The Lymphatic System and Body Defenses

Question 1

What does the lymphatic system consist of?

Answer 1

• A meandering network of lymphatic vessels
• Various lymphoid tissues and organs scattered throughout the body

Question 2

What are lymphatic vessels?

Answer 2

Passageways similar to veins that carry lymph from the tissues back into blood circulation

Question 3

In which direction does lymph flow?

Answer 3

Only ever toward the heart

Question 4

What are the two lymphatic ducts?

Answer 4

• The right lymphatic duct
• The thoracic duct

Question 5

What are lymph nodes?

Answer 5

Masses of lymphatic tissue

Question 6

How do lymph nodes help protect the body?

Answer 6

By removing foreign material from the lymphatic stream and providing a place where lymphocytes that function in the immune response can be activated

Question 7

What are B cells?

Answer 7

Lymphocytes that generate daughter cells called plasma cells

Question 8

What are T cells?

Answer 8

All cortical cells other than B cells

Question 9

What are afferent lymphatic vessels?

Answer 9

Vessels that carry lymph into the lymph node

Question 10

What are the efferent lymphatic vessels?

Answer 10

Vessels that carry lymph out of the node

Question 11

What is the most important function of the spleen?

Answer 11

Destroy worn-out red blood cells and return some of their breakdown products to the liver

Question 12

How do tonsils contribute to bodily defence?

Answer 12

They trap and remove bacteria and other foreign pathogens entering the throat

Question 13

What are the two types of immune system defence mechanisms?

Answer 13

• Innate
• Adaptive

Question 14

What is the difference between innate and adaptive body defences?

Answer 14

• Innate: Responds immediately to protect the body from all foreign substances
• Adaptive: Fights invaders that get past innate defences

Question 15

What is known as the first line of defence?

Answer 15

Surface membrane barriers

Question 16

What is known as the second line of defence?

Answer 16

Cell and chemical barriers

Question 17

What are natural killer cells?

Answer 17

A unique group of lymphocytes that can lyse (burst) and kill targets

Question 18

What is the main purpose of an inflammatory response?

Answer 18

To prevent the spread of damaging agents to nearby tissues and dispose of cell debris and pathogens

Question 19

What are microbial proteins?

Answer 19

Defensive proteins that assist in innate defences by attacking microbes directly or preventing their reproduction

Question 20

What are interferons?

Answer 20

Antimicrobial proteins produced by virus infected cells that stimulate neighbouring cells to produce antiviral proteins that either block binding or replication of the virus

Question 21

What is the third line of defence?

Answer 21

Adaptive body defences

Question 22

What are the two separate but overlapping arms of adaptive body defences?

Answer 22

• Humoral immunity
• Cellular immunity

Question 23

What provides humoral immunity?

Answer 23

Antibodies released by sensitized B cells and their plasma cell progeny present in the body’s “humours”/fluids

Question 24

What provides cellular immunity?

Answer 24

Lymphocytes (T cells)

Question 25

What is an antigen?

Answer 25

Any substance capable of provoking an immune response

Question 26

What is the difference between lymphocytes and antigen-presenting cells

Answer 26

• Lymphocytes: Respond to specific antigens
• Antigen-presenting cells: Don’t respond to specific antigens, but help activate the lymphocytes that do

Question 27

What are the two major types of lymphocytes?

Answer 27

• T cells
• B cells

Question 28

What are antigen-presenting cells?

Answer 28

Cells that engulf antigens and present fragments of them on their own surfaces so they can be recognized by T cells

Question 29

What is active immunity?

Answer 29

Immunity produced by an encounter with an antigen

Question 30

What is the main function of antibodies?

Answer 30

To inactivate antigens

Question 31

What are the two most important antibody reactions for body protection?

Answer 31

• Complement fixation
• Neuralization

Question 32

What is complement fixation?

Answer 32

When a complement is fixed to foreign cells, it activates and causes lysis (among other things)

Question 33

What is opsonization?

Answer 33

The process of antibody binding that “tags” an antigen for phagocytosis

Question 34

What is neutralization?

Answer 34

The blockage of the harmful effects of bacterial exotoxins or viruses by binding antibodies to specific sites on them

Question 35

What is agglutination

Answer 35

The clumping of foreign cells, induced by cross-linking antigen-antibody complexes

Question 36

What is precipitation?

Answer 36

Occurs when cross-linking involves soluble antigenic molecules and the resulting antigen-antibody complexes are so large that they become insoluble and settle out of the solution, allowing them to be more easily captured and engulfed by phagocytes

Question 37

What occurs during a cellular immune response?

Answer 37

T cells fight antigens directly in cell-to-cell combat

Question 38

What are the two main classes of effector T cells?

Answer 38

• Cytotoxic T cells
• Helper T cells

Question 39

What is the difference between cytotoxic T cells and helper T cells?

Answer 39

• Cytotoxic T cells: Directly kill foreign cells
• Helper T cells: Orchestrate cellular immunity through direct contact eith other immune cells