The Thyroid, Hyoid bone and the scalene muscles

The thyroid gland sits just below the projection under your chin. It secretes hormones that regulate your temperature and the rate at which you burn energy. There is another gland surrounding it called the parathyroid. It secretes hormones that regulate the balance of calcium in your bloodstream. Too little and calcium is borrowed from the reserves in your bones. Too much and calcium is deposited into your bones. Above the thyroid is another U shaped bone called the hyoid. It is the only floating bone in the bone and anchors your tongue muscles. You can glide it from side to side if you hold it deep under your chin.
The hyoid is a place where we sometimes hold memories of the past. For instance if you have been accidentally "throttled" say by the chin strap of a helmet you might hold a fear of someone taking you around the neck. A skilled therapist can release that fear by gently holding the hyoid while you are in a supportive setting. There is a muscle between the hyoid and thyroid and between the thyroid and sternum / clavicle (collar bone). If you tip your head right back you can stretch the front of the neck but it will not affect the action of thyroid. However if you tip your head right back while placing the tongue on the roof of your mouth and stretching your tongue upwards you will release the tension in the muscles under your jaw. Making silly faces in the mirror by jutting your jaw out will stretch the platysma muscle that covers all of the front of your jaw. Also try placing your fingers just over your collar bone into a very tender area. Lift your jaw and turn your head. That stretches the scalene muscles. The scalenes help with upper chest breathing. The nerves and blood supply to the arms runs between the front and middle scalenes. That is called the brachial (meaning arm), plexus (meaning nerve bundle).