Unit 3 The Integumentary System. Skin PDF

3.1 General characteristics Unit 3 INTEGUMENTARY SYSTEM. SKIN. 3.2 Structure of the skin 3.2.1. Epidermis 3.2.2. Dermis 3.3 Accessory structures of the skin. 3.3.1 Hair Ve más allá 3.3.2 Glands 3.4 Functions of skin OUTLINE 3.1 General characteristics 3.2 Structure of the skin 3.2.1. Epidermis...

3.1 General characteristics Unit 3 INTEGUMENTARY SYSTEM. SKIN. 3.2 Structure of the skin 3.2.1. Epidermis 3.2.2. Dermis 3.3 Accessory structures of the skin. 3.3.1 Hair Ve más allá 3.3.2 Glands 3.4 Functions of skin OUTLINE 3.1 General characteristics 3.2 Structure of the skin 3.2.1. Epidermis 3.2.2. Dermis 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados GENERAL CHARACTERISTICS § STRUCTURE Tegumentum = cover Skin Only a few mm thick yet the largest organ in the body. Accessory structures: Hair Nails Glands © Copyright Universidad Europea. Todos los derechos reservados GENERAL CHARACTERISTICS § FUNCTION One of the most active systems in our body © Copyright Universidad Europea. Todos los derechos reservados • It is the first line of defense against foreign organisms and the external environment. • It helps to regulate body temperature. • It senses changes in the environment (pain, pressure, touch). • It supports the removal of wastes (as sweat). • It aids in the production of vitamin D. SKIN FACTS § CUTANEOUS MEMBRANE Surface: 2m2 surface Weight: 4.5-5 Kg Largest organ Depth: 0.5-4 mm (1-2mm) Acid pH (5.5) Covered by hair (except palmar and plantar region) Pigmentation: melanin. Homeostasis. © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.1 General characteristics 3.2 Structure of the skin 3.2.1. Epidermis 3.2.2. Dermis 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE OF THE SKIN § CUTANEOUS MEMBRANE TWO LAYERS Epidermis = epithelial tissue Dermis = connective tissue Innervation Vascularization Hypodermis or subcutaneous tissue (adipose tissue + areolar connective tissue) Energy storage / Physical protection © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE OF THE SKIN § CUTANEOUS MEMBRANE Epidermis Dermis Adipose tissue Blood vessel Loose connective tissue © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados EPIDERMIS Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum or malpighian stratum Stratum basale Keratinized stratified squamous epithelium •Avascular. •Nervous sensory ends. •4 types of tightly bound cells. •5 distinct strata (layers) of cells. © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados CELLs IN EPIDERMIS § Keratinized stratified squamous epithelium 90% © Copyright Universidad Europea. Todos los derechos reservados 8% KERATINOCYTES - The most abundant cell of skin (90%) - Arranged in 5 layers at different developmental stages: continuous renewal. - They produce keratin: fibrous protein _ protection (abrasion, heat, microbes). - They produced lamellar granules (water repellent). © Copyright Universidad Europea. Todos los derechos reservados Primary Human Epidermal Keratinocytes cultured in NHEK-GM were stained for Keratin 14 (pink), Phalloidin (blue) and Ki67 (yellow). MaTek © Copyright Universidad Europea. Todos los derechos reservados 15 MELANOCYTES -They represent 8% of the cells of the skin. -Location: stratum basale. -They produce melanin (granules). -Melanin: colour absorption). © Copyright Universidad Europea. Todos los derechos reservados and protection (UV MELANOCYTES - KERATINOCYTES § MELANIN • Melanin granules form a protective veil over the nucleus of keratinocytes, on the side toward the skin surface. They shield the nuclear DNA from damage by UV light. • Melanin granules = MELANOSOMES. Transferred to keratinocytes by means of a secretion process from the “dendrite like” extensions of melanocytes. © Copyright Universidad Europea. Todos los derechos reservados LANGERHANS CELLS § IMMUNE CELLS - They represent 3-4% of epidermal cells - Located in strata with living cells (most abundant in the spinosum). - Epidermal dendritic cells. - Function: immune response: antigenpresenting cells. - Derive from the bone marrow. © Copyright Universidad Europea. Todos los derechos reservados MERKEL CELLS ANDE MERKEL DISCS (NERVE TERMINALS) § SENSORY CELLS - Located in the stratum basale, associated with sensory neurons. - Function: tactile sensations. © Copyright Universidad Europea. Todos los derechos reservados © Copyright Universidad Europea. Todos los derechos reservados 21 OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados EPIDERMAL LAYERS § 4 or 5 different layers or strata © Copyright Universidad Europea. Todos los derechos reservados STRATUM BASALE § DEEPEST layer Deepest layer, on top of basement membrane. Monolayer of cuboidal cells. Keratinocytes: present a cytoskeleton of tonofilaments (precursors of keratin). Intercalated Merkel cells, Langerhans cells and melanocytes. Function: germinative, proliferation. Stem cells: high proliferation rate. Function: structural and support. Skin grafts require a healthy stratum basale. © Copyright Universidad Europea. Todos los derechos reservados STRATUM SPINOSUM OR MALPIGHI’S STRATUM § Second DEEPEST layer •8 to 10 layers of (mechanical strength). keratinocytes Ø In histological preparations, cells shrink and appear spiny (where attached to other cells by desmosomes). In live skin they are rounded and big. Ø Langerhans cells and cellular projections from melanocytes (melanin captured by keratinocytes). Function: provides strength and flexibility to skin. © Copyright Universidad Europea. Todos los derechos reservados STRATUM GRANULOSUM 3-5 layers of flat keratinocytes. Keratinocytes contain lamellar granules (secretory organelles with lipids that repel water). •Cells contain dark keratohyalin granules. Ø Keratohyalin is a protein that assembles tonofilaments into keratin. In the top layers the cells degenerate and die. Function: prevents water loss physical barrier to microorganisms © Copyright Universidad Europea. Todos los derechos reservados STRATUM LUCIDUM § ONLY present in THICK SKIN •3 to 5 layers of clear, flat, dead keratinocytes (without nucleus). •Present only in the palms of the hands and soles of the feet. •Cells contain large amounts of keratin. •Function: protection © Copyright Universidad Europea. Todos los derechos reservados STRATUM CORNEUM § Most SUPERFICIAL layer •25 to 30 layers of flat dead keratinocytes filled with keratin and surrounded by lipids. –continuous shedding. •Barrier to light, heat, water, chemicals & bacteria •Lamellar granules in this layer make it water-repellent. •Constant exposure to friction will cause this layer to increase in depth with the formation of a callus, an abnormal thickening of the epidermis. •Functions: •Impermeable •Protection © Copyright Universidad Europea. Todos los derechos reservados LAYERS OF THE EPIDERMIS: THICK AND THIN SKIN Thin skin / Thick skin • Stratum corneum. • Stratum lucidum. • Stratum granulosum. • Stratum spinosum or Malpighi’s. • Stratum basale or germinative. © Copyright Universidad Europea. Todos los derechos reservados http://www.youtube.com/watch?v=OZzYrRf0ICE http://www.youtube.com/watch?v=o3so9gKQItE&feature =relmfu © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados GROWTH AND KERATINIZATION GROWTH: constant cell division from stratum basale. Keratinization: replacement of keratinocytes’ intracellular content by keratin during their migration towards the surface. Scaling and replacement occurs in a two to three week’s period time. Abrasion / burns: increased mitotic rate in stratum basale. Epidermal growth factor (EGF) © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados STRUCTURE OF THE DERMIS § Connective tissue. Cells: fibroblasts, macrophages and adipose cells. - Extracellular matrix : Collagen: resistance. Elastic fibers: flexibility. Ground surface: GAGs. •Function: structural, immunological, mechanical protection, homeostasis control (thermoregulation, water retention) Blood vessels (deep & superficial) Hair follicles. Sebaceous glands, sweat glands. Nerve endings © Copyright Universidad Europea. Todos los derechos reservados DETECTING SENSATIONS through your skin Free nerve terminals and corpuscular receptors FINE touch; localization of the stimulus FINE touch; localization of the stimulus Vibration Vibration CRUDE touch; non localized stimulus Stretch of skin, Sustained pressure - Mechanoreceptors - Thermoreceptors - Nociceptors (pain receptors) - Proprioceptors (receptors of position) © Copyright Universidad Europea. Todos los derechos reservados Functions of Mechanoreceptors Mnemonic: The superficial receptors detect touch and the deep receptors detect pressure. Meissner is smooth to pronounce – found on smooth skin and detects smooth (fine) touch. Merkel is harder