Lymphatic System Flashcards
What are the components of the lymphatic system?
Lymph- fluid connective tissue
Lymphatic vessels- network all throughout the body
Lymphatic tissues and organs- important immune functions
What are the functions of the lymphatic system?
- Produce, maintain, and distribute lymphocytes (immunity)
- Maintain normal blood volume and the normal composition of the interstitial fluid
- Facilitate fat absorption in the digestive system
- Provide an alternative route for the transport of hormones, nutrients, and waste
What is the purpose of the thymus?
Important for T-cell maturation; degenerates as we age.
Where is the thymus located?
Just superior to the heart.
What are the primary lymphatic organs?
Red bone marrow and the thymus. This is where lymphocytes are formed and mature. In the red bone marrow, B cells mature, while T cells mature in the thymus.
What are the secondary lymphatic structures?
Lymph nodes, spleen, tonsils, Peyer’s patches (ileum), and MALT (mucosa associated lymphoid tissues).
These structures are where lymphocytes are activated and initiate an immune response by encountering antigens.
What is the difference between primary and secondary lymphatic structures?
Lymphocytes (B cells and T cells) mature in the primary lymphatic structures. Once mature, they migrate to secondary lymphatic structures (spleen, lymph nodes, tonsils, and MALT) where they encounter antigens and initiate immune responses.
What are the features of a lymph node?
Filtration hub where lymph enters, immune cells interact, and cleansed lymph exits
Shape: Oval/bean shaped
Covering: Connective tissue
Hilus: This is an indentation where certain vessels and nerves enter or leave
Vessels:
Afferent vessels bring lymph into the lymph node
Efferent vessels carry lymph out of the lymph node at the hilus
Cortex: the outer region, containing follicles filled with lymphocytes
Medulla: The inner region, rich in macrophages that help filter lymph
Germinal center: Located in the follicle, it expands when B cells (plasma cells) are produced during an immune response
What does the lymphatic system maintain?
Normal blood volume and chemical composition of the interstitial fluid
How does fluid move through the lymphatic system?
- Fluid leaves the circulatory system: Blood plasma leaks out of capillaries into surrounding tissues.
- Fluid occupies the interstitial space: This fluid becomes interstitial fluid, filling the spaces around cells.
- Into lymphatic capillaries: The interstitial fluid enters lymphatic capillaries and is now called lymph
- Larger lymphatic vessels: The lymph flows into larger lymphatic vessels, moving towards lymph nodes and eventually back to the circulatory system
What is the structure of lymphatic capillaries?
Compared to systemic/blood/vascular capillaries
- Lymphatic capillaries are larger in size
- They have uneven/irregularly shaped walls
- Thinner walls
- Remember that they have high permeability (fluid can easily enter into them)
What are the size differences between arteries, veins, and lymphatic vessels?
Arteries are the smallest, followed by veins (they are larger than arteries because they contain most of the blood in the body), followed by lymphatic vessels (largest in body, very thin walls)
There is very low pressure within the lymphatic system. How do we get movement in the system?
Valves in larger lymphatic vessels help with one way movement of the lymph fluid.
What are the two vessels that are the end points for the movement of lymph fluid back into the circulatory system?
What regions of the body do each of them cover?
The thoracic duct and the right lymphatic duct.
The thoracic duct is pretty much all-encompassing. It covers all of the body except for the right side above the diaphragm. The right lymphatic duct covers the right upper extremity, the head and neck, and the portion until the diaphragm.
Lymph ultimately drains into where?
The superior vena cava and into the right atrium.
