Integument System

Chapter 5

Functional Organization of Integument

The Skin as an Organ• Largest of the body• All 4 epithelial tissue types represented• Ranges in thickness– Thick (palms, fingertips, soles of feet)– Thin (rest of body)

• 2 layers– Epidermis is stratified squamous

• 4/5 layers and 4 cell types– Dermis is dense irregular CT

• Multiple cell types and accessory structures; 2 layers• Hypodermis not true integument

• Connective tissue and fat cells

Epidermal Layers• Stratum basale

– Single row, many nuclei– Attached to basal lamina

• Stratum spinosum– Thick layers of ‘spiny’ keratinocytes

• Stratum granulosum– Thin, 3-5 layers– Keratincoytes fill w/ keratin– Cells ‘toughen’ and die

• Stratum lucidum– Thin, translucent layer– Only in thick skin– Few, dead, densely packed keratinocytes

• Stratum corneum– 20-30 cells thick– 14 days for cells to reach and remain up to 14

Epidermal Cells

• Merkel cells– Touch sensitive cells– Epidermal/dermal border

• Langerhans cells– Phagocytic cells– Assist immune system response– Formed in bone marrow

Epidermal Cells (cont.)• Keratinocytes

– Produce keratin– Joined by desmosomes– Formed deep– Dead at surface

• Accelerated on feet/hands• Calluses from constant friction

• Melanocyte– Produce melanin– Formed deep– Keratinocytes take up

• Skin color due to activity not number• Tans signal DNA damage, fades as

keratinocytes destroy

Skin Coloration

• Melanin is black, yellow-brown, or brown– Made by skin and stimulated by sun– Freckles and moles are accumulations

• Carotene is yellow to orange pigments– Accumulates in st. corneum and fatty tissue in skin– Most obvious where stratum corneum is thickest

• Hemoglobin is crimson colored respiratory pigment– Reduced blood supply turns skin white– Poorly oxygenated blood appears blue = cyanosis

• Response to extreme cold or from respiratory disorders

Skin Color Disruptions

• Leathery skin – clumping of elastin fibers from excessive sun (cancer too)

• Redness – embarrassment, fever, inflammation or allergy• Pallor/blanching – emotional distress, anemia, low BP• Jaundice – liver disease, bile pigment deposition• Bronzing – hypofunctioning of adrenal cortex, Addison’s• Hematomas – black n blue bruises, escaped blood clots in

tissue

Dermis

• Flexible and strong CT– Nerve fibers, blood vessels, and lymphatic vessels

• Tearing causes striae or strech marks• Blisters when epi- and dermis separate by

fluid-filled pocket• 2 layers– Papillary layer– Reticular layer

Dermal Layers

Papillary layer (20%)• Areolar CT • Ridged surface projections =

dermal papillae/epidermal ridges– On feet and palms– Increase friction, enhance

grip, and fingerprints (sweat gland)

• Contain light pain and touch receptors (Meissner’s corpuscle)

Reticular layer (80%)• Dense irregular CT• Accessory structures • Collagen fibers and adipose

– Holds water = hydration• Cleavage lines

– Orientation related to skin stresses

– Parallel cuts remain closed = faster healing

– Right angles pulled open with recoil

• Flexure lines (elbow)

ACCESSORIES OF THE SKIN

Sudoriferous (Sweat) Glands• Almost everywhere• Innervation contracts causing secretion• Eccrine sweat glands

– Palms, soles, forehead– Hypotonic blood filtrate released by exocytosis

• Body cooling• Emotional

– Gland in dermis, duct into surface pore• Apocrine* sweat glands

– Axillary and anogenital regions– Secretions into hair follicle ducts– Similar to eccrine secretion

• Starts at puberty = body odor when mixed w/ bacteria

• Ceruminous– Cerumen (earwax)

• Mammary glands

Sebaceous (Oil) Gland

• Almost everywhere, but palms and soles• Holocrine glands (describe secretion mode)• Secreted onto hair follicle or into a pore– Softens hair and prevents water loss = brittle– Lubricates skin– Antibacterial function

• Disorders– Whitehead, blackhead, acne– ‘Cradle cap’– Dandruff , seborrheic dermatitis

http://z.about.com/d/dermatology/1/0/p/6/Comedone_papule.jpg

Hair• Other mammals = warmth• Humans = protection, sensation, filters

– Few areas lack (palms, soles, lips)• ‘Hair’ (shaft and root) are dead, keratinized

cells– Ribbonlike = kinky, oval = wavy, round = straight– Matrix with 3 layers: medulla, cortex, cuticle

• Follicle into dermis expands to bulb– Receptors surround– Papilla w/ capillaries = nutrients

• Arrector pili muscle• Hair pigment from melanocytes

Nails

• Modified hard keratinized epidermis– Protect, grasp, and itch

• Richly vascularized• Free edge, nail body (stratum corneum), nail

bed (stratum spinosum), and root (lunula)• Nail folds (lateral and proximal) extend =

eponychium (cuticle)• Hyponychium (quick)

Burns

• Loss of fluids renal shut down, denatured proteins– IV of fluids immediately– Extra caloric intake

• Rule of nines– 11 areas at 9% body (genitals 1%)– Estimate

• Sepsis– Protective role decreased after 24 hours– Immune system done 1 -2 days after

• Classifying– 1st degree: epidermal damage; redness and swelling (sunburn)– 2nd degree: epidermis and upper dermis; blisters form (cooking)– 3rd degree: epidermis and dermis; gray-white/blackened, nerve destruction

• Skin grafting

Integument Functions• Protection

– Barrier to microorganisms, abrasions, and water loss• Thermoregulation

– Vasoconstriction or –dilation of blood vessels, – Goose bumps or sweat– Fat and hair

• Sensation– Nerve endings to detect external stimuli throughout– Meissner’s corpuscles, Merkel discs, Pacinian corpuscles, hair follicle

receptors, and free nerve endings• Metabolic roles

– Vitamin D from cholesterol– Proteins to deter wrinkles

• Excretion– Removes wastes from body (sweat)