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The Lymphatic System
The Lymphatic System
The circulatory system normally leaks proteins from the capillaries into the extracellular fluid. It is important for the body to reabsorb these proteins to avoid tissue swelling. This is accomplished by the lymphatic system.
- Lymph is a fluid, similar to blood plasma, that is transported by the lymphatic system
- The lymph is transported in vessels that are similar to veins, called lymph vessels
- Lymph vessels contain valves to prevent the lymph from flowing in the wrong direction
- The lymphatic system returns the lymph fluid back to the circulatory system
The lymphatic system also contains lymph nodes. These are enlargements located along the lymph vessels that contain white blood cells which destroy bacteria and other pathogens that might be present in the fluid.
Lymphoid Organs
- The bone marrow is the site of blood cell production
- The spleen is a large lymphoid organs located in the upper left side of the abdominal cavity. It acts as a reservoir for blood and a filtering site for lymph. The spleen can hold about 150 mL of blood.
- The thymus gland is located in front of the trachea, just above the heart, and is where T cells (a specific type of white blood cell) mature.
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Example: The Lymphatic System
Describe the pathway of fluid filtration in the lymphatic system from the capillaries back into the venous system.
- After plasma has delivered nutrients to the cells, 90% of it returns to the circulation through the venules and continues as venous blood.
- The remaining 10% of this fluid becomes lymph and contains waste products. This waste is rich in protein.
- Unlike blood, which flows in a continue loop of the circulatory system, lymph flows in one direction. It flows upward toward the neck where it then flows into the venous blood stream through the subclavien veins on either sides of the neck near the collarbones.
Mark Yourself Question
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Practice: Lymph & The Immune System
Why do lymph nodes swell when you have a sore throat?
Practice: Thymus
True or false, T cells are produced in the thymus while all other blood cells are produced in the bone marrow?