15.8
Muscles of the Anterior Neck
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Q1: How are anterior neck muscles classified?
Anterior neck muscles are classified into three groups based on location and function. Superficial muscles like the platysma and sternocleidomastoid lie just under the skin. Suprahyoid muscles are positioned above the hyoid bone, while infrahyoid muscles are located below it. This classification helps organize the complex anatomy of the anterior neck region.
Q2: What are the suprahyoid muscles and where do they originate?
The four suprahyoid muscles—digastric, mylohyoid, geniohyoid, and stylohyoid—all insert into the hyoid bone. The digastric has two bellies: the anterior originates from the mandible and the posterior from the temporal bone, joining at an intermediate tendon. The mylohyoid and geniohyoid originate from the mandible, while the stylohyoid arises from the styloid process of the temporal bone.
Q3: What are the infrahyoid muscles and their attachments?
The infrahyoid muscles include the sternohyoid, omohyoid, sternothyroid, and thyrohyoid. The sternohyoid originates from the manubrium and clavicle. The omohyoid has two bellies connected by a central tendon, with the inferior belly originating near the suprascapular notch. The thyrohyoid arises from the thyroid cartilage, and the sternothyroid originates from the manubrium and first costal cartilage.
Q4: What is the sternocleidomastoid muscle and what does it do?
The sternocleidomastoid (SCM) is a prominent superficial muscle running along each side of the neck with attachment points at the sternum, clavicle, and mastoid process of the skull. This easily visible muscle is primarily responsible for rotating and flexing the head, making it one of the most functionally important anterior neck muscles for head movement.
Q5: How does the digastric muscle differ from other suprahyoid muscles?
The digastric muscle is unique among suprahyoid muscles because it has two distinct bellies connected by an intermediate tendon. The anterior belly originates from the mandible while the posterior belly originates from the temporal bone. This two-part structure distinguishes it from the mylohyoid, geniohyoid, and stylohyoid, which have single origins from the mandible or temporal bone.
Q6: What is the platysma and what role does it play in the neck?
The platysma is a broad, thin superficial muscle stretching from the chest and shoulders to the lower jaw and face. Located just under the skin, it is one of the superficial muscles that contributes to neck expression and appearance. Its wide surface area and superficial position make it visible during certain facial and neck movements.
Q7: How does the omohyoid muscle structure differ from other infrahyoid muscles?
The omohyoid muscle has a distinctive two-part structure with an inferior belly originating near the suprascapular notch and a superior belly connected via a central tendon. This arrangement allows the muscle to change direction as it courses through the neck. Unlike the sternohyoid and thyrohyoid, which have single continuous origins, the omohyoid's divided structure provides unique mechanical advantages for neck movement.