Flashcards in The lymphatic system Deck (22)
What are the functions of the lymphatic system?
• Tissue drainage
• Return of plasma and plasma proteins
• Absorbed fat transport from gut
What do lymphatic vessels carry?
Lymph vessels act as reservoirs for plasma and other substances including cells and proteins that have leaked from the vascular system and transport lymph fluid back from the tissues to the circulatory system. Without functioning lymph vessels, lymph cannot be effectively drained and edema typically results.
How much cell-free plasma (tissue fluid) is drained on average every day?
What factors influence lymphatic flow?
Infection and inflammation
Why is lymphatic flow unidirectional?
Valves prevent back flow of lymph
How does infection affect lymphatic flow?
Fluid flow into extracellular spaces increases during infection due to protein accumulation (osmosis) and exudation, this drives increased lymph flow as its responsible for maintaining the balance of fluid in the body works to transport extravasated fluid in the lymphatic vessels. As well as this, is results in increased immune response in nodes, as more antigens are presented and phagocytosis occurs.
How much of the daily fluid that enters the lymphatic system reenters circulation through the lymph nodes?
How many lymph nodes are there in average in young adults?
Describe the structure of the lymph nodes
Lymph nodes are kidney or oval shaped and range in size from a few millimeters to about 1–2 cm long.
Each lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae.
The substance of the lymph node is divided into the outer cortex and the inner medulla.
Where are the B cells in the lymph nodes?
Follicles (germinal centres)
Where are the T cells in the lymph nodes?
Which lymph nodes are associated with the midline of the body?
Pre-aortic lymph nodes
Which lymph nodes are associated with paired, lateral branches to body wall and paired organs?
Para-aortic (lateral/ lumbar) nodes
Where are lymphatic vessels absent?
What % of nodes are associated with the gut and found around the abdomen and pelvis?
Describe some lymph node pathologies
Primary tumours (lymphomas) such as Hodgkins
Secondary tumours as a result of metastasis
Infections such as tuberculosis and glandular fever (mononucleosis)
Lymphodenopathy - abnormal no., size or consistency
What are the two lymph ducts and what regions of the body do they drain?
Thoracic - rest of body
Right lymphatic duct - upper right quadrant of body
Whats the difference between primary and secondary lymphoid tissue?
• Primary lymphoid tissues - where lymphocytes are generated and mature
• Secondary or peripheral lymphoid organs, which include lymph nodes and the spleen, maintain mature naive lymphocytes and initiate an adaptive immune response. The peripheral lymphoid organs are the sites of lymphocyte activation by antigens. Activation leads to clonal expansion and affinity maturation.
Give some examples of primary lymphoid organs
Give some examples of secondary lymphoid organs
– Lymph nodes
– Peyer’s patches
What is the largest lymphatic organ?