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ANATOMY & PHYSIOLOGY

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Lesson 9: Immune System Please submit to me in webmail for grading. Please answer in complete sentences. You may use a different color or highlight your answers. At the end of this lesson, you will be able to do the following: ● Identify the anatomical structures of the immune system ●

Describe how immunity works

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Explain how the immune system contributes to the homeostasis of the body

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Describe selected immune system diseases and disorders

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Describe issues and changes related to the immune system at different points in the lifespan

KEY VOCABULARY Topic 1: Anatomy of the Immune System Lymph:The watery fluid in the lymph vessels collected from the tissue spaces. Lymphocytes:Granular white blood cells formed in the bone marrow that mature in the lymphoid tissue. Topic 2: Physiology of the Immune System Pathogens:Disease-causing microorganism microorganism such as some bacteria, fungi, and viruses. Phagocytes:A cell capable of engulfing and digesting particles or cells harmful to the body. Histamine:A substance that causes vasodilation and increased vascular permeability. Complement:A group of plasma proteins that normally circulate in inactive forms; when activated by complement fixation, causes lysis of foreign cells and enhances phagocytosis and inflammation. Immunity:The ability of the body to resist many agents (both living and nonliving) that can cause disease; resistance to disease Antigen:Any substance-including toxins, foreign proteins, or bacteria-that, when introduced to the body, is recognized as foreign and activates the immune system. Topic 3: Common Immune System Disorders

Allergies: Overzealous immune response to an otherwise harmless antigen; also called hypersensitivity. Chemotherapy:Use of chemicals, including drugs, to treat or control infections such as cancer. Radiation therapy:Use of x-rays to treat disease, especially cancer. NOTES & ACTIVITIES Topic 1: Anatomy of the Immune System Lymphatic System

Lymphatics A:Lymph duct (top) and trunk(bottom) B:Lymph node C:Lymphatic collecting vessels with valves D: Lymph capillary E:tissue fluid (becomes lymph) F: Loose connective tissues around capillaries G:Blood capillaries

Lymph Nodes

A:Cervical nodes

B:Axillary nodes

C: Inguinal nodes

D: Lymphatics

Lymph Node Structure A: Cortex B: Follicle C: Germinal center in follicle

Lymph Node Process

Lymphoid Organs Spleen

Thymus

Tonsils

Peyer’s Patches

The spleen is a blood-rich organ that filters blood. It is located on the left side of the abdominal cavity and curls around the anterior aspect of the stomach. The spleen filters and cleans the blood of bacteria, viruses, and other debris. Its most important job is to destroy worn-out red blood cells and return some of their breakdown products to the liver. The thymus gland, which functions at peak levels only during youth, is a lymphatic mass found low in the throat overlying the heart. The thymus produces hormones that help in the programming of certain lymphocytes so they can carry out their protective roles in the body. The tonsils are small masses of lymphatic tissue that ring the throat where they are found in the mucosa. Their job is to trap and remove any bacteria or other foreign pathogens entering the throat. Sometimes they do their job so well, they become congested with bacteria resulting in tonsillitis. Peyer’s patches, which resemble tonsils, are found in the wall of the small intestine. The macrophages are in an ideal position to catch and destroy bacteria, stopping it from entering the intestinal wall. Peyer’s patches and the tonsils are part of the collection of small lymphoid tissues referred to as mucosa-associated lymphatic tissue (MALT).

Topic 2: Physiology of the Immune System Nonspecific Defenses

Lines of Defense Some nonspecific resistance to disease is inherited. The term nonspecific body defense refers to the mechanical barriers that cover our body surfaces and to cells

and chemicals that act on the initial battlefronts to protect the body from invading pathogens, or harmful or disease-causing microorganisms. The body’s first line of defense against disease is the skin. As long as the skin is unbroken, it is a strong physical barrier to most microorganisms that swarm on the skin. Intact mucous membranes also provide mechanical barriers within the body. For the second line of defense, the body uses an enormous number of cells and chemicals to protect itself. These defenses rely on the destructive powers of phagocytes and natural killer cells. Fever is also considered to be a nonspecific protective response.

Phagocytes and Natural Killer Cells Pathogens that make it through the mechanical barriers are confronted by phagocytes in nearly every body organ. A phagocyte, such as a macrophage or neutrophil, technically eats the foreign particle. Natural killer (NK) cells police the body in blood and lymph. They are a unique group that can kill cancer cells and virus-infected body cells well before the immune system is enlisted in the fight. NK cells are NOT phagocytic. They attack the target cell’s membrane and release a chemical called perforins, which causes the target cell’s membrane and nucleus to disintegrate.

