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:
- 1. Lymphoid organs (thymus, bone marrow, spleen) Primary secondary
- 2. lymph nodes
- 3. Lymph vessels
- 4. 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 :
- 1. 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.
- 2. Basement membrane :
- Supportive layer
- beneath the endothelium.
- 3. Anchoring filaments :
- Between endothelial cells and surrounding tissues.
- Anchore the endothelial ↓ ↑ to tissues
- 4. Smooth muscle layer : Contract to move the lymph.
- 5. Connective tissue layer
- 6. Adventitia : contains collagen fibers
In large lymphatic vessels