-22 Epidermis  Layers of the skin Epidermis – Stratum corneum – Stratum lucidim (thick skin only) – Stratum granulosum – Stratum spinosum – Stratum basale Dermis – Papillary layer – Reticular layer 6-24  The Epidermis Epidermis—keratinized stratified squamous epithelium – Dead cells at the surface packed with tough protein called keratin – Lacks blood vessels – Depends on the diffusion of nutrients from underlying connective tissue – Sparse nerve endings for touch and pain 6-25  Cells of the Epidermis Five types of cells of the epidermis – Stem cells – Keratinocytes – Melanocytes – Tactile (Merkel) cells – Dendritic (Langerhans) cells 6-26  Cells of the Epidermis Five types of cells of the epidermis – Stem cells Undifferentiated cells that give rise to keratinocytes In deepest layer of epidermis (stratum basale) – Keratinocytes Great majority of epidermal cells Synthesize keratin – Melanocytes Occur only in stratum basale Synthesize pigment melanin that shields DNA from ultraviolet radiation Branched processes that spread among keratinocytes 6-27  Cells of the Epidermis Cont. – Tactile (Merkel) cells In basal layer of epidermis Touch receptor cells associated with dermal nerve fibers – Dendritic (Langerhans) cells Macrophages originating in bone marrow that guard against pathogens Found in stratum spinosum and granulosum Stand guard against toxins, microbes, and other pathogens that penetrate skin 6-28  Cells of the Epidermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sweat pore Stratum corneum Exfoliating Stratum lucidum keratinocytes Stratum granulosum Dead keratinocytes Sweat duct 1. keratinocytes Stratum spinosum 2. Dendritic cell 3.Tactile cell 4. Melanocyte 5. Stem cell Stratum basale Dermal papilla Tactile nerve fiber Dermis Dermal blood vessels Figure 6.3 6-29  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) 5. Stratum corneum  Layers of the Epidermis 1. Stratum basale – A single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane – Melanocytes and tactile cells are scattered among the stem cells and keratinocytes Stem cells of stratum basale divide – Give rise to keratinocytes that migrate toward skin surface – Replace lost epidermal cells 6-31  Layers of the Epidermis 2. Stratum spinosum – Produce more and more keratin filaments which causes cell to flatten; the higher up in this stratum, the flatter the cells appear Dendritic cells found throughout this stratum Named for artificial appearance created in histological section – Numerous desmosomes and cell shrinkage produces spiny appearance – Consists of several layers of keratinocytes 6-32  Layers of the Epidermis Stratum spinosum: Thickest stratum in most skin – In thick skin, exceeded by stratum corneum Deepest cells remain capable of mitosis – Cease dividing as they are pushed upward 6-33  Layers of the Epidermis 3. Stratum granulosum – Consists of three to five layers of flat keratinocytes – Contains coarse dark-staining keratohyalin granules 6-34  Layers of the Epidermis 4. Stratum lucidum – Seen only in thick skin Thin translucent zone superficial to stratum granulosum Keratinocytes are densely packed with eleidin Cells have no nucleus or other organelles Zone has a pale, featureless appearance with indistinct boundaries 6-35  Layers of the Epidermis 5. Stratum corneum – Up to 30 layers of dead, scaly, keratinized cells Form durable surface layer – Surface cells flake off (exfoliate) Resistant to abrasion, penetration, and water loss 6-36  Cells of the Epidermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sweat pore Stratum corneum Exfoliating Stratum lucidum keratinocytes Stratum granulosum Dead keratinocytes Sweat duct Living keratinocytes Dendritic cell Stratum spinosum Tactile cell Melanocyte Stem cell Stratum basale Dermal papilla Tactile nerve fiber Dermis Dermal blood vessels Figure 6.3 6-37  Stratified Squamous Epithelium (Keratinized) Epidermi Dermi s s (Stratified squamous epithelium) Stratum Stratum Stratum Stratum spinosum granulosum corneum basale  Thin Skin Stratum corneum High Magnification Stratum Epidermis granulosum Stratum spinosum Stratum Dermis basale  Thin Skin Histology Epidermis Dermis Subcutaneous layer Sweat glands Hair follicle Sebaceous gland  The Life History of a Keratinocyte Keratinocytes are produced deep in the epidermis by stem cells in