Masticatory muscles and their fasciae

Question 1

Masticatory muscles

Answer 1

• Temporalis
• Masseter
• Medial pterygoid
• Lateral pterygoid
• All innervated by the trigeminal nerve (CN V)

Question 2

Temporalis muscle

Answer 2

• Flat, fan-like muscle
• In fossa temporalis
• Origin: Temporal plane and the internal surface of the temporal fascia
• Insertion: coronoid process of the mandible
• Innervation: Deep temporal nerves
• Function: Mandibular elevation, dorsal horizontally running fibres pull mandible dorsally (mendibular retraction)

Question 3

Masseter

Answer 3

• Flattened quadrangular muscle
• Located on ramus et angulus mandibulae
• Has two parts:

1. Superficial layer (oblique course) originates on the inferior edge of the zygomatic arch and to the body of the zygomatic bone, runs dorsocaudally and inserts into tuberositas masseterica on angulus mandibulae
2. Profound layer (vertical course) originater on the inner side of the zygomatic arch, descends caudally and inserts into the external side of ramus mandibulae (below incisura mandibulae)

• Some muscle fibres join m. temporalis at the coronoid process of the mandible
• Innervation: masseteric nerve
• Function: mandibular elevation

Question 4

Medial pterygoid muscle

Answer 4

• Short muscle
• In infratemportal fossa
• Two parts:

1. Pars medialis - originates from the pterygoid fossa of the sphenoid bone
2. Pars lateralis - originates on tuber maxillae

• Both run dorsocaudally
• Insertion: Pterygoid tuberosity at the inner surface of the mandibular angle
• Some fibres can be connected to masseter and create a loop around angulus mandibulae
• Innervation: medial pterygoid nerve
• Function: Mandibular elevation and at UC pulls jaw to CLS

Question 5

Lateral pterygoid muscle

Answer 5

• Short
• Located in the upper part of the infratemporal fossa
• Two heads:

1. Pars superior - originates at facies infratemporalis alae majoris ossis sphenoidalis
2. Pars inferior - originates from lamina lateralis processus pterygoideus

• Run posterolaterally and have a common belly
• Insertion: Anterior border of discus articularis and fovea pterygoideus of the mandibular processus condylaris
• Innervation: Lateral pterygoid nerve
• Function: Protraction of the mandible and partly mandibular retraction, and at UC pulls the jaw to the CLS

Question 6

Mandibular adductors

Answer 6

• Temporalis
• Masseter
• Pterygoideus medialis

Question 7

Mandibular abductors

Answer 7

• Lateral pterygoid
• Mylohyoid
• Anterior belly of the digastric muscle

Question 8

Fascia temporalis

Answer 8

• Tough, partly aponeurotic
• Starts on linea temporalis superior and caudally divides into:

1. Lamina superficialis - attaches to the lateral side of the zygomatic arch
2. Lamina profunda: medial side of the zygomatic arch

• Between the laminas is the spatium interfasciale, which is filled by adipose tissue
• Part of the temporal muscle fibres starts from its temporal plane

Question 9

Fascia masseterica

Answer 9

• Covers masseter from the lateral side
• Frontally transitions into the fascia buccopharyngea, which reaches forwars to angulus oris, in the back it passes over raphe bucopharyngea into the pharyngeal fascia
• Caudally passes into fascia cervicalis superficialis
• Cranially attaches to the zygomatic arch
• Part of the fascia transits onto the surface of glandula parotis (fascia parotideomasseterica), covers the masseter