Wednesday, April 29, 2015

Sternocleidomastoid Muscle

Posted by Radiology Madeeasy

Sternocleidomastoid Muscle

image

The sternocleidomastoid is 1 of the 2 large, supf muscles of the neck

Origin

sternal head

· tendinous

· arises from superolat part of front of manubrium sterni

clavicular head

· musculotendinous

· arises from med 1/3 of upper surface of clavicle

Insertion

It is inserted by:

1. a tendon into mastoid process of the temporal bone

2. a thin aponeurosis into lat part of sup nuchal line of occipital bone

Nerve Supply

spinal part of accessory n

motor

ventral rami of C2 & C3

sensory (proprioceptive)

Blood Supply

by branches from occipital artery

Actions

When both muscles contract:

1. extend head at atlanto-occipital jt

2. flex cervical part of vertebral column

When 1 muscle contracts:

1. tilt the head towards the shoulder

2. rotates head so that the face looksupwards on the oppo side

If the head is fixed, the 2 muscles can also act as accessory muscles of inspiration

Relations

Supf

1. skin

2. fascia & platysma

3. ext jugular vein (EJV)

4. great auricular, tnvs cut & med supraclavicular nerves

5. supf cervical LN along EJV

6. parotid gland

Deep

1. carotid sheath & its contents: common & ICA, IJV & vagus n

2. muscles: sternohyoid, sternothyroid, omohyoid, scaleni ant, med & post

levator scapulae, splenius capitis & post belly of digastric

3. besides common carotid art (CCA) & int carotid art (ICA)

there are also

   1. ext carotid art (ECA)

   2. occipital art

   3. subclavian art & suprascapular art

4. besides int jugular vein (IJV), there are also

    1. ant jugular vein

    2. facial vein

    3. lingual vein

5. besides vagus nerve there also:

    1. accessory nerve

    2.cervical plexus

    3. upper part of brachial plexus

    4. phrenic n & ansa cervicalis

6. deep cervical LN

Clinical Notes

1. the sternocleidomastoid divides the neck into ant & post triangles

2. congenital torticollis

3. spasmodic torticollis