Thymus
The thymus, a bilobed organ located above and anterior to the heart, develops as an outgrowth from the developing pharynx. The thymus is a primary lymphoid organ with no filtering ability. The thymus produces mature T lymphocytes that recognize and react to “non-self” and eliminate cells that recognize (and, thus, could destroy) “self.” Immature T lymphocytes migrate to the thymus from the bone marrow; mature T lymphocytes seed T-dependent areas of secondary lymphoid structures. 10x
Capsule >
The thymus possesses a thin connective tissue capsule from which trabeculae extend into the parenchyma of the organ. The capsule and trabeculae convey blood vessels into and out of the thymus. Trabeculae subdivide the organ into thymic lobules, which consist of an outer cortex and a central medulla. This medullary tissue is continuous between lobules.
Trabeculae
The thymus possesses a thin connective tissue capsule from which trabeculae extend into the parenchyma of the organ. The capsule and trabeculae convey blood vessels into and out of the thymus. Trabeculae subdivide the organ into thymic lobules, which consist of an outer cortex and a central medulla. This medullary tissue is continuous between lobules.
Lobules
The thymus possesses a thin connective tissue capsule from which trabeculae extend into the parenchyma of the organ. The capsule and trabeculae convey blood vessels into and out of the thymus. Trabeculae subdivide the organ into thymic lobules, which consist of an outer cortex and a central medulla. This medullary tissue is continuous between lobules.
Cortex >
The dark-staining, cortex is readily differentiated from the pale-staining medulla. The cortex is composed primarily of densely packed, developing T lymphocytes (thymocytes). The medulla contains mature and maturing thymocytes and Hassall’s corpuscles, derived from epithelial reticular cells. Mature T lymphocytes exit the thymus from the medulla.
Medulla
The dark-staining, cortex is readily differentiated from the pale-staining medulla. The cortex is composed primarily of densely packed, developing T lymphocytes (thymocytes). The medulla contains mature and maturing thymocytes and Hassall’s corpuscles, derived from epithelial reticular cells. Mature T lymphocytes exit the thymus from the medulla.
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