The early development of the parotid gland around the facial nerve and its branches in man

The manner in which the parotid gland forms around the related facial nerve branches was studied with the aid of reconstructions in 15 human embryos and fetuses 18 to 80 mm, crown‐rump length, 7+ to 13.5 weeks ( w ), menstrual age. Peripheral branches of the nerve terminate in the cervicomandibular region at 18 mm (7+ w ), when the unbranched parotid bud is farther rostral. By 22 mm (8 w ), a small nerve branch approaches the buccal region superficial to the bud that extends toward the preauricular region. At 26 mm (8.5 w ), several nerve branches course superficial to the parotid primordium which has first order ductules and is adjacent to the masseter muscle. Second order ductules form quickly (27 mm, 8.5 w ) as the primordium approaches the superficial aspect of the lower buccal, marginal mandibular and cervical nerve branches. The primordium enters the parotid space by 32 mm (9 w ) as third order ductules develop. At 37 mm (10 w ), it has fourth order ductules and the buccal nerve branches are superficial to the main duct. Nerve branches of the temporofacial ramus (temporal, zygomatic and upper buccal) occupy a superficial position in the primordium whereas branches of the cervicofacial ramus (lower buccal, marginal mandibular and cervical) are deeper. A similar arrangement is evident at 56–80 mm (11.5–13.5 w ) when the complex primordium has connections with its superficial and deep portions between many nerve branches.