On of a pair of medial protrusions of the intra-pharyngeal ostium (an oval opening within the soft palate that connects the oral and nasal portions of the pharynx), used in vocalization in Koalas. [ http://dx.doi.org/10.1016/j.cub.2013.10.069 ]
Term information
Muscle notes: Because the larynx is attached to the caudal end of the pharynx where the IPO is situated, laryngeal retraction brought about by the sternothyroid muscle will automatically put tension on the rostro-caudally oriented velar vocal folds, and could also induce length changes of the folds. Contractions of the palatopharyngeal muscles may also influence the length and shape of the velar vocal folds directly (inducing width changes of the IPO).