190 THE HEAD AND NECK 



through the choanae so as to touch the posterior extremities of 

 the inferior and middle conchse (turbinated bones). In the 

 adult the choanse (posterior nares) measure one inch long and 

 half an inch wide, but in the child the relative width is much 

 greater. In the roof the basilar portion of the occipital bone 

 can be felt, and half an inch below, on the posterior wall, the 

 anterior arch of the atlas can be recognised. The pharyngeal 

 tonsil is situated on the posterior wall, and in children a pro- 

 liferation of its lymphoid tissue (adenoids) may fill up the naso- 

 pharynx and render nasal breathing impossible. On the lateral 

 wall the orifice of the auditory (Eustachian) tube leads back- 

 wards, laterally, and upwards to the tympanum (Fig. 50). The 

 posterior lip of the opening forms a prominent elevation the 

 tubal projection (Eustachian cushion) due to the cartilaginous 

 wall of the tube, and behind it lies the pharyngeal recess (of 

 Rosenmuller). When the orifice of the tube is occluded, e.g. 

 in adenoids, the air in the tympanic cavity gradually becomes 

 absorbed and deafness results. Inflation of the tympanum may 

 be carried out through the pharyngeal orifice of the tube by 

 means of a Eustachian catheter. The instrument is passed 

 backwards along the floor of the inferior meatus until the down- 

 turned point reaches the posterior wall of the nasal pharynx. 

 The catheter is then rotated laterally through one right angle, 

 and in this way its point is lodged in the pharyngeal recess. It 

 is then slowly withdrawn from the nose till the point is felt to 

 catch on the tubal projection. Slight upward rotation of the 

 point at this stage, accompanied by partial withdrawal, conducts 

 it past the obstruction, and if it is now directed laterally again, 

 the instrument passes into the orifice of the auditory tube. 



The lymph vessels of this region join the retro-pharyngeal 

 lymph glands (p. 114) and the upper posterior group of the deep 

 cervical lymph glands. 



The Superior Constrictor Muscle arises mainly from the pterygo-mandibular 

 raphe, and is on the same plane as the buccinator (p. 176). Its upper fibres 

 are inserted into a tubercle on the under surface of the basilar part of the 

 occipital bone, while the rest of the muscle is inserted into a median raphe 

 posteriorly. The Middle Constrictor Muscle, which overlaps the lower part of 

 the insertion of the superior constrictor, arises from the cornua of the hyoid 

 bone, and its fibres spread out as they pass backwards to the median raphe. 

 The Inferior Constrictor arises from the sides of the thyreoid and cricoid 

 cartilages. The lower fibres blend with the muscular wall of the oesophagus, 

 and the upper fibres overlap the lower portion of the middle constrictor. 



The constrictor muscles are supplied by the pharyngeal plexus, which 

 is formed on the lateral aspect of the middle constrictor by the union! of 

 the pharyngeal branches of the vagus and glosso-pharyngeal nerves, with 



