Lymphatic system

The lymphatic system is an extensive network of vessels and organs that performs three key functions: tissue drainage, transport of fats from the intestines and immune defense. It is closely related to the circulatory and immune systems.

Lymphatic vessels

Lymphatic capillaries begin with blind ends in tissues, collecting excess intercellular fluid, which, after entering the lymphatic system, is called lymph. 2–4 liters of lymph are produced per day.

Capillaries → vessels → trunks → two large ducts:

• Thoracic duct (ductus thoracicus) - collects lymph from 3/4 of the body (legs, abdomen, left half of the chest and left arm). Drains into the left venous angle (confluence of the left subclavian and internal jugular veins)
• Right lymphatic duct - from the right arm, the right half of the chest and the right half of the head

Lymphatic vessels have valves (like veins), and the movement of lymph is ensured by contractions of the surrounding muscles and the smooth muscle walls of the vessels.

Lymph nodes

In the human body there are about 600 lymph nodes - biological filters ranging in size from 1 mm to 2 cm. Main groups:

• Cervical - filters lymph from the head and neck
• Axillary - from the upper limbs and mammary glands
• Inguinal - from the lower extremities and pelvic organs
• Mesenteric - from the intestines (there are more than 200 of them!)
• Mediastinal - from the lungs and chest organs

Inside the node, lymph slowly leaks through a network of reticular fibers, where macrophages engulf microbes and foreign particles, and lymphocytes recognize antigens and trigger an immune response.

Lymphoid organs

thymus (thymus gland) - located behind the sternum. Here, T-lymphocytes undergo “training” - they learn to distinguish their own cells from others. Maximally developed in childhood, after puberty it is gradually replaced by adipose tissue.

Tonsils - a ring of lymphoid tissue in the pharynx (palatine, pharyngeal, lingual), the first barrier to infections entering through the mouth and nose.

Peyer's patches are accumulations of lymphoid tissue in the wall of the small intestine that control the intestinal microflora.

Clinical significance

• Lymphadenopathy - enlargement of lymph nodes due to infections or tumors
• Lymphedema - swelling due to impaired lymph outflow (after removal of lymph nodes for oncology)
• Lymphoma - malignant tumor of lymphoid tissue

During oncological operations, the surgeon must examine the sentinel lymph nodes - the first nodes on the path of lymph outflow from the tumor, to determine whether metastases have begun.

All structures of the lymphatic system - nodes, vessels, thymus and spleen - can be studied in 3D atlas Humio. Rotate the model and trace the paths of lymph outflow.