stratum basale – Some deepest keratinocytes in stratum spinosum also multiply and increase their numbers Mitosis requires an abundant supply of oxygen and nutrients – Deep cells acquire oxygen from blood vessels in nearby dermis – Once epidermal cells migrate more than two or three cells away from the dermis, their mitosis ceases 6-41  The Life History of a Keratinocyte Newly formed keratinocytes push the older ones toward the surface In 30 to 40 days a keratinocyte makes its way to the skin surface and flakes off – Slower in old age – Faster in injured or stressed skin (mechanical stress) Calluses or corns—thick accumulations of dead keratinocytes on the hands or feet As keratinocytes are pushed upward by the cell below they flatten and produce – More keratin filaments and – lipid-filled membrane-coating vesicles (lamellar granules) 6-42  The Life History of a Keratinocyte In stratum granulosum Four important developments occur 1.Keratohyalin granules release a protein filaggrin Binds the cytoskeletal keratin filaments together into coarse, tough bundles 2.The cell produce very though layer of envelope protein just beneath the plasma membrane resulting in nearly indestructible protein sac around the keratin bundle 3.Membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it 4.As these barriers cut kerotinocytes from the nutrient supply, Keratinocyte nucleus and other organelles degenerate; cells die, leaving waterproof sac enclosing coarse bundle of keratin. Epidermal water barrier—these process along with the tight junctions b/w keratinocytes forms epidermal water barrier-crucial to water retention 6-43  The Life History of a Keratinocyte Water barrier consists of: – Lipids secreted by keratinocytes – Tight junctions between keratinocytes – Thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes Critical to retaining water in the body and preventing dehydration Cells above the water barrier quickly die – Barrier cuts them off from nutrients below – Dead cells exfoliate (dander) – Dandruff: clumps of dander stuck together by sebum (oil) – Dead skin and dust mites. 6-44 Dermis  The Dermis Dermis—connective tissue layer beneath the epidermis – Ranges from 0.2 mm (eyelids) to 4 mm (palms, soles) – Composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts – Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings 6-46  The Dermis Hair follicles and nail roots are embedded in dermis – Smooth muscle (piloerector muscles) associated with hair follicles – Contract in response to stimuli such as cold, fear, and touch—goose bumps 6-47  The Dermis Dermal papillae— upward fingerlike extensions of the dermis, Dermal – Friction ridges on papillae fingertips that leave fingerprints Epidermal ridges- downward epidermal waves b/w dermal Epidermal papillae ridges 6-48  The Dermis There are 2 zones of the dermis: – Papillary layer Epidermis – Reticular layer Papillary layer Dermis Reticular layer 6-49  The Dermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6-50 Figure 6.5a  The Dermis There are 2 zones of the dermis: papillary and reticular layers: Papillary layer—superficial zone of dermis – Thin zone of areolar tissue in and near the dermal papilla – Allows for mobility of leukocytes and other defense cells should epidermis become broken – Rich in small blood vessels Reticular layer—deeper and much thicker layer of dermis – Consists of dense, irregular connective tissue – Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity 6-51 Hypodermis  The Hypodermis Hypodermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display – Subcutaneous tissue – More areolar and adipose than dermis – Pads body – Binds skin to underlying tissues Drugs introduced by injection – Highly vascular and absorbs them Subcutaneous fat: quickly Energy reservoir Thermal insulation 8% thicker in women, infants and elderly has less SubQ fat so they are more sensitive to cold 6-53  Skin Color Melanin—most significant factor in skin color – Pigment produced by melanocytes – Accumulate in the keratinocytes of stratum basale and stratum spinosum – Eumelanin—brownish black – Pheomelanin—a reddish yellow sulfur-containing pigment 6-54  Skin Color People of different skin colors have the same number of melanocytes – Dark-skinned people Produce greater quantities of melanin Melanin granules in