to pronounce – found also on hairy skin and detects crude touch. ViP STaR Vibration: Pacinian corpuscle Stretch and Temperature (warm): Ruffini endings Krause bulb = Kelvin = Kold (Cold) © Copyright Universidad Europea. Todos los derechos reservados 38 DETECTING SENSATIONS through your skin Mechanoreceptors: pressure, vibrations and texture © Copyright Universidad Europea. Todos los derechos reservados © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados DERMIS: PAPILLARY REGION § Areolar connective tissue (thin collagen and fine elastic fibers) 20% of dermis- Close to epidermis Structure: Pilous follicles (scarce). Sebaceous and sweat glands (ducts). Free nerve endings (pain, warmth, coolness, tickling, itching). Fine touch receptors. Hair Arrector pili muscle Pore Sebaceous glands Epidermis Krause corpuscle Dermis Free nerve terminals Ruffini corpuscle Fat layer Meissner corpuscle © Copyright Universidad Europea. Todos los derechos reservados Pacinian corpuscle DERMIS: PAPILLARY REGION DERMAL PAPILLAE ØIncrease contact surface between dermis and epidermis (stratum basale). ØInterdigitations into the epidermis form epidermal ridges. ØContains capillaries: nutrition of the epidermis. ØContains corpuscular receptors (mechanoreceptors: Meissner corpuscles) and free nerve endings (pain, burn, itching). © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.2 Structure of the skin 3.2.1. Epidermis 3.2.1.1 Cells 3.2.1.2 Layers: thin and thick skin 3.2.1.3 Growth and keratinization of the epidermis 3.2.2. Dermis 3.2.2.1 Structure 3.2.2.2 Papillary region 3.2.2.3 Reticular region © Copyright Universidad Europea. Todos los derechos reservados DERMIS: RETICULAR REGION DENSE IRREGULAR CONNECTIVE TISSUE •Thick collagen fibers (resistance) and elastic fibers (elasticity) •Sweat and oil glands, pilous follicles, Pacinian corpuscles, adipocytes and fibroblasts. •Function: provides resistance, extensibility and elasticity. © Copyright Universidad Europea. Todos los derechos reservados DERMIS: INFOGRAPHICS © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados ACCESSORY STRUCTURES OF THE SKIN Origin: embryonic epidermis Accessory structures: Hair Nails Sebaceous glands Sweat glands Functions: Hair/Nails: Protection Glands: thermoregulation, protection © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados HAIR § Wide distribution (except palm and sole surface and heels). Structure: three concentric layers: ØMedulla (with pigment granules) ØCortex ØCuticle (heavily keratinized) SHAFT- visible ROOT– within dermis-hypodermis HAIR FOLLICLE (surrounds the root) • Epithelial root sheath. • Dermal root sheath . Hair regeneration from the hair bulb (enlargement at the base). Function: protection and sensorial (root hair plexus) © Copyright Universidad Europea. Todos los derechos reservados HAIR § Wide distribution (except palm and sole surface and heels). Germinal layer of cells from stratum basale © Copyright Universidad Europea. Todos los derechos reservados Areolar connective tissue HAIR § Wide distribution (except palm and sole surface and heels). Sensory nerves: touch Smooth muscle in dermis that contracts with cold or fear. Extends from superficial dermis – dermal root sheath “goosebumps” © Copyright Universidad Europea. Todos los derechos reservados OUTLINE 3.3 Accessory structures of the skin. 3.3.1 Hair 3.3.2 Glands Sebaceous Sweat Ceruminous 3.4 Functions of skin © Copyright Universidad Europea. Todos los derechos reservados SEBACEOUS GLANDS Simple branched acinar glands ØThey open to the hair follicle or directly to the skin ØSecretory portion of the gland in the dermis ØAbsent in the palms and soles. ØHolocrine glands that produce sebum onto the epidermal surface: Composition: triglycerides, cholesterol, proteins and salts. Functions: Protection (avoids skin and hair dehydration) Makes hair and skin smooth Inhibits bacterial and fungal growth © Copyright Universidad Europea. Todos los derechos reservados SEBACEOUS GLANDS Clinical connection: acne © Copyright Universidad Europea. Todos los derechos reservados SWEAT GLANDS © Copyright Universidad Europea. Todos los derechos reservados SWEAT GLANDS: ECCRINE or MEROCRINE glands Simple coiled tubular glands ØExcretory conduct releases sweat on the surface of epidermis. ØStart working soon after birth. ØSweat contains water, salts, uric acid, urea, ammonia. ØPresent