Lecture: Muscles of the Head and Neck

Muscles of Mastication

• Temporalis Muscle

  • Origin: Temporal fossa
  • Insertion: Coronoid process on the ramus of the mandible
  • Action: Elevates the mandible

• Masseter Muscle

  • Superficial and Deep Masseter
  • Origin: Zygomatic bone and arch
  • Insertion: Ramus of the mandible and angle of the mandible
  • Action: Elevates the mandible

• Buccinator

  • Action: Compresses cheek contents, moves food for chewing

• Lateral and Medial Pterygoid

  • Part of the muscles of mastication

Muscles of Facial Expression

• Occipital Frontalis

  • Frontal Belly: Raises eyebrows
  • Occipital Belly: Connected by epicranial aponeurosis

• Orbicularis Oculi

  • Action: Squinting and blinking

• Levator Labii Superiororis

  • Action: Elevates upper lip

• Zygomaticus Minor and Major

  • Action (Minor): Pulls upper lip upward and backward
  • Action (Major): Draws mouth angle upward and backward for smiling

• Risorius

  • Action: Pulls corner of the mouth laterally (grimace)

• Depressor Anguli Oris (Triangularis)

  • Action: Pulls down the angle of the mouth

• Depressor Labii Inferioris

  • Action: Pulls the lower lip downward

• Mentalis

  • Action: Protrudes the lower lip (sad face)

• Orbicularis Oris

  • Action: Closes the mouth

• Transverse Nasalis

  • Located around nose cartilage

• Auricular Muscles

  • Anterior, Superior, Posterior: Move the ear and skin in respective directions

Lateral Neck Muscles

• Sternocleidomastoid (SCM)

  • Origin: Anterior surface of manubrium and clavicle
  • Insertion: Mastoid process and superior nuchal line
  • Action: Flexes neck, assists in inhalation

• Scalenes

  • Anterior, Middle, Posterior: Flex neck, assist in inhalation

Posterior Neck Muscles

• Levator Scapulae

  • Action: Elevates scapula

• Splenius Capitis and Semispinalis Capitis

  • Action: Extend neck

• Trapezius

  • Superficial compared to other neck muscles
  • Action: Extends neck, elevates scapula

Additional Muscles

• Platysma
  • Action: Depresses mandible

Suprahyoid Muscles

• Digastric

  • Anterior Belly and Posterior Belly: Elevate hyoid, depress mandible if hyoid is fixed

• Mylohyoid and Geniohyoid

  • Action: Elevate hyoid

• Stylohyoid

  • Action: Elevate hyoid

Infrahyoid Muscles

• Omohyoid

  • Superior and Inferior Belly: Connected by intermediate tendon
  • Action: Depress hyoid

• Sternohyoid and Sternothyroid

  • Action: Depress hyoid

Functions

All these muscles contribute to movements necessary for chewing, facial expressions, neck mobility, and phonation (voice production).

---

These notes encompass the primary muscles discussed in the lecture with their origins, insertions, actions, and any significant features.