intro to lymphatic system

Question 1

Name the 2 primary functions of the lymphatic system

Answer 1

1. Maintaining fluid balance in the internal environment, by filtering and returning interstitial fluid to the venous circulation.
2. Houses and supports the immune system and its cells in the lymph nodes and tissue.

Question 2

What are the organs of the lymphatic system?

Answer 2

The thymus, spleen, tonsils and lymph nodes.

Question 3

Do lymphatic vessles form a closed circuit?

Answer 3

No. The circuit is open and begins in the intercellular spaces of soft tissue.

Question 4

How is lymph moved through the lymphatic vessels?

Answer 4

The pressure of body movement, so through the skeletal muscle and respiratory pumps.

Question 5

What key protein is found in lymph?

Answer 5

Albumin

Question 6

Why is there higher protein levels in the lymph fluid in the thoracic duct?

Answer 6

The thoracic duct drains lymph from the liver and small intestine.

Question 7

What are the 2 functions of the lymph nodes?

Answer 7

1. Defense; via mechanical and biological filtration of cells and microoganisms.
2. Haematopoeisis; training of t-lymphocytes for self tolerance (thymus).

Question 8

What and where is the thymus gland?

Answer 8

The thymus gland is a lymph node in the mediastinum.

Immature t-lymphocytes develop into mature ones here, before migrating to peripheral nodes.

Question 9

Innate immunity has multiple defensive mechanisms. What are the 4 main ones?

Answer 9

1. Epithelial barriers
2. Innate immune cells (neutrophils, macrophages, NK cells).
3. Granulocytes, and the cytokines they release (prostaglandins, interferons, interleukins, histamine, leukotrienes)
4. Complement system-humoral (protein based).

Question 10

Compare innate immunity to adaptive using the following words: specificity, natural, acquired, fast and slow.

Answer 10

Adaptive immunity: acquired, specific, slow

Innate immunity: innate, non-specific, fast

Question 11

What are mechanical barriers with respect to the innate immune system?

Answer 11

Barriers made up of skin layers and mucous membranes.

They seperate the inside of our bodies from he external environment.

Question 12

What are chemical barriers with respect to the innate immune system?

Answer 12

Sebum (oil), mucous, lysozymes in tears and saliva, stomach acid (HCL), urine.

Question 13

What is the aim of the innate immune system’s 1st line of defense (mechanical and chemical barriers)?

Answer 13

The aim is to prevent unwanted microorganisms from entering and infecting the body.

Question 14

What is the aim of the innate immune system’s 2nd like of defense, the infalmmatory response?

Answer 14

The aim is to minimise the damage to the body tissue and to eliminate the pathogen from the body.

Question 15

What are the 5 cardinal signs of inflammation?

Answer 15

Redness, heat, oedema, pain and loss of function.

Question 16

When is the innate inflammatory response triggered?

Answer 16

Whenever body tissue is damaged, by either chemical or physical agents.

Question 17

What are the vascular effects of innate inflammation?

Answer 17

1. Initial vasoconstriction (minimise blood loss)
2. Vasodilation- (increase vascular permeability, increase blood flow).
3. Oedema-( increased hydrostatic pressure causes exudate build-up in the interstitium).
4. Inflammatory mediators-( cause shrinkage of endothelial cells, neutrophil recruitment).

Question 18

What are the 3 steps of neutrophil migration to the site of injury in inflammation?

Answer 18

1. Margination- leukocytes pulled out of bloodstream, start rolling and adhesion to vessel.
2. Diapedesis- leukocytes leave vessel and enter interstitium via the gap in endothelial vessels.
3. Chemotaxis-travelling throguh interstitium along chemical gradient to site of injury.

Question 19

What are the cells involved in innate inflammation and tissue injury?

Answer 19

1. Granulocytes (neutrophils, eosinophils and basophils)
2. NK cells
3. Macrophages (start as monocytes)
4. Platelets (blood clotting)

Question 20

What are the proteins involved in tissue inflammation/injury?

