Overview
The lymphatic (immune) system returns tissue fluid to the blood and houses the lymphocytes that defend the body. This topic covers its organs and vessels, and the structure and function of the central and peripheral lymphoid organs.
Lymphatic system and lymphatic vessels
- The lymphatic System is a part of the circulatory system (It collects the excess body fluid and return it to the venous circulation) As well as a part of immune system (It circulates lymphocytes throughout the body).
- Lymphatic system is composed of:
- Lymphoid organs (thymus, bone marrow, spleen) Primary secondery
- lymph nodes
- Lymph vessels
- lymph
Lymphatic vessels form an extensive and complex inter-connected network of channels, which begin as “porous” blind-ended lymphatic capillaries in tissues of the body and converge to form a number of larger vessels, which ultimately connect with large veins in the root of the neck.
- Main layers of the wall:
- Endothelium:
- innermost layer
- Single layer of specialized cells
- Creating flap-like structures, that act as one-way valves.
allow fluid to enter the lymphatic vessel but prevent backflow.
- Basement membrane:
- Supportive layer
- Beneath the endothelium.
- Anchoring filaments:
- Between endothelial cells and surrounding tissues.
- Anchore the endothelial to tissues
- Smooth muscle layer: contract to move the lymph.
- Connective tissue layer
- Adventita: contains collagen fibers
In large lymphatic vessels