Human Anatomy and Physiology-Integumentary System Lec 4 PDF

Human Anatomy and Physiology Eleventh Edition Chapter 05 The Integumentary System PowerPoint® Lectures Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College...

Human Anatomy and Physiology Eleventh Edition Chapter 05 The Integumentary System PowerPoint® Lectures Slides prepared by Karen Dunbar Kareiva, Ivy Tech Community College Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Integumentary System Integumentary system consists of: – Skin – Hair – Nails – Sweat glands – Sebaceous (oil) glands Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.1 Structure of Skin Skin consists of two distinct regions: – Epidermis: superficial region  Consists of epithelial tissue and is avascular – Dermis: underlies epidermis  Mostly fibrous connective tissue, vascular – Hypodermis (superficial fascia)  Subcutaneous layer deep to skin  Not part of skin but shares some functions  Mostly adipose tissue that absorbs shock and insulates  Anchors skin to underlying structures: mostly muscles Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Structure Hair shaft Dermal papillae Epidermis Papillary layer Sweat pore Appendages of skin Dermis Reticular Eccrine sweat gland layer Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Subcutaneous tissue(hypodermis; not part of skin) Dermal vascular plexus Nervous structures Sensory nerve fiber Adipose tissue with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Figure 5.1 Skin structure. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.2 Epidermis Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Cells of the Epidermis Epidermis consists mostly of keratinized stratified squamous epithelium Four cell types found in epidermis: 1. Keratinocytes  A specialized type of epithelial cell  Produce fibrous keratin (protein that gives skin its protective properties)  Major cells of epidermis  Tightly connected by desmosomes  Millions slough off every day Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Cells of the Epidermis Epidermis consists mostly of keratinized stratified squamous epithelium Four cell types found in epidermis: 1. Keratinocytes  Produce fibrous keratin (protein that gives skin its protective properties) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Cells of the Epidermis 2. Melanocytes  Spider-shaped cells located in deepest epidermis  Produce pigment melanin, which is packaged into melanosomes – Melanosomes are transferred to keratinocytes, where they protect nucleus from UV damage 3. Dendritic (Langerhans) cells  Star-shaped subset of macrophages that patrol deep epidermis – Are key activators of immune system 4. Tactile (Merkel) cells  Sensory receptors that sense touch Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 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 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Layers of the Epidermis 1. Stratum basale (basal layer) – Deepest of all epidermal layers (base layer) – 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 days to reach surface – 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 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Layers of the Epidermis 2. Stratum spinosum (prickly layer) – Several cell layers thick – 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 Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Layers of the Epidermis 3. Stratum granulosum (granular layer) – Four to six cells thick, but cells are flattened, so layer is thin – Cell appearance changes  Cells flatten, nuclei and organelles disintegrate  Keratinization begins – Cells accumulate keratohyaline granules that help form keratin fibers in upper layers  Cells also accumulate lamellar granules, a water-resistant glycolipid that slows water loss – Cells above this layer die  Too far from dermal capillaries to survive Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Layers of the Epidermis 4. Stratum lucidum (clear layer) – Found only in thick skin – Consists of thin, translucent band of two to three rows of clear, flat, dead keratinocytes – Lies superficial to the stratum granulosum Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Layers of the Epidermis 5. Stratum corneum (horny layer) – 20–30 rows of flat, anucleated, keratinized dead cells – Accounts for three-quarters of epidermal thickness – Though dead, cells still function to:  Protect deeper cells from the environment  Prevent water loss  Protect from abrasion and penetration  Act as a barrier against biological, chemical, and physical assaults Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Layers of the Epidermis Cells change by going through apoptosis (controlled cell death) – Dead cells slough off as dandruff and dander – Humans can