through all body surfaces, except lips, auditory conduct, glans. ØFunctions: oThermoregulation (insensible perspiration-sensible perspiration). oExcretion of urea, uric acid and ammonia, © Copyright Universidad Europea. Todos los derechos reservados SWEAT GLANDS: APOCRINE glands Simple coiled tubular glands ØMerocrine secretion (NO apocrine). ØConduct excretes to the hair follicle. ØSecrete oily substances containing lipids, proteins, and steroids. Secretion starts in puberty. ØFound in armpit, groin, breast areola, pigmented skin around the anus, bearded regions in male face. ØFunctions: oEmotional sweating and sweat during sexual activities. oNo thermoregulatory role. © Copyright Universidad Europea. Todos los derechos reservados SWEAT GLANDS: INFOGRAPHICS Simple coiled tubular glands © Copyright Universidad Europea. Todos los derechos reservados OTHER TYPE OF GLANDS Mammary glands • Compound tubuloacinar glands. • Secretion regulated by hormones. © Copyright Universidad Europea. Todos los derechos reservados Ceruminous glands • Modified sweat glands that produce a waxy secretion called cerumen. • Found in the external auditory meatus. • Barrier against the entrance of foreign bodies. OUTLINE 3.4 Functions of skin Physical and chemical protection. Functions in HOMEOSTASIS: – Thermoregulation (blood reservoir). – Provides sensory information. – Secretion-excretion. – Synthesis of vitamin D. © Copyright Universidad Europea. Todos los derechos reservados PROTECTION Physical protection (wind, dehydration, UV, trauma): due to the pigments such as melanin, also lipids, keratin, GAGs… Chemical protection (detergents, cosmetics): due to the structure. Biological barrier to microorganisms: due to the intercellular junctions, Langerhans’ cells. © Copyright Universidad Europea. Todos los derechos reservados THERMOREGULATION Heat ↑ Perspiration and evaporation. Vasodilation (VD) of the superficial vascular dermal network. Exercise Moderate: Vasodilation (↑ blood flow in the surface, ↓ temperature). Extreme: blood is conducted to the muscles and body temperature increases. Cold: Vasodilation of the deep vascular dermal network, and ↓ perspiration and evaporation. © Copyright Universidad Europea. Todos los derechos reservados THERMOREGULATION Vasoconstrictors: ATP, anti-histaminic agents, angiostensin II, chatecholamines, norinephrine. © Copyright Universidad Europea. Todos los derechos reservados Vasolidators: Heparin, adenosine, NO, histamine, bradykinin. FUNCTIONS • Blood reservoir Extensive network of blood vessels. • Cutaneous sensations Touch, pressure, vibration, heat, cold, pain, tickle… • Excretion 400 mL of water/day, small amounts of salt, CO2, ammonia, and urea. © Copyright Universidad Europea. Todos los derechos reservados VITAMIN D SYNTHESIS • Synthesis of Vitamin D. UV light: activation of vitamin D precursor molecules in skin. Hepatic and renal enzymes modify the activated molecule to produce calcitriol (most active form of vitamin D). Function: It favors calcium absorption. CALCITRIOL © Copyright Universidad Europea. Todos los derechos reservados The acronym SHAPES to to remember the functions of the skin: Sensation. Heating & Cooling (Temperature Regulation) Absorption. Protection. Excretion. Secretion. © Copyright Universidad Europea. Todos los derechos reservados 67 VIDEOS § https://www.youtube.com/watch?v=Orumw-PyNjw § (Crash course on intergumentary system) § https://www.youtube.com/watch?v=EN-x-zXXVwQ § (Crash course on intergumentary system II) § https://www.youtube.com/watch?v=rD8SmacBUcU § (Mosquito bite) § Claudia Aguirre. Ted Ed talk on tattooing. © Copyright Universidad Europea. Todos los derechos reservados Bibliography § Silverthorn DU. "Human Physiology: An Integrated Approach”. 7th Edition. Pearson eds, 2016. § Tortora GJ & Derrickson B. "Principles of Anatomy and Physiology”. 14th Edition. Wiley eds, 2014. § Netter, FH. “Atlas of Human Anatomy: with Student Consult Access”. 6th Edition. Saunders Elsevier eds, 2014. § Sobotta "Sobotta - Atlas of Human Anatomy”. 15th Edition. Elsevier eds, 2011. § Stevens A, & Lowe J.S. “Human Histology: With STUDENT CONSULT Online Access”. 4th Edition. Elsevier eds, 2015. © Copyright Universidad Europea. Todos los derechos reservados Natural Sciences Museum, Madrid THANK YOU Ve más allá © Copyright Universidad Europea. Todos los derechos reservados