A prepositional phrase is comprised of two parts, a preposition and an object of the preposition. Together, they form the prepositional phrase that is then inserted in a sentence to modify some noun or verb.
The epiglottis is a flap made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. It stands open during breathing, allowing air into the larynx.
Epiglottitis: a nasty and dangerous throat infection which may cause severe difficulty breathing, noisy breathing (stridor), hoarseness, drooling and difficulty swallowing. Don't try to look in the throat: just movement of the jaw can precipitate a serious relapse. Professional help needed urgently.