The Integumentary System

The Integumentary System

Integument = skin System includes: skin as well as hair and

nails 3 regions:

Epidermis (epithelial tissue)Dermis (connective tissue)Hypodermis

Functions of skin

Prevents unnecessary water loss (dehydration) Protection (chemical and physical barrier)

Cushions and insulates and is waterproof Protects from chemicals, heat, cold, bacteria, viruses Screens UV

Regulates body temp Synthesizes vitamin D with UV Blood Reservoir Secretion/Excretion

Epidermis *Keratinized stratified squamous epithelium Four basic layers (from top to bottom): We have a

totally “new” epidermis every 25-45 days Stratum corneum (Horny layer) “cornu”

Greek for hornTop layer and fully keratinized 20-30 layers thickProtect skin from abrasion and penetrationGlycolipids provide waterproofing40 lbs of dandruff shed in a lifetimeToo far from blood vessels for diffusion so cells

die

Stratum granulosum (Granular layer) 3-5 cell layers thick

Stratum spinosum (Prickly Layer) Prickly layer (Keratinocytes shrink but desmosomes hold

in place) Stratum basale/germinativum (Base germinating layer)

Deepest layer of the epidermis Single layer thick Contain melanocytes (special spider shaped cells)

*Stratum lucidum (Clear layer) Only a few layers thick; found only in hairless thick skin,

that is, Palms of hands Soles of feet

Epithelium: layers (on left) and cell types (on right)

Dermis *Rich supply of nerves and blood vessels Strong, flexible connective tissue: your “hide”

Strong flexible envelope of connective tissue Dermal Papillae from upper dermis form ridges

in the epidermis for grip (Fingerprints/footprints) Reticular layer of lower dermis (deepest skin

layer) of thickness made up of dense irregular connective tissue

Pigments which affect skin color Melanin (melan is Greek for black) (ONLY PIGMENT

PRODUCED IN THE SKIN – varies in color from yellow to reddish brown to black)

Carotene (Yellow/orange pigment found in plants which accumulates in the thick epidermis)

Hemoglobin (Red from the red blood cells) Cyanosis – bluish hue to the skin due to heart failure or

respiratory distress Erythema – reddish hue to the skin due to blushing, fever,

hypertension, polycythemia Pallor or blanching – pale skin hue due to emotional stress

(fear, anger), anemia, or hypotension Jaundice – yellow hue to the skin due to liver disorder Hematoma – (Bruises) blood leaks out of capillaries due to

trauma and clots under the skin

Dermal structures

1. Sudoriferous (sweat) glands (2.5 million per person) 2 types: Eccrine – Most abundant sweat gland covers; found all over the body

sweat is secreted by exocytosis into pores which empty onto the skin (possible to lose up to 7 L per day)

99% water, remaining solutes are sodium chloride, vitamin C, ammonia, urea, uric acid, and lactic acid (which attracts mosquitoes)

Sweat is acidic; which inhibits the growth of bacteria

Appocrine - Located in the axillary and genital areas Larger than eccrine glands. Secreted/Empty into hair follicles beginning at puberty Contains true sweat, lipids, and proteins and appears as a milky or yellowish

color odorless upon secretion, but bacteria decompose molecules forming body odor Increase of secretions during pain, stress, or sex but physiological function is

unknown (believed to be sexual scent glands as menstruation affects output) Modified apocrine glands: Ceruminous – secrete earwax; Mammary – secrete

milk

2. Sebaceous glands: AKA: oil glands Located all over body except palms and soles Secrete sebum which lubricates and softens hair and

skin, prevents water loss, and has bactericidal properties

Whitehead - occurs when duct is blocked by accumulated sebum and staphylococcus infection begins

Blackhead – when whitehead oxidizes and dries out

3. Hair (and Hair Follicles) Body hair – served early humans by providing insulation The bulk of the hair shaft is dead material and almost entirely

protein Hair color due to melanin (blonde to black hair) gray hair is a

result of lack of melanin or the replacement of melanin with air bubbles in the hair shaft

