Anatomy of Temporalis Muscle

Temporalis Muscle

• Strong membranous sheet of fascia: superior temporal line, zygomatic arch (two layers: lateral and medial border)
• Origin: • Superficial portion: temporal fascia, superior temporal line • Deep portion: temporal fossa (inferior temporal line and infratemporal crest)
• Insertion: • Fibers converge inferior to form a common tendon • Fibers pass between the zygomatic arch and the infratemporal crest (zygomatic canal) • Fibers insert on the coronoid process of the mandible and anterior margin of ramus
• Divided into 3 portions based on the direction of the fibers: • Anterior: verticals, from the anterior portion of the temporal fossa (agonists of the masseter muscle) • Middle: from the wide area in the middle of the temporal fossa, oblique direction toward inferior and anterior • Posterior: from the posterior part of the temporal fossa, horizontals
• Actions: • Bilateral contraction:
  • Anterior fibers: elevation of the mandible
  • Posterior fibers: retraction of the mandible
  • Middle fibers: elevation and retraction of the mandible • Unilateral contraction: lateral movement (side-to-side grinding movements) towards the same side
• Innervation: deep temporal nerves, mandibular nerve, V3 branch of the trigeminal nerve
• Vascularization: deep temporal arteries, branches of maxillary artery (pterygoid portion), itself a branch of external carotid artery

Masseter Muscle

• Powerful muscle of mastication
• Quadrangular in shape
• Overlies the lateral surface of the ramus of the mandible until the zygomatic arch
• 3 portions: superficial, middle, and deep
• Superficial layer: • Origin: thick aponeurosis from maxillary process of the zygomatic bone and from the anterior 2/3 of the inferior and lateral border of the zygomatic arch • Insertion: angle and inferior posterior half of the lateral surface of the ramus of the mandible (tendinous septa and bone ridges)
• Middle layer: • Origin: medial anterior 2/3 of the zygomatic arch and lower border of the posterior third of this arch • Insertion: central part of the lateral surface of the ramus of the mandible
• Deep layer: • Origin: medial surface of the posterior 1/3 of the zygomatic arch • Insertion: superior and lateral part of the mandibular ramus and coronoid process (some of its fibers associate with the superficial part of the temporalis muscle)

Masseteric Fascia

• Strong layer of fascia derived from the deep cervical fascia of the neck
• Covers the masseter
• Attached to the lower border of the zygomatic arch and to the posterior, inferior, and anterior border of the mandible
• Invests the parotid gland and Stensen's duct

Branchial Arches

• Muscles derived from the first branchial arch: • Mastication muscles (temporalis, masseter, lateral pterygoid, and medial pterygoid) • Mylohyoid muscle • Digastric muscle, anterior belly • Tensor veli palatini muscle • Tensor tympani muscle
• Muscles derived from the second branchial arch: • Facial muscles • Stylohyoid muscle • Digastric muscle, posterior belly • Stapedius muscle