title: Postnatal development of the spleen in Didelphis virginiana.
abstract: The postnatal development of the spleen has been examined in 85 opossums ranging in age from newborn to adult. At birth the spleen consists of a well vascularized mass of mesenchymal tissue and lacks lymphatic tissue or any evidence of haemopoietic activity. Haemopoiesis is evident at seven days, increases to a maximum at about two to three weeks and thereafter gradually declines. Although production of granulocytes has disappeared by 60 days postnatum, a small degree of erythropoiesis and megakaryocyte formation continues throughout life. Lymphatic tissue appears by the third week, but germinal centres do not appear until after weaning. A feature of the spleen during the first three to four days is the presence of a population of primitive 'blast' cells.
mesh_terms: D000818:Animals; D005260:Female; D006410:Hematopoiesis; D008297:Male; D008854:Microscopy, Electron; D009893:Opossums / Q000254:growth & development*; D009929:Organ Size; D013154:Spleen / Q000098:blood supply / Q000254:growth & development* / Q000648:ultrastructure