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 a life-threatening condition characterized by inflamed epiglottis tissue. The epiglottis is made of cartilage and is located at the base of the tongue. It helps prevent food from entering your windpipe. The tissue of the epiglottis can swell and block your airway.