Risorius

Definition

The risorius is a small muscle located in the cheek that is responsible for pulling the corners of the mouth laterally, creating a grinning or laughing expression. It is one of the axial muscles of the head, neck, and back that are covered in section 11.3 of the course.

5 Must Know Facts For Your Next Test

1. The risorius muscle is innervated by the buccal branch of the facial nerve (cranial nerve VII).
2. Contraction of the risorius muscle can create a grinning or laughing expression by pulling the corners of the mouth laterally.
3. The risorius muscle is often used in facial expressions to convey emotions like amusement, contempt, or embarrassment.
4. Weakening or paralysis of the risorius muscle can lead to asymmetry in the resting facial expression or difficulty in creating certain facial expressions.
5. The risorius muscle is considered part of the superficial musculature of the face and is located just beneath the skin.

Review Questions

• Describe the primary function of the risorius muscle and how it contributes to facial expressions.
  • The risorius muscle is responsible for pulling the corners of the mouth laterally, creating a grinning or laughing expression. By contracting, the risorius muscle can convey emotions such as amusement, contempt, or embarrassment through its ability to modify the resting facial expression. This muscle is an important component of the superficial musculature of the face and is innervated by the buccal branch of the facial nerve.
• Explain the potential consequences of weakening or paralysis of the risorius muscle.
  • Weakening or paralysis of the risorius muscle can lead to asymmetry in the resting facial expression, as the muscle is no longer able to pull the corner of the mouth laterally. This can result in difficulty creating certain facial expressions, such as a natural-looking grin or laugh. The risorius muscle's role in conveying emotional states through facial expressions may also be compromised, potentially impacting an individual's ability to effectively communicate nonverbally.
• Analyze the relationship between the risorius muscle and other key muscles of the head, neck, and back region covered in section 11.3.
  • The risorius muscle is one of the axial muscles of the head, neck, and back region discussed in section 11.3. It works in coordination with other facial muscles, such as the zygomaticus major, which pulls the corners of the mouth upward and backward to create a smile, and the platysma, which can pull the corners of the mouth downward and tighten the skin of the neck. Additionally, the buccinator muscle, which forms the wall of the cheek, also interacts with the risorius to facilitate functions like chewing and lip puckering. Understanding the relationships and interactions between these various axial muscles is crucial for comprehending the complex mechanics of facial expressions and movements.

Related terms

Zygomaticus Major:

A muscle that originates on the zygomatic bone and inserts on the angle of the mouth, pulling the corners of the mouth upward and backward to create a smile.

Platysma: A broad, thin muscle that covers the front and sides of the neck, which can pull the corners of the mouth downward and tighten the skin of the neck.

Buccinator:

A muscle that forms the wall of the cheek, helping to push food between the teeth during chewing and to pucker the lips.