[SKIN, HAIRS, GLANDS,NAILS]

INTEGUMENTARY SYSTEM

FUNCTIONS1. Protection

– Against abrasion and UV light

– Prevents entry of microorganisms

– Prevents dehydration2. Sensation

– Sensory receptors that can detect heat, cold, touch, pressure, and pain

FUNCTIONS

3. Temperature regulation by controlling

– Blood flow through the skin

– Sweat gland activity4. Vitamin D production5. Excretion of small

amounts of waste products

SKIN SA – 1.2-2.2 m2 and weighs 4-5

kg (9-11 lbs) 2 MAJOR REGIONS:

1. EPIDERMIS2. DERMIS* HYPODERMIS/SUBCUTANEOUS TISSUE (not a part of the skin)

FIG. 5.1

EPIDERMIS Keratinized stratified squamous

epithelium

CELL TYPES:1. Melanocytes 2. Keratinocytes3. Merkel cells4. Langerhans’ cells

5 LAYERS

EPIDERMAL CELLS

Keratinocytes Most abundant cell type Produce the fibrous protein keratin Gives skin its protective properties

Melanocytes Produce the brown pigment melanin Found in the deepest layers of the epidermis

EPIDERMAL CELLS

Langerhans’ cells Epidermal macrophages Help activate the immune system

Merkel cells Touch receptors in association with sensory nerve endings

EPIDERMAL LAYERS STRATUM BASALE/GERMINATIVUM

STRATUM SPINOSUM

STRATUM GRANULOSUM

STRATUM LUCIDUM

STRATUM CORNEUM

EPIDERMAL LAYERS

Stratum Basale (Basal Layer) Deepest epidermal layer firmly

attached to the dermis Structural strength is provided by desmosomes and hemidesmosomes

Consists of a single row of the youngest keratinocytes

Cells undergo mitotic divisions ~every 19 days

10-25% are melanocytes

Stratum Spinosum Melanin granules and Langerhans’ cells

are abundant in this layer Melanin is taken up by the keratinocytes and accumulates on the “sunny side” to protect the nucleus from UV damage

Stratum Granulosum Keratohyaline and lamellated bodies

(waterproofing) accumulate in the cells of this layer

Above this layer the epithelial cells die because they are too far from the dermis

Stratum Lucidum Thin, transparent band superficial to the stratum granulosum

Consists of a few rows of flat, dead keratinocytes

Present only in thick skin

Stratum Corneum Outermost layer of keratinized cells

Accounts for three quarters of the epidermal thickness

20-30 cell layers thick, all dead.

Millions rub off everyday. Totally new every 25-45 days.

FIG. 5.2B

FIG. 5.3

THICK & THIN SKIN Thick skin has all five epithelial strata

Thin skin contains fewer cell layers per stratum Stratum lucidum is usually absent

Hair is found only in thin skin

SKIN COLOR Melanocytes produce melanin inside

melanosomes and then transfer the melanin to keratinocytes

The size and distribution of melanosomes determine skin color

Melanin production is determined genetically but can be influenced by UV light (tanning) and hormones

SKIN COLOR Increased blood flow produces a red

skin color (Erythema), whereas a decreased flow causes pale skin

Decreased oxygen content in the blood results in a bluish color called cyanosis

Carotene, an ingested plant pigment, can cause the skin to appear yellowish

DERMIS Second major skin region

containing strong, flexible connective tissue

Cell types include fibroblasts, a few adipose cells and macrophages

Composed of two layers: papillary and reticular

PAPILLARY LAYER * Areolar connective tissue with collagen and elastic fibers

*Its superior surface contains peg-like projections called dermal papillae Genetically determined Responsible for fingerprints and footprints (films of sweat)

PAPILLARY LAYER Contains blood vessels that supply the overlying epidermis With nutrients Remove waste products Aid in regulating body temperature

RETICULAR LAYER Dense irregular connective tissue Accounts for approximately 80% of

the thickness of the skin Collagen fibers in this layer add

strength and resiliency to the skin Elastin fibers provide stretch-recoil

properties Striae (stretch marks) are caused

when skin is overstretched, the dermis ruptures and leaves visible lines

HYPODERMIS• Deep to the skin• Composed of adipose and areolar

connective tissue• Not really part of the skin• Mostly adipose tissue• Stores fat and connects the skin to the

underlying structures (mainly muscles)• Shock absorber and insulator• Increases greatly as you gain weight

