164 



APPLIED ANATOMY. 



crosses the second, third, and fourth tracheal rings in the adult. In children it may 

 approach nearer to the cricoid cartilage. 



The lateral lobes lie under the sternohyoid and the sternothyroid muscles. 

 They rise as high as the oblique line on the sides of the thyroid cartilages which 

 marks the insertion of the sternothyroid muscles. The lobes descend to the level 

 of the sixth ring of the trachea, which is two rings below the isthmus, about two 

 centimetres above the sternum. The inferior constrictor of the pharynx is beneath 

 the gland. The thyroid gland is covered by the pretracheal fascia and possesses 

 a capsule of its own besides. This fascia envelops the gland and its capsule, and 

 from its posterior surface is prolonged down on the trachea and envelopes the 



Sup. parathyroid 



Sternoth 



Sup. thyroid 

 artery and vein 



Common ca- 

 otid artery 

 [nternal 

 mgular vein 



Inferior 

 constrictor 



Sternomas- 

 toid muscle 



thyroid artery 



nt laryngeal nerve 

 Middle thyroid vein 

 Inferior thyroid veins 



-Sternohyoid muscle 

 FIG. 184. Excision of the thyroid gland. 



vessels coming to and leaving the gland. Therefore we might say that the inferior 

 thyroid veins are in the pretracheal fascia. 



As the fascia leaves the gland at the sides one portion of it blends with and 

 helps to form the sheath of the vessels. The other or deeper portion continues 

 around the pharynx and oesophagus, forming the buccopharyngeal fascia. In freeing 

 the gland and its capsule from the overlying pretracheal fascia care must be taken, 

 as pointed out by James Berry (" Diseases of the Thyroid Gland," p. 269), not to 

 be led by this fascia too far posteriorly and therefore wound, as has been done, the 

 pharynx or trachea. 



The veins of the gland are more prominent and dangerous than the arteries. 

 They ramify beneath the capsule and as long as the capsule is not torn the bleeding 

 is slight. The arteries of the thyroid gland are the superior and inferior thyroids 

 and sometimes the thyroidea ~ ima. The superior t/iyroid comes "off the external 



