Suprahyoid muscles

The suprahyoid muscles are a group of four paired muscles located in the anterior neck above the hyoid bone. These muscles form the floor of the mouth and play a key role in elevating the hyoid bone and larynx during swallowing and speech. They also assist in depressing the mandible, contributing to mouth opening.

Location

These muscles are situated in the suprahyoid region of the neck, superior to the hyoid bone and deep to the platysma and superficial cervical fascia. They span between the mandible, temporal bone, and hyoid bone.

List of Suprahyoid Muscles

There are four muscles in the suprahyoid group:

• Mylohyoid
• Geniohyoid
• Stylohyoid
• Digastric (anterior and posterior bellies)

Individual Muscles

Mylohyoid

• Origin: Mylohyoid line of the mandible
• Insertion: Body of hyoid bone and median fibrous raphe
• Innervation: Mylohyoid nerve (branch of inferior alveolar nerve, CN V3)
• Function: Elevates the hyoid bone and floor of the mouth; assists in depressing the mandible

Geniohyoid

• Origin: Inferior mental spine of the mandible (genial tubercle)
• Insertion: Anterior surface of the body of the hyoid bone
• Innervation: C1 spinal nerve via hypoglossal nerve (CN XII)
• Function: Pulls the hyoid bone anterosuperiorly; shortens the floor of the mouth; assists in mandible depression

Stylohyoid

• Origin: Styloid process of the temporal bone
• Insertion: Body of the hyoid bone (at junction with greater horn)
• Innervation: Facial nerve (CN VII)
• Function: Elevates and retracts the hyoid bone, elongating the floor of the mouth

Digastric

• Origin:
  • Anterior belly: Digastric fossa of mandible
  • Posterior belly: Mastoid notch of temporal bone
• Insertion: Intermediate tendon connected to body and greater horn of the hyoid via a fibrous loop
• Innervation:
  • Anterior belly: Mylohyoid nerve (branch of CN V3)
  • Posterior belly: Facial nerve (CN VII)
• Function: Depresses mandible (when hyoid is fixed); elevates hyoid (when mandible is fixed)

Function

The primary functions of the suprahyoid muscles include:

• Elevating the hyoid bone during swallowing and speaking
• Depressing the mandible to aid in mouth opening
• Supporting and elevating the floor of the oral cavity

Blood Supply

• Mylohyoid: Inferior alveolar artery
• Geniohyoid: Lingual artery
• Stylohyoid: Facial artery
• Digastric: Facial and occipital arteries

Clinical Relevance

• Swallowing disorders (dysphagia): Dysfunction of suprahyoid muscles can impair elevation of the hyoid and larynx.
• Surgical landmarks: These muscles are important landmarks during submandibular gland excisions and neck dissections.
• Infections: Deep neck infections like Ludwig’s angina may spread along the fascial planes surrounding these muscles.