Ellis's demonstrations of anatomy : being a guide to the knowledge of the human body by dissection / by George Viner Ellis.

  • Ellis, George Viner, 1812-1900.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Ellis's demonstrations of anatomy : being a guide to the knowledge of the human body by dissection / by George Viner Ellis. Source: Wellcome Collection.

    40/802 (page 26)
    origin; insertion at corner of the mouth ; parts in con tact with it use on aperture, on cheek, in expelling Orbicular muscle of lips includes fibres of buccinator, levator and depressor anguli oris, naso-labial and incisive slips. Special fibres of lips. clieek, and occupies the interval between the jaws. It arises from the outer surface of the alveolar borders of the upper and lower maxillae, as far forwards in each as the first molar tooth ; and in the interval lietween the jaws behind it is attached to a tendinous band known as the pterygo-niaxillary ligament. From this origin the fibres are directed forwards to the lips, where they pass into the orbicularis ; and as most of the up])er fibres descend to the lower lip while the lower ones ascend to the upper lip, a decussation takes place at the corner of the mouth. The highest and lowest fibres enter the corresponding lip. On the cutaneous surface of the buccinator are the difi'erent muscles converging to the angle of the mouth ; and crossing the uj^per part is the duct of the parotid gland, which perforates the muscle opposite the second upper molar tooth. Internally the muscle is lined by the mucous membrane of the mouth, and ex- ternally it is covered by a fascia (bucco-pharyngeal) that is con- tinued to the pharynx. By its intermaxillary origin the buccinator corresponds with the attachment of the superior constrictor of the pharynx. Action. By one muscle the corner of the mouth is retracted, and by the action of both the aperture of the mouth is widened trans- versely. In mastication the cheek is pressed by the muscular contraction against the dental arches, while the corner of the mouth is fixed by the orbicularis. In the expulsion of air from the mouth, as in whistling, the muscle is contracted so as to prevent bulging of the cheek ; but in the use of a blow-pipe it is stretched over the volume of air contained in the mouth, and maintains a continuous stream by its contraction during inspiration. The ORBICULARIS ORIS is mainlj^ formed by the prolongation of the fibres of the levator and depressor anguli oris and buccinator muscles. The buccinator fibres lie next to the mucous membrane, and are continued across from side to side. Those of the elevator and depressor muscles, having crossed at the corner of the mouth, turn inwards in the opposite lip, in front of the buccinator fibres, and are inserted into the skin, for the most part crossing the middle line and decussating with the fibres entering on the other side. A compact superficial fasciculus at the red margin of the lip is formed solely by buccinator fibres. In the upper lip there are also two slips arising, the one (naso-labial, fig. 6, ') from the hinder part of the septum narium, the other (incisive) from the outer j)art of the incisor fossa of the superior maxilla, and directed outwards to the corner of the mouth ; while in the lower lip there is a similar incisive slip attached to the incisor fossa of the inferior maxilla. To see these attachments, the lip must be everted and the mucous membrane carefully raised. Towards the free margin in each lip there are fibres directed ob- liquely from the skin to the mucous membrane, between the fasciculi of the orbicularis : they constitute the muse, lahii 'proiwiiis.