Integumentary System Chapter 5 PDF

INTEGUMENTARY Chapter 5 SYSTEM  INTRODUCTION TO SKIN Most accessible but often least appreciated organ system. The skin, or simply integument, accounts for approximately 16% of your total body weight. The skin’s surface, 1.5 - 2.0 m2, is constantly worn away Skin is compose...

INTEGUMENTARY Chapter 5 SYSTEM  INTRODUCTION TO SKIN Most accessible but often least appreciated organ system. The skin, or simply integument, accounts for approximately 16% of your total body weight. The skin’s surface, 1.5 - 2.0 m2, is constantly worn away Skin is composed of two major components: 1. Cutaneous membrane 2. Accessory structures  FUNCTIONS Integument Protection of underlying tissues and organs against impact, abrasion, fluid loss, and chemical attack Excretion of salts, water, and organic wastes by integumentary glands Maintenance of normal body temperature Production of melanin which protects underlying tissue from ultraviolet radiation Production of keratin, which protects against abrasion and serves as a water repellent Synthesis of vitamin D3, Storage of lipids in adipocytes Detection of touch, pressure, pain  TWO COMPONENTS OF SKIN Layers of Skin The skin is composed of two main layers: Epidermis made of closely packed epithelial cells Dermis made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures. Hypodermis Beneath the dermis ○ which is composed mainly of loose connective and fatty tissues.  EPIDERMIS The epidermis is composed primarily of keratinocytes arranged into layers called strata. Thin skin epidermis 4 strata layers Thick skin epidermis 5 strata layers (palms and soles)  STRATA (LAYERS) OF THE EPIDERMIS Stratum Corneum = the “horny layer”; outermost layer Cells in surface layer remain about 2 weeks before being shed or washed away 15–30 layers of dead keratinized cells held together by desmosomes Water resistant, not waterproof since we lose water through insensible perspiration (unable to see or feel) and sensible perspiration (sweat)  STRATA (LAYERS) OF THE EPIDERMIS Stratum Lucidum = the “clear layer” Flattened, densely packed dead cells filled with keratin ONLY found in Thick Skin  STRATA (LAYERS) OF THE EPIDERMIS Stratum Granulosum = the “grainy layer” 3–5 layers of keratinocytes that have stopped dividing and started producing keratin Cells grow thinner and flatter and cell membrane becomes less permeable produce granules of keratohyalin Lipid molecules  STRATA (LAYERS) OF THE EPIDERMIS Stratum Spinosum = the “spiny layer” Composed of 8–10 layers of keratinocytes bound together by desmosomes Contains dendritic (Langerhans) cells defending against microorganisms and superficial skin cancers  STRATA (LAYERS) OF THE EPIDERMIS Stratum Basale = the “basement layer”; innermost layer Attached to basement membrane. Most cells here are basal cells, stem cells that divide to replace more superficial keratinocytes. Melanocytes Merkel cells that respond to touch are also found here.  RIDGES OF THE SKIN Forms out fingerprints Holds epidermis & dermis together  DERMIS The dermis supports the epidermis and the hypodermis connects the dermis to the rest of the body. Papillary layer Named for dermal papillae in this region Composed of areolar tissue Contains capillaries, lymphatic vessels, and sensory neurons DERMIS Reticular layer Interwoven meshwork of dense irregular connective tissue Contains both collagen and elastic fibers Collagen fibers from this layer blend into both the papillary layer above and the hypodermis below Contains blood vessels, lymphatic vessels, nerve fibers, and accessory organs (hair follicles, sweat glands)  HYPODERMIS ○Separates skin from deeper structures ○Stabilizes position of skin relative to underlying tissues ○Allows independent movement ○Dominated by adipose tissue Important energy storage site NOT part of cutaneous membrane  PIGMENTATION Factors influencing skin color include epidermal pigmentation via melanin and carotene dermal circulation. ACCESSORY ORGANS OF SKIN Nerve fibers and corpuscles Hair follicles, hair shafts, and arrector pili muscles Oil glands and sweat glands Arteries, veins, and lymph vessels Nails (form from thickened epidermal cells nestled into the dermis forming a nail field) HAIRS AND THEIR ASSOCIATED STRUCTURES ○ Found almost everywhere on the body Except palms of hands, soles of feet, sides of fingers and toes, lips, parts of external genitalia ○ Body has about 2.5 