The principle muscle responsible for the opening of the mouth is:
a- Mylohyoid
B- Anterior temporal
c- Posterior temporal
d- Anterior belly of digastric ***
---------------------
The digastric muscle is one of the few muscles that contain separate muscle scans. These two parts of the muscle are separated by an intermediate rounded tendon, running through the hyoid bone.
There is a digastric muscle on each side of the jaw, which connects from the jaw through the hyoid to the lower part of the skull. This complex arrangement allows pulley actions in the jaw, and work in conjunction with the other muscles of the jaw to complete complex movements such as chewing, speaking, and breathing.
Digastric muscle anatomy:
The muscle connects to the jaw, or mandibular bone, in a place called the chin symphysis. This small crest is in the center of the jaw and connects to many muscles, including a digastric muscle on the left and another on the right.
The anterior belly of the muscle extends from the jaw to the tendon that separates the two bellies. The tendon adheres to the hyoid bone, and allows tension to transfer from any belly along the path of the muscle.
The posterior belly of the muscle connects this intermediate tendon to the temporal bone of the skull. This bone is at the base of the skull and has a small notch, the mastoid notch, where the posterior belly adheres. The anterior belly of the muscle is served by the trigeminal nerve, while the posterior belly joins the facial nerve.
Origin:
- Anterior belly: digastric fossa on the deep surface of the chin symphysis of the jaw
- Posterior belly: mastoid process of the temporal bone.
Insertion:
The digastric muscle is inserted into the hyoid bone via the intermediate tendon.
Irrigation
- Anterior belly: submental branch of the facial artery.
- Posterior belly: occipital artery.
Innervation:
- Anterior belly: mylohyoid nerve, a branch of the posterior division of the trigeminal nerve jaw division (CN V).
- Posterior belly: unnamed branch of the facial nerve (CN VII) that arises between the stylomastoid foramen and the parotid gland.
Digastric muscle function:
Unlike most muscles, the digastric muscle can contract in two different portions. Because the bellies of the muscle are supplied by different nerves, the muscles can contract separately. While the exact functioning of the muscles of the face and jaw is very complicated, the digastric muscle works as a kind of tension pulley to generate forces in various directions in the jaw.
There are two digastrics, one on the left and on the right, that adhere to the lower skull through a pulley mechanism in the hyoid bone. This means that the contraction of this muscle can produce forces that open the jaw and move from side to side.
Therefore, the digastric muscle is responsible for actions such as talking, chewing, swallowing and breathing. Any complex jaw action will probably involve the muscle in some way.
Clinical importance of digastric muscle:
The digastric muscle is often noted as the source in people who experience the jaw, throat, tooth, and general facial pain. The muscle, which has two separate portions innervated by different branches of the cranial nerves and operating a complex tendon pulley, is prone to tension.
Unfortunately, tension in the anterior belly of the muscle and tension in the posterior belly do not produce the same sensation. The posterior belly is connected to the facial nerve. The anterior belly is connected to the trigeminal nerve, which connects to different parts of the face and jaw than the facial nerve.
Therefore, any tension in any part of the muscle can send pain impulses through many parts of the face and jaw. Relaxing the muscle with some simple jaw movements and light massage should relieve tension and reduce pain, even if it feels as if it does not come from the digastric muscle.
---------------------
The digastric muscle is one of the few muscles that contain separate muscle scans. These two parts of the muscle are separated by an intermediate rounded tendon, running through the hyoid bone.
There is a digastric muscle on each side of the jaw, which connects from the jaw through the hyoid to the lower part of the skull. This complex arrangement allows pulley actions in the jaw, and work in conjunction with the other muscles of the jaw to complete complex movements such as chewing, speaking, and breathing.
Digastric muscle anatomy:
The muscle connects to the jaw, or mandibular bone, in a place called the chin symphysis. This small crest is in the center of the jaw and connects to many muscles, including a digastric muscle on the left and another on the right.
The anterior belly of the muscle extends from the jaw to the tendon that separates the two bellies. The tendon adheres to the hyoid bone, and allows tension to transfer from any belly along the path of the muscle.
The posterior belly of the muscle connects this intermediate tendon to the temporal bone of the skull. This bone is at the base of the skull and has a small notch, the mastoid notch, where the posterior belly adheres. The anterior belly of the muscle is served by the trigeminal nerve, while the posterior belly joins the facial nerve.
Origin:
- Anterior belly: digastric fossa on the deep surface of the chin symphysis of the jaw
- Posterior belly: mastoid process of the temporal bone.
Insertion:
The digastric muscle is inserted into the hyoid bone via the intermediate tendon.
Irrigation
- Anterior belly: submental branch of the facial artery.
- Posterior belly: occipital artery.
Innervation:
- Anterior belly: mylohyoid nerve, a branch of the posterior division of the trigeminal nerve jaw division (CN V).
- Posterior belly: unnamed branch of the facial nerve (CN VII) that arises between the stylomastoid foramen and the parotid gland.
Digastric muscle function:
Unlike most muscles, the digastric muscle can contract in two different portions. Because the bellies of the muscle are supplied by different nerves, the muscles can contract separately. While the exact functioning of the muscles of the face and jaw is very complicated, the digastric muscle works as a kind of tension pulley to generate forces in various directions in the jaw.
There are two digastrics, one on the left and on the right, that adhere to the lower skull through a pulley mechanism in the hyoid bone. This means that the contraction of this muscle can produce forces that open the jaw and move from side to side.
Therefore, the digastric muscle is responsible for actions such as talking, chewing, swallowing and breathing. Any complex jaw action will probably involve the muscle in some way.
Clinical importance of digastric muscle:
The digastric muscle is often noted as the source in people who experience the jaw, throat, tooth, and general facial pain. The muscle, which has two separate portions innervated by different branches of the cranial nerves and operating a complex tendon pulley, is prone to tension.
Unfortunately, tension in the anterior belly of the muscle and tension in the posterior belly do not produce the same sensation. The posterior belly is connected to the facial nerve. The anterior belly is connected to the trigeminal nerve, which connects to different parts of the face and jaw than the facial nerve.
Therefore, any tension in any part of the muscle can send pain impulses through many parts of the face and jaw. Relaxing the muscle with some simple jaw movements and light massage should relieve tension and reduce pain, even if it feels as if it does not come from the digastric muscle.
Labels
Promatric