The Stimulus

• A frown begins with an external impulse that causes a person to react negatively. The typical human reaction to a negative event is the slow curling of the mouth downward. This is commonly known as a "frown." Although considered the opposite of a smile, a frown requires different musculature to create the physical appearance. There are 11 face muscles involved in a frown.
  
  

Leading Muscles

• The depressor anguli oris is the muscle that controls the corners of the mouth and pulls the corners of the mouth downward. It is located at the lower border of the mandible (jaw bone) and blends with other muscles in the region of the lower lip. There is an identical muscle on each side of the mouth. There are different muscles for pulling the corners of the mouth upward when someone smiles.
  
  Next, the mentalis muscle depresses the lower lip to assist in the downward curvature of the frown. The Mentalis sits just below the lower lip near the chin and moves upward to cause the lower lip to curve downward. It is the cause for wrinkling in the skin of the chin. A frown also involves pulling the lips inward, which is called "pursing the lips." The orbicularis oris muscles encircle the mouth and cause the lips to "purse" inward, creating wrinkling in the lips. These muscles lie between the skin and the lips. It is a bundle of muscle fibers that extend upward toward the nose and downward to the chin.
  
  The platysma also assists in the overall process of pulling down the lips and it will often cause wrinkling on the skin of the lower face. It is a broad sheet of a muscle that sits just above the chest and runs along the sides of the neck up to the bottom part of the side of the head and underside of the chin.
  
  

Supporting Muscles

• A frown does not only involve muscles near the mouth. The frown uses muscles near the eyes and near the forehead. When someone frowns, the eyes will also crinkle downward, mimicking the mouth movement. The orbicularis oculi is a muscle that surrounds each eye and causes the eyes to turn downward and crinkle as the mouth pulls downward. It is a bilateral muscle, meaning there is an identical muscle surrounding each eye, working independent of one another.
  
  If you notice, a frown also causes "furrowing the brow," which is a horizontal wrinkling of the mid forehead. The corrugator supercilii (a bilateral muscle) and procerus (a singular muscle) furrow the brow. The corrugator supercilii is a thin muscle that sits on the inside of the eyebrow, just above the area where sunglasses sit on a person's nose. The procerus is the muscle that sits just above the middle to upper part of the nose or the "bridge" of the nose. The upper part of the muscle is attached to the skin of the lower forehead.