Integumentary System PDF

Tiny sweat pores open and leave thin film called a fingerprint on most surfaces. Skin (cutaneous membrane) = largest organ (1015% of TBW) 2 main regions: Epidermis – keratinized stratified squamous epithelium Dermis – loose CT and dense irregular CT...

Tiny sweat pores open and leave thin film called a fingerprint on most surfaces. Skin (cutaneous membrane) = largest organ (1015% of TBW) 2 main regions: Epidermis – keratinized stratified squamous epithelium Dermis – loose CT and dense irregular CT © 2016 Pearson Education, Inc.  Skin Structure Note correction of bracket compared to textbook. Figure 5.1 Basic anatomy of the skin.  Skin Structure Accessory structures: - sweat glands, sebaceous glands, hair, nails Sensory receptors - detect heat, cold, pain, pressure Arrector pili muscles - small bands of SMC associated with hair Epidermis is avascular – Transport of O2 and nutrients via diffusion  Skin Structure Hypodermis – aka superficial fascia or subcutaneous fat, is deep to dermis – not part of skin, anchors skin to deeper structures – loose CT and adipose – vascular Figure 5.1 Basic anatomy of the skin. © 2016 Pearson Education, Inc.  Cellulite, p. 162 Dimpled or “orange peel” appearance of skin when collagen bands form around adipose tissue (in hypodermis) Thighs, hips, and gluteal area; due to genetics, gender, age, adipose tissue Normal condition (not disorder) Minimize with a healthy diet and regular exercise © 2016 Pearson Education, Inc.  Functions of Integumentary System 1. Protection- mechanical trauma, pathogens, and environment 2. Sensation –perceive changes in the body’s internal or external environment 3. Thermoregulation (Figure 5.2): – relies on negative feedback loops to maintain stable internal temperature (due to muscle activity and metabolism) 4. Excretion – process where waste products and toxins are eliminated (sweat) 5. Synthesis – Vitamin D, calcitriol © 2016 Pearson Education, Inc.  Thermoregulation [Body Temperature above normal]  Functions of the Integumentary System Stimulus: body is too HOT (due to weather extremes or fever) Receptors: thermoreceptors detect an increase in temperature Control center: thermoregulatory center in brain (hypothalamus) acts as a thermostat Effector/Response: Control center stimulates sweating and vasodilation (VD) of vessels in dermis Homeostasis and negative feedback: - body temp. returns to normal - thermoregulatory center decreases output to glands and vessels © 2016 Pearson Education, Inc.  Thermoregulation [Body Temperature below normal] Figure 5.2b Homeostatic regulation of body temperature by integumentary system. © 2016 Pearson Education, Inc.  Functions of the Integumentary System Stimulus: body temperature drops below normal range; too COLD Thermoreceptors: detect drop in temperature and relay information to hypothalamus Control center reacts Effector/response: blood vessels in dermis vasoconstric (VC) ; decreased sweating; shivering Homeostasis and negative feedback: - body temp. returns to normal - thermoregulatory center decreases output to vessels and muscles (reduce shivering) © 2016 Pearson Education, Inc. Functions of the Integumentary System – Lose heat: sweating and VD – Conserve heat: decreased sweating, VC – Produce heat: muscle contraction © 2016 Pearson Education, Inc. Functions of the Integumentary System Vitamin D synthesis: precursor to Vit.D UV light__  Vit. D3 (cholecalciferol) (dehydrocholesterol) (active form) (in skin)  intermediate product  calcitriol (hormone) (in liver) (in kidneys) Calcitriol - nec. for absorption of Ca++ by S.I. Ca++ nec. for nerve function, muscle contraction, bone © 2016 Pearson Education, Inc.  The Epidermis Epidermis – most superficial region - composed of mostly keratinocytes - produce keratin (protein) © 2016 Pearson Education, Inc.  The Epidermis Organized into 5 layers (strata) : Stratum basale (stratum germinativum) - deepest layer - most metabolically and mitotically active Stratum spinosum – still close to blood supply - metabolically and mitotically active © 2016 Pearson Education, Inc.  The Epidermis Stratum granulosum - three to five layers of cells - keratin filled cells (provides water resistance) Stratum lucidum – narrow layer of clear, dead keratinocytes - found only in thick skin Stratum corneum (outermost) – outermost layer of epidermis - several layers of dead flattened - sloughed off or exfoliated mechanically © 2016 Pearson Education, Inc.  The Epidermis Figure 5.3 Structure of the epidermis. © 2016 Pearson Education, Inc.  