Muscles of the Head and Neck

Overview of Muscles of the Head and Neck
  • Focus on muscles in these regions and their functions.
Sternocleidomastoid Muscle
  • Origin:
    • Sternal end of the clavicle
    • Manubrium of sternum
  • Insertion:
    • Mastoid region of the skull
  • Actions:
    • Bilateral: Neck flexion (both muscles contracting together pulls the neck down).
    • Unilateral: Turns face to opposite side (contracting one side turns head toward the opposite side).
  • Innervation:
    • Accessory nerve (cranial nerve XI).
Semispinalis Capitis Muscle
  • Origin:
    • Articular processes of C5-C7 vertebrae.
  • Insertion:
    • Occipital bone at the back of the skull.
  • Actions:
    • Bilateral: Extends the head (pulls neck back).
    • Unilateral: Lateral flexion of neck to the same side.
  • Innervation:
    • Spinal nerves.
Splenius Capitis Muscle
  • Origin:
    • Spinous processes of inferior cervical vertebrae.
  • Insertion:
    • Mastoid process of the temporal bone and occipital bone.
  • Actions:
    • Bilateral: Extends the head (pulls head backwards).
    • Unilateral: Lateral flexion of neck to the same side.
  • Innervation:
    • Cervical spinal nerves.
Longissimus Cervicis Muscle
  • Origin:
    • Transverse processes of superior thoracic vertebrae.
  • Insertion:
    • Transverse processes of middle and superior cervical vertebrae.
  • Actions:
    • Bilateral: Extends the head (backward).
    • Unilateral: Lateral flexion of neck to the same side.
  • Innervation:
    • Cervical and thoracic spinal nerves.
Longissimus Thoracis Muscle
  • Origin:
    • Transverse processes of all thoracic and lumbar vertebrae.
  • Insertion:
    • Transverse processes of thoracic vertebrae.
  • Actions:
    • Bilateral: Extends the spine.
    • Unilateral: Lateral flexion of the spine to the same side.
  • Innervation:
    • Thoracic and lumbar spinal nerves.
Thyrohyoid Muscle
  • Origin:
    • Thyroid cartilage of the larynx.
  • Insertion:
    • Hyoid bone.
  • Actions:
    • Elevates the thyroid and depresses the hyoid bone.
  • Innervation:
    • Hypoglossal nerve (cranial nerve XII).
Scalene Muscles
  • Sets:
    • Anterior, middle, and posterior scalenes.
  • Origin:
    • Transverse processes of C2-C7.
  • Insertion:
    • First and second ribs.
  • Action:
    • Elevates ribs 1 and 2.
  • Innervation:
    • Cervical spinal nerves.
Erector Spinae Muscle Group
  • Components:
    • Spinalis, Longissimus, Iliocostalis groups.
  • Actions:
    • Main action is spinal extension.
  • Each group has subdivisions based on their locations (thoracis, cervicis, and lumborum).
Conclusion
  • This lecture covered the muscles in the head, neck, and vertebral column, focusing on origins, insertions, actions, and innervation.