Chapter 5 Chapter 5 cc

Functions, Homeostatic Imbalances, Burns,

Cancer, Development

Functions of the Integumentary System

•Protection•Body Temperature Regulation•Cutaneous Sensation•Metabolic Functions•Blood Reservoir•Excretion

Protection

•The skin has three types of barriers:–Chemical–Physical/Mechanical–Biological

Protection•Chemical Barriers• Melanin - pigment that forms a

shield to prevent UV damage•Skin secretions – low (acidic)

pH secretions in sweat called Acid Mantle inhibits bacterial growth

•Skin secretions – sebaceous glands secrete sebum with substances that kill bacteria

Protection•Mechanical Barriers

–Keratinized cells – •hardness

–Continuity of skin• Glycolipids waterproof – block

diffusion of water and water soluble substances–Preventing their loss from and entry into the body

Substances that do penetrate:

• Lipid soluble substances like oxygen, carbon dioxide, vitamins A, D, E, & K, and steroids

• Oleoresins of certain plants like poison ivy and poison oak

Substances that do penetrate:

• Organic solvents such as acetone, drycleaning fluid, and paint thinner (which dissolves the cell lipids)

• Salts of heavy metals such as lead, mercury, and nickel

Homeostatic imbalance

• Organic solvents and heavy metals can be lethal

• Passage of organic solvents through the skin into blood can cause the kidneys to shut down or cause brain damage

• Absorption of lead results in anemia and neurological defects

Never Handle Organic

solvents or heavy metals

with your bare hands

Protection

•Biological Barriers

• Langerhans’ cells of the epidermis–Active elements of the immune system. They present antigens (foreign substances) to specialized white blood cells

•Biological Barriers

• Macrophages in the dermis– If bacteria or viruses get past the Langerhan’s cells in the epidermis, the dermal macrophages will get rid of them

Protection

Protection

•Biological Barriers

• DNA–Usually shielded by melanin but electrons in DNA can absorb UV rays and transfer as heat to water molecules

Body Temperature Regulation

• Our bodies must maintain its temperature within homeostatic limits.

• As long as the external air temperature is lower than our body temperature, the skin surface will lose heat to the air

Body Temperature Regulation

• Body temperature regulation is accomplished by the –Dilation of dermal vessels (to cool)

–Constriction of dermal vessels (to warm)

– Increasing sweat gland secretions (to cool)

Body Temperature Regulation

•When at rest in an environment below 31oC (88oF) sweat glands secretions unnoticeable

•– ½ Liter per day

Body Temperature Regulation

•When body temperature rises, sweating becomes noticeable – loss of fluid up to 12 liters in one day!

Cutaneous Sensation• Cutaneous sensory receptors

–Part of nervous system–Classified as exteroceptors (because the respond to stimuli outside the body)

–Sense touch and pain–Meissner’s corpuscles (in dermal papillae)

–Merkel discs

Metabolic Functions• Synthesis of vitamin D

–When sunlight hits the skin, modified cholesterol molecules in dermal blood vessels are converted to vitamin D

–Need vitamin D for Calcium metabolism (calcium cannot be absorbed from digestive tract without vitamin D)

Metabolic Functions• Also several other Chemical

conversions such as –the disarming of many cancer-causing chemicals that penetrate the epidermis

–Conversion of some harmless chemicals into carcinogens

Metabolic Functions• Also several other Chemical

conversions such as –Activation of some steroid hormones – cortisone cream into hydrocortisone (an anti-inflammatory steroid)

–Production of proteins such as collagenase, an enzyme that aids in detering wrinkles

Blood Reservoir•Can hold 5% of the body’s

entire blood volume•When other body organs need

a greater blood supply, nervous system constricts dermal blood vessels, pushing more blood into circulation, making more available to those organs

Excretion of Wastes

•Limited amounts of ammonia, urea, and uric acid is eliminated from the body in sweat

•Most of these wastes are eliminated in urine

Chapter 5 Chapter 5 cc

Part 2Part 2Functions, Homeostatic

Imbalances, Burns, Cancer, Development

Homeostatic Imbalances of Skin

• Skin can develop more than 1000 different conditions and ailments

• Most common skin disorders are bacterial, viral or fungal infections

• Less common, but more damaging are skin cancer and burns

•Athletes foot

•Caused by fungal infection

Skin Homeostatic ImbalancesSkin Homeostatic ImbalancesInfectionsInfections

•Boils and Carbuncles

•Caused by bacterial infection

Skin Homeostatic ImbalancesSkin Homeostatic ImbalancesInfectionsInfections

•Cold sores•Caused by virus

Skin Homeostatic ImbalancesSkin Homeostatic ImbalancesInfectionsInfections

•Contact dermatitis

•Exposure causes allergic reactions

Skin Homeostatic ImbalancesSkin Homeostatic ImbalancesAllergiesAllergies

Poison Ivy

•Impetigo•Caused by bacterial infection

Skin Homeostatic ImbalancesSkin Homeostatic ImbalancesInfectionsInfections

•Psoriasis•Caused is unknown

•Triggered by trauma, infection, stress

Skin Homeostatic ImbalancesSkin Homeostatic Imbalances

Skin Homeostatic ImbalancesSkin Homeostatic Imbalances

Skin CancerSkin Cancer

Slide 4.29Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cancer – abnormal cell mass

