Chapter 5: Integumentary System PDF

CHAPTER 5: INTEGUMENTARY SYSTEM Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Skin (Integument) The skin (cutaneous membrane) is the largest organ of the body by surface area and weight Consists of three major regions: Epidermis—superficial region Dermis—middle region Hypodermi...

CHAPTER 5: INTEGUMENTARY SYSTEM Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Skin (Integument) The skin (cutaneous membrane) is the largest organ of the body by surface area and weight Consists of three major regions: Epidermis—superficial region Dermis—middle region Hypodermis (superficial fascia)—deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Epidermis givesstrength ● Keratinized stratified squamous epithelium ● Cells of epidermis: ● ● ● ● ● Keratinocytes—produce a tough fibrous protein keratin – provides protection Melanocytes Produce pigment melanin Epidermal dendritic (Langerhans) cells—macrophages that help activate immune system Phagocytes Tactile (Merkel) cells—touch receptors Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Epidermis: Stratum Basale (Basal Layer) ● Deepest epidermal layer firmly attached to the dermis ● ● ● ● Single row of stem cells where cells produced Also called stratum germinativum: cells undergo rapid division Journey from basal layer to surface Takes 25–45 days Cells migrating toward surface Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Epidermis: Stratum Spinosum (Prickly Layer) ● Melanin granules and Langerhans’ cells are abundant in this layer Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Epidermis: Stratum Granulosum (Granular Layer) ● grainy Thin; three to five cell layers in which drastic changes in keratinocyte appearance occurs Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Epidermis: Stratum Lucidum (Clear Layer) sols of Palms of hands feet ● Thin, transparent band superficial to the stratum granulosum ● Consists of a few rows of flat, dead keratinocytes ● Present only in thick skin Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Layers of the Epidermis: Stratum Corneum (Horny Layer) ● Outermost layer of keratinized cells ● Accounts for three quarters of the epidermal thickness ● Functions include: ● ● ● ● Waterproofing Protection from abrasion and penetration Rendering the body relatively insensitive to biological, chemical, and physical assaults Dandruff - an excess of keratinized cells shed from the scalp Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stratum corneum 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 Desmosome dendritic cells. sMelanin Melanocyt granule (b) e Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Keratinocyte s Dermi s Sensory nerve ending Epidermal Tactile dendritic cell (Merkel) cell Figure Dermis ● ● ● ● ● Strong, flexible connective tissue Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells Two layers: Papillary Reticular Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Definite Hair shaft Epidermis Papillar y layer Dermis Reticula r layer Hypodermis (superficial fascia) Nervous structures • Sensory nerve fiber • Pacinian corpuscle • Hair follicle receptor (root hair plexus) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Dermal papillae Subpapillary vascular Por plexus e Appendages of skin • Eccrine sweat •gland Arrector pili muscle • Sebaceous •(oil) Hairgland •follicle Hair Cutaneous root vascular Adiposeplexus tissue Figure 5.1 Layers of the Dermis: Papillary Layer ● ● ● ● ● Papillary layer Areolar connective tissue with collagen and elastic fibers Its superior surface contains peglike projections called dermal papillae Dermal papillae contain capillary loops, Meissner’s corpuscles (light touch receptors) , and free nerve endings Epidermal ridges reflect contours of the underlying dermal papillae and form the basis for fingerprints (and footprints); their function is to increase firmness of grip by increasing friction. Tinder Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings manua Layers of the Dermis: Reticular Layer ● ● ● ● Reticular layer 20 l pasillare layer Accounts for approximately 80% of the thickness of the dermis Collagen fibers in this layer add strength and resiliency to the skin Elastin fibers provide stretch-recoil properties Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hypodermis ● Subcutaneous layer deep to the skin ● Composed of adipose and areolar connective tissue Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skin Color ● ● ● ● ● ● ● Three pigments contribute to skin color: Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors Freckles and pigmented moles (nevus) – result from local accumulations of melanin Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet Hemoglobin – reddish pigment responsible for the pinkish hue of the skin Albinism – an inherited inability to produce melanin Vitiligo – a condition in which there is a partial or complete loss of melanocytes from patches of skin Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Argyria Silver embeds Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings in skin per meant Sweat Glands (Sudoriferous) ● ● ● ● ● ● Different types prevent overheating of the body; secrete cerumen and milk Eccrine sweat glands – found in palms, soles of the feet, and forehead Apocrine sweat glands – found in axillary and anogenital areas Modified sweat glands: Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen Cear wax Mammary glands – specialized sweat glands that secrete milk Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sebaceous (Oil) Glands ● Widely distributed ● Most develop from hair