4.1 The Lymphatic System Flashcards
How does the lymph come about?
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.
How does the lymph enter the lymphatic?
Pressure in the interstitial space is higher than lymphatica, so valves open and allow fluid in, relieving pressure.
Where does the right lymphatic duct connect to the blood supply?
Internal Jugular Vein
Where does the larger left thoracic duct deposit lymph to get back to the blood supply?
Subclavian vein
Where is lymph inspected and cleansed?
Lymphnodes
Lymphatic Tissue - Tonsils, peyers patches, appendix
Describe the structure of a lymphnode (3) and its function
- Afferent lymphatic vessels via convex surface, efferent via hilum
- Feeding artery and draining
- Several germinal centres
- Inspection of lymph fluid
- Trigger macrophage release, inflammation
- Germinal centres contain APCs which present antigen to naive T cells for activation
Briefly describe inflammation, humoral and cell-mediated responses
- Neutrophils and macrophages come to site, red, swelling, heat, pain
- Bcell - plasma cell - antibody production
- APC’s recognise antigen and present to T cell for activation
What is lymphadenopathy?
- Enlarged lymph nodes
2. Germinal centres fill with lymphocytes if infection
What is lymphoma?
Cancer of the lymph
What are the lymph organs and describe their functions?
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
Can the spleen rupture? If yes, what effects does this have?
Yes and could lead to death by exsanguination
What is a spleen removal procedure called? What effects does this have?
- Splenectomy
- Bone marrow and liver take over in removal of RBCs
- But as a huge organ that makes antibodies has been removed, increase risk of infection, malaria, DVT
How many tonsils do we have and what are their names?
- Pharyngeal
- Palatine
- Lingual
What are Follicular Dendritic Cells and their function?
- Antigen-antibody complexes adhere to dendritic processes
- Proliferation of B cell
- Retains antigen for months
Check this one!
Briefly describe Humoral Immunity? How are the cells involved in this activated?
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
Process of Phagocytosis
Bacterium adheres to cell membrane of phagocyte
Phagosome forms
Phagolysosome forms
Enzymes digest bacterium
What is opsonisation?
Binding of opsonin ( antibody ) to a receptor on pathogens cell membrane
Immune system attracted to this to destroy
Briefly describe the complement process (2 pathways)
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.
What is Hydrostatic Blood Pressure?
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
What is oncotic blood pressure?
Pressure of proteins on capillary walls
As proteins cant leave, pressure is constant
HP>OP?
OP>HP?
1) filtration - fluid moves out
2) absorption
Describe oedema and lymphoedem
Oedema
- accumulation of watery fluid causing swelling
Lymphoedema
- accumulation of lymph causing swelling
Why is lymphoedema non pitting?
Fibroblast activity - releasing collagen so hardening
Why does oedema occur first at ankles?
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
Effects of venous hypertension
High BP so RBC leak out.
Phagocytes degrade RBC and also interact with Fe2+ in Hb
Fe2+ ==> Fe3+ -rust - browning of skin (haemosiderin)
Effects of congestive heart failure?
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
Oxygen dependent killing
Look into !
What is MALT?
Mucosal associated lymphoid tissue
- tonsils, peyers patches, vermiform appendix
