Lymphatic vessels are crucial components of the lymphatic system, forming a network of thin-walled, branching tubes that transport lymph—a clear fluid containing excess interstitial fluid, proteins, waste, and immune cells.
They maintain fluid balance by returning excess fluid from tissues to the bloodstream.
Categories of Lymphatic Vessels
1. Lymphatic Capillaries:
Smallest lymphatic vessels, composed of a single layer of endothelial cells.
Specialized structure allows absorption of excess interstitial fluid and large molecules.
Found in nearly all body tissues except the CNS, avascular tissues, and bone marrow.
2. Collecting Lymphatic Vessels:
Larger vessels that gather lymph from lymphatic capillaries.
Contain smooth muscle cells and valves to prevent backflow.
Transport lymph through lymph nodes, where it is filtered, and immune cells detect and eliminate pathogens.
3. Lymphatic Trunks:
Formed by the convergence of collecting lymphatic vessels after they pass through lymph nodes.
Drain lymph from specific body regions, such as the jugular trunk (head and neck) and lumbar trunk (lower limbs and pelvis).
4. Lymphatic Ducts:
The final stage of lymphatic vessels, consisting of the right lymphatic duct and the thoracic duct.
The right lymphatic duct drains lymph from the right side of the head, neck, upper limb, and thorax.
The thoracic duct drains lymph from the rest of the body.
Both ducts empty lymph into the venous system at the junction of the internal jugular and subclavian veins.