Final answer:
The cricoid cartilage serves as an important visual landmark when performing endotracheal intubation under direct visualization.
Step-by-step explanation:
When performing endotracheal intubation under direct visualization, the cricoid cartilage serves as an important visual landmark. The cricoid cartilage is a thick ring of cartilage located inferior to the thyroid cartilage in the larynx. It can be palpated at the base of the throat and provides a reference point for guiding the placement of the endotracheal tube.