The omohyoid muscle is a flat muscle belonging to the infrahyoid muscle group. It is critical to neck surgeries, particularly in the case of lymph node metastasis, which is the spread of cancer through the lymph nodes.
The omohyoid is made up of two bellies, the superior and the inferior, joined through an inter-muscular tendon (a flexible and fibrous tissue). This tendon passes obliquely (in a slanted direction) through the lateral cervical area (the side of the neck), supported by a connective tissue that prevents the internal jugular vein from being squeezed under severe pressure.
The inferior belly of the muscle divides the neck's posterior triangle, an area at the side of the neck, into two sections. These sections are the occipital triangle, which is located in the upper part, and the subclavian triangle, which is located in the lower part.
The superior belly, on the other hand, divides the neck's anterior triangle (an area at the front) into a carotid triangle, located in the upper part, and a muscular triangle, located in the lower part.
The omohyoid muscle is closely connected to the scapula (the triangular bone at back of the shoulder) and obliquely connected to the hyoid bone in the upper neck. The variations of this muscle in different cases may include duplicate muscles or an absence of it. In some cases, one of the two bellies may be missing, or one belly may be present twice. The muscle may also originate from the clavicle, in some unusual cases.