THE HEAD AND NECK 1275 



glands and lymphoid tissue. It is covered by stratified columnar 

 ciliated epithelium. 



Muscles connected with the Eustachian Tube. — The levator palati 

 has an origin from the lower margin of the cartilage of the tube, the 

 tensor palati from the outer side of the cartilage, and the salpingo- 

 pharyngeus is attached to the lower and front part of the tube. 

 During deglutition the orifice of the tube is usually regarded as 

 being kept open. According to Cleland, however, who had unusual 

 opportunities of examining matters on the living person, ' the 

 anatomical facts make it e\ndent that any dilating influence of the 

 tensor palati is exercised on the hinder and smaller part of the 

 tube, whilst the levator palati closes the anterior (that is, phar}^- 

 geal) orifice ' by raising the membranous floor of the tube. 



Arteries. — These are derived from (i) the Vidian branch of the 

 third part of the internal maxillary, and (2) the ascending pharyn- 

 geal branch of the external carotid. 



Kerves. — ^The nerves are derived from (i) the tympanic plexus 

 on the inner wall of the t3mipanum, and (2) the Vidian nerve. 



De?elopnient. — The Eustachian tabe is developed from the hypoblast of 

 the first visceral cleft. 



The Larynx. 



The larynx is the upper part of the respiratory passage, being 

 modified in structure so as to enable it to act as the organ of voice. 

 It is situated in the median line of the neck above the trachea, 

 and it lies opposite the fourth, fifth, and sixth cervical vertebrae. 

 Superiorly it opens into the laryngeal portion of the pharynx, and 

 interiorly into the trachea. It is covered in front by the integiunent 

 and the deep cervical fascia, and the laryngeal portion of the 

 pharynx lies behind it. On either side it is in relation with the 

 upper part of the lateral lobe of the thyroid body, the stemo-hyoid, 

 omo-hyoid, stemo-th5n:oid, and th5n:o-hyoid muscles, and the 

 common carotid artery. 



Structure. — ^The larynx consists of a framework of cartilages, 

 some of which are connected by joints and ligaments ; it is provided 

 with special muscles, spoken of as intrinsic ; and it is lined with 

 mucous membrane. 



Cartilages. — ^These are nine in number, three being single and 

 three arranged in pairs. The single cartilages are the epiglottis, 

 the thyroid, and the cricoid, and the three arranged in pairs are the 

 arytenoid, the comicula laryngis, and the cuneiform. 



The epiglottis is a leaf-like plate of yellow elastic fibro-cartilage, 

 which stands bolt upright between the base of the tongue and the 

 superior aperture of the larjnix. Its lower part forms a narrow 

 pedicle, which is attached to the receding angle of the thyroid 

 cartilage, just below the median notch on its upper border, by 

 means o*^ a fibro-elastic band, called the thyro-epiglottidean liga- 

 ment. Superiorly it presents a broad, round, free margin. Each 

 lateral border is free above, but its lower part is contained within 



