| Name: | thymus |
|---|---|
| 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: | hematopoietic stem cell |
|---|---|
| Synonyms: | colony forming unit hematopoietic, hematopoietic progenitor cell, hemopoietic progenitor cell, hemopoietic stem cell, HSC |
| Definition: | A stem cell from which all cells of the lymphoid and myeloid lineages develop, including blood cells and cells of the immune system. |
| Ontology: | Anatomy Ontology [ZFA:0009014] |