Dr. Mujahid Khan
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The scalenus anterior muscle is a key muscle in
understanding the root of the neck
It is deeply placed
It descends almost vertically from the vertebral
column to the first rib
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Related to the carotid arteries, the vagus nerve,
the internal jugular vein, and the deep cervical
lymph nodes
The transverse cervical and suprascapular
arteries and the prevertebral layer of deep
cervical fascia bind the phrenic nerve to the
muscle
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Related to the pleura, the origin of the brachial
plexus, and the second part of the subclavian
artery
The scalenus medius muscle lies behind the
scalenus anterior muscle
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Related to the vertebral artery and vein and the
sympathetic trunk
On the left side, the medial border is related to
the thoracic duct
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Related to the emerging branches of the
cervical plexus, the roots of the brachial plexus,
and the third part of the subclavian artery
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Origin:
Transverse processes of third, fourth, fifth, and
sixth cervical vertebrae
Insertion:
First rib
Action:
 Elevates first rib, laterally flexes and rotates
cervical part of vertebral column
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It lies behind the scalenus anterior
It extends from the transverse process of the atlas and
the transverse processes of the next five cervical
vertebrae
Inserted into the upper surface of the first rib behind
the groove for the subclavian artery
The muscle lies behind the roots of the brachial plexus
and the subclavian artery
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Origin:
Transverse processes of lower cervical
vertebrae
Insertion:
Second rib
Action:
Elevates second rib, laterally flexes and rotates
cervical part of vertebral column
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Origin:
Anterior tubercle of C1, bodies of C1 to C3 and
transverse processes of C3 to C6 vertebrae
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Insertion:
Bodies of C5 to T3 vertebrae, transverse
processes of C3 to C5 vertebrae
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Action:
Flexes neck with rotation to opposite side
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Origin:
Basilar part of occipital bone
Insertion:
Anterior tubercles of C3 to C6 transverse
processes
Action:
Flexes the head
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Origin:
Base of the skull, just anterior to the occipital
condyle
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Insertion:
Anterior surface of lateral mass of atlas
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Action:
Flexes the head
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Origin:
Jugular process of occipital bone
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Insertion:
Transverse process of atlas
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Action:
Flexes head and helps stabilize it
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The cervical plexus is formed by the anterior
rami of the first four cervical nerves
The rami are joined by connecting branches,
which form loops that lie in front of the origins
of the levator scapulae and the scalenus medius
muscles
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The plexus is covered in front by the
prevertebral layer of deep cervical fascia
Is related to the internal jugular vein within the
carotid sheath
The cervical plexus supplies the skin and the
muscles of the head, the neck, and the
shoulders
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The lesser occipital nerve (C2):
Supplies the back of the scalp and the auricle
The greater auricular nerve (C2 and3):
Supplies the skin over the angle of the
mandible
The transverse cervical nerve (C2 and 3):
Supplies the skin over the front of the neck
The supraclavicular nerves (C3 and 4)
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The medial, intermediate, and lateral branches
supply the skin over the shoulder region
These nerves are important clinically, because
pain may be referred along them from the
phrenic nerve (gallbladder disease)
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Prevertebral muscles, sternocleidomastoid
(proprioceptive, C2 and 3), levator scapulae
(C3 and 4), and trapezius (proprioceptive, C3
and 4)
A branch from C1 joins the hypoglossal nerve
Some of these C1 fibers later leave the
hypoglossal as the descending branch, which
unites with the descending cervical nerve (C2
and 3), to form the ansa cervicalis
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The first, second, and third cervical nerve fibers
within the ansa cervicalis supply the
omohyoid, sternohyoid, and sternothyroid
muscles
Other C1 fibers within the hypoglossal nerve
leave it as the nerve to the thyrohyoid and
geniohyoid
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It arises in the neck from the third, fourth, and
fifth cervical nerves of the cervical plexus
It runs vertically downward across the front of
the scalenus anterior muscle
Enters the thorax by passing in front of the
subclavian artery
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The phrenic nerve is the only motor nerve
supply to the diaphragm
It also sends sensory branches to the
pericardium, the mediastinal parietal pleura,
and the pleura and peritoneum covering the
upper and lower surfaces of the central part of
the diaphragm