THE RESPIRATORY SYSTEM 



341 



muscles are the thyro-arytenoid or vocalis and the cricothyroid, which 

 affect the pitch of the voice. At puberty in the male, the larynx becomes 

 enlarged and the vocal cords within it elongated so that the voice is 

 deepened. The epiglottis and vocal cords are covered with the same 

 kind of squamous stratified epithelium as that which Hues the pharynx, 

 but the rest of the larynx is fined with cifiated columnar epithelium similar 

 to that of the trachea. The action of the cilia is such as to carry the 

 secretions of the mucous glands of the lungs together with particles of 



PARIETAL BONE 



GYRUS CINGULI 



PITUITARY, 



SUBDURAL CAVITY 



FRONTAL LOBE 



FRONTAL BONE 



FRONTA 

 SINUS 



^RICHT CEREBRAL HEMISPHERE 



iRPUS CALLOSUM 



•FORNIX 



PINEAL GLAND 



CORPORA 

 QUADRIGEMINA 



NASAL BONE 

 SPHENOID BONE 

 NASAL CONCHAE 

 EUSTACHIAN TUBE 

 MAXILLA 

 MOUTH CAVITY 

 PALATINE BONE 

 VESTIBULE 

 SOFT PALATE 

 M. GENIOGLOSSUS 

 MANDIBLE 

 M. GENIOHYOID 



M. MYLOHYOID 



.OCCIPITAL 

 LOBE 



dura kmter 

 -occipital bone 

 :erebelljum 



SEMISPINALIS 

 CERVICIS 



esophagus' '^:ENTRA 



Fig. 285. — A median longitudinal section of the human head showing the relations 

 between digestive and respiratory passages in the pharyngeal region. (Redrawn 

 after Braus.) 



dust out into the pharynx. Mucous glands are numerous. The nerve 

 supply is from the vagus and the sympathetic. 



Trachea and Bronchi. The trachea or windpipe is a membranous 

 tube, four to five inches long, supported by fibrous connective tissue and 

 incomplete U-shaped rings of cartilage. It carries air to and from the 

 lungs. The cartilages vary in number from sixteen to twenty and are 

 incomplete on the side next to the esophagus. The trachea divides to 

 form the right and left bronchi. The lining of the trachea is a mucous 

 ciUated stratified columnar epitheUum. Below this is a submucous 

 connective tissue containing many mucous glands derived from the 



