Morgan Parker
10-28-11
7th period
Self-Notes Ch. 4
The Integumentary System (Skin)
I. Functions of the Integumentary System
1. Integument simply means “covering”
2. Keeps water and other precious molecules in/out of the body
3. Most of the functions are protective
a. Insulates and cushions deeper body organs
b. Protects the entire body from mechanical damage, chemical damage thermal
damage, ultraviolet radiation and bacteria
4. Uppermost layer of the skin is full of keratin and is cornified (hardened) to prevent
water loss from the body’s surface
5. Regulates heat loss from the body’s surface through a capillary network and sweat
glands
a. Urea, salts and water are lost when we sweat
6. Skin manufactures several proteins important to immunity and synthesizes vitamin
D
7. Cutaneous sensory receptors (part of the nervous system) are located in the skin
a. Touch, pressure, temperature, and pain receptors
II. Structure of the Skin
1. Epidermis (outer)
a. Made up of stratified squamous epithelium
b. Capable of keratinizing or becoming hard and tough
2. Dermis (under the epidermis)
a. Made up of mostly dense connective tissue
b. Firmly connected to the epidermis
3. Blisters are created when the 2 layers separate allowing interstitial fluid to
accumulate between them
4. Subcutaneous tissue or hypodermis
a. Essentially adipose tissue
b. Anchors the skin to underlying organs
c. Serves as a shock absorber and insulates the deeper tissues from extreme
temperature changes occurring outside the body
A. Epidermis
1. Composed of up to 5 layers or strata
a. From the inside: stratum basale, spinosum, granulosum, lucidum and corneum
b. Avascular (it has no blood supply of its own)
2. Most cells of the epidermis are keratinocytes which produce keratin (fibrous
protein that makes the epidermis a tough protective layer
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Morgan Parker
10-28-11
7th period
Self-Notes Ch. 4
3. Deepest cell layer of the epidermis is the stratum basale
a. Lies closely to the dermis and is connected to it along a wavy borderline
b. Contains epidermal cells that receive nourishment through diffusion of nutrients
from the dermis (which constantly divide)
4. Outermost layer is the stratum corneum
a. 20-30 cell layers thick, but accounts for about ¾ of the epidermal thickness
b. Made of dead cell remnants completely filled with keratin (cornified or horny
cells)
c. Rubs of steadily and slowly in flakes (dandruff)
i. Average person sheds about 18kg (40lbs.) of these flakes in a lifetime
d. We have a totally “new” epidermis every 25-45 days
5. Melanin is a pigment that ranges in color from yellow to brown to black and is
produced by special spider-shaped cells called melanocytes
a. Freckles and moles occur where melanin is concentrated in on spot
B. Dermis
1. This is your “hide”
2. Strong stretchy envelope that helps hold the body together
3. Made of 2 layers of dense (fibrous) connective tissue
a. Papillary and the reticular areas
4. Varies in thickness
5. Papillary layer is the upper dermal regions
a. Uneven and has peg-like projections from its superior surface which is the
dermal papillae
i. Contain capillary loops which furnish nutrients to the epidermis
ii. Some house pain receptors and touch receptors (Meissner’s corpuscles)
6. Reticular layer is the deepest skin layer
a. Contains blood vessels, sweat and oil glands, and deep pressure receptors
(corpuscles)
7. Collagen and elastic fibers are found throughout the dermis
a. Collagen fibers are responsible for the toughness
b. Attract and bind water to keep the skin hydrated
c. Elastic fibers give the skin its elasticity when we’re young
8. The dermis is supplied with blood vessels that help maintain homeostasis
9. Rich nerve supply
III. Skin Color
1. 3 pigments contribute to skin color
a. Melanin – yellow, reddish brown, or black
b. Carotene – deposited in the stratum corneum and subcutaneous tissue
c. Oxygen-rich hemoglobin – pigment in red blood cells
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Morgan Parker
10-28-11
7th period
Self-Notes Ch. 4
2. Emotions also influence skin color. Many alternations in skin color signal certain
disease states
a. Redness or erythema – embarrassment (blushing), fever, hypertension,
inflammation, or allergy
b. Pallor or blanching – emotional stress (fear, anger, etc.), anemia, low blood
pressure, impaired blood flow to an area
c. Jaundice or a yellow cast – liver disorder
d. Bruises or black and blue marks – blood has escaped from circulation and clotted
in tissue spaces (hematomas), deficiency of vitamin C or hemophilia (bleeder’s
disease)
IV. Appendages of the Skin
1. Skin appendages – Cutaneous glands, hair and hair follicles, and nails
A. Cutaneous Glands
1. Exocrine glands that release secretion to the skin through ducts.
a. Sebaceous glands and sweat glands
2. Sebaceous (oil) glands are everywhere except the palms of hands and soles of feet
a. Ducts empty into a hair follicle
b. Sebum is a mixture of oily substances and fragmented cells; contains chemicals
to kill bacteria
3. Sweat glands or sudoriferous glands – more than 2.5 mil. per person
a. Eccrine – more numerous, produce sweat, sweat is acidic 7 inhibits the growth of
bacteria
b. Apocrine – begin to function during puberty under the influence of androgens;
activated by nerve fibers during pain & stress and during sexual foreplay
B. Hair and Hair Follicles
1. Hairs guard the head against bumps, shielding eyes, keep foreign particles out of
the respiratory system, insulation in cold weather
a. A hair, produced by a hair follicle, is a flexible epithelial structure.
