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Origins, insertions, innervation and functions of the suprahyoid muscles.
Hello everyone! It's Megan from Kenhub, and welcome to another anatomy tutorial. In this tutorial, we will talk about the origins, insertions, innervations, and functions of the suprahyoid muscles. Here, we can see an image of the muscles of the neck from an anterior view. If I remove platysma, we can now see several groups of muscles. We can see sternocleidomastoid here, the infrahyoid muscles here, and the muscles we're going to be focusing on today, the suprahyoid muscles.
In the next image, we can see an isolated view of the suprahyoid muscles, which are four muscles running from the mandible to the hyoid bone. Together with adjacent tissue, they form the floor of the mouth.
The suprahyoid muscles lift the hyoid bone up while the infrahyoid muscles do the opposite by depressing the hyoid. The four suprahyoid muscles are the digastric muscle, the mylohyoid muscle, the geniohyoid muscle, and the stylohyoid muscle.
The digastric muscle consists of two parts. The name literally translates from Latin to mean two bellies. These two bellies are separated by an intermediate tendon. The anterior belly originates from the digastric fossa of the mandible and the posterior belly originates from the mastoid notch of the temporal bone. Together, the muscular bellies of digastric insert on the intermediate tendon.
The next muscle we're going to look is mylohyoid. It originates from the mylohyoid line of the mandible which is present on the inner surface of the mandible. The muscle fibers run to a median tendon known as the mylohyoid raphe, where both parts of the muscle meet. The mylohyoid raphe continues its course and inserts on the body of the hyoid bone. The mylohyoid muscle and the anterior belly of the digastric muscle are supplied by the mylohyoid nerve which is a branch from the mandibular nerve which is one of the three branches of the trigeminal nerve, cranial nerve V.
The geniohyoid muscle has its origin on the mental spine of the mandible which is also seen on the inner surface of the mandible. Distally, the geniohyoid muscles insert on the body of the hyoid bone. Geniohyoid is innervated by branches of the cervical plexus C1 to C2, accompanied by the hypoglossal nerve, cranial nerve XII.
The stylohyoid muscle, as the name suggests, originates from the styloid process of the temporal bone. The muscle runs to insert on the body of the hyoid bone. In its distal part, the muscle divides into two tendons. The stylohyoid muscle is supplied by the facial nerve, cranial nerve VII. The posterior belly of digastric is also supplied by the facial nerve.
The suprahyoid muscles form the floor of the mouth and play an important role in chewing, swallowing, and speech. In combination with the infrahyoid muscles, they are responsible for the positioning of the hyoid bone. In detail, the digastric and stylohyoid muscles elevate the hyoid bone during swallowing and keep the mouth open. The geniohyoid muscle moves the hyoid forward and supports the opening and lateral movement of the mandible. The main function of the mylohyoid muscle is the elevation of the floor of the mouth but it can also assist in jaw opening and chewing movements. All in all, due to their contribution during mastication, the suprahyoid muscles are also referred to as accessory muscles of mastication.
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Now, good luck everyone, and I will see you next time.