AH&N- Muscles

Question 1

Describe the location, attachments, action and innervation of the stylohyoid muscle.

Answer 1

Thin muscular strip located superiorly to the digastric muscle
Attachments: arises from the styloid process of the temporal bone & attaches to the lateral side of the hyoid bone.
Actions: initiates a swallowing action by pulling the hyoid bone in an posterior and superior direction.
Innervation: mandibular branch of the facial nerve (CNVII)

Question 2

Describe the location, attachments, actions and innervation of the digastric muscle.

Answer 2

Muscle has 2 muscular bellies, connected by a tendon. In some cadavers it can perforate the stylohyoid.
Attachments: anterior belly arises from the digastric fossa of the mandible. The posterior belly arises from the mastoid process of the temporal bone. The 2 bellies are connected by an intermediate tendon which is attached to the hyoid bone via a fibrous sling.
Actions: depresses the mandible and elevates the hyoid bone
Innervation: anterior belly is innervated by the inferior alveolar nerve, a branch of the mandibular nerve (derived from trigeminal nerve). Posterior belly is innervated by the digastric branch of the facial nerve.

Question 3

Describe the location, attachments, actions and innervation of the mylohyoid muscle.

Answer 3

Broad, triangular shaped muscle, forms the floor of the oral cavity, therefore supporting the floor of the mouth.
Attachments: it originates from the mylohyoid line of the mandible & attaches onto the hyoid bone.
Actions: elevates the floor of the mouth & the hyoid bone.
Innervation: inferior alveolar nerve- branch of mandibular nerve, off trigeminal nerve.

Question 4

Describe the location, attachments, actions and innervation of the Geniohyoid.

Answer 4

Located deep to the mylohyoid muscle and close to the midline of the neck.
Attachments: arises from the inferior mental spine of the mandible. It then travels inferiorly & posteriorly to attach to the hyoid bone.
Actions: depresses the mandible and elevated the hyoid bone
Innervation: C1 nerve roots that run within the hypoglossal nerve.

Question 5

Name then infrahyoid muscles and divide them into planes.

Answer 5

Superficial plane: Sternohyoid & Omohyoid

Deep plane: Sternothyroid & Thyrohyoid

Question 6

Describe the location attachments, actions and innervation of the Sternohyoid muscle.

Answer 6

Lies superficial in the neck.
Attachments: Sternohyoid muscle originates from the sternum & sternoclavicular joint. It ascends to insert onto the hyoid bone.
Actions: depresses the hyoid bone.
Innervation: anterior rami of C1-C3 carried by a branch of the ansa cervicalis.

Question 7

Describe the location, attachments, actions and innervation of the Omohyoid muscle.

Answer 7

Split into two bellies connected by a muscular tendon, located slightly laterally to the sternohyoid.
Attachments: inferior belly of the Omohyoid arises from the scapula. It runs superiomedially moving underneath the SCM. Here it is attached to the superior belly by an intermediate tendon. This tendon is attached to the clavicle by the deep cervical fascia. The superior belly ascends to attach to the hyoid bone.
Actions: depresses the hyoid bone.
Innervation: anterior rami of C1-C3, carried by a branch of the ansa cervicalis.

Question 8

Describe the location, attachments, actions and innervation of the Sternothyroid muscle.

Answer 8

Muscle is wider and deeper than the sternohyoid.
Attachments: Sternothyroid runs from the manubrium of the sternum to the thyroid cartilage.
Actions: depresses the thyroid cartilage.
Innervation: anterior rami of C1-C3, carried by a branch of the ansa cervicalis.

Question 9

Describe the location, attachments, actions and innervation of the thyrohyoid muscle.

Answer 9

Short band of muscle underneath the posterior portions of the Omohyoid & sternohyoid muscles. It is a continuation of the Sternothyroid muscle.
Attachments: it arises from the thyroid cartilage of the larynx & ascends to attach to the hyoid bone
Actions: it depresses the hyoid. However, if the hyoid is fixed, it can raise the larynx.
Innervation: anterior ramus of C1, carried within the hypoglossal nerve.

Question 10

What are the suprahyoid muscles?

Answer 10

Four muscles superior to the hyoid bone, they act to elevate the hyoid bone and initiate swallowing. Paired structures.
Stylohyoid
Digastric
Mylohyoid
Geniohyoid