immune system defenses

lymphocytes

A lymphocyte is the type of white blood cell involved in an immune system response. You can see what a lymphocyte looks like, greatly magnified, in Figure 21.15. Lymphocytes make up about one quarter of all white blood cells, but there are trillions of them in the human body. Usually, fewer than half of the bodys lymphocytes are in the blood. The majority are in the lymph, lymph nodes, and lymph organs. There are two main types of lymphocytes, called B cells and T cells. Both types of lymphocytes are produced in bone marrow. They are named for the sites where they grow and mature. The B in B cells stands for bone marrow, where B cells mature. The T in T cells stands for thymus gland, where T cells mature. Both B cells and T cells must be switched on in order to fight a specific pathogen. Once this happens, they produce an army of cells that are ready to fight that particular pathogen. How can B and T cells recognize specific pathogens? Pathogens have unique antigens, often located on their cell surface. Antigens are proteins that the body recognizes either as self or nonself. Self antigens include those found on red blood cells that determine a persons blood type. Generally, the immune system doesnt respond to self antigens. Nonself antigens include those found on bacteria, viruses, and other pathogens. Nonself antigens are also found on other cells, such as pollen cells and cancer cells. It is these antigens that trigger an immune response.

immune responses

There are two different types of immune responses. Both types involve lymphocytes. However, one type of response involves B cells. The other type involves T cells.

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organs of the immune system

Immune system organs include bone marrow, the thymus gland, the spleen, and the tonsils. Each organ has a different job in the immune system. Bone marrow is found inside many bones. Its role in the immune system is to produce white blood cells called lymphocytes. The thymus gland is in the chest behind the breast bone. It stores some types of lymphocytes while they mature. The spleen is in the abdomen below the lungs. Its job is to filter pathogens out of the blood. The two tonsils are located on either side of the throat. They trap pathogens that enter the body through the mouth or nose.

circulation of lymph

Lymph vessels make up a circulatory system that is similar to the blood vessels of the cardiovascular system. However, lymph vessels circulate lymph instead of blood, and the heart does not pump lymph through the vessels. Lymph that collects in tissues slowly passes into tiny lymph vessels. Lymph then travels from smaller to larger lymph vessels. Muscles around the lymph vessels contract and squeeze the lymph through the vessels. The lymph vessels also contract to help move the lymph along. Eventually, lymph reaches the main lymph vessels, which are located in the chest. From these vessels, lymph drains into two large veins of the cardiovascular system. This is how lymph returns to the blood. Before lymph reaches the bloodstream, it passes through small oval structures called lymph nodes, which are located along the lymph vessels. Figure 21.14 shows where some of the bodys many lymph nodes are concentrated. Lymph nodes act like filters and remove pathogens from lymph.

immunity and vaccination

Most B cells and T cells die after an infection has been brought under control. But some of them survive for many years. They may even survive for a persons lifetime. These long-lasting B and T cells are called memory cells Memory cells allow the immune system to remember a pathogen after the infection is over. If the pathogen invades the body again, the memory cells will start dividing in order to fight it. They will quickly produce a new army of B or T cells to fight the pathogen. They will begin a faster, stronger attack than the first time the pathogen invaded the body. As a result, the immune system will be able to destroy the pathogen before it can cause an infection. Being able to fight off and resist a pathogen in this way is called immunity. You dont have to suffer through an infection to gain immunity to some diseases. Immunity can also come about by vaccination. Vaccination is the process of exposing a person to pathogens on purpose so the person will develop immunity to them. In vaccination, the pathogens are usually injected under the skin. Only part of the pathogens are injected, or else weakened or dead pathogens are used. This causes an immune response without causing the disease. Diseases you are likely to have been vaccinated against include measles, mumps, and chicken pox.

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how b cells respond

B cells respond to pathogens in the blood and lymph. Most B cells fight infections by making antibodies. An antibody is a large, Y-shaped molecule that binds to an antigen. Each antibody can bind with just one specific type of antigen. The antibody and antigen fit together like a lock and key. You can see how this works in Figure 21.16. The antibody in the figure can bind only with the type of antigen that is colored yellow. Once the antibody binds with the antigen, it signals a phagocyte to engulf and destroy them, along with the pathogen that carries the antigen on its surface. You can watch an animation of the antibody-antigen binding process at this link: MEDIA Click image to the left or use the URL below. URL:

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how t cells respond

There are different types of T cells, including killer T cells and helper T cells. Killer T cells destroy infected, damaged, or cancerous body cells. Figure 21.17 shows how a killer T cells destroys an infected cell. When the killer T cell comes into contact with the infected cell, it releases toxins. The toxins make tiny holes in the infected cells membrane. This causes the cell to burst open. Both the infected cell and the pathogens inside it are destroyed. Helper T cells do not destroy infected, damaged, or cancerous body cells. However, they are still needed for an immune response. They help by releasing chemicals that control other lymphocytes. The chemicals released by helper T cells switch on B cells and killer T cells so they can recognize and fight specific pathogens.

