Sternocleidomastoid muscle (SCM)  The sternocleidomastoid muscle is a two-headed neck muscle, which true to its name bears attachments to the manubrium of sternum (sterno-), the clavicle (-cleido-), and the mastoid process of the temporal bone (-mastoid).  sternocleidomastoideus) is a paired superficial muscle in the anterior portion of the neck.  The sternocleidomastoid muscle (SCM) is an important landmark in the neck which divides it into an anterior and a posterior triangle.  This muscle binds the skull to the sternum and clavicle  It is a long, bilateral muscle of the neck, which functions to flex the neck both laterally and anteriorly, as well as rotate the head contralaterally to the side of contraction.  The muscle is closely related to certain neurovascular structures that pass through the neck on their way either to the head or to the periphery of the body.  The sternocleidomastoid muscle plays a central role in the formation of the triangles of the neck  Diagram:  Origin:  The sternal head originates from the manubrium sterni of sternum  The Clavicular head from the medial third of the clavicle.  Insertion:  Insertion is the lateral surface of the mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone.  Relations:  The muscle lies very superficially so that it is both easily visible and palpable.  The carotid pulse may be felt in the middle third of the front edge.  Under the sternocleidomastoid region runs a neurovascular bundle containing: 1. the common carotid artery (medial) 2. the internal jugular vein (lateral) 3. the vagus nerve (dorsal) 4. the cervical ansa (neural loop in the neck formed by connecting the superior root from the cervical spinal nerves (C1–2) and the inferior root descending from C2–C3)  Blood supply: • Sternocleidomastoid branch of the Occipital artery  Nerve supply: • The sternocleidomastoid muscle is innervated by the accessory nerve (cranial nerve XI) and direct branches of the cervical plexus (C2-C3).  Function: o A unilateral contraction of the sternocleidomastoid muscle flesxes the cervical vertebral column to the same side (lateral flexion) and rotates the head to the opposite side. o A bilateral contraction elevates the head by dorsally extending the upper cervical joints. o At the same time, it flexes the lower cervical column causing an overall bending of the neck towards the chest. o If the head is fixed, it elevates the sternum and clavicle and, thus, expands the thoracic cavity (inspiratory breathing muscle).

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Sternocleidomastoid muscle (SCM)
 The sternocleidomastoid muscle is a two-headed neck muscle,
which true to its name bears attachments to the manubrium
of sternum (sterno-), the clavicle (-cleido-), and the mastoid
process of the temporal bone (-mastoid).
 sternocleidomastoideus) is a paired superficial muscle in the
anterior portion of the neck.
 The sternocleidomastoid muscle (SCM) is an important
landmark in the neck which divides it into an anterior and a
posterior triangle.
 This muscle binds the skull to the sternum and clavicle
 It is a long, bilateral muscle of the neck, which functions to flex
the neck both laterally and anteriorly, as well as rotate the head
contralaterally to the side of contraction.
 The muscle is closely related to certain neurovascular structures
that pass through the neck on their way either to the head or to
the periphery of the body.
 The sternocleidomastoid muscle plays a central role in the
formation of the triangles of the neck
 Diagram:

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 Origin:
 The sternal head originates from the manubrium sterni of
sternum
 The Clavicular head from the medial third of the clavicle.
 Insertion:
 Insertion is the lateral surface of the mastoid process of
the temporal bone and the lateral half of the superior nuchal
line of the occipital bone.
 Relations:
 The muscle lies very superficially so that it is both easily
visible and palpable.
 The carotid pulse may be felt in the middle third of the front
edge.
 Under the sternocleidomastoid region runs a neurovascular
bundle containing:

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1. the common carotid artery (medial)
2. the internal jugular vein (lateral)
3. the vagus nerve (dorsal)
4. the cervical ansa (neural loop in the neck formed by
connecting the superior root from the cervical spinal nerves
(C1–2) and the inferior root descending from C2–C3)
 Blood supply:
 Sternocleidomastoid branch of the Occipital artery
 Nerve supply:
 The sternocleidomastoid muscle is innervated by the accessory
nerve (cranial nerve XI) and direct branches of the cervical
plexus (C2-C3).
 Function:
o A unilateral contraction of the sternocleidomastoid
muscle flesxes the cervical vertebral column to the same side
(lateral flexion) and rotates the head to the opposite side.
o A bilateral contraction elevates the head by dorsally extending
the upper cervical joints.
o At the same time, it flexes the lower cervical column causing an
overall bending of the neck towards the chest.
o If the head is fixed, it elevates the sternum and clavicle and, thus,
expands the thoracic cavity (inspiratory breathing muscle).