keratinocytes more spread out than tightly clumped Melanin breaks down more slowly Melanized cells seen throughout the epidermis – Light-skinned people Melanin clumped near keratinocyte nucleus Melanin breaks down more rapidly Little seen beyond stratum basale 6-55  Skin Color Amount of melanin also varies with exposure to ultraviolet (UV) rays of sunlight 6-56  Skin Color Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stratum corneum Stratum corneum Epidermis Epidermis Melanized cells of stratum basale Dermis (a) Dark skin (b) Light skin © The McGraw-Hill Companies, Inc./Dennis Strete, photographer; b(inset): © Creatas/PunchStock © The McGraw-Hill Companies, Inc./Dennis Strete, photographer; a(inset): © Tom & Dee Ann McCarthy/Corbis Hemoglobin—red pigment of red blood cells – Adds reddish to pinkish hue to skin Carotene—yellow pigment acquired from egg yolks and yellow/orange vegetables – Concentrates in stratum corneum and subcutaneous fat 6-57  Skin Color Colors of diagnostic value Cyanosis—blueness of the skin from deficiency of oxygen in the circulating blood – Airway obstruction (drowning or choking) – Lung diseases (emphysema or respiratory arrest) – Cold weather or cardiac arrest – Methemoglobinemia: – Oxidized hemoglobin, acquired and genetic – Blue Fugate of Kentucky – http://abcnews.go.com/Health/blue-skinned-people-kentucky-reve al-todays-genetic-lesson/story?id=15759819 Erythema—abnormal redness of the skin due to dilated cutaneous vessels – Exercise, hot weather, sunburn, anger, or embarrassment 6-58  Skin Color Colors of diagnostic value Pallor—pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen is visible – Emotional stress, – low blood pressure, – circulatory shock, – cold, – anemia Albinism—genetic lack of melanin that results in white hair, pale skin, and pink eyes – Have inherited recessive, nonfunctional tyrosinase allele 6-59  Skin Color Cont. Jaundice—yellowing of skin and sclera due to excess of bilirubin in blood – Cancer, hepatitis, cirrhosis, other compromised liver function Hematoma (bruise)—mass of clotted blood showing through skin 6-60  The Evolution of Skin Color Skin color varies from people to people; – Results from combination of different factors – Especially differences in exposure to ultraviolet radiation (UVR) – Populations native to the tropics and their descendants tend to have well-melanized skin to screen out excessive UVR – Populations native to far northern or southern latitudes where the sunlight is weak, tend to have light skin to allow for adequate UVR penetration – High altitude and dry air increases skin pigmentation Andes, Tibet, Ethiopia 6-61  The Evolution of Skin Color Ancestral skin color is a compromise between vitamin D and folic acid requirements Women have skin averaging about 4% lighter than men – Need greater amounts of vitamin D and folic acid to support pregnancy and lactation UVR accounts for up to 77% of variation in human skin color 6-62  UVR and Skin UVR has two adverse effects – Causes skin cancer – Breaks down folic acid needed for normal cell division (synt. DNA), fertility, and (sperm count, birth defects etc,) fetal development UVR has one desirable effect – Stimulates synthesis of vitamin D necessary for dietary calcium absorption 6-63  Skin Markings Friction ridges—(made by dermal papillae) the markings on the fingertips that leave oily fingerprints on surfaces we touch – Everyone has a unique pattern formed during fetal development that remains unchanged throughout life – Not even identical twins have identical fingerprints – Allow manipulation of small objects Flexion lines (flexion creases)—lines on the flexor surfaces of the digits, palms, wrists, elbows – Marks sites where the skin folds during flexion of the joints 6-64  Skin Markings Freckles and moles—tan to black aggregations of melanocytes – Freckles are flat, melanized patches – Moles (nevus) are elevated melanized patches often with hair Moles should be watched for changes in color, diameter, or contour May suggest malignancy (skin cancer) Hemangiomas (birthmarks)—patches of discolored skin caused by benign tumors of dermal blood capillaries – Some disappear in childhood, others last for life – Capillary hemangiomas, cavernous hemangiomas, port- wine stain, mongolian spots 6-65 Mongolian spot: congenital dermal melanocytosis