what is the immune system

The immune system is the body system that fights to protect the body from specific pathogens. It has a special response for each type of pathogen. The immune systems specific reaction to a pathogen is called an immune response. The immune system is shown in Figure 21.13. It includes several organs and a network of vessels that carry lymph. Lymph is a yellowish liquid that normally leaks out of tiny blood vessels into spaces between cells in tissues. When inflammation occurs, more lymph leaks into tissues, and the lymph is likely to contain pathogens.

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instructional diagrams

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The diagram shows the main parts of the lymphatic system. The lymphatic system is part of the circulatory system and a vital part of the immune system, comprising a network of lymphatic vessels that carry a clear fluid called lymph directionally towards the heart. The lymphatic system also functions as a defense mechanism in the immune system. A lymph node is an oval- or kidney-shaped organ of the lymphatic system, present widely throughout the body including the armpit (axillary), pelvic, lumbar and stomach and linked by lymphatic vessels. Lymph nodes are major sites of B, T, and other immune cells called Lymphocytes. Lymphocytes are concentrated in the lymph nodes. The spleen and the thymus are also lymphoid organs of the immune system. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles and cancer cells.

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This diagram shows the same of the organs in the human body that are involved in the immune system. The organs shown here include bone marrow, the thymus gland, the spleen, and the tonsils and the adenoids. Each organ has a different job in the immune system. Bone marrow is found inside many bones. Its role in the immune system is to produce white blood cells. The thymus gland is in the chest behind the breast bone. It stores some types of white blood cells while they mature. The spleen is in the abdomen below the thymus gland. Its job is to filter pathogens out of the blood. The two tonsils are located on either side of the throat and is located above the thymus gland. They trap pathogens that enter the body through the mouth or nose. The lymph nodes are present in the head just below the jaw. They are also located under the armpits and in the groin area. Lymph nodes act like filters and remove pathogens from lymph. Lymph vessels make up a circulatory system that is similar to the blood vessels of the cardiovascular system. However, lymph vessels circulate lymph instead of blood.

questions

What is the function of the thymus gland?

-->  a. It stores T cells while they mature.

b. It produces white blood cells.

c. It filters pathogens from lymph.

d. two of the above

The immune system includes all of the following structures and tissues except the

-->  a. pancreas.

b. bone marrow.

c. spleen.

What is the function of the tonsils?

a. They help produce speech.

-->  b. They trap pathogens in the throat.

c. They produce lymphocytes.

d. They store B cells while they mature.

How does lymph circulate through lymphatic vessels?

a. The heart pumps lymph through the vessels.

b. Gravity moves lymph through the vessels.

-->  c. Muscle contractions move lymph through the vessels.

d. none of the above

All lymphocytes

-->  a. are produced in bone marrow.

b. mature in bone marrow.

c. destroy damaged cells.

d. become memory cells.

How do lymph vessels differ from blood vessels?

a. They contain lymph instead of blood.

b. The heart does not pump fluid through them.

c. The fluid they contain does not circulate.

-->  d. two of the above

Which statement about lymphocytes is false?

a. They make up about one quarter of all white blood cells.

b. There are normally trillions of them in the human body.

c. A minority of them are in the blood.

-->  d. none of the above

Any protein that the body recognizes as either self or nonself is called a(n)

a. antibody.

b. allergen.

-->  c. antigen.

d. carcinogen.

What triggers an immune response?

a. inflammation

b. fever

c. phagocytes

-->  d. antigens

The immune response launched by killer T cells against pathogens involves the

a. release of toxins.

b. destruction of infected cells.

c. production of antibodies.

-->  d. two of the above

Both B and T cells

-->  a. are produced in bone marrow.

b. mature in the thymus gland.

c. fight infections by destroying infected cells.

d. two of the above

What happens to lymph when it reaches the main lymph vessels?

a. It is excreted in urine by the kidneys.

-->  b. It is returned to the blood in the chest.

c. It is stored in the thymus gland.

d. It is filtered out of the vessels by the spleen.

The majority of lymphocytes are in the lymphatic system

-->  a. true

b. false

B cells respond to pathogens that are inside infected cells.

a. true

-->  b. false

Helper T cells release chemicals that switch on B cells and killer T cells.

-->  a. true

b. false

The only way to develop immunity to an infectious disease is by vaccination.

a. true

-->  b. false

Vaccines have been developed to prevent measles, mumps, and chicken pox.

