Henry Gray (18251861). Anatomy of the Human Body. 1918.
thyroid cartilage; the space intervening between the hyoid bone and the thyroid cartilage is occupied by the hyothyroid membrane. The outlines of the thyroid cartilage are readily palpated; below its lower border is a depression corresponding to the middle cricothyroid ligament. The level of the vocal folds corresponds to the middle of the anterior margin of the thyroid cartilage. The anterior part of the cricoid cartilage forms an important landmark on the front of the neck; it lies opposite the sixth cervical vertebra, and indicates the junctions of pharynx with esophagus, and larynx with trachea. Below the cricoid cartilage the trachea can be felt, though it is only in thin subjects that the separate rings can be distinguished; as a rule there are seven or eight rings above the jugular notch of the sternum, and of these the second, third, and fourth are covered by the isthmus of the thyroid gland.
Muscles.The posterior belly of Digastricus is marked out by a line from the tip of the mastoid process to the junction of the greater cornu and body of the hyoid bone; a line from this latter point to a point just lateral to the symphysis menti indicates the position of the anterior belly. The line of Omohyoideus begins at the lower border of the hyoid bone, curves downward and lateralward to cross Sternocleidomastoideus at the junction of its middle and lower thirds, i. e., opposite the cricoid cartilage, and then runs more horizontally to the acromial end of the clavicle.
Arteries.The position of the common carotid artery in the neck is indicated by a line drawn from the upper part of the sternal end of the clavicle to a point midway between the tip of the mastoid process and the angle of the mandible. From the clavicle to the upper border of the thyroid cartilage this line overlies the common carotid artery, beyond this it is over the external carotid. The external carotid artery may otherwise be marked out by the upper part of a line from the side of the cricoid cartilage to the front of the external acoustic meatus, arching the line slightly forward.
The points of origin of the main branches of the external carotid in the neck are all related to the tip of the greater cornu of the hyoid bone as follows: (1) the superior thyroid, immediately below it; (2) the lingual, on a level with it; (3) the facial, and (4) the occipital a little above and behind it.