THE HEAD AND NECK 



1127 



The veins terminate in the inferior thyroid plexus and inferior 

 thyroid veins. 



The lymphatics pass to the lower group of deep cervical glands. 



Pretracheal Lymphatic Glands. — These glands lie upon the front 

 of the cervical part of the trachea, below the istjimus of the thyroid 

 body. Their afferent vessels are derived from (i) the front of the 

 trachea, and (2) the lower part of the isthmus of the thyroid body. 

 Their efferent vessels pass to the inferior deep cervical glands. The 



Epiglottis 



Lateral Thyro-hyoid Ligament ^.-' 

 Upper JJorder of Thyroid Cartilage ... 



Cartilage Triticea 



Corniculum Laryngis 

 Arytenoid Cartilage 



Cricoid Cartilage 



Lateral Lobe of Thyroid Body 



Fig. 460. — The Epiglottis. Larynx, Trachea, Bronchi, and Thyroid 

 Body (Posterior View). 



lymphatic vessels of the cervical part of the trachea pass to the pre- 

 tracheal, inferior thyroid, and inferior deep cervical glands. 



Nerve-supply. — The nerves are derived from the pneiunogastric, 

 recurrent laryngeal, and sympathetic. 



Structure. — The trachea is composed of about twenty so-called rings of 

 hyaline cartilage, which are incomplete posteriorly. They serve to keep the 

 tube permanently open for the transmission of £iir, and are embedded in 

 fibrous tissue, which also connects together their contiguous borders. They 

 are shaped thus — Q , and each forms rather more than two-thirds of a circle, 

 being flat externally, and convex internally. The deficient portions of the 

 rings are, as stated, placed posteriorly, and here each ring ends in two round 

 extremities. The intervals between these extremities are bridged over by 

 fibrous tissue, continuous with that which connects the borders of the rings 

 and in which they are embedded. In some cases a ring may terminate in a 

 bifurcated extremity, or it may join one of the adjacent rings. The lowest 



