The inferior pharyngeal constrictor (IPC) originates from the thyroid and cricoid cartilages and inserts to the pharyngeal raphe. In serial sagittal sections of 37 embryos and fetuses at 6-15 weeks (crown rump length 15-115mm), we found (1) the IPC connecting to the sternothyroideus and thyrohyoideus muscles (16 fetuses at 6-11 weeks) or (2) the cricothyroideus muscle (6 fetuses at 12-15 weeks) in addition to the usual cricoid origin. These aberrant connections were most likely to be transient origins of the IPC not from a hard tissue but nearby striated muscles. In four of the latter six specimens, a tendinous band from the IPC inferior end connected to the cricothyroideus muscle to provide a digastric muscle-like appearance. These aberrant connections with nearby muscles seemed to become separated by a growing protrusion of the thyroid cartilage. Therefore, these aberrant origins were, even if developed, most likely to be "corrected" to the adult morphology during midterm or late prenatal period. The aberrant or transient origin of the IPC seemed to result from a discrepancy in growth of the cartilage and muscles. Such a discrepancy in growth seems to resemble the IPC wrapping around the superior cornu of thyroid cartilage. In addition, a final or adult-like morphology was found in two of the present 37 fetal specimens. It seemed to suggest a significant redundancy in growth rate of the laryngeal structures.

中文翻译：

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胎儿发育过程中下咽缩管的短暂连接或起源：一项使用人类胎儿矢状切面的研究。

咽下收缩器（IPC）起源于甲状腺和环软骨，并插入咽沟。在6-15周（冠状臀长15-115mm）处的37个胚胎和胎儿的连续矢状切面中，我们发现（1）IPC连接到胸甲和甲状腺舌肌（16-11个胎儿在6-11周）或（2）除了通常的环状环起源之外，还包括环甲肌（12到15周时有6胎）。这些异常连接最有可能是IPC的短暂起源，而不是硬组织而是附近的横纹肌。在后六个标本中的四个中，来自IPC下端的腱带连接至环甲膜肌，以提供类似胃肌的外观。这些与附近肌肉的异常连接似乎被甲状腺软骨的突出突起所分隔。因此，即使发育异常，这些异常起源也很可能在中期或产前后期被“校正”为成人形态。IPC的异常或短暂起源似乎是由于软骨和肌肉生长的差异引起的。这种增长差异似乎类似于IPC包裹在甲状腺软骨上角膜周围。另外，在目前的37个胎儿标本中有两个发现了最终的或类似成人的形态。似乎表明喉部结构的生长速度有明显的冗余。IPC的异常或短暂起源似乎是由于软骨和肌肉生长的差异引起的。这种增长差异似乎类似于IPC包裹在甲状腺软骨上角膜周围。另外，在目前的37个胎儿标本中有两个发现了最终的或类似成人的形态。似乎表明喉部结构的生长速率存在明显的冗余。IPC的异常或短暂起源似乎是由于软骨和肌肉生长的差异引起的。这种增长差异似乎类似于IPC包裹在甲状腺软骨上角膜周围。另外，在目前的37个胎儿标本中有两个发现了最终的或类似成人的形态。似乎表明喉部结构的生长速度有明显的冗余。