The soft depression between the lower margin of the thyroid cartilage and the arch of the cricoid is the position of the median cricothyroid ligament.
A tube passed through the median cricothyroid ligament enters the airway just inferior to the position of the vocal folds of the larynx.
Structures that may occur in or cross the midline between the skin and the median cricothyroid ligament include the pyramidal lobe of the thyroid gland and small vessels, respectively.