BL - The Lymphatic System Flashcards
How many litres of interstitial fluid a day does the lymphatic system collect?
3 litres
What does the lymphatic system consist of?
FLUID (lymph), VESSELS (lymphatics), CELLS (lymphocytes and supporting cells), TISSUES and ORGANS
How is lymph propelled through the body?
Skeletal muscle movement, pressure changes in thorax during breathing, pulsation of adjacent arteries and veins.
What do larger lymphatic contain in their walls to help lymph flow?
Smooth muscle, which can contract to move lymph along.
What are the two types of tissue found in the lymphatic system?
Diffuse (MALT/GALT/BALT) and lymphatic nodules (Tonsils, Payer’s patches, vermiform appendix)
What does GALT stand for?
Gut associated lymphatic tissue
Which organs are included in the lymphatic system?
Lymph nodes, thymus, spleen
What do lymph nodes do?
They filter lymph as it percolates on its way to the vascular system.
Roughly how many lymph nodes are there n the human body?
700
Each lymph node has a feeding artery and a draining vein. What do these enter and leave via?
The hilum
What are Payer’s patches?
Small masses of lymph tissue found in the small intestine. They monitor bacteria populations and prevent growth of pathogenic bacteria.
Where are follicular dendritic cells located?
Terminal centres of lymph nodes.
What are follicular dendritic cells used for?
Antigen antibody complexes adhere to the dendritic processes and the cell can retain its antigen for months.
What do follicular cells do to B cells?
They cause them to proliferate.
Why do T cells require the help of professional antigen-presenting cells?
They are unable to recognise antigens in the absence of antigen presentation.
What is the inflammatory response?
The initial reaction of a body to an antigen. It is mediated mostly by neutrophils and macrophages.
What is the role of B lymphocytes in humoral immunity?
They mediate it, producing antibodies which transform into plasma cells that synthesise/secrete a specific antibody.
What is cell-mediated immunity mediated by?
T cells, which require antigen presenting cells to recognise the antigen.
Why is cell-mediated immunity important?
Defence against viral, fungal and mycobacterial infections, tumour cells and transplant rejection.
What is lymphadenopathy and what causes it?
Enlarged lymph nodes, caused by the germinal centres filling with increased numbers of lymphocytes to fight infection. Often associated with cancer.
What are the immune functions of the spleen?
Antigen presentation by APCs, activation and proliferation of B and T lymphocytes, production of antibodies, removal of macromolecular antigen from blood.
What are the haemopoietic functions of the spleen?
Removal and destruction of old/damaged erythrocytes, retrieval of iron from red blood cell Hb.
Why is a ruptured spleen dangerous?
It has a very rich blood supply and can easily lead to death through exsanguination.
Why is it better not to remove the spleen?
Splenectomy increases the risk of infection by certain bacteria and malaria, and increases the risk of DVT and pulmonary embolism.
By what age as the thymus mostly turned into fat?
The late teenage years (it involutes after puberty).
What is the role of the thymus?
Maturation of bone marrow derived stem cells into immunocompetent T cells - “thymic cell education”.
What does complement consist of and what is its function?
A group of serum proteins that activates inflammation, destroys cells and participates in opsonisation.
What two pathways can activate the complement cascade?
Classical or alternative
What is the difference between the classical and alternative complement pathways?
In the classical pathway C1 is activated when it binds to an antigen-antibody complex, while in the alternative pathway C3b is activated when it reacts with antigens
What is oedema?
Accumulation of an excessive amount of watery fluid in cells, tissues or serous cavities.
What is lymphoedema?
Swelling as a result of obstruction of lymph vessels or nodes with accumulation of large amounts of lymph.
How can lymphoedema be identified?
It does not pit, unlike oedema
What do the complement pathways both lead to?
Inflammation, opsonisation, membrane attack complex.
Why does oedema often appear first at the ankles?
Gravity in human body causes a vertical gradient of venous pressures