Answer 20

1. Bradykinin, histamine, prostaglandins (activate nociceptors for pain, smooth muscle contraction)
2. Interferons
3. C-reactive protein (CRP): produced by the liver under instruction from macrophages. CRP used to mark foreign antigens for destruction and also activates the complement system.

Question 21

What is the aim of the 3rd line of response, addaptive immunity?

Answer 21

The aim is to induce a targeted, specific immune response towards the invading organism.

Question 22

What are the 2 components of the adaptive immune sytem?

Answer 22

Antibody-mediated immunity and cell-mediated immunity.

Question 23

Which lymphocyte type facilitates the cell-mediated immune response?

Answer 23

T-lymphocytes, via the T-helper cells.

Question 24

Which 2 activating signals are required for the lymphocytes to start their immune response?

Answer 24

1. The foreign antigen

2. The chemical signal from the T-helper cell

Question 25

What is the cell-mediated adaptive pathway involving cytotoxic T-cells?

Answer 25

Cytotoxic t-cells can detect infected cells. They bind to these infected cells and induce apoptotic cell death.

Question 26

What is the cell-mediated pathway involving t-helper cells?

Answer 26

T-helper cells facilitate and coordinate the T-lymphocyte response to the pathogen. They also regulate the B-lymphocyte response to the pathogen. T-helper cells recruit both B & T cells, phagocytes and leukocytes through secretion of cytokines.

Question 27

How are B-cells prepared for an antibody mediated immune response?

Answer 27

1. Naive B-cells released into blood from bone marrow and lymph nodes. 2. Naive B-cells bind to antigen and become activated. 3. The Ag-Ab binding triggers rapid division and replication of the B-cell. 4. Activated B-cells destined to become either memeory b-cells or effector B-cells (plasma cells) producing antibodies.

Question 28

Name the 5 classes of Immunoglobulins.

Answer 28

M,G,A,D&E

Question 29

Describe the function of the IgG antibody.

Answer 29

IgG antibody is found in the blood in the largest amounts of all antibodies. IgG is the main antibody released during primary, but especially secondary exposure to an antigen. It can cross the placenta to boost fetal immunity and protect babies during pregnancy.

Question 30

Describe the function of the IgA antibody

Answer 30

IgA is found in the body fluids (tears, saliva and GI secretions) aswell as blood. IgA protects GI and respiratory tracts by preventing pathogenic attachment to epithelial surfaces.

Question 31

Describe the function of the IgD antibody

Answer 31

Secreted in small amounts. Usually found as a cell surface receptor on B-cells. It is associated with B-cell activation.

Question 32

Describe the function of IgE antibody

Answer 32

IgE is also secreted in low amounts. | Mediates allergic reactions by triggering mast cell degranulation and histamine release.

Question 33

What is active humoral immunity with regard to B-lymphocytes?

Answer 33

Active immunity refers to the B-cells encountering the antigen directly and producing antibodies for it. It can occur either naturally, via pathogenic infection or artificially via vaccination.

Question 34

What is passive humoral immunity with regard to B-lymphocytes?

Answer 34

This occurs when the antibodies for a paticular antigen are either not produced, or obtained artificially. They could come from the placenta or via an antibody infusion.

Question 35

What interaction is required to activate a t-cell?

Answer 35

The lymphocyte must either bind directly to the antigen, or have the antigen presented to itself on an APC.

Question 36

What is the role of cytotoxic CD8+ t-cells?

Answer 36

They target and kill infected host cells/viral infections via apoptosis.

Question 37

What is the role of the T-helper cells?

Answer 37

T-helper cells facilitate and coordinate other immune activities by regulating b-cells and other t-cells. They also promote b-cell recruitment via cytokine release.

Question 38

What is the role of the memory t-cell?

Answer 38

they enable a more rapid response the next time the same antigen is encountered.

Question 39

What is the role of the t-regulatory/t-suppressor cells?

Answer 39

These cells both downregulate or shut off the t-cell immune response, once the antigen has been successfully cleared.

Question 40

What is the relationship between immune function and old age/youth?

Answer 40

Newborn babies have a weaker immune system because of low exposure to the environment. Older people have a weaker immune system because of decreased immune functioning with age.