LYMPHOID SYSTEM
- 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
Structure of the wall of lymphatic vessels
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 blackflow.
- 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