shed ~50,000 cells every minute Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Epidermal Cells and Layers of the Epidermis Keratinocytes Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and tactile Dermis epithelial cells. (a) Dermis Melanin Sensory Tactile granule nerve epithelial ending cell Figure 5.2 Epidermal cells and layers of the epidermis. (b) Desmosomes Melanocyte Dendritic cell Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.3 Dermis Strong, flexible connective tissue Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells Fibers in matrix bind body together – Makes up the “hide” that is used to make leather Contains nerves, blood vessels, and lymphatic vessels Contains epidermal hair follicles, oil glands, and sweat glands Two layers – Papillary – Reticular Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Light Micrograph of the Dermis Epidermis Dermis: Papillary dermis (areolar connective tissue) Reticular dermis (dense irregular connective tissue) Dermal papillae Figure 5.3 Light micrograph of the dermis. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Papillary Layer Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels Loose fibers allow phagocytes to patrol for microorganisms Dermal papillae: superficial region of dermis that sends fingerlike projections up into epidermis – Projections contains capillary loops, free nerve endings, and touch receptors (tactile corpuscles, also called Meissner’s corpuscles) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Papillary Layer In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges – Collectively ridges are called friction ridges  Enhance gripping ability  Contribute to sense of touch  Sweat pores in ridges leave unique fingerprint pattern Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Dermal Modifications Result in Characteristic Skin Markings Friction ridges Sweat duct openings consist of epidermal along the crests of ridges that lie on top friction ridges help of dermal ridges. make fingerprints. Figure 5.4c Dermal modifications result in characteristic skin markings. (c) Friction ridges of fingertip (SEM 12X) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Reticular Layer Makes up ~80% of dermal thickness Consists of coarse, dense fibrous connective tissue – Many elastic fibers provide stretch-recoil properties – Collagen fibers provide strength and resiliency  Bind water, keeping skin hydrated Cutaneous plexus: network of blood vessels between reticular layer and hypodermis Extracellular matrix contains pockets of adipose cells Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Reticular Layer Cleavage (tension) lines in reticular layer are caused by many collagen fibers running parallel to skin surface – Externally invisible – Important to surgeons because incisions parallel to cleavage lines heal more readily Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Dermal Modifications Result in Characteristic Skin Markings Cleavage lines Represent separations between underyling collagen fiber bundles in the reticular dermis. Run circularly around the trunk and longitudinally in the limbs. Surgical incisions parallel to cleavage lines heal better than those made across them. (a) Cleavage lines Figure 5.4a Dermal modifications result in characteristic skin markings. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Reticular Layer Flexure lines of reticular layer are dermal folds at or near joints – Dermis is tightly secured to deeper structures – Skin’s inability to slide easily for joint movement causes deep creases – Visible on hands, wrists, fingers, soles, toes Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Dermal Modifications Result in Characteristic Skin Markings Flexure lines form where the dermis is closely attached to the underlying structures. (b) Flexure lines Figure 5.4b Dermal modifications result in characteristic skin markings. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical – Homeostatic Imbalance 5.1 Extreme stretching of skin can cause dermal tears, leaving silvery white scars called striae – Also known as “stretch marks” Acute, short-term traumas to skin can cause blisters, fluid-filled pockets that separate epidermal and dermal layers Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Stretch Marks (Striae) Figure 5.5 Stretch marks (striae). Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  5.4 Skin Color Three pigments contribute to skin color 1. Melanin  Only pigment made in skin; made by melanocytes  Made from amino acid tyrosine by tyrosinase  Packaged into melanosomes that are sent to shield DNA of keratinocytes from damaging UV sunlight  The more sun, the more need for protective shield, the more melanin will be produced  Two forms: reddish yellow to brownish black  Skin color differences are due to amount and form of melanin  Freckles and pigmented moles are local accumulations of melanin Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.4 Skin Color 2. Carotene  Yellow to orange pigment  Most obvious in palms and soles  Accumulates in stratum corneum and hypodermis  Can be converted to vitamin A for vision and epidermal health 3. Hemoglobin  Pinkish hue of fair skin is due to lower levels of melanin – Skin of Caucasians is more transparent, so color of hemoglobin shows through Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical – Homeostatic Imbalance 5.3 Alterations in skin color can indicate disease – Cyanosis  Blue skin color: low oxygenation of hemoglobin – Pallor (blanching or pale color)  Anemia, low blood pressure, fear, anger – Erythema (redness)  Fever, hypertension, inflammation, allergy – Jaundice (yellow cast)  Liver disorders, impaired removal of bilirubin Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Concept review Which of the following layers of the epidermis is associated with the presence of intermediate prekeratin filaments? A) stratum basale B) stratum spinosum C) stratum granulosum D) stratum lucidem E) stratum corneum Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.5 Hair Consists of dead keratinized cells None located on palms, soles, lips, nipples, and portions of external genitalia Functions: – Warn of insects on skin – Hair on head guards against physical trauma – Protect from heat loss – Shield skin from sunlight Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Structure of a Hair Hairs (also called pili): flexible strands of dead, keratinized cells Produced by hair follicles Contains hard keratin, not like soft keratin found in skin – Hard keratin is tougher and more durable, and cells do not flake off Regions: – Shaft: area that extends above scalp, where keratinization is complete – Root: area within scalp, where keratinization is still going on Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Structure of a Hair Three parts of hair shaft: – Medulla: central core of large cells and air spaces – Cortex: several layers of flattened cells surrounding medulla – Cuticle: outer layer consisting of overlapping layers of single cells Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Structure of a Hair Hair pigments are made by melanocytes in hair follicles – Combinations of different melanins (yellow, rust, brown, black) create all the hair colors  Red hair has additional pheomelanin pigment  Gray/white hair results when melanin production decreases and air bubbles replace melanin in shaft Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Appendages: Structure of a Hair and Hair Follicle Follicle wall Peripheral connective tissue (fibrous) Glassy sheath membrane Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla (b) Photomicrograph of a cross (a) Diagram of a cross section of a hair within its follicle section of a hair and hair follicle (100×) Figure 5.6a, b Structure of a hair and hair follicle. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved  Structure of a Hair Follicle Extends from epidermal surface to dermis Hair bulb: expanded area at deep end of follicle Hair follicle receptor (or root hair plexus): sensory nerve endings that wrap around bulb – Hair is considered a sensory touch receptor Wall of follicle composed of: – Peripheral connective tissue sheath  Derived from dermis  Also called fibrous sheath – Glassy membrane: thickened basal lamina – Epithelial root sheath Follicle wall Peripheral  Derived from epidermis connective tissue  Internal and external (fibrous) Glassy sheath membrane Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla (b) Photomicrograph of a cross (a) Diagram of a cross section of a hair within its follicle section of a hair and hair follicle (100×) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Structure of a Hair Follicle Hair matrix: actively dividing area of bulb that produces hair cells – As matrix makes new cells, it pushes older ones upward Arrector pili: small band of smooth muscle attached to follicle – Responsible for “goose bumps” Hair papilla – Dermal tissue containing a knot of capillaries that supplies nutrients to growing hair Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Appendages: Structure of a Hair and Hair Follicle Follicle wall Peripheral connective tissue (fibrous) Glassy sheath membrane Epithelial root sheath External root sheath Internal root sheath Hair root Cuticle Cortex Medulla Hair matrix Hair papilla Melanocyte Subcutaneous adipose tissue (c) Diagram of a longitudinal view of the expanded hair (d) Photomicrograph of longitudinal view bulb of the follicle, which encloses the matrix of the hair bulb in the follicle (150×) Figure 5.6c, d Structure of a hair and hair follicle. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Types and Growth of Hair Vellus hair: pale, fine body hair of children and adult females Terminal hair: coarse, long hair – Found on scalp and eyebrows – At puberty  Appear in axillary and pubic regions of both sexes  Also on face and neck of males Nutrition and hormones affect hair growth Follicles cycle between active and regressive phases – Average 2.25 mm growth per week – Lose 90 scalp hairs daily Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Hair Thinning and Baldness Alopecia: hair thinning in both sexes after age 40 True (frank) baldness – Genetically determined and sex-influenced condition – Male pattern baldness caused by follicular response to DHT (dihydrotestosterone)  Androgens cause shorter and shorter growth cycles Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.6 Nails Lunule Lateral nail fold Scale-like modifications of epidermis that contain hard keratin Act as a protective cover for distal, dorsal surface of fingers and toes Consist of free edge, nail plate, (a) and root Free edge Nail Eponychium Nail root of nail plate (cuticle) Proximal Nail Nail bed is epidermis underneath nail fold matrix keratinized nail plate Nail matrix: thickened portion of bed responsible for nail growth (b) Hyponychium Nail bed Phalanx (bone of fingertip) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.6 Nails Lunule Lateral nail fold Nail folds: skin folds that overlap border of nail Eponychium: nail fold that projects onto surface of nail body – Also called cuticle Hyponychium: area under free edge of plate that accumulates dirt Nails normally appear pink (a) Free edge Nail Eponychium Nail root because of underlying capillaries plate (cuticle) of nail – Lunule: thickened nail matrix, Proximal Nail nail fold matrix appears white Abnormal color or shape can be an indicator of disease (b) Hyponychium Nail bed Phalanx (bone of fingertip) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical - Homeostatic Imbalance 5.6 Nail appearance can help in diagnosing some diseases such as: – Yellow-tinged may indicate respiratory or thyroid gland disorder – Thickened yellow nails can be due to fungal infection of nail – Koilonchya, also called “spoon nail” – an outward concavity of nail may signal iron deficiency – Beau’s lines – horizontal lines across nails may indicate severe illnesses such as uncontrolled diabetes, heart attack or cancer chemotherapy Koilonychia Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.7 Sweat Glands Also called sudoriferous glands All skin surfaces except nipples and parts of external genitalia contain sweat glands – About 3 million per person Two main types – Eccrine (merocrine - exocytosis) sweat glands – Apocrine (actually merocrine - exocytosis) sweat glands Contain myoepithelial cells – Contract upon nervous system stimulation to force sweat into ducts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Eccrine (Merocrine) Sweat Glands Most numerous type Abundant on palms, soles, and forehead Ducts connect to pores Function in thermoregulation – Regulated by sympathetic nervous system Their secretion is sweat – 99% water, salts, vitamin C, antibodies, dermcidin (microbe-killing peptide), metabolic wastes Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Appendages: Cutaneous Glands Sweat Sebaceous pore gland Eccrine gland Duct Dermal connective tissue Secretory cells (b) Eccrine gland (140×) Figure 5.9b Cutaneous glands. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Apocrine Sweat Glands Despite name, are also merocrine glands that use exocytosis Confined to axillary and anogenital areas Secrete viscous milky or yellowish sweat that contains fatty substances and proteins – Bacteria break down sweat, leading to body odor Larger than eccrine sweat glands with ducts emptying into hair follicles Begin functioning at puberty – Function unknown but may act as sexual scent gland Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Apocrine Sweat Glands Modified apocrine glands – Ceruminous glands: lining of external ear canal; secrete cerumen (earwax) – Mammary glands: secrete milk Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Sebaceous (Oil) Glands Widely distributed, except for thick skin of palms and soles Most develop from hair follicles and secrete into hair follicles Relatively inactive until puberty – Stimulated by hormones, especially androgens Secrete sebum – Oily holocrine secretion – Bactericidal (bacteria-killing) properties – Softens hair and skin Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Appendages: Cutaneous Glands Sweat pore Sebaceous gland Dermal connective Sebaceous Hair in tissue gland duct hair follicle Eccrine gland Secretory cells (a) Sebaceous gland (90×) Figure 5.9a Cutaneous glands. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Table 5.1 Summary of Cutaneous Glands Table 5.1 Summary of Cutaneous Glands. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical – Homeostatic Imbalance 5.7 Acne is usually an infectious inflammation of the sebaceous glands, resulting in pimples (pustules or cysts) – Associated with Propionibacterium acne infection Whiteheads are blocked sebaceous glands – If secretion is oxidized, whitehead becomes a blackhead Overactive sebaceous glands in infants can lead to seborrhea, known as “cradle cap” – Begins as pink, raised lesions on scalp that turn yellow/brown and flake off Cradle Cap (Seborrhea) in a Newborn Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.8 Functions of Skin Skin is first and foremost a barrier Its main functions include: – Protection – Body temperature regulation – Cutaneous sensations – Metabolic functions – Blood reservoir – Excretion of wastes Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Protection Skin is exposed to microorganisms, abrasions, temperature extremes, and harmful chemicals Constitutes three barriers: – Chemical barrier – Physical barrier – Biological barrier Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Protection Chemical barrier – Skin secretes many chemicals, such as:  Sweat, which contains antimicrobial proteins  Sebum and defensins, which kill bacteria  Cells also secrete antimicrobial defensin – Acid mantle: low pH of skin retards bacterial multiplication – Melanin provides a chemical barrier against UV radiation damage Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Protection Physical barrier – Flat, dead, keratinized cells of stratum corneum, surrounded by glycolipids, block most water and water-soluble substances – Some chemicals have limited penetration of skin:  Lipid-soluble substances  Plant oleoresins (e.g., poison ivy)  Organic solvents (acetone, paint thinner)  Salts of heavy metals (lead, mercury)  Some drugs (nitroglycerin)  Drug agents (enhancers that help carry other drugs across skin) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Protection Biological barriers – Epidermis contains phagocytic cells  Dendritic cells of epidermis engulf foreign antigens (invaders) and present to white blood cells, activating the immune response – Dermis contains macrophages  Macrophages also activate immune system by presenting foreign antigens to white blood cells – DNA can absorb harmful UV radiation, converting it to harmless heat Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Clinical – Homeostatic Imbalance 5.8 If organic solvents or heavy metals pass through skin and enter blood, multiple organ systems can be devastated which can be lethal – Examples:  Kidneys can shut down  Brain can be damaged  Absorption of lead can result in anemia and neurological defects. Care must always be used when handling organic solvents or heavy metals – Should never be touched with bare hands Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Body Temperature Regulation Under normal, resting body temperature, sweat glands produce about 500 ml/day of unnoticeable sweat – Called insensible perspiration If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce 12 L (3 gallons) of noticeable sweat – Called sensible perspiration; designed to cool body Cold external environment – Dermal blood vessels constrict – Skin temperature drops to slow passive heat loss Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Cutaneous Sensations Cutaneous sensory receptors are part of the nervous system – Exteroreceptors respond to stimuli outside body, such as temperature and touch – Free nerve endings sense painful stimuli Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Cutaneous Sensations Free nerve endings – sense pain, temperature Merkel disk – free nerve ending associated with epidermal cell, sustained touch, skin indentation e.g. reading Braille Root hair plexus – wrapped around hair follicles, sense movement on surface e.g. insect crawling on skin Lamellar (Pacinian) corpuscle – deep pressure, fast vibrations Bulbous (Ruffini) corpuscle – sensitive to stretch e.g. pulling of skin Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Structure Hair shaft Dermal papillae Epidermis Papillary layer Sweat pore Appendages of skin Dermis Reticular Eccrine sweat gland layer Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Subcutaneous tissue(hypodermis; not part of skin) Dermal vascular plexus Nervous structures Sensory nerve fiber Adipose tissue with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Figure 5.1 Skin structure. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Metabolic Functions Skin can synthesize vitamin D needed for calcium absorption in intestine Chemicals from keratinocytes can disarm some carcinogens Keratinocytes can activate some hormones – Example: convert cortisone into hydrocortisone Skin makes collagenase, which aids in natural turnover of collagen to prevent wrinkles Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Blood Reservoir Skin can hold up to 5% of the body’s total blood volume Skin vessels can be constricted to shunt blood to other organs, such as an exercising muscle Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Excretion Skin can secrete limited amounts of nitrogenous wastes, such as ammonia, urea, and uric acid Sweating can cause salt and water loss Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved 5.9 Skin Cancer and Burns Skin can develop over 1000 different conditions and ailments Many internal diseases reveal themselves on skin Most common disorders are infections Less common, but more damaging, are: – Skin cancer – Burns Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Cancer Most skin tumors are benign (not cancerous) and do not spread (metastasize) Risk factors – Overexposure to UV radiation – Frequent irritation of skin UV radiation damages DNA, causing formation of thymine dimers Three major types of skin cancer – Basal cell carcinoma – Squamous cell carcinoma – Melanoma Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Cancer Basal cell carcinoma – Least malignant and most common – Stratum basale cells proliferate and slowly invade dermis and hypodermis – Cured by surgical excision in 99% of cases Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Cancer Squamous cell carcinoma – Second most common type; can metastasize – Involves keratinocytes of stratum spinosum – Usually is a scaly reddened papule on scalp, ears, lower lip, or hands – Good prognosis if treated by radiation therapy or removed surgically Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Skin Cancer Melanoma – Cancer of melanocytes; is most dangerous type because it is highly metastatic and resistant to chemotherapy – Treated by wide surgical excision accompanied by immunotherapy – Key to survival is early detection: ABCD rule  A: asymmetry; the two sides of the pigmented area do not match  B: border irregularity; exhibits indentations  C: color; contains several colors (black, brown, tan, sometimes red or blue)  D: diameter; larger than 6 mm (size of pencil eraser)  E: evolution or evolving changes over time Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Photographs of Skin Cancers (c) Melanoma Figure 5.11c Photographs of skin cancers. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Burns Tissue damage caused by heat, electricity, radiation, or certain chemicals – Damage caused by denaturation of proteins, which destroys cells Immediate threat is dehydration and electrolyte imbalance – Leads to renal shutdown and circulatory shock To evaluate burns, the Rule of Nines is used – Body is broken into 11 sections, with each section representing 9% of body surface (except genitals, which account for 1%) – Used to estimate volume of fluid loss Add front and back for: - Chest (9%) and upper back (9%) - Abdomen (9%) and lower back (9%) Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Burns Burns can be classified by severity – First-degree  Epidermal damage only – Localized redness, edema (swelling), and pain – Second-degree  Epidermal and upper dermal damage – Blisters appear – First- and second-degree burns are referred to as partial-thickness burns because only the epidermis and upper dermis are involved Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Burns Burns can be classified by severity (cont.) – Third-degree  Entire thickness of skin involved (referred to as full-thickness burns)  Skin color turns gray-white, cherry red, or blackened  No edema is seen and area is not painful because nerve endings are destroyed  Skin grafting usually necessary Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Partial-Thickness and Full-Thickness Burns 1st-degree burn 2nd-degree burn (a) Skin bearing partial-thickness burn (1st- and 2nd-degree burns) 3rd-degree burn (b) Skin bearing full-thickness burn (3rd-degree burn) Figure 5.12 Partial-thickness and full-thickness burns. Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Burns Burns are considered critical if: – >25% of body has second-degree burns – >10% of body has third-degree burns – Face, hands, or feet bear third-degree burns Treatment includes: – Debridement (removal) of burned skin – Antibiotics – Temporary covering – Skin grafts Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved Copyright Copyright © 2019, 2016, 2013 Pearson Education, Inc. All Rights Reserved