Which of the following is a muscle for chewing (mastication)?
a. sternohyoid
b. orbicularis oris
c. scalenes
d. temporalis
The correct answer and explanation is:
The correct answer is d. temporalis.
The temporalis is one of the primary muscles responsible for chewing, or mastication. It is located on the side of the head, above the ear, and is a large, fan-shaped muscle. Its primary function is to elevate the mandible (lower jaw), which is essential for the process of biting and grinding food. The temporalis muscle works together with other muscles of mastication, such as the masseter, lateral pterygoid, and medial pterygoid, to facilitate the complex movements required for effective chewing.
The temporalis muscle is innervated by the mandibular branch of the trigeminal nerve (cranial nerve V), which is responsible for motor control of the muscles of mastication. When the temporalis contracts, it pulls the mandible upward, enabling the teeth to come together and crush food. Additionally, the temporalis can also assist in retracting the mandible, depending on the direction of the muscle fibers.
The other muscles listed in the options do not play a direct role in chewing:
- Sternohyoid: This is a muscle in the neck that helps depress the hyoid bone and larynx during swallowing and speaking, but it does not contribute to chewing.
- Orbicularis oris: This is the muscle around the mouth that controls movements like puckering the lips and closing the mouth, but it does not contribute directly to mastication.
- Scalenes: These are muscles in the neck that assist in breathing and neck movement but are not involved in chewing.
In summary, the temporalis is crucial for chewing, especially for biting and grinding food, making it a key muscle in the mastication process.