Questions and Answers
What is the origin of the sternocleidomastoid?
Sternal head: manubrium of sternum; Clavicular head: medial 1/3 of clavicle
Where does the sternocleidomastoid insert?
Mastoid process of temporal bone
What are the actions of the sternocleidomastoid?
Rotation of the head to the contralateral side; lateral flexion to the ipsilateral side; neck flexion and capital extension when both sides act bilaterally.
What is the innervation of the sternocleidomastoid?
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How can the sternocleidomastoid be palpated?
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Which of the following is NOT an action of the sternocleidomastoid?
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Study Notes
Sternocleidomastoid
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Origin:
- Sternal head originates from the manubrium of the sternum.
- Clavicular head originates from the medial one-third of the clavicle.
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Insertion:
- Inserts at the mastoid process of the temporal bone.
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Action:
- Rotates the head to the contralateral side.
- Allows lateral flexion to the ipsilateral side.
- When acting bilaterally, it facilitates neck flexion and capital extension.
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Innervation:
- Motor innervation is provided by the spinal accessory nerve (CN XI).
- Sensory innervation comes from the ventral rami of C2 and C3.
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Palpation:
- To palpate, place the patient supine, seated, or standing with the head rotated to one side.
- Palpating fingers should be placed along the muscle fiber direction; ask the patient to flex or rotate their neck to feel muscle contraction.
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