420 THE MUSCLES AND FASCIAE. 



entire pharynx. Behind, it is in relation with the vertebral column and the 

 Longus colli muscle ; laterally, with the thyroid gland, the common carotid artery, 

 and the Sterno-thyroid muscle ; by its internal surf ace, with the Middle constrictor, 

 the Stylo-pharyngeus, Palato-pharyngeus, the fibrous coat and mucous membrane 

 of the pharynx. 



The Middle constrictor is a flattened, fan-shaped muscle, smaller than the pre- 

 ceding. It arises from the whole length of the upper surface 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 Infe- 

 rior constrictor, the middle fibres passing transversely, and the upper fibres 

 ascending and overlapping the Superior constrictor. The muscle is inserted into 

 the posterior median fibrous raphe, blending in the middle 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 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 

 phai'ynx. 



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 fibrous membrane. This interval 

 is known as the sinus of Morgagni. 



Relations. By its outer surface, with the vertebral column, the internal carotid 

 artery, the internal jugular vein, the glosso-pharyngeal, pneumogastric, spinal 

 accessory, hypoglossal, and sympathetic nerves, the Middle constrictor, which 

 overlaps it, and the Stylo-pharyngeus ; by its internal surface, with the Palato- 

 pharyngeus, the tonsil, the fibrous coat and mucous membrane of the pharynx. 



The Stylo-pharyngeus is a long, slender muscle, round above, broad and thin 

 below. It arises from the inner side of the base of the styloid process, passes 

 downward along the side of the pharynx between the Superior and Middle 

 constrictors, and spreads out beneath the mucous membrane, where some of its 

 fibres are lost in the Constrictor muscles ; and others, joining with the Palato- 

 pharyngeus, are inserted into the posterior border of the thyroid cartilage. The 

 glosso-pharyngeal nerve runs on the outer side of this muscle, and crosses over it 

 in passing forward to the tongue. 



Relations. Externally, with the Stylo-glossus muscle, the parotid gland, the 

 external carotid artery, and the Middle constrictor ; internally, with the internal 

 carotid, the internal jugular vein, the Superior constrictor, Palato-pharyngeus, and 

 mucous membrane. 



Nerves. The Constrictors are supplied by branches from the pharyngeal 

 plexus, the Stylo-pharyngeus by the glosso-pharyngeal nerve, and the Inferior 

 constrictor by an additional branch from the external laryngeal nerve and by the 

 recurrent laryngeal. 



Actions. When deglutition is about to be performed, the pharynx is drawn 



