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The Skin and Immune System

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36–3 The Integumentary SystemThe Skin

1.Epidermis2.Dermis3.Skin Cancer

Section Outline

Section 36-3

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Roles of the Skin

•The skin has four roles

– It acts as a barrier against infection and injury

– It helps to regulate body temperature

– It removes waste products from the body

– Provides protection against UV radiation from the sun

•It also serves as a way through which sensations are transmitted to the nervous system

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Layers of the Skin

•Made of two main layers

– Epidermis – outer layer• The outer layer consists of dead skin cells• The inner layer is made of living cells

– These undergo rapid cell division, constantly making new cells and pushing older cells to the surface

– Also contains melanin (pigment)

– Dermis – contains collagen fibers, blood vessels, nerve endings, glands, smooth muscle and hair follicles

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Figure 36-13 The Structure of Skin

Section 36-3

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Disorder of the Skin

•Skin cancer

– Excessive exposure to UV radiation can lead to an abnormal growth of cells in the skin

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Section Outline

40–2 The Immune System A. Nonspecific Defenses

1. First Line of Defense2. Second Line of Defense

B. Specific Defenses1. Humoral Immunity2. Cell-Mediated Immunity

C. Acquired Immunity1. Active Immunity2. Passive Immunity

D. Diseases of the Immune System

Section 40-2

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The Immune System

•The body’s primary defense mechanism

•May destroy invaders by engulfing them by special cells or by marking them for destruction and elimination

•Functions by being able to recognize proteins on the surface of cells

•It can distinguish between self and non-self

– The non-self, or invading foreign proteins are referred to as antigens

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Nonspecific vs. Specific

•Two types of defense mechanisms

– Non-specific – physical and chemical barriers

• 1st line of defense - Keep pathogens out of your body

– Done by skin, mucous, sweat and tears

• 2nd line of defense – inflammatory response

– If pathogens do enter your body, phagocytic white blood cells move into the area to destroy the bacteria

– The immune system also releases a chemical that increases your body temperature

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SkinWound

Bacteria enter the wound

Phagocytes move into the area and engulf the bacteria and cell debris

Capillary

Section 40-2

Figure 40–7 The Inflammatory Response

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Specific Defense

•A specific defense against a pathogen is called an immune response

– Pathogens that trigger this response are called antigens

• These may be viruses, bacteria, fungi, parasites

•The immune response attacks the particular pathogen with a response designed especially for it

•Two types of wbc’s that recognize specific antigens

– B cells – pathogens and antigens in body fluids

– T cells – pathogens and antigens inside living cells

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Interval between exposures

First exposure

Second exposure

Time

Ant

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once

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tion

Section 40-2

Primary and Secondary Immune Responses

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Acquired Immunity

•Two types of acquired immunity

– Active – appears after exposure to an antigen• May be natural (you get sick)• May be artificial (through vaccination)

– Vaccine – injection of a weakened form of an antigen to produce an immune response

– Passive – receiving antibodies to fight off an infection • May be natural – antibodies are passed to a baby

through the placenta and through breast milk• May be artificial – vaccines may contain antibodies

to protect and prevent disease

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Section Outline

40–3 Immune System DisordersA. AllergiesB. Autoimmune DiseasesC. HIV and AIDS

Section 40-3

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Allergies

•An overreaction of the immune system

– Allergy causing antigens enter the body and attach themselves to certain white blood cells

– Produce chemicals called histamines

– Asthma – a chronic respiratory disease where the air passages become narrower than normal, causing wheezing, coughing and difficulty breathing

• May be treated with medications that relieve the symptoms of asthma

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Autoimmune Disorders

•The immune system has the ability to recognize self and non-self

– When the immune system makes a mistake and attacks its own cells, it produces an autoimmune disease

• Examples– Type I diabetes – insulin-producing cells of

the pancreas are destroyed– Multiple sclerosis – antibodies destroy the

functions of the neurons in the brain and spinal cord

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HIV and AIDS

•AIDS is an autoimmune disease that results from infection with HIV

– Normally healthy patients die from microorganisms that don’t normally cause disease, from extremely rare forms of cancers and pneumonia and from pathogens that healthy people can normally fight off

•HIV – a virus that can evade the defenses of the immune system and attacks key cells in the immune system

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Transmission and Prevention of HIV

•Transmitted through bodily fluids

– Through any form of sexual intercourse

– Through shared needles that are contaminated with infected blood

– Through contact with blood or blood products

– From infected mother to child, through pregnancy, birth and/or breast feeding