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How does lymph travel from tiny lymphatic capillaries into larger lymphatic vessels?

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Diagram of the human lymphatic system highlighting lymphatic vessels and major lymphoid organs, including lymph nodes, adenoids, tonsils, thymus gland, spleen, appendix, bone marrow, and ducts. — lymphatic system The human lymphatic system, showing the lymphatic vessels and lymphoid organs.

Lymph travels from tiny lymphatic capillaries into larger lymphatic vessels through a process of convergence. These minute capillaries, which permeate most tissues of the body, act as the starting point for the lymphatic system.12

As extracellular fluid—now referred to as lymph—enters these capillaries, it drains into progressively larger lymphatic vessels. In areas such as the skin, for example, superficial lymphatic nets collect fluid from smaller vessels and channel it into increasingly larger vessels located in deeper tissue layers. These vessels eventually converge to form larger lymphatic trunks, which ultimately return the lymph to the bloodstream at the subclavian veins.123

The movement of lymph through this system is facilitated by muscle contractions and external pressure, which provide the necessary force for transport. To ensure the fluid moves in only one direction and does not flow backward, the vessels are equipped with a system of valves.123