Muscles of the Head and Neck

Overview

• Focus on two main groups: Muscles of Mastication and Muscles of Facial Expression

Muscles of Mastication (Chewing Muscles)

1. Temporalis Muscle

   • Origin: Fossa temporalis and temporal fascia
   • Insertion: Coronoid process and ramus of the mandible
   • Action: Elevates the mandible

2. Masseter Muscle

   • Origin: Zygomatic bone and zygomatic arch
   • Insertion: Ramus and angle of the mandible
   • Action: Elevates the mandible (superficial masseter)

3. Buccinator Muscle

   • Function: Compresses contents of the cheek for chewing

4. Lateral Pterygoid Muscle

   • Function: Assists in chewing (not visible on model)

5. Medial Pterygoid Muscle

   • Function: Assists in chewing (not visible on model)

Muscles of Facial Expression

1. Frontal Belly of Occipitofrontalis

   • Action: Raises eyebrows

2. Orbicularis Oculi

   • Action: Squinting and blinking the eyes

3. Levator Labii Superioris

   • Action: Elevates the upper lip

4. Zygomaticus Minor

   • Action: Pulls upper lip upward and backwards

5. Zygomaticus Major

   • Action: Draws the mouth corners upwards and backwards (smiling)

6. Risorius

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

7. Depressor Anguli Oris (Triangularis)

   • Action: Pulls the mouth downward

8. Depressor Labii Inferioris

   • Action: Pulls the lower lip downward

9. Mentalis

   • Action: Protrudes the lower lip (sad face)

10. Orbicularis Oris

    • Action: Closes and purses the lips

11. Transverse Nasalis

    • Action: Wrapping around the cartilage of the nose

Lateral Neck Muscles

1. Sternocleidomastoid (SCM)

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

2. Scalene Muscles

   • Anterior Scalene
   • Middle Scalene
   • Posterior Scalene
   • Action: Flexes neck and assists in inhalation

Posterior Neck Muscles

1. Levator Scapulae

   • Action: Elevates the scapula

2. Splenius Capitis

   • Action: Extends the neck

3. Semispinalis Capitis

   • Action: Extends the neck

4. Trapezius

   • Action: Extends the neck and elevates the scapula

Additional Neck Muscles

1. Platysma

   • Action: Depresses the mandible

2. Suprahyoid Muscles

   • Includes:
     • Anterior Belly of Digastric
     • Posterior Belly of Digastric
     • Mylohyoid
     • Geniohyoid
     • Stylohyoid
   • Action: Elevates the hyoid bone, with anterior belly also depressing the mandible if hyoid is fixed

3. Infrahyoid Muscles

   • Includes:
     • Omohyoid (Superior and Inferior bellies)
     • Sternohyoid
     • Sternothyroid
   • Action: Depresses the hyoid bone

Conclusion

• Understanding the function and anatomical positioning of these muscles helps in areas like phonation (voice production).