Suprahyoid Muscles

INTRODUCTION:
  • The suprahyoid muscles are four muscles located above the hyoid bone in the neck.
  • They are the digastric, stylohyoid, geniohyoid, and mylohyoid muscles.
  • Anterior belly of digastric, Mylohyoid dervied from 1st branchial arch
  • Second branchial arch give rise to stylohyoid, posterior belly of digastric muscles
  • They are all pharyngeal muscles, with the exception of the geniohyoid muscle.
  • The digastric is uniquely named for its two bellies eg Muscle fibers in the ligament of Treitz, Omohyoid, Occipitofrontalis
Muscle Origin Insertion Innervation
Digastric (anterior belly) Digastric fossa of Mandible Intermediate Tendon Mylohyoid nerve - branch of CN V3
(Mandibular division of Trigeminal nerve)
Digastric (posterior belly) Mastoid notch Intermediate Tendon Facial nerve
Geniohyoid Inferior mental spine of Symphysis menti Hyoid C1 via the hypoglossal nerve (XII)
Stylohyoid Temporal styloid process Hyoid Facial nerve
Mylohyoid Mylohyoid line of mandible Hyoid Mylohyoid nerve - branch of CN V3
(Mandibular division of Trigeminal nerve)
FUNCTIONS:
  • These four muscles have different actions, but in general assist in elevating the hyoid bone and widening the esophagus during swallowing.
  • Submandibular gland is divided into superficial and deep parts by mylohyoid
  • When the two bellies of the digastric contract, they pull upward on the hyoid bone; but if the hyoid is fixed from below, the digastric assists in extreme opening of the mouth such as yawning or taking a large bite of an apple.
  • Stylohyoid & digastric are elevators of larynx
  • The mylohyoid elevates the hyoid bone, tenses the floor of the mouth.
  • The Geniohyoid pulls the hyoid bone anterosuperiorly, shortening the floor of the mouth and widening the pharynx during swallowing.
  • The Stylohyoid elevates and retracts the hyoid bone, elongating the floor of the mouth during swallowing
Exam Question
  • Digastric muscles refers to muscles with two bellies are Muscle fibers in the ligament of Treitz, Omohyoid, Occipitofrontalis
  • Posterior belly of digastric is supplied by Facial nerve
  • Mylohyoid nerve - branch of CN V3 (Mandibular division of Trigeminal nerve) innervates anterior belly of trigeminal nerve
  • Second branchial arch give rise to stylohyoid, posterior belly of digastric muscles
  • Stylohyoid & digastric are elevators of larynx
  • Submandibular gland is divided into superficial and deep parts by mylohyoid
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