Mastication & Tongue Muscles
Directions
- Print this PDF worksheet for a hardcopy guide as you work through this lesson.
- Within the lesson click the red linked headings to bring up the desired starting point within the cadaver for your work.
- Use the provided images on the worksheet to annotate and identify specific anatomical structures.
We'll start with four pairs of mastication (chewing) muscles. All four are innervated by the mandibular division of cranial nerve V (the trigeminal nerve). Using your specimen, identify the following:
- masseter - The masseter muscle ("chewer") has its origin at the zygomatic arch and its insertion at the angle and ramus of the mandible. The masseter is the prime mover of jaw closure; it elevates the mandible. To fully observe the masseter, dissect away the platysma.
- temporalis - The origin of this fan-shaped muscle is the temporal fossa (hence the name for the muscle) and the insertion is the coronoid process of the mandible via a tendon that passes deep to the zygomatic arch. The temporalis closes the jaw. It elevates and retracts the mandible and maintains the position of the mandible at rest.
- lateral pterygoid - These paired muscles are rather difficult to find so it's done for you. As you can see the ramus of the mandible is obscuring some of your view. Dissect it away and then relocate the right lateral pterygoid (both inferior and superior heads). This deep, two-headed muscle originates at the greater wing and lateral pterygoid plate of the sphenoid bone (hence its name). Its insertion is the condyle of the mandible and capsule of the temporomandibular joint. The lateral pterygoid protrudes the mandible (pulls it anteriorly) and provides forward sliding and side-to-side grinding movements of the lower teeth.
- medial pterygoid - Deeper still is the medial pterygoid. You can initially locate it from this view but dissect away the lateral pterygoid to more fully expose it. This muscle originates from the medial surface of the lateral pterygoid plate of the sphenoid bone, the maxilla, and the palatine bone. Its insertion is the medial surface of the mandible near its angle. The medial pterygoid a synergist of the temporalis and masseter in elevating the mandible. It also acts with the lateral pterygoid to promote side-to-side (grinding movements of the lower teeth.)
- buccinator - You examined this muscle with facial expression but it also has a role in chewing. The trampoline-like action of the buccinator muscles help keep food between grinding surfaces of the teeth during chewing.
Those are your 5 muscles of mastication (biting and chewing).
- masseter
- temporalis
- medial pterygoid
- lateral pterygoid
- buccinator
That's all; there aren't any more! I know, its kind a disappointment after the 11 facial muscles. OK, since you have that hurt look in your eyes I'll give you 3 muscles that work the tongue, but that's my limit!
The tongue is composed of muscle fibers peculiar to itself that curl, squeeze, and fold the tongue during speaking and chewing. These intrinsic tongue muscles, arranged in several planes, change the shape of the tongue and contribute to its exceptional nimbleness, but they do not really move the tongue. You will see these lingual muscles in your dissection, however, we will NOT study these muscles in this virtual dissection.
Now, let's examine the extrinsic muscles that control tongue movement.
- genioglossus (geni = chin; glossus = tongue) - This fan-shaped muscle forms the bulk of the inferior part of the tongue. Its attachment to the mandible prevents the tongue from falling backward and obstructing respiration. Its origin is the internal surface of the mandible near the symphysis and its insertion is along the inferior aspect of the tongue and the body of the hyoid.
- hyoglossus - This muscle derives its name from its connection to the hyoid bone. This muscle depresses the tongue and draws its sides downward.
- styloglossus - The styloglossus retracts (and elevates) the tongue. You can see the styloglossus "extending superiorly" toward the styloid process (hence its name) of the temporal bone and inserts along the lateral inferior aspect of the tongue.
That's it for this virtual dissection, seven new muscles and one that you already knew from the face.
Self-test Labeling Exercises