The nasalis muscle is a facial muscle located in the nose region of the face. It consists of two parts, the transverse portion, and the alar portion. The transverse portion of the nasalis muscle is a thin muscle that extends horizontally across the bridge of the nose, from the maxilla bone to the nasal bone. It is responsible for flaring the nostrils, especially during deep inspiration or when detecting certain odors. The transverse portion of the nasalis muscle works in conjunction with the alar portion to produce certain facial expressions, such as distaste or disgust. The nasalis muscle is innervated by the buccal branch of the facial nerve (cranial nerve VII) and works in conjunction with other facial muscles to produce a range of facial expressions. Dysfunction or weakness of the nasalis muscle can lead to difficulties with speech, eating, and facial expressions, such as flaring the nostrils or wrinkling the nose.