Thymus

• The thymus is a flat, bi-lobed organ situated above the heart.
• Immature T-cells are simply referred as "Thymocyte", these are densely packed outer compartment (or) cortex of the thymus lobule.
• Some of the thymic epithelial cells in the outer cortex, called "nurse cells", have long membrane extensions that surround as many as so thymocytes, forming large multicellular complexes
• The average weight of the thymus is 70 grams in infants; its age dependent involution levels an organ with an average weight of only 3 grams in the elderly.

Explanations about Thymus:

• The thymus covered by a fibrous capsule. It is formed of two lobes.
• Each lobe of the thymus is organized into lobule which is separated from one another by septa called trabeculae.
• With in each lobule, the cells are arranged into an outer cortex and an inner medulla.
• The cortex is tightly packed with proliferating immature lymphocytes while the medulla contains more mature cells.
• As the cells mature, they move from the cortex to the medulla.
• The cortex consists of lymphocytes (thymocytes) and reticular cells.
• The medulla consists of vascular structure, reticular epithelial cells and scattered lymphocytes.
• There are also some interdigitating cells associated with the epithelial network and these cells are rich in MHC class II antigens.