Which of the following is not an infrahyoid muscle?

The mylohyoid muscle is not classified as an infrahyoid muscle because it is located above the hyoid bone. Infrahyoid muscles are those that are situated below the hyoid bone and play a role in depressing the hyoid and larynx during swallowing and phonation. The mylohyoid, on the other hand, forms the floor of the mouth and is considered a suprahyoid muscle, which means it is positioned above the hyoid bone. This positioning allows it to assist in elevating the hyoid and the floor of the mouth during activities like swallowing and speaking.

In contrast, the sternohyoid, thyrohyoid, and sternothyroid are all categorized as infrahyoid muscles. These muscles specifically function to lower the hyoid bone or the thyroid cartilage, contributing to the overall modulation of the laryngeal structure during articulation and phonation.