1: Microbe adheres to phagocyte 2:Phagocyte engulfs the particle 3: Phagocytic vesicle is fused with a lysosome 4: Microbe is fused vesicle is killled and digested by lysosomal enzymes within the phagolysosome 5: Indigestible and residual material is removed by exocytosis

Inflammatory Response A:Cells damaged B: Blood vessels date C: Capillaries become “leaky” D: Neutrophils and then monocytes and other (WBCs) enter area E:Redness F: Heat G:Pain H:Swelling I: Possible temporary limitation of joint movement

Complement, Interferon, and Fever The term complement refers to a group of at least 20 plasma proteins that circulate in the blood in an inactive state. However, when a complement becomes fixed to foreign cells, it is activated and becomes a major factor in the fight against the foreign cells. Viruses do their dirty work by entering tissue cells and taking over the cellular machinery needed to reproduce themselves. Although the virus-infected cells can do little to defend themselves, they can secrete small proteins called interferons. The interferon molecules diffuse to nearby cells and bind to their membrane receptors. Somehow this binding hinders the ability of the viruses to multiply within these cells. Fever, or abnormally high body temperature, is a systematic response to invading microorganisms. Although high fevers are dangerous, mild or moderate fever seems to benefit the body by increasing the metabolic rate of tissue cells in general, speeding up the repair process. Specific Defenses

A: Macrophage B: Antigen-presenting cell C: Cytotoxic T cell D: Active cytotoxic T cells E: Memory T cells

G: B cell H: Plasma Cells I: Memory B cells

Immune System and Homeostasis When the body is invaded by microbes and other foreign agents, the invasion interferes with homeostasis of the body by damaging or killing healthy cells so that they cannot do their assigned job in the body. The immune system attempts to stop this invasion by either killing the cells directly or creating an environment that is not conducive to the survival of the foreign bodies. The immune system is a critical agent for homeostasis. Topic 3: Common Immune System Disorders Diseases and Disorders of the Immune System Allergies

AIDS

Cancer

Chronic fatigue syndrome

Rheumatoid arthritis (RA)

Allergies or hypersensitivities are abnormally vigorous immune responses in which the immune system causes tissue damage as it fights off a perceived threat that would otherwise be harmless to the body. These are triggered by the release of histamine, which causes small blood vessels to become dilated and leaky, which explains the runny nose and watery eyes. Over-the-counter anti-allergy drugs contain antihistamines that counteract these effects. The most important and devastating of the acquired immunedeficiencies is acquired immune deficiency syndrome (AIDS). AIDS cripples the immune system by interfering with the activity of helper T cells. Cancer is a group of many related diseases that describe when cells do not act as they should within the body. They grow and spread rapidly to other places, destroying tissues and using up body resources. Cancer cells can clump together to form tumors and can break away from the original site and cause cancer in other parts of the body. This is called metastasis. The signs, symptoms, and treatment depend upon the type of cancer and location in the body. Chronic fatigue syndrome is thought to be shared by several different underlying diseases. Others think it may be a problem with the immune system. Symptoms include depression, sleep disorders, and severe lack of energy. Rheumatoid arthritis (RA) is a chronic autoimmune disease where the body produces antibodies that stick to the body’s

Systemic lupus erythematosus

own cells, causing the body to attack itself. Those who suffer from RA have severe pain and stiffness in the joints. Systemic lupus erythematosus is where abnormal antibodies in the blood target tissues within the body. Most lupus patients are women. Signs and symptoms include pain and swelling in the joints, general fatigue, fever, chills, and headache among other symptoms.

Therapeutic Procedures Chemotherapy Chemotherapy is the use of anticancer drugs in an attempt to slow or halt the cancerous growth of cells. It may be in a pill form or given intravenously over several weeks.

Radiation therapy Radiation therapy is the use of high-energy waves, such as x-rays. The goal is to damage or destroy cancer cells completely

Changes Across the Life Span Infants

Children

Adolescents

The various components of the immune system are already present at birth or are finishing their development. The inflammatory response may be inefficient. Also, the ability to produce antibodies is limited. In order to develop a fully functioning immune system, the infant requires the gradual exposure to foreign bodies and infectious agents, which is accomplished easily and safely in the environments of most children. As infants grow, the antibodies have been established to the most commonly encountered organisms, though toddlers are often prone to gastrointestinal and respiratory infections when exposed to new organisms. Lymphatic tissues such as adenoids, tonsils, and lymph nodes enlarge as growth continues as well as from exposure to microorganisms. Adenoid tissue peaks in size at about three years and tonsils peak at about seven years. There are actually more lymphoid tissues in children than in adults. Immunizations are important to the health of children and in many cases, required by law. The immune system of the adolescent is similar to that of the adult. Functioning of the tonsils begins to decline. Antibodies to common microorganisms have been developed. Immunizations are as important to teenagers as they are for children. Combined tetanus and diphtheria toxoids (adult-type Td) should be given between 14 and 16 years old. Influenza virus vaccine should be given for adolescents in high-risk groups.

Adults

Later Adulthood

As adults mature, healthy individuals maintain healthy immune systems. Disease, poor nutrition, or poor environments can damage the immune system and open the door to pathogens. Common diseases of adults include simple diarrhea caused by viral infections, cystitis (inflammation of the bladder that is especially seen in women), as well as an increase in dental caries (tooth cavity) and periodontal disease. Tetanus diphtheria (Td) toxoid should be administered every 10 years as a booster. Influenza, hepatitis B, and pneumonia vaccines are recommend for health workers and those with chronic disease or heart or lung disease. As adults move into later life, the thymus gland starts to degenerate, decreasing the number of lymphocytes circulating through the body and lymphoid tissue decreases causing a general decline in immune response. The immune system becomes less efficient. Autoimmune responses may increase, which increases diseases such as rheumatoid arthritis....