A&P I Chapter 5 - The Integumentary System PDF

A&P I Chapter 5 The Integumentary System  Integument Two major parts: 1. Cutaneous membrane 2. Accessory/appendage structures that originate in the dermis Hair, nails, exocrine glands  Skin (Integument) Consists...

A&P I Chapter 5 The Integumentary System  Integument Two major parts: 1. Cutaneous membrane 2. Accessory/appendage structures that originate in the dermis Hair, nails, exocrine glands  Skin (Integument) Consists of two major regions 1. Epidermis—superficial region (has 4 to 5 layers) 2. Dermis—middle region (has 2 layers) Along with the Hypodermis (superficial fascia)— deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue Hypodermic shots go here Functions of the Integumentary System 1. Protection—three types of barriers Chemical Low pH secretions (acid mantle) and defensins retard bacterial activity Physical/mechanical barriers Keratin and glycolipids block most water and water- soluble substances Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs Biological barriers Dendritic cells, macrophages, and DNA Functions of the Integumentary System cont.. 2. Body temperature regulation ~500 ml/day of routine insensible perspiration (at normal body temperature) At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body 3. Cutaneous sensations Temperature, touch, and pain Functions of the Integumentary System cont.. 4. Metabolic functions Synthesis of vitamin D precursor and collagenase Chemical conversion of carcinogens and some hormones 5. Blood reservoir—up to 5% of body’s blood volume 6. Excretion—nitrogenous wastes and salt in sweat  Epidermis Epidermis—superficial region has 4 to 5 layers (thin skin, thick skin respectively) 1. Stratum corneum 2. Stratum lucidum (thick skin only) 3. Stratum granulosum 4. Stratum spinosum 5. Stratum basale Avascular, nourished through diffusion from dermis Only lower layers are alive  Cells of the Epidermis Is keratinized stratified squamous epithelium Multiple cells of epidermis Keratinocytes—produce fibrous protein keratin (majority) Melanocytes 10–25% of cells in lower epidermis Produce pigment melanin Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system Tactile (Merkel) cells—touch receptors  Stratum corneum Keratinocytes Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated 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 epidermal Dermis dendritic cells. Desmosomes Sensory Melanin granule nerve ending Epidermal Melanocyte Tactile dendritic cell 4 Layers of the epidermis (Merkel) cell Figure 5.2b Layers of the Epidermis: Stratum Corneum (Horny Layer) 20–30 rows of dead, flat, keratinized membranous sacs Three-quarters of the epidermal thickness Functions Protects from abrasion and penetration Waterproofs Barrier against biological, chemical, and physical assaults Layers of the Epidermis: Stratum Lucidum (Clear Layer) In thick skin Thin, transparent band superficial to the stratum granulosum A few rows of flat, dead keratinocytes Layers of the Epidermis: Stratum Granulosum (Granular Layer) Thin; three to five cell layers in which keratinocytes flatten The proteins keratin and keratohyaline accumulate  Layers of the Epidermis: Stratum Spinosum (Prickly Layer) 8 – 10 layers thick, daughter cell form lower basale layer push up into this layer Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes Abundant melanin granules and dendritic cells Melanin granules come from melanin cells Dendritic cells are part of the immune system and defend against microorganisms that made it through superficial layers and cancer cells  Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer firmly attached to the dermis via the basement membrane Single row of stem cells Also called stratum germinativum: cells undergo rapid division Forms epidermal ridges (e.g., fingerprints) Specialized Cells of Stratum Basale Merkel cells Found in hairless skin Respond to touch (trigger nervous system) Melanocytes Contain the pigment melanin Scattered throughout stratum basale  Perspiration Insensible perspiration Interstitial fluid lost by evaporation through the stratum corneum Sensible perspiration Water excreted by sweat glands Dehydration results: From damage to stratum corneum (e.g., burns and blisters [insensible perspiration]) From immersion in hypertonic solution (e.g., seawater [osmosis])  Dermis Strong, flexible connective tissue Elastic fibers provide stretch-recoil properties Collagen fibers provide strength and resiliency and bind water Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells Two layers: Papillary Reticular Stretch marks result when weight gain/size increase is faster then the fibers of the dermis can stretch.  