4.1 The Lymphatic System

Question 1

How does the lymph come about?

Answer 1

20L Blood plasma is forced out of capillary beds to help the transfer of nutrients and gases from blood vessels to surrounding tissue.
Venous blood capillaries absorb most of this fluid back (17L) due to osmotic pressure, but what is left behind is soaked up by the lymphatics.

Question 2

How does the lymph enter the lymphatic?

Answer 2

Pressure in the interstitial space is higher than lymphatica, so valves open and allow fluid in, relieving pressure.

Question 3

Where does the right lymphatic duct connect to the blood supply?

Answer 3

Internal Jugular Vein

Question 4

Where does the larger left thoracic duct deposit lymph to get back to the blood supply?

Answer 4

Subclavian vein

Question 5

Where is lymph inspected and cleansed?

Answer 5

Lymphnodes

Lymphatic Tissue - Tonsils, peyers patches, appendix

Question 6

Describe the structure of a lymphnode (3) and its function

Answer 6

1. Afferent lymphatic vessels via convex surface, efferent via hilum
2. Feeding artery and draining
3. Several germinal centres
4. Inspection of lymph fluid
5. Trigger macrophage release, inflammation
6. Germinal centres contain APCs which present antigen to naive T cells for activation

Question 7

Briefly describe inflammation, humoral and cell-mediated responses

Answer 7

1. Neutrophils and macrophages come to site, red, swelling, heat, pain
2. Bcell - plasma cell - antibody production
3. APC’s recognise antigen and present to T cell for activation

Question 8

What is lymphadenopathy?

Answer 8

1. Enlarged lymph nodes

2. Germinal centres fill with lymphocytes if infection

Question 9

What is lymphoma?

Answer 9

Cancer of the lymph

Question 10

What are the lymph organs and describe their functions?

Answer 10

1) Spleen
- filters blood by removal/destruction of old RBC, platelets and retrieval of iron from haemoglobin
- immune function (APC, activation and proliferation of B and T cells, removal of macromolecular antigens in blood)

2) Thymus
- located superior mediastinum
- fully formed at birth and involutes post-puberty
- Thymic Cell Education - maturation of bone marrow into T cells

Question 11

Can the spleen rupture? If yes, what effects does this have?

Answer 11

Yes and could lead to death by exsanguination

Question 12

What is a spleen removal procedure called? What effects does this have?

Answer 12

1. Splenectomy
2. Bone marrow and liver take over in removal of RBCs
3. But as a huge organ that makes antibodies has been removed, increase risk of infection, malaria, DVT

Question 13

How many tonsils do we have and what are their names?

Answer 13

1. Pharyngeal
2. Palatine
3. Lingual

Question 14

What are Follicular Dendritic Cells and their function?

Answer 14

1. Antigen-antibody complexes adhere to dendritic processes
2. Proliferation of B cell
3. Retains antigen for months

Check this one!

Question 15

Briefly describe Humoral Immunity? How are the cells involved in this activated?

Answer 15

Specific
Memory B cells produce antibodies
Complement proteins

APC presents antigen to T helper cell - activated T helper cell
Binds to B cell and educates it
B cell differentiates into memory B cell and plasma cell
Plasma cell secretes antibodies specific to antigen

Question 16

Process of Phagocytosis

Answer 16

Bacterium adheres to cell membrane of phagocyte
Phagosome forms
Phagolysosome forms
Enzymes digest bacterium

Question 17

What is opsonisation?

Answer 17

Binding of opsonin ( antibody ) to a receptor on pathogens cell membrane
Immune system attracted to this to destroy

Question 18

Briefly describe the complement process (2 pathways)

Answer 18

1) classical - c1 binds to antigen-antibody complex
2) alternative - c3a and c3b activated when reacts with antigens

Both process lead to

1) inflammation
2) opsonisation
3) Membrane attack complex - structure formed on surface of pathogen causing a pore in its membrane. Free diffusion in and out of cell causing death of pathogen.

Question 19

What is Hydrostatic Blood Pressure?

Answer 19

The pressure of fluid on capillary walls
Blood moves along from arterial to venous end and fluid moves out due to osmotic pressure and so pressure exerted by blood is lower at venous end

Question 20

What is oncotic blood pressure?

Answer 20

Pressure of proteins on capillary walls

As proteins cant leave, pressure is constant

Question 21

HP>OP?

OP>HP?

Answer 21

1) filtration - fluid moves out

2) absorption

Question 22

Describe oedema and lymphoedem

Answer 22

Oedema
- accumulation of watery fluid causing swelling
Lymphoedema
- accumulation of lymph causing swelling

Question 23

Why is lymphoedema non pitting?

Answer 23

Fibroblast activity - releasing collagen so hardening

Question 24

Why does oedema occur first at ankles?

Answer 24

Vertical gradient of venous pressure means higher pressure at ankle (as need more pressure to pump up to heart), so more water pushed out near here.

If lying down - where skin is lax
If sitting - sacral region

Question 25

Effects of venous hypertension

Answer 25

High BP so RBC leak out.
Phagocytes degrade RBC and also interact with Fe2+ in Hb
Fe2+ ==> Fe3+ -rust - browning of skin (haemosiderin)

Question 26

Effects of congestive heart failure?

Answer 26

Inability to pump blood effectively from heart
Increased hydrostatic pressure at venous end
So HP>OP at venous end meaning fluid is being filtered out rather than absorbed
Lymph overwhelmed causes lymphoedema

Question 27

Oxygen dependent killing

Answer 27

Look into !

Question 28

What is MALT?

Answer 28

Mucosal associated lymphoid tissue

- tonsils, peyers patches, vermiform appendix