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, 208 (5), 601-7

An Anatomical Study of the Buccinator Muscle Fibres That Extend to the Terminal Portion of the Parotid Duct, and Their Functional Roles in Salivary Secretion

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An Anatomical Study of the Buccinator Muscle Fibres That Extend to the Terminal Portion of the Parotid Duct, and Their Functional Roles in Salivary Secretion

Hyo-Chang Kang et al. J Anat.

Abstract

Until now there has been no definitive anatomical study describing the area where the parotid duct enters the buccinator muscle. In this study, we performed anatomical and histological examinations to investigate the relationship between the parotid duct and the buccinator muscle. Thirty specimens (including the buccinator and the terminal portion of the parotid duct) were obtained from embalmed Korean cadavers. Dissection was performed on 22 of these specimens, and the remaining eight specimens were prepared for histological examination and stained with haematoxylin-eosin or Gomori trichrome. In all specimens, small, distinct muscle fibres originating from the buccinator muscle extended to and inserted into the terminal portion of the parotid duct. The topography of these fibres varied, and we classified them into three categories according to where they originated. Type I buccinator muscle fibres, which inserted into the terminal portion of the parotid duct, originated simultaneously from the anterior and posterior aspects of the duct (ten cases, 45.5%). Type II fibres originated from the anterior aspect of the duct and inserted into the anterior side of the duct (seven cases, 31.8%). Type III fibres originated from the posterior aspect of the parotid duct and ran anteriorly toward the duct (five cases, 22.7%). These results were confirmed in the histological examination of all eight specimens. Based on these findings, we have proposed a tentative description of the physiological role of the buccinator muscle fibres in salivary secretion and in the formation of the sialoliths.

Figures

Fig. 1
Fig. 1
Photograph and corresponding illustration of the small muscle fibres (arrowheads) originating from the buccinator that extend to the terminal portion of the parotid duct.
Fig. 2
Fig. 2
Photographs showing the patterns of origin of the buccinator muscle fibres (arrowheads) that extend to the terminal portion of the parotid duct. The muscle fibres originated from the superficial (a), deep (b) or both superficial and deep layers (c) of the buccinator muscle.
Fig. 3
Fig. 3
Photographs and corresponding illustrations of three categories of fibre characterized according to their origin and location (arrows). The muscle fibres simultaneously originated (a) from the anterior and posterior aspects of the duct, (b) from the anterior and superior aspects of the duct and then inserted into the anterior aspect of the duct, and (c) from the posterior and inferior aspects of the duct. Ant., anterior; Post., posterior; Sup., superior; Inf., inferior.
Fig. 4
Fig. 4
Light micrograph of a transverse section of the parotid duct. The duct was composed of three layers: the adventitia (A), muscle layer (Muscle) and mucosa (M). Haematoxylin–eosin. Scale bar = 1 mm.
Fig. 5
Fig. 5
(a) Light micrograph of a longitudinal section along the axis of the parotid duct. (b) Higher magnification view of the boxed area in (a) showing distinct muscle fibres originating from the buccinator and running parallel to the duct (Duct). Bu, buccinator. Gomori trichrome. Scale bar = 100 µm.
Fig. 6
Fig. 6
(a,b) Light micrographs of longitudinal sections along the axis of the parotid duct showing the valve-like structure (arrowheads) within the lumen of the terminal duct of the parotid. Bu, buccinator. Gomori trichrome. Scale bar = 100 µm (a), 50 µm (b).

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