Hair shaft Dermal papillae Epidermis Subpapillary Papillary vascular plexus layer Pore Appendages of skin Dermis Reticular Eccrine sweat layer gland Arrector pili muscle Hypodermis Sebaceous (superficial fascia) (oil) gland Hair follicle Nervous structures Hair root Sensory nerve fiber Cutaneous vascular Pacinian corpuscle plexus Hair follicle receptor Adipose tissue (root hair plexus) Figure 5.1  Layers of the Dermis: Papillary Layer Papillary layer Areolar connective tissue with collagen and elastic fibers and blood vessels Dermal papillae contain: Capillary loops Meissner’s corpuscles (touch receptors) Free nerve endings (pain receptors)  The Reticular Layer of the Dermis Deepest skin layer Dense irregular CT Highly vascularized Sweat glands Oil glands Pressure receptors Pacinian corpuscles ~80% of the thickness of dermis Collagen fibers provide strength and resiliency Cleavage Lines are in this layer, collagen fibers parallel to skin surface Elastic fibers provide stretch-recoil properties  How the Dermis Works Abundant Collagen & elastic fibers Elastic fibers gives elasticity, which decreases with age Collagen = strength Contains fibroblasts, adipose cells, macrophages High vascularity of dermis helps regulate body temperature (thermoregulation) Cutaneous vasodilation Cutaneous vasoconstriction Skin Markings: Friction Ridges Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints  Skin Color Three pigments contribute to skin color: 1. Melanin, a yellow to reddish-brown to black, responsible for dark skin colors Produced in melanocytes; migrates to keratinocytes where it forms “pigment shields” for nuclei Freckles and pigmented moles 2. Carotene, yellow to orange, most obvious in the palms and soles, can be converted to Vit A, accumulates in fatty tissue 3. Hemoglobin Responsible for the pinkish hue of skin  Skin Color Can be a diagnostic tool Flushed (fever, embarrassment, hypertension) Cyanotic (low O levels) blue color Pale (pallor) (anemia) Jaundiced (liver issues) yellowish tinge Bronze hue (Addison’s disease) hypoactive adrenal cortex  Vitamin D3 Sunlight/UV radiation converts cholesterol-related steroid into Cholecalciferol (vitaminD3) Cholecalciferol is then converted in the liver and used by the kidneys to make calcitriol, which is needed for calcium and phosphorus absorption Appendages of the Skin Derivatives of the epidermis Sweat glands Oil glands Hairs and hair follicles Nails  Sweat Glands (aka Sudoriferous) Two main types of sudoriferous glands 1. Eccrine (merocrine) sweat glands—abundant on palms, soles, and forehead Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes Ducts connect to pores Function in thermoregulation 2. Apocrine sweat glands—confined to axillary and pubic areas Sebum: sweat + fatty substances and proteins Ducts connect to hair follicles Functional from puberty onward (as sexual scent glands?) Specialized apocrine glands Ceruminous glands—in external ear canal; secrete cerumen Mammary glands  Sweat pore Eccrine gland Sebaceous gland Duct Dermal connective tissue Secretory cells (b) Photomicrograph of a sectioned eccrine gland (220x) Figure 5.5b  Sebaceous (Oil) Glands Widely distributed Most develop from hair follicles Become active at puberty Sebum Oily holocrine secretion Bactericidal Softens hair and skin  Sweat pore Sebaceous Dermal gland connective tissue Sebaceous Eccrine gland duct gland Hair in hair follicle Secretory cells (a) Photomicrograph of a sectioned sebaceous gland (220x) Figure 5.5a  Hair Functions Alerting the body to presence of insects on the skin Guarding the scalp against physical trauma, heat loss, and sunlight Distribution Entire surface except palms, soles, lips, nipples, and portions of external genitalia Consists of dead keratinized cells Contains hard keratin; more durable than soft keratin of skin Hair pigments: melanins (yellow, rust brown, black) Gray/white hair: decreased melanin production, increased air bubbles in shaft  Hair Follicle Extend from epidermal surface to dermis Two-layered wall - part dermis, part epidermis Hair follicle is where hair is made Hair bulb w/in follicle has superficial layer of cells (hair