title: Morphological study of the fetal parotid duct and buccinator muscle and the relationship to salivary secretion.
abstract: The parotid glands secrete about 25% of all saliva produced. In the presence of a stimulus, the amount of saliva secreted from the parotid gland increases to 50%. A decrease in the amount of produced saliva due to aging and parotiditis results in a dry mouth. Therefore, the parotid duct is important to maintaining a healthy oral cavity. In human adults, the parotid duct, approximately 6-8-cm long, travels over the masseter muscle and penetrates the buccinator muscle to enter the oral cavity. Although there have been various studies regarding the parotid gland, only few suggest a functional role of the parotid duct, especially its area of penetration of the buccinator muscle. In this study, 34 fetal specimens ranging from 4 to 10 months of age at death were dissected for anatomical and histological examinations. The area of the parotid duct penetrating the buccinator muscle was fully formed in 5-month-old fetuses. This study found buccinator muscle fibers invading the parotid duct wall near its opening in 6-month-old fetuses and older. Our results support the claim that the buccinator muscle may act as a sphincter, playing a role in regulating and possibly preventing the reflux of salivary secretions into the parotid duct.
authors.affiliation: First Department of Anatomy, Kyorin University School of Medicine, Tokyo, Japan. kaori26@ks.kyorin-u.ac.jp
authors.forename: Kaori
authors.initials: K
authors.lastname: Amano
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moriyama
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Shimada
authors.forename: George
authors.initials: G
authors.lastname: Matsumura
mesh_terms: D002610:Cheek; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D018482:Muscle, Skeletal / Q000196:embryology* / Q000502:physiology; D010306:Parotid Gland / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D012463:Saliva / Q000378:metabolism*; D018987:Salivary Ducts / Q000196:embryology* / Q000378:metabolism