Why is the thymus no longer present in adults and just children?
The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells).
Answer and Explanation: 1
The thymus in most vertebrate organisms shrinks rapidly with age putting older individuals at greater risk for life-threatening infections, even though such a shrinkage process begins within the first year of life for organisms such as humans. While it is unknown why such a process occurs, some studies have revealed that thymus atrophy may stem from a decline in its ability to protect against DNA damage from free radicals. Furthermore, another theory that exists is that the thymus degenerates with age as to reduce the chance that T-cells that recognize body cells as harmful (i.e. would cause autoimmune disease), would be more likely to arise if the thymus persists for longer.
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fromChapter 17 / Lesson 8
This lesson will cover something known as the lymphatic system. You'll learn about bone marrow, lymph, the thymus, lymph nodes, spleen, and much more as we explore this critical component of your immune system.