The Depressor Septi Nasi muscle is a small facial muscle located in the upper lip that extends from the nasal septum to the upper lip. It is responsible for pulling the nasal septum downward and contributing to the widening of the nostrils.

The Depressor Septi Nasi muscle is used in a variety of facial expressions, including expressions of sadness or disapproval, as well as in certain speech sounds. It is also involved in regulating the flow of air through the nostrils during breathing.

The importance of the Depressor Septi Nasi muscle lies in its role in maintaining proper nasal function. By widening the nostrils, it can help to increase airflow and improve breathing. It also plays a role in facial expression and nonverbal communication, particularly in conveying emotions such as sadness or disapproval. Dysfunction of the Depressor Septi Nasi muscle can lead to various issues, including difficulty breathing through the nose, nasal congestion, and difficulty conveying certain emotions through facial expressions.