PoD - Lymphatic Systems

Question 1

what is the function of the lymphatic system?

Answer 1

• drain tissue
• return plasma and plasma proteins
• absorbed fat transport from gut
• immunity

Question 2

how is fluid returned to the lymph?

Answer 2

• lymph system drains escaped, cell-free plasma from the extracellular spaces back to the venous system
• lymph is fluid and plasma proteins only but gains lymphocytes as it flows through the lymphatic capillaries and channels
• gain of these lymphocytes is how the lymphatic system has an immune function
• Flow is similar to that in veins, relying upon muscle contraction, pressure changes and gravity. Unidirectional because of valves.
• Fluid flow into extracellular spaces increases during infection due to protein accumulation (osmosis), this drives increased lymph flow and therefore immune response in nodes, as more antigens are presented and phagocytosis occurs.

Question 3

what are lymph nodes?

Answer 3

• lymphatic vessels transverse lymph nodes
• lymph nodes are where immunological function resides (acquired immunity)
• lymph nodes are connected to an incoming and outgoing lymph vessel
• cancer can metastasise to lymph nodes via the lymph’s blood supply

Question 4

what are cancers of the lymph nodes called?

Answer 4

• Primary tumours is where there is a tumour in the node itself (lymphomas) such as Hodgkins
• Secondary tumours (non-Hodgkin’s lymphoma) as a result of metastasis from other sites

Question 5

how is lymph drained?

Answer 5

• Initially drainage is symmetrical from limbs, head and neck and trunk.
• As a rule, deep lymphatic drainage follows routes of arterial supply.
• Ultimately all lymph congregates into 2 large lymph ducts – the right lymphatic duct (upper RHS portion of upper limb, torso, H&N) & thoracic duct (everything else)
• These empty into the venous system at the Jugular/ Subclavian junction

Question 6

what are lymphoid tissues?

Answer 6

• lymphoid tissues are tissues where lymphocytes are generated and matured
• Thymus and Bone marrow (1)
• Spleen (2)
• Lymph nodes (2)

Question 7

what is the spleen?

Answer 7

• spleen is the largest lymphatic organ
• deals with immunity
• located in upper left quadrant of abdomen
• contains large amount of blood, routinely discharged via smooth muscle action
• histology of white pulp is similar to lymph node - contains T and B cells