Hair appearance due to shaft shape (Flat shaft = curly hair, oval shaft = wavy hair, round shaft = straight hair)

Hormones account for the development of hair Average hair growth is 2 mm per week

*Hair follicle Extend from epidermis into the dermis Arrector pili (small bands of smooth muscle cells)

cause “Goose bumps” upon contraction Trap air close to skin for warmth Make us appear larger to predators

4. Nails Corresponds to the hoof or claw of other animals Nail matrix is responsible for growth of new nail Nails look pink due to blood supply in underlying

dermis, with the exception to this being the white crescent shaped area called the lunula

*Dermis layers

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*Dermal papillae

Epidermis and dermis of (a) thick skin (5 layers) and (b) thin skin (4 layers)

Hair and hair follicles: complexDerived from epidermis and dermisEverywhere but palms, soles, nipples, parts of genitalia

*“arrector pili” is smooth muscle

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Hair papilla is connective tissue________________

Hair bulb: epithelial cells surrounding papilla

Functions of hairWarmth – less in man than other mammalsSense light touch of the skinProtection - scalp

PartsRoot imbedded in skinShaft projecting above skin surface

Make up of hair – hard keratin Three concentric layers

Medulla (core)Cortex (surrounds medulla)Cuticle (single layers, overlapping)

Nails

keratin Corresponds to hooves and claws Grows from nail matrix

The dermis is the receptive site for the pigment of tattoos

Lunula vs. No/few lunula

Hypodermis

Hypodermis (Gk) = below the skin“Subcutaneous” (Latin) = below the skin; AKA:

“superficial fascia”Fatty tissue which stores fat and anchors skin

(areolar tissue and adipose cells)Different patterns of accumulation

(male/female)

Pathophysiology: homeostatic imbalances of skin Skin Cancer

Benign (Non-spreading) vs. malignant (spread into other tissue)

One in five Americans now develops skin cancer at some point in his or her life

Basal cell carcinoma – most common and least malignant Shiny lesions in the stratum basale which grow into the

dermis Full cure is the rule in 99% of cases after surgery

 Squamous cell carcinoma

Cells of the stratum spinosum form a lesion which appears a papule (small, rounded elevation)

Lesion usually forms on scalp, ears, dorsum of hands, and lower lip

Grows rapidly and can metastasize if not removed If caught early and removed, chance of cure is good

Melanoma (5% of skin cancers) Cancer of the melanocytes Most dangerous of the skin cancers Usually appears as a spreading brown to black patch Metastasizes rapidly to lymph and blood Chance for survival is about 50% (early detection helps) ABCDE rule to detect:

Asymmetry – two sides don’t match Border irregularity – not smooth and have indentations Color – more than one color Diameter – larger than 6 mm in diameter Elevation – elevated above skin surface

Basal cell carcinoma

Sqaumous cell carcinoma

Melanoma

Skin Cancer

BurnsBurns 1st degree – only epidermis is damaged e.g. sunburn

Heal in 2-3 days 2nd degree – epidermis and upper region of dermis damaged

Blisters form (Fluid collects between dermis and epidermis) Heal in 3-4 weeks Critical if over 25% of body has 2nd degree burns

3rd degree – epidermis and all of dermis is damaged (entire thickness of skin = full-thickness burns)

Burn area appears blanched (gray-white) or blackened Nerve endings are destroyed, so burned area is not painful Skin grafting necessary to cover exposed tissues Fluid loss can be catastrophic (dehydration & electrolyte imbalance

lead to renal failure and shock) Infection can be rampant Critical if more than 10% of the body is affected or if the face, hands,

or feet have 3rd degree burns

BurnsFirst-degree(epidermis only; redness)

Second-degree(epidermis and dermis,with blistering)

Third-degree(full thickness, destroying epidermis, dermis, often part of hypodermis)

Critical burns Over 10% of the

body has third-degree burns

25 % of the body has second-degree burns

Third-degree burns on face, hands, or feet

Estimate by “rule of 9’s”