Anatomy of the Anterior Triangle

Cranial Nerves and Tongue Muscles

• The hypoglossal nerve (CN XII) innervates the tongue muscles.

Carotid Sheath

• The carotid sheath encloses the common carotid artery, internal carotid artery, and vagus nerve (CN X).

Mandible and Hyoid Bone

• The digastric muscle depresses the mandible when the hyoid bone is fixed.

Mylohyoid Muscle

• The mylohyoid muscle is innervated by the nerve to the mylohyoid (a branch of the mandibular division of the trigeminal nerve, CN V3).

Geniohyoid Muscle

• The geniohyoid muscle elevates the hyoid bone and depresses the mandible.

Stylohyoid Muscle

• The stylohyoid muscle is innervated by the facial nerve (CN VII).

Extrinsic Tongue Muscles

• The hypoglossal nerve (CN XII) innervates three of the four extrinsic tongue muscles.

Salivary Glands

• The submandibular gland is a major salivary gland.

Submandibular Duct

• The submandibular duct drains the submandibular gland into the oral cavity.

Neck Anatomy

• The common carotid artery has no branches in the neck.

Muscle Attachments

• The sternohyoid muscle attaches to the sternum inferiorly and hyoid bone superiorly.

Infrahyoid Muscles

• The infrahyoid muscles are innervated by the ansa cervicalis nerve.

Laryngeal Innervation

• The vagus nerve (CN X) provides sensory innervation to the larynx.
• The recurrent laryngeal nerve (a branch of the vagus nerve, CN X) provides motor innervation to the cricothyroid muscle.
• The recurrent laryngeal nerve (a branch of the vagus nerve, CN X) provides sensory innervation to the larynx and motor innervation to all intrinsic laryngeal muscles except the cricothyroid muscle.

Ansa Cervicalis Nerve

• The thyrohyoid muscle is not innervated by the ansa cervicalis nerve.

Autonomic Innervation

• The vagus nerve (CN X) provides autonomic (parasympathetic) innervation to thoracic organs.

Carotid Sheath Contents

• The vagus nerve (CN X) is located within the carotid sheath.

Infrahyoid Region

• The thyrohyoid muscle is not part of the infrahyoid region.

Muscle Attachments

• The thyrohyoid muscle attaches to the thyroid cartilage inferiorly and hyoid bone superiorly.