million hairs 75 percent on general body surface (not the head) ○ Non Living structures Each hair produced by a hair follicle Two types of hair 1. Terminal hairs Large, coarse, darkly pigmented Examples: hairs found on scalp or in armpit 2. Vellus hairs Smaller, shorter, delicate Found on general body surface Structure of Hair and Follicle Hair is a filament of keratinized cells – shaft is fully keratinized and is visible above skin – root is within follicle and not yet fully keratinized Follicle is oblique tube/sack within the skin – bulb is swelling in base where hair originates (mitosis) – vascular tissue (dermal papilla) in bulb provides nutrients – cells lining the follicle interlock with scales of cuticle to resist pulling on the hair  Associated Hair Structures Hair receptors entwine each follicle Arrector pili muscles – smooth muscles that cause goose bumps Sebaceous glands are located alongside the hair root  Nails Clear, hard derivative of stratum corneum – densely packed cells filled with hard keratin Flat nails allow for fleshy, sensitive fingertips plate  Cutaneous Glands Sweat glands eccrine apocrine Sebaceous glands Produce sebum Ceruminous glands Produce earwax Mammary glands Produce milk Sweat Glands Filtrate of blood plasma containing some waste products lactic acid forms “acid mantle” Eccrine glands millions of them cool the body Apocrine glands produce sweat containing fatty acids found only near hair follicles and respond to stress and sexual arousal fatty acids support bacteria → body odor  Sebaceous Glands Oily secretion called sebum that contains broken-down cells Makes hair and skin pliable antibacterial properties Arrector pili muscles help squeeze sebum up to skin surface Assists with waterproof barrier of skin  Other Apocrine Glands Ceruminous Glands Mammary Glands – Their secretion combines modified sweat gland with sebum to produce thicker secretions released earwax by ducts that open at the waterproof nipple keeps eardrum flexible bitterness repel mites & other pests SENSORY RECEPTORS IN THE SKIN ~400 cm of nerve fibers per cm2 of skin Receptors in the epidermis Free nerve endings Sensitive to touch and pressure Between epidermal cells Tactile discs (Merkel cells) Detect texture and steady pressure Found in deepest layer of epidermis extending into dermis Tactile (Meissner’s) corpuscles Detect light touch, pressure, and vibration Found in the papillary layer Lamellated (Pacinian) corpuscles Detect deep pressure and vibration Found in both dermal layers and in hypodermis SKIN CANCER Basal cell carcinoma Most common form of skin cancer Originates in stratum basale due to mutations caused by overexposure to UV radiation Virtually no metastasis and most people survive  SKIN CANCER Squamous cell carcinoma Effects the keratinocytes of the stratum spinosa and presents as lesions. Squamous cell carcinoma presents here as a lesion on an individual’s nose. Second most common skin cancer ABCDE rule Asymmetrical Borders Color Diameter Evolving  SKIN CANCER Malignant melanoma Most serious form of skin cancer Extremely dangerous Cancerous melanocytes grow rapidly and metastasize through lymphatic system If detected early and removed surgically, the 5-year survival rate is 99 percent If not detected until after metastasis, the 5-year survival rate drops to 14 percent ○ABCDE rule  ACNE Acne Acne is a result of over-productive sebaceous glands, which leads to formation of blackheads and inflammation of the skin.  First-degree – involves epidermis only; red and swollen Second-degree – involves epidermis and upper layer of dermis; skin is red and painful with blisters Burns Third-degree – entire thickness (both epidermis and dermis) is destroyed. Skin grafting is required because regeneration will not occur – only scar tissue forms. Arthritis and stiffness are serious problems associated with third-degree burns.  SKIN FUNCTIONS AFFECTED BY BURNS Fluid and electrolyte balance Skin loses effectiveness as a barrier In full-thickness burns, fluid loss rate increases up to five times normal level Thermoregulation Increased fluid loss = increased evaporative cooling Takes more energy to maintain body temperature Protection from infection Dampness (from fluid loss) encourages bacterial growth If skin is broken, infection likely to occur Sepsis (sepsis, rotting) Widespread bacterial infection Leading cause of death in burn victims AGE-RELATED CHANGES IN SKIN