328 



THE MUSCLES AND FASCIA. 



The inferior fibres are horizontal, and continuous with the fibres of the oesophagus : 

 the rest ascend, increasing in obliquity, and overlap the Middle constrictor. 



Relations. It is covered by a thin membrane which surrounds the entire 



pharynx (bucco-pharyngeal fascia). Behind, it is in relation with the vertebral 



column and the prevertebral fascia and 

 muscles ; laterally, with the thyroid gland, 

 the common carotid artery, and the 

 Sterno-thyroid muscle ; by its internal 

 surface, with the Middle constrictor, the 

 Stylo-pharyngeus, Palato-pharyngeus, the 

 fibrous coat and mucous membrane of the 

 pharynx. The internal laryngeal nerve 

 and the laryngeal branch of the Superior 

 Thyroid artery pass near the upper bor- 

 der, and the inferior, or recurrent laryn- 

 geal nerve, and the laryngeal branch of 

 the Inferior Thyroid artery, beneath the 

 lower border of this muscle, previous to 

 their entering the larynx. 



The Middle constrictor is a flattened, 

 fan-shaped muscle, smaller than the pre- 

 ceding. It arises from the whole length 

 of the upper border of the greater cornu 

 of the hyoid bone, from the lesser cornu, 

 and from the stylo-hyoid ligament. The 

 fibres diverge from their origin, the lower 

 ones descending beneath the Inferior con- 

 strictor, the middle fibres passing trans- 

 versely, and the upper fibres ascending 

 and overlapping the Superior constrictor. 

 The muscle is inserted into the posterior 

 median fibrous raphe', blending in the mid- 

 dle line with the one of the opposite side. 

 Relations. This muscle is separated from the Superior constrictor by the 

 glosso-pharyngeal nerve and the Stylo-pharyngeus muscle and Stylo-hyoid liga- 

 ment ; and from the Inferior constrictor by the superior laryngeal nerve. Behind, 

 it lies on the vertebral column, the Longus colli, and the Rectus capitis anticus 

 major. On each side it is in relation with the carotid vessels, the pharyngeal 

 plexus, and some lymphatic glands. Near its origin it is covered by the Hyo- 

 glossus, from which it is separated by the lingual vessels. It lies upon the 

 Superior constrictor, the Stylo-pharyngeus, the Palato-pharyngeus, the fibrous 

 coat, and the mucous membrane of the pharynx. 



The Superior Constrictor is a quadrilateral muscle, thinner and paler than the 

 other constrictors, and situated at the upper part of the pharynx. It arises from 

 the lower third of the posterior margin of the internal pterygoid plate and its 

 hamular process, from the contiguous portion of the palate bone and the reflected 

 tendon of the Tensor palati muscle, from the pterygo-maxillary ligament, from the 

 alveolar process above the posterior extremity of the mylo-hyoid ridge, and by a 

 few fibres from the side of the tongue. From these points the fibres curve back- 

 ward, to be inserted into the median raphe, being also prolonged by means of a 

 fibrous aponeurosis to the pharyngeal spine on the basilar process of the occipital 

 bone. The superior fibres arch beneath the Levator palati and the Eustachian 

 tube, the interval between the upper border of the muscle and the basilar process 

 being deficient in muscular fibres and closed by the pharyngeal aponeurosis. This 

 interval is known as the sinus of Morgagni. 



Relations. By its outer surface, with the prevertebral fascia and muscles, 

 the vertebral column, the internal carotid and ascending pharyngeal arteries, the 



FIG. 208. Muscles of the pharynx. External view. 



