The blood circulatory system consists smaller tubular structures responsible for carrying blood known as blood vessels.Some intercellular fluid (tissue fluid), however does not re enter capillaries or veins directly, is picked up by thin-walled blind ended lymph vessels.
These lymph vessels are part of the lymphatic system, which works in parallel with the blood circulatory system to transport fluid and waste products from the tissues back to the bloodstream. The lymphatic system also plays a vital role in the immune response, as it contains lymph nodes that filter out foreign substances and produce immune cells.
Lymph vessels are similar in structure to blood vessels, consisting of a single layer of endothelial cells surrounded by smooth muscle. They are much thinner and less numerous than blood vessels, and they can be found throughout the body. The lymph vessels collect the excess fluid, known as lymph, from the tissues and transport it towards the heart.
The lymphatic system is a one-way system, with lymph flowing in the direction of the heart. Lymphatic capillaries collect the tissue fluid, which contains various waste products, proteins, and cells. These capillaries have overlapping endothelial cells that act as one-way valves, allowing fluid to enter but not exit. The tissue fluid, now called lymph, moves through larger lymphatic vessels and eventually reaches the lymph nodes.
Lymph nodes are small, bean-shaped structures scattered along the lymphatic vessels. They contain specialized immune cells that help filter the lymph and remove any harmful substances, such as bacteria or viruses. If an infection or inflammation occurs in a particular area of the body, the lymph nodes in that region may become swollen and tender.
After passing through the lymph nodes, the lymph is eventually returned to the bloodstream via larger lymphatic vessels. These vessels merge to form the thoracic duct, which empties the lymph into the left subclavian vein near the heart.
In summary, the lymphatic system works alongside the blood circulatory system to remove excess fluid and waste products from the tissues, while also playing a crucial role in immune function. The lymph vessels and nodes form a network that collects, filters, and returns lymph back to the bloodstream to maintain fluid balance and support the body's defense mechanisms.