Study Boost: Remembering the Strata of the Epidermis Here is a simple trick to remember strata of epidermis: “Brilliant Studying Gives Loads of Confidence” “B” in “basale” as stands for “bottom”; it is bottom layer Figure 5.3 Structure of the epidermis. © 2016 Pearson Education, Inc.  The Epidermis Keratinocyte life cycle: - Dead keratinocytes are replaced by mitosis of cells in stratum basale and spinosum close to blood supply - As keratinocytes in deeper strata divide they push cells above them into more superficial layers (40-50 days) - Mitosis takes place at night?! © 2016 Pearson Education, Inc. Concept Boost: Understanding Epidermal Growth © 2016 Pearson Education, Inc.  Other Cells of the Epidermis Dendritic (Langerhans) cells – located in stratum spinosum - phagocytes of immune system - protect skin and deeper tissues from pathogens Merkel cells - located in stratum basale - sensory receptors detect light touch - fingertips, lips, and at base of hairs Melanocytes – located in stratum basale - produce melanin (protein skin pigment) ranging from orange-red to brown-black © 2016 Pearson Education, Inc.  Thick and Thin Skin Thick skin - all five epidermal layers - thick stratum corneum - no hair follicles, many sweat glands Thin skin - has only four layers (no stratum lucidum) - Many hairs, sweat glands, and sebaceous glands Callus – additional layers of st.corneum; form in either thick or thin skin due to repetitive pressure © 2016 Pearson Education, Inc.  Thick and Thin Skin Figure 5.4 Thick and thin skin. © 2016 Pearson Education, Inc.  The Dermis Dermis – highly vascular layer deep to epidermis Functions: – Provides blood supply for epidermis – Contains sensory receptors – Anchors epidermis in place Composed of two distinct layers – Papillary – Reticular © 2016 Pearson Education, Inc.  The Papillary Layer Papillary layer – composed of loose CT Dermal papillae - tiny projections - capillary loops - Tactile (Meissner) corpuscles (light touch) © 2016 Pearson Education, Inc.  The Reticular Layer Reticular layer – deepest thicker layer of dermis - mostly dense irregular (collagen and elastic fibers) - rich in proteoglycans ( keeps skin firm and hydrated) - Lamellated (Pacinian) corpuscles (pressure and vibration associated with skin) - Blood vessels, sweat glands, hairs, sebaceous glands, and adipose tissue are found in reticular layer © 2016 Pearson Education, Inc.  Skin Markings Epidermal ridges - enhance gripping ability of hands and feet: – characteristic patterns; loops, arches, and whorls; genetically determined – Sweat pores open along these ridges and leave a thin film or fingerprint most surfaces © 2016 Pearson Education, Inc.  Skin Wrinkles, p. 170 Due to age-related decrease in collagen and elastic fibers, proteoglycans, and adipose tissue in the dermis Reduces skin’s firmness, hydration, and recoil ability after stretching © 2016 Pearson Education, Inc.  Skin Wrinkles Appearance can be minimized by: – Botox – bacterial toxin; temporarily paralyzes facial muscles – Fillers – adipose tissue, collagen, and/or proteoglycans are injected into wrinkles – Topical creams – (esp. non-Rx) claim to reduce wrinkles (little to no effect) Delay wrinkles: avoid sun, use sunscreens, hydrate, and avoid smoking © 2016 Pearson Education, Inc. Skin color Melanin (melanocytes) -protect keratinocyte DNA from mutations induced by UV rays - number of melanocytes is virtually identical among all individuals - spectrum of skin tones due to differences in amount of melanin produced Carotene (ingest yellow orange vegetables) – Imparts yellowish color to stratum corneum Hemoglobin (RBCs) – coloration depends on blood flow to dermis © 2016 Pearson Education, Inc.  Diagnostic Skin color changes Erythema – increased blood flow Pallor – decreased blood flow Cyanosis - low oxygenated blood © 2016 Pearson Education, Inc.  Melanin Figure 5.8 Melanocytes and melanin function. © 2016 Pearson Education, Inc.  Melanin Common variations of pigmentation: – Freckle – small area of increased pigmentation (melanin production) – Mole or nevus – area of increased pigmentation due to proliferation of melanocytes (not increase in melanin production) – Albinism – melanocytes fail to manufacture tyrosinase (enzyme) results in lack of pigmentation © 2016 Pearson Education, Inc.  Tanning and a “Healthy Tan” p. 172 Tanning – salons promote notion of “healthy tan” THERE IS NO SUCH THING AS A HEALTHY TAN! UVA and UVB rays are associated with sunburning; UVA rays are linked with tanning; salons to claim UVA rays are safe; both damage DNA equally, UVA ages skin at much faster rate ANY amount of tanning damages melanocytes and other skin elements, ages skin prematurely, and increases risk of skin cancer © 2016 Pearson Education, Inc.  Hair Accessory structures (appendages): - hair, nails, and glands - derived from epithelium only Hair (pili) – protrude from surface of skin over entire body except thick skin, lips, and parts of external genitalia (Figure 5.9) © 2016 Pearson Education, Inc.  Hair Cuticle - outer Cortex -middle Medulla -inner Figure 5.9 Hair structure. © 2016 Pearson Education, Inc.  Hair Hair – Protect by preventing substances and organisms entering eyes and nose – Protect underlying skin of scalp from UV radiation and mechanical trauma - Sensory neuron detect changes in environment © 2016 Pearson Education, Inc.  Hair Structure Hair - stratified squamous keratinized epithelial – Shaft projects from skin’s surface dead keratinized cells – Root embedded in dermis surrounded by sensory neuron hair papilla -projection of blood vessels in indented base hair bulb = root and hair papilla many epithelial cells are still alive (have not completed keratinization process) Figure 5.9 Hair structure. © 2016 Pearson Education, Inc.  Hair Structure – Matrix – small number of actively dividing keratinocytes found at base of root – Root is embedded in hair follicle Figure 5.9b Hair structure. © 2016 Pearson Education, Inc.  Hair Structure – Strand of hair has three visible regions: Inner medulla – soft keratin Middle cortex – hard keratin provides strength to strand Outermost cuticle – single layer of overlapping keratinocytes containing hard keratin; provides mechanical strength Figure 5.9a Hair structure. © 2016 Pearson Education, Inc.  Hair Structure arrector pili muscles = small band of SMC “goosebumps” = hair stands up (piloerection) hair growth varies, averages ~ 11.5 cm per month Figure 5.9 Hair structure. © 2016 Pearson Education, Inc.  Hair Pigment and Texture Hair color is determined by melanin produced Blond hair has little melanin Black hair which contains a lot of melanin Red hair has a special reddish pigment containing iron Gray or white hair melanocytes produce less melanin with aging © 2016 Pearson Education, Inc.  Nails Nails – composed of stratified squamous epithelium filled with hard keratin o Nail plate – sits on top of nail bed o Lunula - half-moon shaped region of proximal nail plate o Eponychium - cuticle o Hyponychium – St. corneum under free edge of nail Figure 5.10a Nail structure. © 2016 Pearson Education, Inc.  Glands Sweat (sudoriferous) glands  sweat – Eccrine : widespread, mostly water , wastes, electrolytes Merocrine – Apocrine: axillary, & anal regions, functional at puberty, odoriferous, associated with hair follicle Modified sweat glands: – Ceruminous: cerumin (ear canal) – Mammary: milk Holocrine Sebaceous glands  oily sebum – Thin skin only – Hydrophobic barrier © 2016 Pearson Education, Inc. Figure 5.11 Sweat glands and sebaceous glands.  Glands Figure 5.11b Sweat glands and sebaceous glands. © 2016 Pearson Education, Inc.  Acne, p. 177 Acne vulgaris – affects 96% of adolescents and young adults to some degree Cause – accumulation of sebum and dead cells comedone (blackhead); - may be infected by bacteria  pustule (pimple) - male sex hormones (testosterone) © 2016 Pearson Education, Inc.  Skin Cancer Cancer – one of most common diseases in world; caused by mutations in DNA that induce a cell to lose control of cell cycle (Figure 5.14): – Unchecked cell division eventually leads to formation of a large population of undifferentiated cells known as a tumor – Cancerous tumors are able to metastasize; tumor cells spread through blood or lymphatic vessels to other tissues and continue to divide – Damage caused by metastatic tumor cells alters function of invaded organs © 2016 Pearson Education, Inc.  Skin Cancer Three cancers affect skin - linked to UV radiation exposure - carcinogens (Cancer-inducing chemicals, toxins) 1. Basal cell carcinoma – Most common of all cancer types, including skin cancer – Arises from keratinocytes in stratum basale 2. Squamous cell carcinoma – Second most common skin cancer – Cancer of keratinocytes of stratum spinosum 3. Malignant melanoma – cancer of melanocytes - Arms” of cancerous melanocytes extend down into dermis and access dermal blood vessels (metastasis) © 2016 Pearson Education, Inc.  Skin Cancer Malignant melanoma can be distinguished from other skin cancers and normal moles using ABCDE rule: – (A): Asymmetrical shape (two sides do not match) – (B): Border irregularity – (C): Color, usually blue-black or a variety of colors – (D): Diameter generally larger than 6 mm (pencil eraser size) – (E): Evolving (changing) shape and size Figure 5.14c The three main forms of skin cancer. © 2016 Pearson Education, Inc.  Decubitus Ulcer – Lack of oxygen to tissues, usually in a high pressure location, tissue becomes necrotic – Ischial tuberosity