Human Anatomy: Part 2 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2008

Special Part
Lymphatic System (systema lymphaticum [systema lymphoideum]) - General Overview
Components of the Lymphatic System - Lymph Nodes

Lymph Nodes, nodi lymphatici (PNA); or lymphoid nodes, [nodi lymphoidei] BNA, are located along the path of Lymphatic vessels. They consist of lymphoid tissue, are predominantly bean-shaped (Fig. 103) and grey in color, with dimensions ranging from 1 to 15-20 mm. The total mass of all human lymph nodes reaches 500-1000 g. According to various authors, the number of Lymph Nodes in humans ranges from 300 to 460, increasing from lower mammals to primates (D. A. Zhdanov). Lymph nodes enrich lymph with lymphocytes and act as "filters" that collect pathogenic microbes that have penetrated the body and arrived here through lymphatic vessels (barrier-filtration function). Due to the retention of Microorganisms in the lymph nodes, they do not always enter the bloodstream; the nodes respond by enlarging and intensely proliferating lymphocytes. Therefore, certain infectious diseases (tonsillitis, bronchoadenitis) cause a painful enlargement of the lymph nodes of the Pharynx, neck, and the ROOT lymph nodes of the Lungs (the latter is frequently observed in childhood).

In addition to the vital function of fighting infection, lymph nodes serve as regulators of the volume of lymph draining from the organ in the region where they are situated.

Thus, before entering the lymphatic collectors and subsequently draining into the Blood, the lymph passes through lymph nodes, which function as mechanical and biological filters. According to R. Sappey and D. A. Zhdanov, in certain PARTS OF THE body (upper and lower extremities, Stomach, Kidneys), lymph passes through 5-6 or 6-10 lymph nodes. Exceptions include the short lymphatic Vessels of the human Thyroid Gland, which drain directly into the Thoracic duct (M. S. Spirov), and the esophageal lymphatic vessels, which empty directly into the thoracic duct (D. A. Zhdanov). This exception must be taken into account in oncology, because foreign particles (for instance, malignant tumor Cells) from The Thyroid Gland and esophageal walls can penetrate directly into the venous stream along with the lymph. Consequently, most lymph nodes are interconnected via lymphatic vessels.

Class="center">

Fig. 104. Thoracic duct, ductus thoracicus, Lymphatic vessels and nodes (axillary, lumbar, and iliac) (after R. D. Sinelnikov)

Externally, lymph nodes are covered by a Connective Tissue capsule, from which single thin trabeculae extend into the parenchyma, while thick, short hilar trabeculae extend from the hilum of the node. In some cases, the hilar trabeculae merge with the capsular ones, giving the lymph node a lobular Structure.

Lymph enters the sinuses of the lymph nodes through 2-11 afferent lymphatic vessels, vasa afferenda, which empty into the nodes via their upper or lower pole. Upon entering the node, the afferent vessels open into sinuses where lymph flow slows down, creating optimal conditions for Metabolic exchange between the lymph and the lymphoid tissue of the node. On the Medial surface of the node is the hilum, hilum, through which Arteries and nerves enter, and Veins (1-2) and efferent lymphatic vessels exit (for more details on The structure of the lymph node, see the chapter "Organs of Hematopoiesis and Immune Defense").

Lymph nodes are located either singly or in groups (regional). A significant portion of them is situated within Body Cavities and around Internal Organs, predominantly near their hila. Such nodes are termed internal, or visceral, nodi lymphatici viscerales. Lymph nodes located in the walls of cavities are called parietal, nodi lymphatici parietales.

Furthermore, lymph nodes are classified according to topographical-anatomical criteria, or their Location, into: pelvic, inguinal, HEAD and Neck nodes. Lymph nodes situated in specific regions of The Human Body are called regional (from Lat. regio - region). In certain body areas, lymph nodes are arranged in two layers: superficial and deep, separated by fascia. For example, superficial inguinal nodes, nodi lymphatici inguinales superficiales, are located on the fascia lata of the thigh, whereas deep nodes, nodi lymphatici inguinales profundi, lie beneath the fascia. The topography of lymph nodes, the body regions from which lymph is collected via afferent lymphatic vessels, and the pathways of lymph outflow from the nodes are presented in the summary table (see p. 218).

Blood supply and innervation of LYMPH NODES AND lymphatic vessels are provided by adjacent small blood Vessels and nerves.

Alongside regional lymph nodes, formations in the form of small lymphatic nodules have been discovered in human parenchymal organs (O. O. Sushko, L. V. Chernyshenko, 1956, 1966). They are located along the Links of the microcirculatory bed and adhere to their walls, hence their designation as perivascular lymphatic nodules. According to L. V. Chernyshenko et al. (1994), they should be classified as part of The Immune System.