The Integumentary SystemChapter 5

Cool Skin Facts:Surface Area = 1.2-2.2 sq.m(1/2 white board)

Weight = 4-5 kg (8-9lbs)7% of body weight

Thickness – 1.5-4.0 mmMillions rub off each day- New epidermis every 25-45 days

Two Regions

Epidermis

Dermis

Composed of epithelial tissue Outermost layer Non-vascular Keratinized stratified squamous

epithelium

Composed of fibrous connective tissue Underlying layer vascularized

Cells of the epidermis Keratinocytes- produce keratin, tightly

connected by desmosomes, continuous mitosis Melanocytes-pigment called melanin(protects

from UV), spider-shaped cells, found in deepest layer of epidermis

Merkel cells-shaped like spikey hemisphere, Merkel disc has sensory function

Langerhans cells -made on bone marrow, macrophages

Layers of Epidermis Stratum Basale- ( Basal Layer) bottom,

attached to dermis, youngest keratinocytes, 10-25% are melanocytes

Stratum Spinosum (Prickly Layer) intermediate filaments resist tension attach to desmosomes, keratinocytes appear spiny

Stratum Granulosum (Grandular layer) 3-5 layers thick, keratinocytes flatten, accumulate keratohyaline and lamellated granules

Epidermis layers cont. Stratum Lucidum (clear layer)- thin,

translucent, dead keratinocytes Stratum Corneum (Horny Layer)- 20-30

layers thick, ¾ of epidermal thickness, 40 lbs shed in lifetime

DermisPapillary and Reticular Layers

Papillary Thin, blood vessel rich, areolar

connective, collagen and elastin fibers, loosely woven

Dermal papillae- indent overlying epidermis, touch receptors(Meissner’s corpuscles), fingerprints

Reticular Layer 80% of thickness of dermal layer Dense irregular connective tissue Extra cellular matrix contains thick

bundles of interlacing collagen fibers, form cleavage, tension and lines in the skin, flexure lines (at joints)

Skin Pigments Melanin-

› Protects from UV› All have same

number only make different amounts

Carotene-› Yellow to orange› Accumulates in fatty

tissue and stratum corneum (soles of feet and palms)

› *Hemoglobin (found in Red blood cells) can give reddish hue

Skin color signs of diseases Redness (erythema)- embarrassment,

fever, hypertension, inflammation, allergy

Pallor (pale)- fear, anger, stress, anemia, low blood pressure

Jaundice (yellow)- liver disorder, bile pigments accumulate in body tissues, bilirubin secreted by liver cells as component of bile

Skin diseases continued…. Bronzing-Addison’s disease,

hypofunction of adrenal cortex Black and blue marks- hematomas

(bruise)

Appendages of the skin Nails Sweat glands (sudiferous glands) pH 4-6

› Eccrine (merocrine)-palms, soles of feet, forehead

› Apocrine gland- hair follicles, body odor, musky, unknown function

› Other- ceruminous glands (ear wax)› Mammary glands- milk

Sebaceous glands (oil) Hair

Sebaceous Oil glands Found everywhere except palms, soles

of feet Holocrine gland Sebum- oily Soften and lubricates hair Bactericidal action Seborrhea – “cradle cap”

Nails Hard Keratin

http://www.thaimedicalnews.com/wp-content/uploads/healthy-finger-nails-diagram.gif

Hairs and Hair Follicles Sense insects before they sting Head hair protects against UV, heat

loss, physical trauma Eye lashes- shield eyes Nose hairs- filter large particles like lint

and insects

Structure of Hair Pili-”hairs” consist of largely dead,

keratinized cells. Hard keratin-tough and durable,

individual cells do not flake off Soft Keratin- found in typical epidermal

cells

3 Concentric Layers of the Hair

Medulla- core, large cells and air spaces, not found in fine hairs

Cortex- bulky layer surrounding medulla,

several layers of flattened cells Cuticle-single layer of cells, overlaps on

another like shingles *Red heads have trichosiderin- iron-

containing pigment

Hair Follicle Structure

Types of Hair Vellus Pale, fine Females and

children

Terminal Coarser Scalp and eyebrows Androgen

stimulates

Hair Growth Facts Hirsutism- excessive

hairiness, caused by excessive androgens

2.5 mm/week Lose about 90

hairs/day

Growth cycle› Active (anagen)› Regressive

( catagen)› Resting phase

(telogen)

Hair thinning and Baldness Alopecia- hair

thinning or baldness Drug induced Excessive vitamin A Chemotherapy Burns Radiation Alopecia areata-

autoimmune

Male Pattern Baldness

Minoxidil treatment

Functions of the Integumentary System

Protection› Chemical, physical, and biological barriers

Body Temperature Regulation Cutaneous Sensation Metabolic Functions Blood Reservoir Excretion

Additional Facts . . . Low pH retards bacterial growth (acid

mantle) Natural antibiotic (human defensin) Cathelicidins – fights strep bacteria Some substances can penetrate skin,

ie. Lipid-soluble substances (oxygen, Carbon dioxide, vitamins A,E,D,K), oleoresins (poison ivy)

More . . . Organic solvents (ie. Acetone, paint

thinner, etc.) Salts of heavy metals (lead, mercury,

nickel) May lose 12 L of body fluid per day Can transform cortisone into

hydrocortisone 5% of blood volume in skin Lose water and salt through skin

Homeostatic Imbalances Skin Cancer- benign and malignant,

p53 gene (tumor suppressor gene) Types of Skin cancer:

› 1)Basal Cell carcinoma› 2)Squamous cell carcinoma-arises from

keratinocytes in stratum spinosum› 3)Melanoma- cancer of melanocytes

Skin cancer checklist

A rule : asymmetry B rule : border irregularity C rule: color D rule: diameter E rule : elevation

Burns First degree: epidermis only damaged,

redness, swelling, pain, heals in 2-3 days

Second degree: epidermis and upper region of dermis, blisters, 3-4 weeks no scarring

Third degree: all layers, appears gray-white, cherry red, or blackened, not painful because nerve endings, skin grafing

Other interesting facts: Lanugo coat- 5-6 month fetus, delicate

coat of hairs Vernix caseosa- cheesy substance on

newborns