-->  a. true

b. false

The bodys third and final line of defense against pathogens involves the immune system.

-->  a. true

b. false

Lymph is moved through lymphatic vessels by the force of gravity.

a. true

-->  b. false

Types of lymphocytes include phagocytes, B cells, and T cells.

a. true

-->  b. false

T cells are produced by the thymus gland.

a. true

-->  b. false

Lymphocytes must be switched on in order to fight a specific pathogen.

-->  a. true

b. false

One type of immune response involves killer T cells and one type involves helper T cells.

a. true

-->  b. false

Antibodies are proteins that the body recognizes as either self or nonself.

a. true

-->  b. false

__liquid that normally leaks out of tiny blood vessels into tissues

a. spleen

b. lymph node

c. thymus gland

d. bone marrow

e. immune response

f. lymphocyte

-->  g. lymph

__organ in the abdomen that filters pathogens out of the blood

-->  a. spleen

b. lymph node

c. thymus gland

d. bone marrow

e. immune response

f. lymphocyte

g. lymph

__immune systems reaction to a specific pathogen

a. spleen

b. lymph node

c. thymus gland

d. bone marrow

-->  e. immune response

f. lymphocyte

g. lymph

__type of white blood cell involved in an immune response

a. spleen

b. lymph node

c. thymus gland

d. bone marrow

e. immune response

-->  f. lymphocyte

g. lymph

__small structure that removes pathogens from lymph

a. spleen

-->  b. lymph node

c. thymus gland

d. bone marrow

e. immune response

f. lymphocyte

g. lymph

__tissue that produces both B cells and T cells

a. spleen

b. lymph node

c. thymus gland

-->  d. bone marrow

e. immune response

f. lymphocyte

g. lymph

__organ that stores T cells until they mature

a. spleen

b. lymph node

-->  c. thymus gland

d. bone marrow

e. immune response

f. lymphocyte

g. lymph

diagram questions

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Identify the Thoracic duct

a. U

b. E

c. J

-->  d. K

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Which label marks the cervical lymph nodes?

-->  a. X

b. U

c. P

d. M

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What is C in this image of the human immune system?

a. INGUINAL LYMPH NODES

-->  b. CISTERNA CHYLI

c. CERVICAL LYMPH NODES

d. INTESTINAL TRUNK

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Which label refers to the tonsils?

-->  a. S

b. X

c. L

d. E

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Which letter is representative of the Spleen in this diagram?

a. C

b. X

c. E

-->  d. L

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Which part of the immune system traps pathogens as the enter in through the mouth?

-->  a. S

b. E

c. L

d. X

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Identify the spleen in this picture

a. S

-->  b. C

c. A

d. P

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Which letter represents the thymus?

a. P

b. C

c. W

-->  d. Y

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Identify the appendix in the following image:

a. C

b. W

-->  c. P

d. A

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Where is the thymus?

a. P

-->  b. Y

c. N

d. A

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Which immune system part is located on the large intestine?

a. C

b. A

c. N

-->  d. P

question_image

Which label refers to the spleen?

-->  a. D

b. L

c. U

d. J

question_image

Which letter represents the Tonsils?

a. U

b. J

c. D

-->  d. L

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By what letter is the spleen represented in the diagram?

a. R

-->  b. T

c. N

d. V

question_image

Which label refers to the spleen?

a. R

b. A

-->  c. T

d. S

question_image

Which label shows the Tonsils and Adenoids?

a. W

b. L

-->  c. R

d. E

question_image

Locate the letter representing the tonsils?

a. N

-->  b. R

c. U

d. J

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What would happen if H is removed from the body?

a. THE BODY CAN'T PRODUCE ANTID-IURETIC HORMONES.

-->  b. THE BODY CAN'T PRODUCE LYMPHOCYTES.

c. THE BODY CAN'T PRODUCE T CELLS.

d. THE BODY CAN'T PRODUCE B CELLS.

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Which label stands for the spleen?

a. S

b. W

-->  c. N

d. T

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Which letter indicates lymph circulation?

a. H

b. Y

c. S

-->  d. F

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Identify the spleen in the figure.

a. W

b. Y

c. X

-->  d. N

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What connects the Cisterna chyli and the left jugular trunk?

a. Right subclavian trunk

-->  b. Thoracic duct

c. Right lymphatic duct

d. Intestinal trunk

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How many types of lymph node are shown?

a. 1

b. 4

-->  c. 3

d. 2

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What collects most of the lymph in the body?

a. intestinal trunk

b. left jugular trunk

c. cervical lymph nodes

-->  d. thoracic duct

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Which organ filters pathogens out of the blood?

a. Thymus

b. Lymph Nodes

-->  c. spleen

d. Tonsils

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Which organ of the immune system produces white blood cells called lymphocytes?

