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Questions and Answers
What is the origin of the sternocleidomastoid?
What is the origin of the sternocleidomastoid?
Sternal head: manubrium of sternum; Clavicular head: medial 1/3 of clavicle
Where does the sternocleidomastoid insert?
Where does the sternocleidomastoid insert?
Mastoid process of temporal bone
What are the actions of the sternocleidomastoid?
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?
What is the innervation of the sternocleidomastoid?
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How can the sternocleidomastoid be palpated?
How can the sternocleidomastoid be palpated?
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Which of the following is NOT an action of the sternocleidomastoid?
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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