Cells in Lymph and the thymus

Lymphocytes in blood smear are shown in the image to the right.

Thymus

First note the capsule and septa. Next notice the organization of lobes into a basophilic cortex and eosinophilic medulla. A key feature of the medulla is the presence of Hassal’s corpuscles, which are masses of degenerated epithelial cells. The epithelial reticular cells make up the framework of the thymus.

• The capsule,
• Septa, and
• The organization of lobes into a basophilic cortex and eosinophilic medulla.

Identify the epithelial-reticular cells or epitheliocytes  which make up the framework of the thymus.

• These are larger and paler than the lymphocytes. In the medulla, identify the masses of epithelial cells, thymic or Hassal's corpuscles.

Identify macrophages in the thymic cortex (they are typically larger and more pale than lymphocytes and less numerous than the epithelial-reticular cells) and look for mitotic figures among the lymphocytes of this region.

What is the function of the individual epithelial reticular cells?

How do the lymphocytes seen here differ from those in the blood smears studied earlier?

Next let's look at a lymph node.