Embryological development of human parotid gland: A Review

The parotid, submandibular, and sublingual glands are major salivary glands (SG). The parotid gland (PG) is composed mainly of serous acini and produces watery secretion. Development of major SG begins in the human embryo as a result of complex interaction between the oral epithelium and underlying mesenchyme. Parotid bud originates near the angle of the stomodeum at its ectodermal region and grows out laterally towards the otic placode. As bud formation begins, the portion closest to the stomodeum eventually differentiates into the main excretory duct, and the most distal portion of the bud forms the secretory acini.  Parotid duct (PD) development begins as an elongated furrow running dorsally from the angle of the mouth, between the mandibular and maxillary prominences of the 1st pharyngeal arch. The size of oral fissure is reduced by partial fusion between the maxillary and mandibular prominences, and the PD opening is found in front of the buccopharyngeal membrane (BPM) on the inner surface of the cheek, which is opposite to the future second upper molar tooth. The buccinator muscle originates from the alveolar process of the maxilla and mandible, and the pterygomandibular raphe and its fibers converge towards the modiolus. In addition, the buccinator may act as a sphincter and play a role in regulating the PD. Embryologically, the development of the parotid gland (PG) is closely associated with the developing buccinator muscle and the derivatives of the first and second pharyngeal arches. The deep part of the gland, situated in the infratemporal fossa, is related to first pharyngeal arch derivatives, including the muscles of mastication and the mandibular division of the trigeminal nerve. In contrast, the superficial part of the gland is associated with second pharyngeal arch derivatives, namely the muscles of facial expression and the facial nerve.