follicles ● Become active at puberty ● Sebum ● ● ● Oily holocrine secretion Bactericidal Softens hair and skin Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair ● ● ● ● ● Filamentous strands of dead keratinized cells produced by hair follicles Contains hard keratin which is tougher and more durable than soft keratin of the skin Made up of the shaft projecting from the skin, and the root embedded in the skin Pigmented by melanocytes at the base of the hair Gray/white hair: decreased melanin production Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair Function and Distribution ● ● ● ● Functions of hair include: Helping to maintain warmth Alerting the body to presence of insects on the skin Guarding the scalp against physical trauma, heat loss, and sunlight Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair Function and Distribution ● ● ● Hair is distributed over the entire skin surface except: Palms, soles, and lips Nipples and portions of the external genitalia Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair Follicle ● ● ● ● ● ● Hair follicle receptor (root hair plexus) Sensory nerve endings around each hair bulb Stimulated by bending a hair Arrector pili Smooth muscle attached to follicle Responsible for “goose bumps” Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Types of Hair ● ● Vellus – pale, fine body hair found in children and the adult female Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hair Thinning and Baldness ● Alopecia – hair thinning in both sexes ● True (frank) baldness ● ● Genetically determined and sex-influenced condition Male pattern baldness – caused by follicular response to DHT Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of a Nail ● Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5.6 Functions of the Integumentary System ● ● ● ● ● 1) Protection – chemical, physical, and mechanical barrier 2) Body temperature regulation is accomplished by: Dilation (cooling) and constriction (warming) of dermal vessels Increasing sweat gland secretions to cool the body 3) Cutaneous sensation – temperature, touch, and pain Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Integumentary System ● ● ● 4) Metabolic functions – synthesis of vitamin D in dermal blood vessels 5) Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume 6) Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skin Cancer ● ● ● ● ● Most skin tumors are benign and do not metastasize Risk factors Overexposure to UV radiation Frequent irritation of the skin A crucial risk factor for nonmelanoma skin cancers is the disabling of the p53 gene Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skin Cancer ● ● ● ● ● ● ● Three major types: 1) Basal cell carcinoma Least malignant, most common 2) Squamous cell carcinoma Second most common 3) Melanoma Most dangerous Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Basal Cell Carcinoma ● ● Slow growing and do not often metastasize Can be cured by surgical excision in 99% of the cases Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure Squamous Cell Carcinoma ● Arises from keratinocytes of stratum spinosum ● Arise most often on scalp, ears, and lower lip ● Grows rapidly and metastasizes if not removed ● Prognosis is good if treated by radiation therapy or removed surgically Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure Melanoma ● ● ● Cancer of melanocytes is the most dangerous type of skin cancer because it is: Highly metastatic Resistant to chemotherapy Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Melanoma ● ● ● ● ● Melanomas have the following characteristics (ABCD rule) A: Asymmetry; the two sides of the pigmented area do not match B: Border is irregular and exhibits indentations C: Color (pigmented area) is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Normal Vs. Melanoma Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Melanoma ● ● Treated by wide surgical excision accompanied by immunotherapy Chance of survival is poor if the lesion is over 4 mm thick Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure Partial-Thickness Burns ● ● ● ● ● ● First degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 1st degree burn 2nd degree burn (a) Skin bearing partial thickness burn (1st and 2nd degree burns) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure Full-Thickness Burns ● ● ● ● ● Third degree Entire thickness of skin damaged Gray-white, cherry red, or black No initial edema or pain (nerve endings destroyed) Skin grafting usually necessary Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 3rd degre e burn (b) Skin bearing full thickness burn (3rd degree burn) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5.10b Rule of Nines ● Estimates the severity of burns ● Burns considered critical if: ● ● ● Over 25% of the body has second-degree burns Over 10% of the body has third-degree burns There are third-degree burns on face, hands, or feet Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Totals 4 1 /2 % Anterior and posterior head and neck, 9% 4 1 /2 % Anterior trunk, 18% 9% Anterior and posterior upper limbs, 18% 4 1 /2 % Anterior and posterior trunk, 36% 9% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5.9 Developmental Aspects of the Integument: Old Age ● ● ● ● ● Epidermal replacement of cells slows and skin becomes thinner Skin becomes dry and itchy Subcutaneous fat layer diminishes, leading to intolerance of cold Decreased elasticity and loss of subcutaneous tissue leads to wrinkles Decreased numbers of melanocytes and Langerhans’ cells may increase the risk of skin cancer Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings