8/19/2015 MODULE 5.1 OVERVIEW OF THE ERIN C. AMERMAN INTEGUMENTARY SYSTEM FLORIDA STATE COLLEGE AT JACKSONVILLE Lecture Presentation by Suzanne Pundt University of Texas at Tyler © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. SKIN STRUCTURE SKIN STRUCTURE • Skin accounts for 1015% of an individual’s total body weight making it largest organ in body; more than just an outer covering; complex organ with many functions important for homeostasis (Figure 5.1) • Known as cutaneous membrane; has two main components: . Epidermis – superficial layer that consists of keratinized stratified squamous epithelium resting on a basement membrane . Dermis – deep to epidermis and basement membrane; consists of loose connective tissue and dense irregular connective tissue Figure 5.1 Basic anatomy of the skin. © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. SKIN STRUCTURE SKIN STRUCTURE • Accessory structures of skin – embedded in cutaneous • Hypodermis – also known as superficial fascia or membrane: sweat glands, sebaceous glands, hair, and nails subcutaneous fat, is deep to dermis • Skin contains sensory receptors and arrector pili muscles . Although not part of skin, it does anchor skin to deeper (small bands of smooth muscle associated with hair) structures like muscle and bone • Epidermis is avascular: . Made of loose connective and . Must rely on diffusion of oxygen and nutrients from blood adipose tissues; has an vessels in deeper dermis; example of Gradients Core abundant blood supply Principle; limits epidermal thickness . About 50% of cells in epidermis are too far from adequate blood supply to sustain life; superficial layers are made up entirely of dead cells Figure 5.1 Basic anatomy of the skin. © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. 1 8/19/2015 FUNCTIONS OF THE CELLULITE INTEGUMENTARY SYSTEM • Term used to describe dimpled or “orange peel” Integumentary system has following functions that are appearance of skin when collagen bands form around critical for protecting underlying organs or for maintaining adipose tissue in the hypodermis homeostasis: • Tends to develop in thighs, hips, and gluteal area; • Protection from mechanical trauma, pathogens, and influenced by many factors; genetics, gender and amount environment is most obvious function: and distribution of adipose tissue, and age . Stratified squamous, keratinized epithelium provides a durable but flexible surface; protects body from mechanical trauma like • Now thought to be normal condition (not disorder) stretching, pressure, or abrasions • Little evidence that any “cures” for cellulite work; only . Provides a continuous barrier to invasion by microorganisms or proven way to minimize appearance is a healthy diet and pathogens that can cause disease regular exercise; however, even diet and exercise do not . Contains cells of immune system that destroy pathogens before generally eliminate it all together they invade deeper tissues © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. FUNCTIONS OF THE FUNCTIONS OF THE INTEGUMENTARY SYSTEM INTEGUMENTARY SYSTEM • Protection (continued): • Sensation – process that enables nervous system to . Glands secrete a variety of antimicrobial substances; perceive changes in the body’s internal or external sebaceous gland secretions give surface of skin a slightly surroundings; critical to homeostasis: acidic pH (called acid mantle); inhibits growth of many pathogens . Skin has numerous sensory receptors or cellular structures that detect changes in internal and/or . Provides protection from a number of environmental hazards including absorption of ultraviolet light (UV) external environment before it damages deeper tissues . Receptors allow us to detect potentially harmful . Skin secretes hydrophobic lipid-based chemicals; repel stimuli such as heat, cold, and pain; could lead to ionic and polar covalent molecules like salt and water; tissue damage critical for maintaining water and electrolyte homeostasis in a wide range of weather conditions © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. FUNCTIONS OF THE FUNCTIONS OF THE INTEGUMENTARY SYSTEM INTEGUMENTARY SYSTEM • Thermoregulation (Figure 5.2): . Sequence of events that occur when body temperature rises above normal range; may be caused by extremes of weather . Process that relies on negative feedback loops for or due to abnormal conditions that cause fever (Figure 5.2a): maintenance of a stable internal temperature o Sensory receptors (thermoreceptors) in skin detect an . Example of Feedback Loops Core Principle increase in temperature in both skin itself and internal body fluids . Internal body temperature is determined mostly by o Control center in hypothalamus of brain acts as a thermostat muscle activity and many chemical reactions involved or thermoregulatory center; receives input from in metabolism thermoreceptors; processes and then responds to sensory inputs o Control center stimulates sweating; sweat glands are stimulated to release a watery fluid called sweat; water carries a great deal of heat with it when it evaporates; provides for an effective cooling mechanism © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. 