Life and Medical Sciences
Cell & Developmental Biology
Wiley InterScience Backfile Collection 1832-2000
This report on the early human ilium is based on the Streeter collection, Carnegie Institution of Washington, Department of Embryology, Baltimore. The five phases in chondrogenesis, described by Streeter for the humerus ('49) and the horizons (Streeter, '42) are used in the description of the changes observed in the ilium. From horizon XV (7-8 mm, 30-32 days) to horizon XVIII (14-16 mm, 36-38 days) component cells of the ilium are mesoblasts. In horizon XIX (17-20 mm, 38-40 days) young cartilage cells have appeared. Both phase 1 and phase 2 cells appear in horizon XX (21-23 mm, 40-42 days), the former characterized mainly by the first appearance of intercellular material, the latter by their slender shape and arrangement in tiers. Phase 3 cartilage cells, cuboidal with many vacuoles, appear in horizon XXI (22-24 mm, 42-44 days). Increasing vacuolization of the cytoplasm of cells is noted throughout horizons XXII and XXIII until, in horizon XXIII (28-30 mm, 46-48 days) total disintegration of cells, a feature of phase 5, is evident. Thus the phases of cartilage differentiation described for the humerus are present also in the ilium.
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