128 DISSECTION OF THE PHARYNX. 



The isthmus faucium, H, is the narrowed aperture of communication 

 between the mouth and the fauces, whose size is altered by the elevated 

 or pendent position of the soft palate. Laterally it is bounded by the 

 anterior arches of the soft palate, which are named pillars of the fauces. 



The aperture of the larynx, N, is wide in front, where it is bounded by 

 the epiglottis, and pointed behind between the arytrenoid cartilages. The 

 sides are sloped from before back, and are formed by folds of the mucous 

 membrane extending between the arytaenoid cartilages and the epiglottis. 

 Posteriorly it is limited by the cornicula laryngis, and by the aryta?noid 

 muscle covered by mucous membrane. During respiration this aperture is 

 unobstructed, but in the act of deglutition it is closed by the epiglottis. 



The opening into the oesophagus, o, is the narrowest part of the pha- 

 rynx, and is opposite the cricoid cartilage and the fifth cervical vertebra. 

 Internally the mucous membrane in the oesophagus is paler than that in 

 the pharynx : and externally the point at which the pharynx ends is 

 marked by a slight contraction, and by a change in the direction of the 

 muscular fibres. 



The SOFT PALATE, Q (velum pendulum palati), is a movable structure 

 between the mouth and the pharynx, which can either close the opening 

 of the mouth, or cut off the passage to the nose, according as it is de- 

 pressed or elevated. In the usual position of the soft palate (the state of 

 relaxation) the anterior surface is somewhat curved, and is continuous 

 with the roof of the mouth, whilst the opposite surface is convex and 

 turned to the pharynx. The upper border is fixed to the posterior margin 

 of the hard palate ; and each lateral part joins the pharynx. The lower 

 border is free, and presents in the centre a conical pendulous part the 

 uvula, P. Along its middle is a slight ridge, indicative of the original 

 separation into two halves. 



Springing from the lower part of the soft palate, near the uvula, are two 

 folds on each sides, containing muscular fibres, which are directed down- 

 wards on the sides of the fauces. These are named arches or pillars of the 

 palate, and are distinguished from one another by their relative position. 

 The anterior, i, reaches from the fore part to the side of the tongue near 

 the middle ; and the posterior, L, longer than the other, is continued from 

 the lower border to the side of the pharynx. As they diverge from their 

 origin to their termination, they limit a triangular space in which the ton- 

 sil lies. 



The velum consists of an aponeurosis, with muscles, vessels, nerves, and 

 mucous glands ; and the whole is enveloped by the mucous membrane. 



Dissection Some of the muscles of the palate are readily displayed, 

 but others require care in their dissection. 



On the right side the two principal muscles of the soft palate the ele- 

 vator and tensor, are very plain. These have been partly dissected on the 

 right side ; but to follow them to their termination, let the upper attach- 

 ment of the pharynx on the same side, and the part of the superior con- 

 strictor which arises from the internal pterygoid plate, be cut through. 

 The levator will be fully laid bare by the removal of the mucous mem- 

 brane, and a few muscular fibres covering its lower part. The tendon of 

 the tensor palati should be followed round the hamular process of the 

 pterygoid plate ; and its situation in the palate beneath the levator should 

 be made evident. The position of the Eustachian tube with respect to 

 those muscles should be ascertained. 



