| Name: | thymus |
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| Synonyms: | |
| Definition: | Paired organ where maturation of T-lymphocytes occurs. The adult thymus located on the dorsomedial aspect of the branchial cavity above the third pharyngeal cartilage. The thymus undergoes a period of rapid growth beginning at about the third week and continuing for several more weeks. Accompanying this growth is a dramatic change in the shape of the thymus. It is ovoid initially and then starts to grow dorsally along the skull, forming a characteristic protrusion. During this growth period the adult pattern of rag1-positive cortex and rag1-negative medulla becomes established. The protrusions diminish with age and the thymus gradually shrinks; at two years, the thymus is again confined to the pharynx with minimal if any protrusion. |
| Ontology: | Anatomy Ontology [ZFA:0001078] |
| Name: | T cell |
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| Synonyms: | immature T cell, immature T lymphocyte, immature T-cell, immature T-lymphocyte, mature T cell, mature T lymphocyte, mature T-cell, mature T-lymphocyte, T lymphocyte, T-cell, T-lymphocyte |
| Definition: | A type of lymphocyte whose defining characteristic is the expression of a T cell receptor complex. |
| Ontology: | Anatomy Ontology [ZFA:0009046] |