The omohyoideus muscle belongs to the lower hyoid muscles. He also represents a respiratory aid muscle and is involved in chewing.

What is the omohyoid muscle?

The lower hyoid bone musculature is also known as the infrahyoid musculature, and includes not only the omohyoid muscle but also the levator glandulae thyroideae, the sternohyoid muscle, the sternothyroid muscle, and the thyrohyoid muscle.

These five muscles are swallowing and part of the striated skeletal muscle. The striated pattern goes back to the structure of the tissue: Within a muscle are numerous muscle fibers (muscle cells), each consisting of several myofibrils. These can be divided into transverse sections, which designate the anatomy as sarcomeres.

A sarcomere is bounded by the Z-disks and has two types of filaments. These are on the one hand strands of myosin and on the other hand a complex of tropomyosin and actin. These two protein structures are arranged alternately and can interlock, causing the muscle to contract and contract.

Anatomy & Construction

The musculus omohyoideus has an intermediate tendon, which connects the two bellies of the muscle. It arises from the scapula and attaches to the lower hyoid bone (Os hyoideum).

The anatomy also refers to the upper part of the omohyoid muscle as the superior venter ("upper abdomen"). This muscle belly is located near the sternohyoid muscle, which, like the omohyoid muscle, belongs to the infrahyoid musculature. The inferior venter of the omohyoid muscle extends up the neck.

In fine construction, the omohyoideus muscle consists of muscle fibers that correspond to the muscle cells and contain many cell nuclei. The muscle fiber is surrounded by a membrane, which separates it from adjacent tissue. Small tubes, the T-tubules, pass through the membrane and are located at the level of the Z-slices of sarcomeres. Within the membrane are several myofibrils that are thread-like strands. In the interstices, the sarcoplasmic reticulum is similar to the endoplasmic reticulum in other cell types. Mitochondria are responsible for cellular respiration and play a central role in energy metabolism, which is why they are also known as "cell power plants."

Function & Tasks

The ansa cervicalis profunda connects the omohyoid muscle to the nervous system and controls its activity. The Ansa cervicalis profunda is the deep part of the cervical nerve loop, which also innervates the other muscles of the infrahyoid muscles. The signals of the nerve loop originate from the cervical nerves (cervical plexus). The ansa cervicalis profunda runs transversely to the internal jugular vein.

Low-oxygen blood flows from the head back to the lungs through this vein. The omohyoid muscle is responsible for keeping the internal jugular vein open by tensing the middle neck fascia (praetracheal lamina).

The omohyoid muscle can also pull the hyoid bone back down by contracting. This movement is especially relevant when swallowing. In this process, different muscles work together: In addition to the infrahyoid muscles, the muscles of the floor muscles (suprahyoid muscles) and the muscles of the palate are active during swallowing. Subsequently, the tunica muscularis of the esophagus supports the transport of food or fluid into the stomach. The swallow center in the medulla (medulla oblongata) coordinates the swallowing process and triggers the swallowing reflex.

Through the ninth and tenth cranial nerves (glossopharyngeal nerve and vagus nerve), the swallow center receives sensitive information and uses various nerve tracts to trigger the motor response in the appropriate muscles. The neuronal structures involved include the ninth through twelfth cranial nerves, the fifth cranial nerve, and the cervical plexus, which also controls the omohyoid muscle.

Furthermore, the omohyoid muscle contributes to certain head movements. When a person moves his head forward, the infrahyoid muscles (including the omohyoid muscle) cause the hyoid bone to move back down. In its role as a respiratory aid muscle, the omohyoid muscle also helps to a lesser extent in breathing.

Diseases

One of the tasks of the omohyoideus muscle is to keep the internal jugular vein open. Physicians use this vein partly to create a central venous catheter (CVC). To do this, insert a thin tube into the vein and push it inside the blood vessel to the right atrium.

A central venous catheter is used in different situations. For example, physicians can use it to determine central venous pressure, which is an indicator of cardiac preload and plays an important role in various cardiac disorders. In addition, CVC allows the close-to-heart administration of various substances, including electrolytes and medications. For the central venous catheter not only the internal jugular vein is considered, but also the subclavian vein. In addition to these two preferred ZVK variants, access can also be made to the anterior vena or the basal vein, more rarely via other veins.

Damage and functional limitations of the omohyoid muscle may contribute to dysphagia. Neurological disorders, for example in connection with a stroke or a neurodegenerative disease, can damage the nerve fibers responsible for the supply of the omohyoid muscle and the remaining infrahyoid muscles. Injuries, tumors, and other lesions in the medulla (medulla oblongata) may also affect the swallowing center and interfere with coordinated swallowing. The swallowing reflex may also be affected.

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