EPIDERMAL APPENDAGES

HAIRS

GLANDS

NAILS

HAIRS Lanugo (fetal hair) is replaced near the time of

birth by terminal hairs (scalp, eyelids, and eyebrows) and vellus hairs

At puberty, vellus hairs can be replaced with terminal hairs

Hairs are columns of dead, keratinized epithelial cells

A shaft above the skin A root below the skin A hair bulb at the site of hair formation

3 CONCENTRIC LAYERS INNER MEDULLA - with pigment granules & air

spaces

MIDDLE CORTEX - pigment granules in dark hair - mostly air in white hair

OUTER CUTICLE - keratinized thin flat cells

FIG. 5.6

HAIRS HAIR FOLLICLE: surrounds hair root HAIR BULB: houses 1. hair papillae: provides

nourishment to growing hairs;

contains blood vessels

2. hair matrix: germinal layer

hair growth & production

GROWTH CYCLE OF HAIRS GROWTH STAGE - cells at the hair matrix differentiate, divide, become keratinized, & die -as new cells are added at the hair root,

hair grows longer

RESTING STAGE - matrix is inactive - hair follicle atrophies

HAIRS Normal hair loss in an adult scalp: 70-100 hairs

Rate of growth/replacement depends on:

Illness Surgery Diet Blood loss High fever Severe emotional stress

HAIR COLOR Melanin in dark-colored hair

Melanin and more of S in blond hair

Melanin and more of Fe in red hair

Gray hair: progressive decline of TYROKINASE

White hair: accumulation of air bubbles in the medullary shaft

SEBACEOUS GLANDS Simple or compound alveolar

glands Found all over the body except

on the palms and soles Soften skin when stimulated

by hormones Secrete an oily secretion called

sebum Acne is an active inflammation

of the sebaceous glands.

FIG. 5.7

SWEAT /SUDORIFEROUS GLANDS

MEROCRINE SWEAT GLANDS: Produce sweat, which cools the body Most numerous in the palms and soles of the

feet

APOCRINE SWEAT GLANDS: Found in axillary and genital areas Ducts empty into hair follicles Produce an organic secretion that can be broken down by bacteria to cause body odor

SWEAT GLANDS

CERUMINOUS GLANDS: Modified merocrine glands in external ear canal that secrete cerumen (ear wax)

MAMMARY GLANDS: Specialized sweat glands that secrete milk

FIG. 5.7

NAIL Stratum Corneum containing hard keratin

PARTS:1. Nail body2. Free edge3. Lunula4. Nail root5. Nail matrix

NAILS Nail growth: 1 mm/week

Slower in toenails

The longer the digit, the faster the nail grows

INTEGUMENTARY SYSTEM FUNCTIONS Protection

Skin Protects against

abrasion and UV light Prevents the entry of

microorganisms Helps regulate body

temperature Prevents water loss

Hair Protects against

abrasion and UV light Acts as a heat insulator

Nails protect the ends of the digits

Sensation Skin contains

sensory receptors for heat cold touch pressure pain

INTEGUMENTARY SYSTEM FUNCTIONS Temperature Regulation Skin

Controls heat loss from the body by dilation and constriction of blood vessels

Sweat glands Produce sweat, which evaporates and lowers body temperature

Vitamin D Production UV light stimulates the

production of a precursor molecule in the skin that is modified by the liver and kidneys into vitamin D

Vitamin D increases calcium uptake in the intestines

Excretion Skin glands remove

small amounts of waste products but are not important in excretion

BASAL CELL CARCINOMA Least malignant and most common skin

cancer Stratum Basale cells proliferate and invade

the dermis and hypodermis Slow growing and do not often metastasize Can be cured by surgical excision in 99% of

the cases

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

MELANOMA Cancer of melanocytes is the most

dangerous type of skin cancer because it is: Likely to metastasize Resistant to chemotherapy

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)

Treated by wide surgical excision accompanied by immunotherapy

Chance of survival is poor if the lesion is over 4 mm thick

BURNS First-degree: only the epidermis is damaged

Symptoms include localized redness, swelling, and pain

Second-degree: epidermis and upper regions of dermis are damaged

Symptoms mimic first degree burns, but blisters also appear

Third-degree: entire thickness of the skin is damaged

Burned area appears gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)

RULE OF NINES Estimates the

severity of burns Divides body into

areas that are ~ 9%, or multiples of 9%, of the total body area

Younger patients are different

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

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EFFECTS OF AGING ON THE INTEGUMENTARY

SYSTEM Epidermal replacement of cells slows and skin becomes thinner

Decreased elasticity and loss of subcutaneous tissue leads to wrinkles

Subcutaneous fat layer diminishes, leading to intolerance of cold

Skin becomes dry and itchy Sweat and sebaceous glands

are less active, and the number of melanocytes decreases