Human Anatomy - Kotsan I. Ya. 2009

Organs of Hematopoiesis and the Immune System
Lymphoid tissue of the walls of the digestive and respiratory system organs
Aggregated lymphoid nodules of the vermiform appendix

The aggregated lymphoid nodules of the Appendix (noduli lymphatici aggregati appendicis vermiformis) are located within the mucosa and submucosa along the entire length of the organ, extending from its base near the cecum to the apex. In children and adolescents, the total number of lymphoid nodules in the appendiceal wall reaches 600–800. These nodules are frequently arranged in 2–3 overlapping rows. The transverse diameter of a single nodule does not exceed 1.0–1.5 mm. Interspersed between the nodules are smooth Muscle Cells, reticular and Collagen fibers, as well as the deep portions of intestinal glands that extend into this region.

The formation of lymphoid nodules in the wall of the appendix begins during the 4th month of fetal development. Nodules first appear in the mucosa and subsequently in the submucosa. By the 5th month of intrauterine life, the nodules are well-formed and present as rounded accumulations of lymphoid tissue. Immediately before and after birth, germinal centers emerge within the nodules. In newborns, the transverse diameter of the nodules ranges from 0.5 to 1.25 mm, with their total number in the appendiceal wall reaching 150–200. In children over 10 years of age, clusters of adipocytes appear in the submucosa of the appendix, accompanied by an increase in collagen and elastic fibers, while reticular fibers become thicker. At 16–18 years of age, There is a marked decrease in the number of lymphoid nodules alongside an increase in adipose tissue mass. This accumulation of adipose tissue in the appendiceal wall becomes particularly prominent between the ages of 20 and 30. In individuals over 60 years old, lymphoid nodules in the wall of the appendix are rarely observed.

The arterial Vessels and nerves supplying the lymphoid nodules originate from the branches that vascularize the appendiceal wall (specifically, the appendiceal artery and autonomic nerve fibers). Venous Blood drains from the lymphoid nodules into the appendiceal vein. Lymphatic vessels, originating from the internodular capillaries, direct toward the cecal and ileocolic Lymph Nodes.