Muscle Anatomy of the Sternocleidomastoid

Sternal Head: Upper part of the anterior surface of the manubrium
Clavicular Head: Superior surface of the medial one third of clavicle
Insertion: Lateral surface of the mastoid process of the occipital bone, from its apex to its superior border, and by a thin aponeurosis to the lateral half of the superior nuchal line
Actions: Bilaterally: Flexion of the head and neck, extension of the head and neck
Unilaterally: Rotation of head to opposite side, lateral flexion
Innervation: Accessory nerve: cranial nerve XII and ventral rami of the (C2, C3)
Blood Supply: Branches from the vertebral artery

SCM Origin, Insertion, Action, Innervation

Muscle Anatomy: Sternocleidomastoid Actions

Primary Actions of the Sternocleidomastoid

1. Extension of the head and cervical spine when posterior fibers act bilaterally


  • Longissimus Capitis
  • Spinalis Capitis
  • Splenius Capitis
  • Semispinalis Capitis


  • Longus Capitis
  • Sternocleidomastoid (anterior fibers)

2. Flexion of the head and cervical spine when anterior fibers act bilaterally

  Agonists: Longus Capitis


  • Longissimus Capitis
  • Spinalis Capitis
  • Splenius Capitis
  • Semispinalis Capitis
  • Sternocleidomastoid (posterior fibers)

3. Lateral flexion of the head and cervical spine when acting unilaterally

  Agonists: Splenius Capitis

  Antagonists: Splenius Capitis - contralateral side

4. Contralateral rotation of the head and cervical spine when acting unilaterally

  Agonists: Semispinalis Capitis

  Antagonists: Splenius Capitis -  contralateral side

Information about cause and effect of Sternocleidomastoid pain:

Sternocleidomastoid Muscles: Affects Head, Eyes, Sinus, Ears, Throat, Pain, Dizziness, Whiplash

Recommended Anatomy Books:

Anatomy Coloring Book

The Anatomy Coloring Book is one of the best study and reference books for beginning anatomy students. The diagrams are clearly labeled and allow you to see the relationship and placement of the various structures of the body. You will also be surprised how the act of coloring will help with recall. But this is not just a beginners book, it is also great for practitioners and therapists to have on hand to use with clients and patients to use as a visual reference.

Human Muscle Anatomy

The Trail Guide To The Body is another excellent book to help you learn the musculature of the human body. Though the book is geared toward massage therapists and physical therapist assistants, the book with its illustrations and text helps anyone gain a thorough understanding of the human musculoskeletal system and movement. I highly recommend this book for anyone studying anatomy and believe that MTs, PTAs, and teachers of body movements should have this book in their possession. I also highly recommend this book for the lay person who wants to gain understanding of the muscle, skeletal system and how our bodies move. This book will not disappoint!

Basic Clinical Massage Therapy

Out of the scores of books in my office Basic Clinical Massage Therapy is by far the most referenced book in my library. The musculoskeletal system is overlaid on human models allowing you to learn the precise location, origin and insertions of each muscle. The models are pictured in various poses throughout the book which also helps you visualize muscles in motion and their actions relationship with the skeletal structure and other muscles. Though it is written for massage therapists, it is an excellent book for anyone who wants to learn about the muscular system. MT's will benefit from recommended treatments for each muscle.

Muscle Anatomy Flashcards

Musculoskeletal Anatomy Flashcards Are you a student or professional therapist who needs to brush up on the musculoskeletal system? Dr. Joseph E. Muscolino DC has developed a comprehensive set of flashcards that will help develop a mind's picture of exactly where the muscles lie under the skin. A highly recommended study aid for students. Great for non students who want an easy comprehensive anatomy guide.

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