Skin cancer is the most common type of cancer

CancerCancer•Two types

–Benign•Does not spread (encapsulated)

–Malignant•Metastasized (moves) to other parts of the body

Skin CancerSkin Cancer

Slide 4.30Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

•The three major types of skin cancer are:

Basal cell carcinoma Squamous cell carcinoma Melanoma

Basal Cell Carcinoma• Least malignant• Most common type (90% of all skin

cancer)• Arises from the Basal layer

• Stratum basale cells proliferate and invade the dermis and hypodermis

Basal Cell Carcinoma

• Slow growing and often does not metastasize

• Can be cured by surgical excision in 99% of the cases

Squamous Cell Carcinoma• Arises from keratinocytes of the

stratum spinosum• Arise most often on scalp, ears,

and lower lip

• Grows rapidly & metastasizes if not removed

• Metastasizes to lymph nodes

• Early removal allows a good chance of cure

• Prognosis is good if treated by radiation therapy or removed surgically

Squamous Cell Carcinoma

Malignant melanomaMalignant melanoma• Most deadly of skin cancers

–because it is highly metastatic and resistant to chemotherapy

Malignant melanomaMalignant melanoma

• Cancer of melanocytes• Metastasizes rapidly to lymph

and blood vessels

• Detection uses ABCD rule

ABCD(E) RuleABCD(E) Rule

Slide 4.32Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

A = AsymmetryTwo sides of pigmented mole do not match

B = Border irregularityBorders of mole are not smooth, it is irregular and exhibits indentations

C = ColorDifferent colors in pigmented area, black, brown, tan, and sometimes red or blue

ABCD(E) RuleABCD(E) Rule

•D = Diameter–Spot is larger than 6 mm in diameter (size of a pencil eraser)

•E = Elevation–Spot is elevated above the skin surface.

Melanoma

• Treated by wide surgical excision accompanied by immunotherapy

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

Skin Cancer

• A crucial risk factor for nonmelanoma skin cancers is the disabling of the p53 gene (tumor suppressor gene) by overexposure to UV radiation in sunlight

• Most skin tumors are benign and do not metastasize

Skin Homeostatic ImbalancesSkin Homeostatic Imbalances

Slide 4.25Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Burns

Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

Associated dangers

Dehydration

Electrolyte imbalance

Circulatory shock

Rule of Rule of NinesNines

• Way to determine the extent of burns

• Body is divided into 11 areas for quick estimation

• Each area represents about 9%

Figure 5.8a

•First-degree burns

• Only epidermis is damaged

• Skin is red and swollen

• Pain

Severity of BurnsSeverity of Burns

•Second-degree burns

• Epidermis and upper dermis are damaged

• Skin is red and swollen with blisters

• Pain

Severity of BurnsSeverity of Burns

•Third-degree burns• Entire thickness of the

skin is damaged• Burn area appears gray-

white, cherry red, or black

• No initial edema or pain since nerve endings are destroyed

Severity of BurnsSeverity of Burns

Severity of BurnsSeverity of Burns

• Burns extend through the skin to injure muscle, ligaments , tendons , nerves, blood vessels, and bones.

•Fourth-degree burns

Critical BurnsCritical Burns

Slide 4.28Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Burns are considered critical if:

Over 25% of body has second degree burns

Over 10% of the body has third degree burns

There are third degree burns of the face, hands, or feet

Developmental Aspects of the Integument: Fetal

•Epidermis develops from ectoderm

•Dermis and hypodermis develop from mesoderm

Developmental Aspects of the Integument: Fetal

•Lanugo – downy coat of delicate hairs covering the fetus during 5th and 6th monthsShed by 7th month when vellus hairs start to appear

Developmental Aspects of the Integument: Fetal

•Vernix caseosa – a white, cheesy looking substance produced by sebaceous glands that protects the skin of the fetus in the amnion (babies are born with it)

Developmental Aspects of the Integument: Fetal

•Milia – small white spots on forehead and nose caused by accumulations in sebaceous glands

Disappears by third week after birth

• Skin and hair become oilier and acne may appear in adolescence

• Skin shows the effects of cumulative environmental assaults around age 30

• Scaling and dermatitis become more common as we age

Developmental Aspects of the Integument: Adolescent

to Adult

• Epidermal replacement of cells slows and skin becomes thinner

• Skin becomes dry and itchy• Subcutaneous fat layer diminishes,

leading to intolerance of cold

Developmental Aspects of the Integument:

Old Age

• Decreased elasticity and loss of subcutaneous tissue leads to wrinkles

• Decreased numbers of melanocytes and Langerhans’ cells increase the risk of skin cancer

Developmental Aspects of the Integument:

Old Age

• By 50 the number of active hair follicles is less, and hair thins.

• Hair loses its luster• Delayed-action genes responsible

for graying and male pattern baldness become active

Developmental Aspects of the Integument:

Old Age

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