matrix) that produce the hair cells via division Medulla, cortex, cuticle Hair follicle receptor (root hair plexus) Sensory nerve endings around each hair follicle Stimulated by bending a hair Arrector pili Smooth muscle from papillary region of dermis attached to follicle CT sheath Responsible for “goose bumps”  Hair Follicles Hair bulb Expanded deep end Hair follicle receptor (root hair plexus) Sensory nerve endings - touch receptors Hair matrix Actively dividing area Arrector pili Smooth muscle attached to follicle Responsible for "goose bumps" Hair papilla Dermal tissue - blood supply © 2013 Pearson Education, Inc. Figure 5.5a Skin appendages: Structure of a hair and hair follicle. Follicle wall Peripheral connective tissue (fibrous) sheath Glassy membrane Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Hair shaft Cortex Medulla Diagram of a cross section of a hair within its follicle Arrector pili Sebaceous gland Hair root Hair bulb © 2013 Pearson Education, Inc. Figure 5.5c Skin appendages: Structure of a hair and hair follicle. Hair shaft Arrector pili Sebaceous gland Follicle wall Hair root Peripheral connective tissue (fibrous) sheath Hair bulb Glassy membrane Epithelial root sheath External root sheath Internal root sheath Hair root Cuticle Cortex Medulla Hair matrix Hair papilla Melanocyte Subcutaneous adipose tissue Diagram of a longitudinal view of the expanded hair bulb of the follicle, which © 2013 Pearsonencloses Education, Inc.the matrix Types and Growth of Hair Vellus hair Pale, fine body hair of children and adult females Terminal hair Coarse, long hair of eyebrows, scalp At puberty Appear in axillary and pubic regions of both sexes 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 © 2013 Pearson Education, Inc. Nails Scalelike modifications of epidermis Protective cover for distal, dorsal surface of fingers and toes Contain hard keratin Nail growth is from nail root Nail body, the part that is painted Covers an area called the nail bed © 2013 Pearson Education, Inc. Figure 5.6 Skin appendages: Structure of a nail. Lunule Lateral nail fold Free edge Body Eponychium Root of nail of nail of nail (cuticle) Proximal Nail nail fold matrix Hyponychium Nail bed Phalanx (bone of fingertip) © 2013 Pearson Education, Inc. Burns Tissue damage caused by heat, electricity, radiation, certain chemicals Denatures proteins Kills cells Immediate threat: Dehydration and electrolyte imbalance Leads to renal shutdown and circulatory shock To evaluate burns Rule of nines Used to estimate volume of fluid loss © 2013 Pearson Education, Inc. Figure 5.9 Estimating the extent and severity of burns using the rule of nines. Totals 41/2% Anterior and posterior head and neck, 9% Anterior and posterior upper limbs, 18% 41/2% Anterior 41/2% Anterior and posterior trunk, trunk, 36% 18% 9% 9% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% © 2013 Pearson Education, Inc. Burns Classified by Severity Partial-thickness burns First degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear Full-thickness burns Third degree Entire thickness of skin involved Skin gray-white, cherry red, or blackened Not painful (nerve endings destroyed) or swollen Skin grafting usually necessary © 2013 Pearson Education, Inc. Figure 5.10 Partial thickness and full thickness burns. 1st-degree burn 3rd-degree burn 2nd-degree burn Skin bearing partial thickness Skin bearing full thickness burn (1st- and 2nd-degree burns) burn (3rd-degree burn) © 2013 Pearson Education, Inc. Severity and Treatment of Burns 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 © 2013 Pearson Education, Inc.  Skin Cancer Three major types: Basal cell carcinoma Least malignant, most common Squamous cell carcinoma Second most common Melanoma Most dangerous  Major Types of Skin Cancer Basal Cell Carcinoma Stratum basale cells proliferate and slowly invade dermis and hypodermis Cured by surgical excision in 99% of cases Squamous Cell Carcinoma Involves keratinocytes of stratum spinosum Most common on scalp, ears, lower lip, and hands Good prognosis if treated by radiation therapy or removed surgically Melanoma Involves melanocytes Highly metastatic and resistant to chemotherapy Treated by wide surgical excision accompanied by immunotherapy  Melanoma Characteristics to Look For… Characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser) Can add E in there too… E: Elevation is higher then surrounding tissue