2 8/19/2015 FUNCTIONS OF THE FUNCTIONS OF THE INTEGUMENTARY SYSTEM INTEGUMENTARY SYSTEM . Sequence of events that occur when body temperature rises above normal range (continued): o Control center stimulates cutaneous vasodilation; response triggered by hypothalamus; causes blood vessels in dermis to widen (dilate); increased blood flow through dilated vessels increases amount of heat radiated away from body into environment; cools body o Body temperature returns to normal range and cooling mechanisms decline by negative feedback; when thermoreceptors no longer sense body temperatures above normal range they stop sending signals to hypothalamus; ends control center responses; sweating and vasodilation ends Figure 5.2a Homeostatic regulation of body temperature by integumentary system. © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. FUNCTIONS OF THE FUNCTIONS OF THE INTEGUMENTARY SYSTEM INTEGUMENTARY SYSTEM . Sequence of events that occur when body temperature . Sequence of events that occur when body temperature drops below normal range; usually due to cold drops below normal range (continued): environmental conditions (Figure 5.2b): o Vasoconstriction also redirects blood flow to deeper tissues; o Thermoreceptors detect body temperature drop below normal helps to conserve heat range; relay information to thermoregulatory center in o When body temperature rises back into normal range, hypothalamus thermoreceptors stop sending information to hypothalamus; o Hypothalamus generates a different response than it does for an response that hypothalamus generated for heat conservation increased body temperature; blood vessels in dermis narrow ends; feedback loop is closed (vasoconstrict) reducing amount of blood flow; limits heat lost to environment © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. FUNCTIONS OF THE FUNCTIONS OF THE INTEGUMENTARY SYSTEM INTEGUMENTARY SYSTEM • Excretion – process where waste products and toxins are eliminated from body; most occurs at other organs like kidneys; skin and its accessory structures make a small but significant contribution Figure 5.2b Homeostatic regulation of body temperature by integumentary system. © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. 3 8/19/2015 FUNCTIONS OF THE INTEGUMENTARY SYSTEM • Skin plays a critical role in vitamin D synthesis; cells found deep in epidermis convert vitamin D from an inactive form (precursor) to active form: . Precursor – modified cholesterol molecule; converted to cholecalciferol when epidermis is exposed to UV radiation MODULE 5.2 THE EPIDERMIS . Cholecalciferol is released into blood; modified first by liver, then by kidneys, to form calcitriol (active form of vitamin D) . Vitamin D is required for calcium ion absorption from small intestine; calcium ion is critical for nerve function, muscle contraction, building and maintaining bone tissue, and many other physiological functions © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. THE EPIDERMIS THE EPIDERMIS • Epidermis – most superficial layer; composed of • Keratinocytes – organized from deep to superficial into several cell types; most numerous are keratinocytes five structurally distinct strata (layers) (Figure 5.3): • Make up about 95% of epidermis; have two structural . Stratum basale – (stratum germinativum) single layer features that make epidermis stronger and less of stem cells resting on basement membrane; closest susceptible to mechanical trauma: cells to blood supply in dermis; therefore most metabolically and mitotically active cells in epidermis; . Manufacture keratin – tough fibrous protein that involved in vitamin D synthesis and replacement of dead makes epidermis more resistant to mechanical trauma; keratinocytes (lost from more superficial layers) demonstrates Structure-Function Core Principle . Stratum spinosum – thickest layer, sits on top of . Linked to each other by desmosomes; makes stratum basale so still close to blood supply; also epidermis stronger metabolically and mitotically active © 2016 Pearson Education, Inc. © 2016 Pearson Education, Inc. THE EPIDERMIS THE EPIDERMIS • Five structurally distinct strata (continued): • Five structurally distinct strata (continued): . Stratum granulosum . Stratum lucidum – narrow layer of clear, dead o Three to five layers of cells