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 is the term used to describe inflammation and swelling of the epiglottis which lies just behind the root of your tongue. It is usually caused by infection with a germ (bacterium). The usual symptoms are a severe sore throat, pain or difficulty swallowing and a high temperature (fever).