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The thymus is located in the upper front part of the chest, in the anterior superior mediastinum, behind the sternum, and in front of the heart. It is made up of two lobes, each consisting of a central medulla and an outer cortex, surrounded by a capsule.
Histology of the thymus showing the cortex and medulla Minute structure of thymus. The ability of T cells to recognize foreign antigens is mediated by the T cell receptor (TCR), which is a surface protein able to recognize short protein sequences that are presented on MHC. The purpose of thymocyte development is to produce mature T cells with a ...
AIRE is a transcription factor expressed in the medulla [broken anchor] (inner part) of the thymus. It is part of the mechanism which eliminates self-reactive T cells that would cause autoimmune disease. It exposes T cells to normal, healthy proteins from all parts of the body, and T cells that react to those proteins are destroyed.
In most species, the thymus consists of lobules divided by septa which are made up of epithelium which is often considered an epithelial organ. T cells mature from thymocytes, proliferate, and undergo a selection process in the thymic cortex before entering the medulla to interact with epithelial cells.
Hassall's corpuscles (also known as thymic bodies) are structures found in the medulla of the human thymus, formed from eosinophilic type VI thymic epithelial cells arranged concentrically. These concentric corpuscles are composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells.
Thymus tissue is compartmentalized into cortex and medulla and each of these two compartments comprises its specific thymic epithelial cell subset. cTECs reside in the outer part- cortex, which mostly serves as a developmental site for T cells.
About 90% of T cells displays badly rearranged TCRs, they cannot reach the positive selection and they die by neglect in the cortex. [18] The rest starts to express CCR7, which is a receptor for mTEC-generated chemokine CCL21, and migrate after concentration gradient to the thymic medulla to encounter mTECs. [19]
The senses of vision, audition, and touch are served by the primary visual cortex, the primary auditory cortex, and primary somatosensory cortex. The cerebellar cortex is the thin gray surface layer of the cerebellum , consisting of an outer molecular layer or stratum moleculare , a single layer of Purkinje cells (the ganglionic layer), and an ...