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The pterygoid fossa is a term used for a V-shaped depression that is located at the back of each of the two pterygoid processes that the sphenoid bone bears. Shaped like the wings of a butterfly, the sphenoid bone is one of the bones of the human skull, responsible for helping to form the back of the sockets where the eyes are situated. The pterygoid fossa is created from the two plates that converge from each pterygoid process of the sphenoid bone. The adjective “pterygoid” is applied to the depression because of its location at the sphenoid bone.
One of the plates responsible for forming the pterygoid fossa is the medial pterygoid plate. It does so by using its lateral surface. The other plate, the lateral pterygoid plate, is the much smaller member of the pair. Also known as the lateral lamina of pterygoid process, it forms part of the pterygoid fossa via its medial surface.
The pterygoid fossa contains the medial pterygoid. Also referred to as the internal pterygoid muscle, it possesses a quadrilateral shape and is a thick muscle crucial for mastication, or chewing food. It also contributes to the protrusion and elevation of the mandible, or lower jaw. The medial pterygoid comprises two parts, which consist of a much larger part that arises above the lateral pterygoid plate’s medial surface, and a smaller portion that traces its origin to sections of the upper jaw called the maxillary tuberosity and the palatine bone. The lateral pterygoid plate is responsible for providing an attachment for the medial pterygoid muscle.
Also found in the pterygoid fossa is the tensor veli palatini, also known as the tensor palatini. This structure is best described as a broad and thin muscle with a ribbon-like shape. It is so named because it tightens the soft palate, which is the soft tissue that forms the back of the mouth’s roof. It works with the levator veli palatini, the muscle that acts as the soft palate’s elevator, in preventing food or drink from entering the part of the throat directly behind it. The tensor veli palatini’s tendon glides around a hook-like process of the medial pterygoid plate.
Another mastication muscle is the lateral pterygoid muscle. Located above the medial pterygoid, it is also attached by the lateral pterygoid plate. The fossa, however, does not carry this particular muscle.