Tran S, Hall B K
Department of Biology, Dalhousie University, Halifax, N.S., Canada.
Acta Anat (Basel). 1989;135(3):200-7. doi: 10.1159/000146754.
Whether secondary cartilage develops in the mammalian clavicle has been a matter of controversy. This study documents, in the embryonic mouse: (a) the onset of clavicular osteogenesis at 14 days of gestation (Theiler stage 22); (b) the appearance of secondary cartilage at 16 days of gestation (Theiler stage 24) and its persistence as a prominent cartilage until 18 days of gestation; (c) that the relative growth rate of the clavicle is much higher (0.097 mg/g body weight/day) between 16 and 17 days of gestation than at later ages (mean of 0.005 mg/g/day between 17 days of gestation and 4 days postnatally), and (d) that secondary cartilage failed to form in clavicles from 15-day-old embryos maintained in vitro. We conclude that secondary cartilage is a feature of the developing mouse clavicle, that it arises when the relative growth rate of the clavicle is highest, and that the most likely stimulus for differentiation of this cartilage is mechanical, muscle-based and associated with rapid relative clavicular growth.
哺乳动物锁骨中是否会形成继发性软骨一直存在争议。本研究记录了胚胎小鼠的情况：(a) 在妊娠14天（泰勒尔分期22期）时锁骨成骨开始；(b) 在妊娠16天（泰勒尔分期24期）时出现继发性软骨，并作为显著的软骨持续存在至妊娠18天；(c) 妊娠16至17天期间锁骨的相对生长速率（0.097毫克/克体重/天）远高于后期（妊娠17天至出生后4天的平均值为0.005毫克/克/天）；以及(d) 在体外培养的15日龄胚胎的锁骨中未形成继发性软骨。我们得出结论，继发性软骨是发育中小鼠锁骨的一个特征，它在锁骨相对生长速率最高时出现，并且这种软骨分化最可能的刺激因素是机械性的、基于肌肉的，且与锁骨的快速相对生长有关。
