1. The Immune System Lesson 1: The Immune Systems28
The Immune System
Lesson 1:
The Immune Systems

2. Lesson Objectives
Upon completion of this lesson, students should be able to …
Define and spell the terms to learn for this chapter.
Identify and discuss the anatomy of the immune system.
Discuss the functions of the immune system.
Explain the immune system and its response.

3. Composition of the Immune System
Tissues
Organs
Physiological processes that identify abnormal cells
Foreign substances
Foreign tissues, such as transplants

4. Structures Central to the Immune System
Central lymphoid tissue
Comprised of the bone marrow
Peripheral lymphoid tissue
Consisting of the lymph nodes, spleen, and mucosa-associated lymphoid tissue

5. Critical Thinking Questions
What is so critical about the immune system to one’s overall health?
If one has a compromised immune system would that shorten the person’s life?

6. The Immune System Operates throughout the body
Structures are part of the lymphatic system, which is a subsystem of the circulatory system
Primary function of the lymphatic system is to defend the body against invasion by pathogens such as viruses, bacteria, and fungi
Immunosuppressants, medications, and stress can suppress the immune system

7. The Lymphatic System

8. Bone Marrow Comprises the central lymphoid tissue
Contains stem cells that create all the cells that make up the tissues and structures of the immune system
Produces red blood cells, white blood cells, and platelets, along with B cells and natural killer cells

9. Location and Purpose of the Thymus Gland
Comprises the central lymphoid tissue
Located posterior to the sternum, in the anterior mediastinum
Manufactures infection-fighting T cells and helps distinguish normal T cells from those that attack the body’s own tissues
Enlarges during childhood but shrinks again after maturity, continuing to function throughout life

10. Compartments of the Thymus Gland
Outer cortex and an internal medulla
Immature lymphoid cells enter the cortex, reproduce and mature, then move to the medulla where they reenter the circulation

11. Peripheral Lymphatic System
Consists of the lymph nodes, spleen, and other lymphoid tissue
Lymphatic capillaries, lymphatic vessels, and lymphatic ducts are part of the peripheral lymphatic system

12. Lymph Nodes Take many different sizes and shapes
Most are bean-shaped and about 1 inch long
Covered with a thick fibrous capsule
Node is subdivided into different compartments by inward-pointing trabeculae

13. Two Parts of Lymph Nodes
Cortex
Populated mainly with lymphocytes
Medulla
Primarily made up of macrophages attached to reticular fibers

14. B Lymphocytes
The germinal centers are the primary locations where B lymphocytes reproduce quite prolifically
Cells responsible for production of circulating antibodies
Each unique type of B cell produces only one type of antibody
When an antigen enters the body, these B lymphocytes rapidly undergo mitosis and divide
This produces a large quantity of an antibody to seek out and help destroy the antigen

15. The spleen is not an essential organ for life.
Located in the upper left quadrant of the abdomen
Consists of lymphatic tissue that is highly infiltrated with blood vessels
Spleen’s blood vessels are lined with macrophages, which swallow and digest debris in the blood such as worn-out red blood cells and platelets
Factoid:
The spleen is not an essential organ for life. 15

16. Tonsils are often removed when infected.
Located in the depressions of the mucous membranes of the throat and the pharynx
The function of the tonsils is to filter bacteria and aid in the formation of white blood cells
Factoid:
Tonsils are often removed when infected. 16

17. The Immune System
The body’s defense against infectious organisms and other pathogenic invaders
Through the immune response, the cells, tissues, and organs work together to attack organisms and substances that invade body systems and cause disease
Leukocytes, or white blood cells (WBCs), combine to seek out and destroy harmful organisms

18. Phagocytes and Lymphocytes
A type of WBC that attacks the invading organism
A number of different cells are considered to be phagocytes, but the most common are neutrophils, which primarily fight off bacteria

19. Phagocytes and Lymphocytes
A type of WBC that allows the body to remember and recognize previous invading organisms
Originate in the bone marrow and either stays there and matures into B cells or move to the thymus gland, where they mature into T cells

20. B and T Lymphocytes
B lymphocytes and T lymphocytes have separate responsibilities within the immune system
B lymphocytes
Seek out invading organisms and send defenses to attach onto them
T cells
Destroy the organisms that the B lymphocytes have identified

21. Antigen Foreign substance that invades the body
When an antigen is detected, several types of cells work together to recognize and respond to it
These cells trigger the B lymphocytes to produce antibodies
This process is known as humoral immunity

22. Antibodies Specialized proteins that lock onto specific antigens
Immunoglobulins are glycoproteins that function as antibodies
The terms antibody and immunoglobulin are often used interchangeably
Antibodies are found in blood, tissue fluids, and many secretions

23. Antibodies
Structurally antibodies are globulins, which means they are synthesized and secreted by plasma cells derived from the B cells of the immune system

24. B Cells of the Immune System
Activated upon binding to their specific antigen and differentiating into plasma cells
In some cases the interaction of the B cell with a T cell is necessary
Once antibodies have been produced, they remain in the body

25. B Cells of the Immune System
If the same antigen is presented to the immune system again, the antibodies are already there to neutralize it
Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it alone. That is the job of the T cells.

26. T Cells
Part of the system that destroys antigens which have been tagged by antibodies or cells that have been infected or somehow changed
Assist other cells, such as phagocytes
Antibodies can neutralize toxins produced by different organisms
Antibodies can activate a group of proteins called complement that are also part of the immune system
Complement assists in destroying bacteria, viruses, or infected cells

27. Immunity The body’s ability to defend itself against pathogens
Forms of immunity
Innate
Active
Passive 27

28. Innate Immunity Everyone is born with innate, or natural, immunity
Renders many of the viruses and bacteria that affect other species incapable of harming human beings
Provided in part by the external barriers of the body
Including the skin and mucous membranes that line the nose, throat, and gastrointestinal tract

29. Innate Immunity
If this outer defensive wall is broken, such as by a cut in the skin, special immune cells on the skin attack any invading microorganisms

30. Active Immunity
The introduction of immunity by infection or with a vaccine
Is permanent, meaning that the individual has lifelong protection against the disease

31. Types of Active Immunity
Acquired active immunity
Occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response
Artificially acquired active immunity
Active immunity is induced by a vaccine, a substance that contains the antigen and stimulates a primary response against the antigen without causing symptoms of the disease

32. Passive Immunity
“Borrowed” from another source and lasts for only a short time
An inherited immunity to certain diseases

33. Questions? 33