Development of the pharynx in normal and malformed fetuses.

We studied the development of the pharynx in human embryos and fetuses. Embryos and fetuses from 4.5 mm crown-rump length (CRL) to 40 mm CRL were processed for microscopic examination. Normal fetuses from 32 mm CRL to 250 mm CRL and fetuses with malformations of the central nervous system (CNS) were cut sagittally through the midline and their pharyngeal regions were examined macroscopically. Our observations suggested that, at an early embryonic stage, the notochord and basicranium might play important roles in the formation of the human pharynx. At a later stage, the growth of the maxillomandibular portion also appears to be important in the formation of the pharynx. The finding of malformation of the pharynx in fetuses with maldevelopment of the CNS suggests that the brain may play an important role in the formation of the pharynx.