Lymphatic system of fish - does not have lymph glands and is represented by a number of paired and unpaired lymphatic trunks, in which lymph is collected from organs, transports nutrients absorbed in the gastrointestinal tract, in particular fats, and removal of waste products, participates in immunity reactions.

The lymphatic system of fish is not closed. Lymph is a tissue fluid with a composition similar to blood plasma, except that it contains only lympho

cytes. The lymphatic system is connected to the circulatory system and plays an important role in metabolism.

As the blood circulates, some of the plasma washes over tissue cells into the lymphatic capillaries and then back into the blood via the lymphatic system.

The lymphatic system is made up of lymphatic capillaries that merge into medium and large lymphatic vessels that carry lymph to the heart. The lymphatic system, which complements the function of the venous system, is responsible for the drainage of tissue fluid. The main lymphatic vessels in fish are

1) Paired subvertebral (running along the sides of the dorsal aorta from the tail to the head);

2) paired lateral (running under the skin along the lateral line).

Through these and the head vessels, lymph flows into the posterior cardinal veins at the cuvier ducts.

Fish also have unpaired lymphatic vessels: dorsal, ventral, dorsal. Fish do not have lymph nodes, but in some species there are paired lymphatic hearts in the form of oval bodies under the last vertebrae, which push the lymph to the heart.

The movement of lymph is also facilitated by the work of trunk muscles and respiratory movements. In cartilaginous fish lymphatic hearts and lateral lymphatic vessels are absent. In roundworms, the lymphatic system is not yet isolated from the circulatory system. For the first time, the separation of the lymphatic and circulatory systems occurs in bony fishes.