MUSCLES OF THE PHARYNX.

Muscles of pharynx

1. MUSCLES OF THE PHARYNX DEPARTMENT OF ANATOMY

2. Preliminary Remarks about the Constrictors of the Pharynx 2 The muscular basis of the wall of the pharynx is formed mainly by the three pairs of constrictors - superior, middle and inferior. The origins of the constrictors are situated anteriorly in relation to the posterior openings of the nose - the mouth and the larynx. From here their fibres pass into the lateral and posterior walls of the pharynx , the fibres of the two sides meeting in the midline in a fibrous raphe .

3. Preliminary Remarks about the Constrictors of the Pharynx 3 The three constrictors are so arranged that the inferior overlaps middle which in turn overlaps the superior. The fibres of the superior constrictor reach the base of skull posteriorly , in the middle line. On the sides , however, there is a gap between the base of the skull and the upper edge of the superior constrictor. This gap is closed by the pharyngobasilar fascia which is thickened in this situation. The lower edge of the inferior constrictor becomes continuous with the circular muscle of the oesophagus . These muscles develop from IV and VI pharyngeal arches.

4. Origin of Constrictors 4 The superior constrictor takes origin from the following (from above downwards): Pterygoid hamulus ( pterygopharyngeus ) Pterygomandibular raphe ( buccopharyngeus ) Medial surface of the mandible at the posterior end of the mylohyoid line, i.e. near the lower attachment of the pterygomandibular raphe ( mylopharyngeus ). Side of posterior part of tongue ( glossopharyngeus ).

5. 5

6. Origin of Constrictors 6 The middle constrictor takes origin from: The lower part of the stylohyoid ligament Lesser cornua of hyoid bone Upper border of the greater cornua of the hyoid bone

7. Origin of Constrictors 7 The inferior constrictor consists of two parts. T he thyropharyngeus , arises from the thyroid cartilage . T he cricopharyngeus , arises from the cricoid cartilage . The thyropharyngeus arises from: The oblique line on the lamina of thyroid cartilage, including the inferior tubercle. A tendinous band that crosses the cricothyroid muscle and is attached above to the inferior tubercle of the thyroid cartilage. The inferior cornua of the thyroid cartilage. The cricopharyngeus arises from the cricoid cartilage behind the origin of the cricothyroid muscle.

8. 8

9. Insertion of Constrictors 9 All the constrictors of the pharynx are inserted into a median raphe on the posterior wall of the pharynx. The upper end of the raphe reaches the base of the skull where it is attached to the pharyngeal tubercle on the basilar part of the occipital bone.

10. Longitudinal Muscle Coat 10 The pharynx has three muscles that run longitudinally . The stylopharyngeus arises from the styloid process . It passes through the gap between the superior and middle constrictors to run downwards on the inner surface of the middle and inferior constrictors. The fibres of the palatopharyngeus descend from the sides of the palate and run longitudinally on the inner aspect of the constrictors. The salpingopharyngeus descends from the auditory tube to merge with palatopharyngeus .

11. Longitudinal Muscle Coat 11

12. STRUCTURES IN BETWEEN PHARYNGEAL MUSCLES 12 The large gap between the upper concave border of the superior constrictor and the base of the skull is semilunar and is known as the sinus of Morgagni . It is closed by the upper strong part of the pharyngobasilar fascia. The structures passing through this gap are: a . The auditory tube b . The levator veli palatini muscle c . The ascending palatine artery Features

13. STRUCTURES IN BETWEEN PHARYNGEAL MUSCLES 13 The structures passing through the gap between the superior and middle constrictors are: The stylopharyngeus muscle and the glossopharyngeal nerve. The internal laryngeal nerve and the superior laryngeal vessels pierce the thyrohyoid membrane in the gap between the middle and inferior constrictors. The recurrent laryngeal nerve and the inferior laryngeal vessels pass through the gap between the lower border of the inferior constrictor and the oesophagus . Features

14. STRUCTURES IN BETWEEN PHARYNGEAL MUSCLES 14

15. CLINICAL ANATOMY 15 Difficulty in swallowing is known as dysphagia .

16. CLINICAL ANATOMY 16 Pharyngeal diverticulum : Killian’s Dehiscence In the posterior wall of the pharynx, the lower part of the thyropharyngeus is a single sheet of muscle, not overlapped internally by the superior and middle constrictors. This weak part lies below the level of the vocal folds or upper border of the cricoid lamina and is limited inferiorly by the thick cricopharyngeal sphincter. This area is known as Killian’s dehiscence. Pharyngeal diverticula are formed by outpouching of the dehiscence. Such diverticula are normalin the pig. Pharyngeal diverticula are often attributed to neuromuscular incoordination in this region which may be due to the fact that different nerves supply the two parts of the inferior constrictor.

17. CLINICAL ANATOMY 17 The propulsive thyropharyngeus is supplied by the pharyngeal plexus , and sphincteric cricopharyngeus by the recurrent laryngeal nerve. If the cricopharyngeus fails to relax when the thyropharyngeus contracts, the bolus of food is pushed backwards, and tends to produce a diverticulum .

18. 18