Muscles of the head and neck

Muscles of the Neck, Head, and Back

Muscles of the Anterior Neck

• Crucial muscles involved in swallowing and speech

  • Control positions of the larynx and hyoid bone

• Key anatomical structures:

  • Hyoid Bone: Provides a stable base for tongue movement

  • Thyroid Cartilage: Part of the larynx

  • Thyroid Gland: Endocrine gland located in the anterior neck

  • Suprahyoid Muscles: Muscles above the hyoid bone, elevate hyoid and larynx during swallowing

  • Inferior Muscles: Muscles below the hyoid bone, depress hyoid and control larynx position

Suprahyoid Muscles

1. Digastric Muscle

   • Consists of anterior and posterior bellies, elevates hyoid and larynx, depresses mandible

2. Stylohyoid Muscle

   • Moves hyoid bone posteriorly, elevates the larynx

3. Mylohyoid Muscle

   • Elevates hyoid bone, presses tongue against the roof of the mouth

4. Geniohyoid Muscle

   • Raises hyoid bone, depresses mandible

Infrahyoid Muscles

1. Omohyoid Muscle

   • Composed of superior and inferior bellies, depresses hyoid bone

2. Thyrohyoid Muscle

   • Elevates the thyroid cartilage of the larynx

3. Sternothyroid Muscle

   • Depresses the thyroid cartilage, aids in voice tone control

Muscles that Move the Head

• Neck muscles essential for head stability and movement

  • Sternocleidomastoid

    • Major muscle responsible for lateral flexion and rotation; divides the neck into triangles

• Table of Head Movements: Overview of various muscles involved in head movements

Key Muscles and Functions

1. Sternocleidomastoid

   • Functions:

     • Unilateral: Rotates head to opposite side

     • Bilateral: Flexes the head

   • Origin: Sternum and clavicle

   • Insertion: Temporal bone and occipital bone

2. Semispinalis Capitis

   • Functions: Extends and laterally flexes the head, rotates

   • Origin: Transverse processes of cervical and thoracic vertebrae

   • Insertion: Occipital bone

3. Splenius Capitis

   • Functions: Rotates and extends the head

   • Origin: Spinous processes of cervical and thoracic vertebrae

   • Insertion: Temporal bone and occipital bone

4. Longissimus Capitis

   • Functions: Rotates and extends the head

   • Origin: Transverse processes of cervical and thoracic vertebrae

   • Insertion: Temporal bone

Muscles of the Posterior Neck and the Back

• Functions: Stabilization and movement of the vertebral column

Muscle Groups

1. Splenius Muscles

   • Originate at midline, insert laterally and superiorly

   • Functions: Extension, lateral flexion, and rotation of head

2. Erector Spinae Group

   • Main extensor of the vertebral column

   • Subgroups:

     • Iliocostalis: Cervicis, thoracis, lumborum

     • Longissimus: Capitis, cervicis, thoracis

     • Spinalis: Capitis, cervicis, thoracis

3. Transversospinales Muscles

   • Stabilize the vertebral column through connections between vertebrae

   • Include semispinalis muscles related to their regions

4. Multifidus Muscle

   • Located in the lumbar region, aids in vertebral column extension and lateral flexion

5. Segmental Muscle Group

   • Includes interspinales and intertransversarii muscles, contributes to vertebral stability

6. Scalene Muscles

   • Function in head movement and assist in breathing

   • Include anterior, middle, and posterior scalene muscles

Terms to Know

• Fascicles: Bundles of muscle fibers that work together for movement.

• Flexion: Bending of a joint to decrease the angle between body parts (e.g., neck bending forward).

• Extension: Straightening a joint to increase the angle (e.g., tilting the head backward).