| Muscle | Origin | Insertion | Actions | Nerve Supply |
|---|---|---|---|---|
| Stylohyoid | Styloid process | Body of the hyoid | Elevates the hyoid Retracts the hyoid | Facial n. |
| Mylohyoid | Mylohyoid line of the mandible | Mylohyoid of opposite side at the raphe Body of the hyoid | Elevates the hyoid Elevates the floor of the oral cavity | Trigeminal n. (mandibular division) |
| Digastric Muscle (posterior and anterior bellies connected by a tendon attached to the hyoid) | Mastoid process | Digastric fossa of the mandible | Elevates hyoid Helps depress and retract the mandible | Facial n. (posterior belly) Trigeminal n. (anterior belly—mandibular division) |
| Geniohyoid | Inferior genial tubercle | Body of the hyoid | Helps move the hyoid and tongue anteriorly | C1 (ventral ramus, which follows the hypoglossal n.) |
Digastric Muscle
- Arises as the Posterior Belly from the Digastric Groove on medial surface of base of Mastoid Process
- Tapers down to Intermediate Tendon held beneath a fibrous sling attached to junction of body and Greater Horn of Hyoid
- Anterior Belly lies on inferior surface of Mylohyoid and connects to the Digastric Fossa on the inner surface of the mandible near the midline
- Nerve Supply:
- Posterior Belly – Facial Nerve (by a branch arising between the Stylomastoid Foramen and Parotid Gland)
- Anterior Belly – Nerve to Mylohyoid
- Action: Depress and retract the chin, and assist Lateral Pterygoid in opening mouth
The posterior digastric is supplied by facial nerve and crosses (from posterior to anterior) the following: - Accessory nerve
- Transverse process of the atlas
- Internal jugular/internal carotid
- Hypoglossal nerve
- External carotid
Stylohyoid
- Arises from back of Styloid Process
- Lower end divides to embrace the Digastric Tendon
- Inserted by 2 slips into the junction of the Greater Horn and Body of Hyoid
- Nerve Supply: Facial nerve
- Action: Retract and elevate Hyoid when swallowing
Mylohyoid
- Forms diaphragm of floor of the mouth
- Arises from Mylohyoid Line on inner aspect of Mandible
- Posterior quarter of each side inserts onto body of Hyoid
- Anterior three quarters interdigitate in a midline raphe extending from chin to Hyoid bone
- Nerve Supply: Own nerve – Branch of the Inferior Alveolar Nerve (From Mandibular Division of Trigeminal Nerve) – Also supplies anterior belly of Digastric
- Action: Contraction elevates the ‘gutter’ of the mouth causing tongue and hyoid bone elevation
Geniohyoid
- Extends from Inferior Mental Spine (Genial Tubercle) of Mandible to body of Hyoid Bone
- Nerve Supply: Branch from Hypoglossal Nerve (consisting of fibres from C1)
- Action: Protract and elevate Hyoid Bone in swallowing or, if the Hyoid is fixed, to depress the Mandible