Читать книгу Immunology - Richard Coico - Страница 37

The thymus gland is a bilobed structure, derived from the endoderm of the third and fourth pharyngeal pouches. During fetal development, the size of the thymus increases. The growth continues until puberty. Thereafter, the thymus undergoes atrophy with aging.

The thymus is a lymphoepithelial organ and consists of epithelial cells organized into cortical (outer) and medullary (central) areas that are infiltrated with lymphoid cells (thymocytes) (Figure 2.3A). The cortex is densely populated with lymphocytes of various sizes, most of which are immature, and scattered macrophages involved in clearing apoptotic thymocytes. Figure 2.3B shows a section through normal human thymus tissue.