The thymus leads a double life as part of both the immune and endocrine system. As an endocrine organ, it produces thymus hormone which aids in the maturation of T lymphocytes and possible B lymphocytes. As an immune organ, it aids in the development and maturation of T lymphocytes and natural killer cells. . The thymus is a bi-lobed gland. Each lobe is made up of several smaller lobules which are divided into an outer cortex and an inner medulla. The lobules are held together by a dense irregular connective tissue capsule. The job of the cortex is to ensure the surface receptors on the T lymphocytes are able to bind to the major histocompatibility complex II (MHC II) protein on macrophages. This process occurs in several rounds to ensure that the T lymphocytes can become active in the immune response. Cells that are able to bind to MHC II are positively selected for and brought into the medulla. The medulla modifies and arranges gene receptors so that they target specific cell markers (called antigens). The cells then go through negative selection for auto reactive T lymphocytes. If the T lymphocytes is auto reactive, attacks the body's own cells, it is destroyed before being sent into circulation.
The slides on this page were generated by students in the spring of 2019. Observe the student slides by clicking on the arrows and compare them to your lab book picture.
| Lab Book Image | Student Images |
|---|---|
|
|
|