b. Formed by division of stratum basale epithelial cells in the matrix of the inferior
end of the follicle
c. Each hair consists of a central core (medulla) surrounded by a bulky cortex layer
d. Cuticle is the most heavily keratinized region
e. Pigment is made by melanocytes & varying amounts of melanin
f. Found everywhere except palms, soles of feet, nipples and lips
2. Hair Follicles have an inner epidermal sheath composed of epithelial tissue, the
outer dermal sheath is dermal connective tissue
a. Arrector pili (bands of smooth muscle cells) connect each side of the follicle;
when these muscle contract, the hair is pulled upright causing “goose bumps”
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Morgan Parker
10-28-11
7th period
Self-Notes Ch. 4
V. Nails
1. Nail – scale-like modification of the epidermis
a. Each nail has a free edge, a body (visible attached portion, and a root (embedded
in the skin
2. Stratum basale of the epidermis extends beneath the nail as the nail bed
a. The nail matrix is responsible for nail growth
3. Mostly nonliving material
4. The rich blood supply in the underlying dermis gives the nail a pink tint
VI. Homeostatic Imbalances of Skin
A. Infections and Allergies
1. Athlete’s Foot
a. Red, itchy and peeling; between toes; fungus infection; also called tinea pedis
2. Boils and carbuncles
a. Inflammation of hair follicles & sebaceous glands; common on dorsal neck
b. Carbuncles are composite boils; caused by bacterial infection (Staphyloccus
aureus)
3. Cold Sores (fever blisters)
a. Itch and sting; caused by herpes simplex infection; virus localizes in a Cutaneous
nerve; lies dormant until activated by emotional upset, fever or UV radiation;
occur around the lips & in the oral mucosa
4. Contact Dermatitis
a. Itching, redness and swelling of the skin; can lead to blistering; caused by
exposure to chemicals (poison ivy)
5. Impetigo
a. Pink, water-filled, raised lesions (mouth & nose); develop yellow crust and
rupture; caused by staphyloccus infection
6. Psoriasis
a. Overproduction of skin cells leads to red epidermal lesions covered with dry,
silvery scales; itch, burn, crack and sometimes bleed; autoimmune disorder
B. Burns
1. Nearly every body system suffers when the skin is damaged
2. Burn – tissue damage and cell death caused by intense heat, electricity, UV
radiation or certain chemicals
3. Rule of nines – determines how much of the body surface is burned (extent of
burns)
4. Infection becomes the leading cause of death in burn victims
5. Immune system becomes depressed within 1 or 2 days after severe burn injury
6. 1st degree burn – only the epidermis is damaged
a. Red, swollen, heal in 2 or 3 days
b. Partial-thickness burn
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Morgan Parker
10-28-11
7th period
Self-Notes Ch. 4
nd
7. 2 degree burn – injury to the epidermis and upper region of the dermis
a. Red and painful, blisters appear
b. Partial-thickness burn
8. 3rd degree burn – destroy entire thickness of skin
a. Full-thickness burn
b. Blanched or blackened, not painful, regeneration is impossible
9. Burns are considered critical if…
a. Over 25% of the body has 2nd degree burns
b. Over 10% of the body has 3rd degree burns
c. 3rd degree burns are on the face, hands, or feet
10. Facial burns are dangerous because the possibility of burns to the respiratory
passage
C. Skin Cancer
1. Neoplasms (tumors) arise on the skin; most are benign and don’t spread; some are
malignant (cancerous) and can invade other areas
2. 1 in 5 Americans develop skin cancer
3. Basal Cell Carcinoma – least malignant & most common
a. no longer honors the line between epidermis & dermis
b. lesions occur on sun-exposed areas
4. Squamous Cell Carcinoma – arises from cells of the stratum spinosum
a. Scaly, reddened papule (small, rounded elevation)
b. Shallow ulcer with firm raised border
c. Often on the scalp, ears, dorsum of the hands & lower lip; sun-induced
5. Malignant Melanoma – cancer of melanocytes
a. Accounts for about 5% of skin cancers
b. Arises from accumulated DNA damage
c. Spreading brown or black patch; metastasizes rapidly to nearby lymph and blood
vessels
d. Survival is about 50%
6. Apply the ABCD Rule for recognizing melanoma:
(A) Asymmetry – 2 sides of the pigment/mole don’t match
(B) Border irregularity – borders of lesion aren’t smooth, but have indentations
(C) Color – pigmented spot contains areas of different colors (black, brown, tan, &
sometimes blue or red)
(D) Diameter – spot is larger than 6mm in diameter (size of pencil eraser)
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