-->  a. Bone Marrow

b. Thymus

c. Spleen

d. Lymph nodes

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Which part of the immune system produces lymphocytes?

a. Spleen

b. Lymph nodes

c. Tonsils

-->  d. Bone marrow

question_image

What is directly next to the lymph nodes in the throat?

a. Spleen

-->  b. Lymphatic vessels

c. Bone marrow

d. Nose

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What stays between the tonsils and the lymphatic vessels?

a. thymus

b. bone marrow

-->  c. Lymph nodes

d. Spleen

question_image

How many lymph nodes are there in our body?

a. 4

-->  b. 3

c. 1

d. 2

question_image

How many parts include a strong immune system?

a. 12

b. 9

-->  c. 10

d. 11

question_image

Which of the following is located in the abdomen?

-->  a. Spleen

b. Thymus

c. Tonsils

d. Nose

question_image

Which organ of the immune system produces white blood cells?

-->  a. bone marrow

b. Lymphatic vessels

c. Thymus

d. Peyer's patches

question_image

Where is the spleen located?

-->  a. In the abdomen below the lungs

b. In the head

c. In the pulmons

d. In the leg

question_image

Organ of the immune system that is located near the throat and mouth

a. Appendix

b. Peyer's patches

-->  c. Tonsils and adenoids

d. Spleen

question_image

How many organs of the immune system has been identified in the diagram?

a. 9

b. 8

c. 10

-->  d. 11

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Which feature of the immune system is located directly below the spleen on the diagram?

a. Appendix

b. Thymus

-->  c. Peyer's patches

d. Lymph nodes

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What is in the neck?

a. thymus

-->  b. lymph nodes

c. liver

d. spleen

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Which muscle separates the chest from the abdomen?

-->  a. Diaphragm

b. Spleen

c. Neck

d. Thymus

question_image

What organ is located in the abdomen below the lungs?

a. Lymph vessels

b. Lymph nodes

c. Thymus

-->  d. Spleen

question_image

How many parts of the lymphatic system are shown?

-->  a. 8

b. 6

c. 9

d. 7

question_image

What organ filters pathogens from the blood?

a. Thoracic duct

-->  b. Spleen

c. Thymus

d. Tonsils

question_image

What connects the lymph nodes?

a. thymus

b. tonsils

c. spleen

-->  d. lymph vessels

question_image

What is the following diagram of?

a. Tympanic organs

b. Endocrine organs

c. Nervous system organs

-->  d. Lymphoid organs

question_image

How many immune system organs do you see in the diagram?

a. 1

b. 5

-->  c. 3

d. 2

question_image

What is the purpose of the spleen?

a. to produce white blood cells called lymphocytes

b. trap pathogens that enter the body through the mouth or nose.

c.  It stores some types of lymphocytes while they mature

-->  d. It filters pathogens out of the blood

question_image

What are the green round circles called?

a. spleen

b. thymus

-->  c. lymph nodes

d. bone marrow

question_image

What part of the immune system filters pathogens out of the blood?

a. Lymph Nodes

b. Tonsils & Adenoids

c. Bone Marrow

-->  d. Spleen

question_image

Each immune system organ is connected to this swelling in the lymphatic system where lymph is filtered and lymphocytes are formed.

a. appendix

b. tonsils

-->  c. lymph nodes

d. spleen

question_image

How many parts of the immune system are identified in the diagram?

-->  a. 7

b. 4

c. 6

d. 5

question_image

In the diagram, how many lymph nodes does the body have?

-->  a. 5

b. 4

c. 7

d. 2

question_image

What part of the immune system is just behind the mouth?

a. spleen

-->  b. tonsils and adenoids

c. appendix

d. bone marrow

question_image

Which part of the body is likely to be infected by bacteria first?

a. Spleen

b. Bone marrow

-->  c. Tonsils and adenoids

d. Thymus

question_image

Which organ has the job of filtering pathogens out of the blood?

a. Thymus

b. Tonsils

c. Liver

-->  d. spleen

question_image

Organ of the immune system that is located besides the liver

a. tonsils

-->  b. spleen

c. thymus

d. liver

question_image

How many MAJOR organs can be seen in this diagram?

a. 3

b. 1

c. 4

-->  d. 2

question_image

How many parts of the lymphatic system are shown?

-->  a. 4

b. 3

c. 5

d. 6

question_image

Which of these is larger; the spleen, liver, tonsils, thymus?

a. thymus

-->  b. liver

c. tonsils

d. spleen

question_image

Which of the following is located below the spleen?

a. adenoids

-->  b. Peyer's patches

c. appendix

d. spleen

question_image

How many items in the body are shown here?

a. 9

-->  b. 8

c. 7

d. 10