Scalenus Anterior
Origin: From the transverse processes of the 3rd; 4th ; 5th and 6th cervical vertebrae.
Insertion: Into the scalene tubercle on the inner border of the 1st rib and into the ridge on the
upper surface of the 1st rib.
Nerve Supply: From the anterior rami of the 4th; 5th and 6th cervical nerves.
Action: It assists in elevation the 1st rib. When acting from below, it laterally flexes the
cervical part of the vertebral column.
Relation of scalenus anterior muscle
Anteriorly:
The prevertebral layer of deep cervical
fascia, which binds the phrenic nerve
down to the anterior surface of the
muscle; the superficial cervical and
suprascapular arteries which cross the
phrenic nerve; and the internal jugular
and subclavian veins.
Posteriorly:
The subcalvian artery; brachial plexus
and the cervical dome of the pleura.
Medially:
The vertebral artery&vein; inferior thyroid
artery; thyrocervical trunk; sympathetic
trunk and on the left side, thoracic duct.
Laterally:
The roots of the phrenic nerve unite at the
lateral border of the muscle at the level of
the cricoid cartilage. Then it descends on
its anterior surface. The roots of the
brachial plexus & subclavian artery
emerge from behind the lateral border of
it to enter the posterior triangle of neck.
Scalenus Medius
Origin: From the transverse processes of the upper six cervical vertebrae.
Insertion: Into the upper surface of the 1st rib behind the groove for the subclavian artery.
It lies behind the roots of the brachial plexus and behind the subclavian artery.
Nerve Supply: Branches from the anterior rami of the cervical nerves.
Action: like scalenus anterior.
Scalenus Posterior
Origin: From the transverse processes of the lower cervical vertebrae.
Insertion: Into the outer surface of the second rib.
Nerve supply: branches from the anterior rami of the lower cervical nerves.
Action: Elevates the 2nd rib. When active from below, it laterally flexes the cervical part of
the vertebral column.
4
3
2
1
Anterior vertebral ( prevertebral ) muscles
1- Longus coli.
2- Longus capitis.
3- Rectus capitus anterior.
4- Rectus capitus lateralis.
Origin:
Anterior tubercle of C1, bodies of C1 to C3 and 
transverse processes of C3 to C6 vertebrae
Insertion:
Bodies of C5 to T3 vertebrae, transverse processes of 
C3 to C5 vertebrae
Action:
Flexes neck with rotation to opposite side 
Origin:
Basilar part of occipital bone 
Insertion:
Anterior tubercles of C3 to C6 transverse 
processes
Action:
Flexes the head 
Origin:
Base of the skull, just anterior to the 
occipital condyle
Insertion:
Anterior surface of lateral mass of atlas 
Action:
Flexes the head 
Origin:
Jugular process of occipital bone 
Insertion:
Transverse process of atlas 
Action:
Flexes head and helps stabilize it 
Scaleno-vertebral triangle
Its boundaries are the Longus colli ; scalenus anterior and the transverse
process of 6th cervical vertebra.
It contains 1st part of subclavian artery ; sympathetic chain ; vertebral
artery and the thoracic duct ( on left side ).
Cervical plexus
It is formed by anterior rami of
1, 2, 3 ; 4 cervical
nerves.
The rami are joined by
connecting branches forming a
loops on the levator scapulae
and scalenus medius
muscles.
It is covered by the prevertebral
fascia. It is related to the
internal jugular vein within the
carotid sheath.
C2
Branches:
1- Cutaneous
lesser occipital; greater
auricular; transverse cutaneous
and supraclavicular nerves.
2- Phrenic nerve to the diaphragm
2- Muscular
- Prevertebral muscles
•
- Sternocleidomastoid (C2 & C3
as proprioceptive ).
- Levator scapule (C3&C4motor•
- Trapezius ( C3 & C4 as
•
proprioceptive ).
- A branch of C1 joins the
•
hypoglossal nerve then it
leaves it to supply the
thyrohoid & geniohyoid.
- Some of C1 fibers
•
(descending branch) unites with
the descending cervical nerves
of C2& C3 to form the ansa
cervicalis which supplies
omohyoid; sternohyoid and
sternothyroid muscles.
Phrenic Nerve
It arises from the 3rd ; 4th and 5th cervical nerves of cervical plexus.
It runs vertically downward acrosses the front of the scalenus anterior from its
lateral to medial border behind the prevertebral layer of deep cervical fascia.
It enters the thorax by passing in front of the subclavian artery and behind the
beginning of the brachiocephalic vein.
Relations
Anteriorly:
The prevertebral layer of the deep fascia; internal jugular vein; superficial cervical
and suprascapular arteries; beginning of the brachiocephalic vein and on the left
side the thoracic duct.
Posteriorly:
The scalenus anterior; subclavian artery and the cervical dome of pleura.
Branches:
1- It is the only motor nerve supply to the diaphragm.
2- It contains sympathetic fibers.
3- It contains proprioceptive sensory fibers ( stimulation of the sensory nerve
ending in the muscles& tendons and joints ) for the muscles of the diaphragm.
4- It contains sensory fibers for the mediastinal pleura and the pericardium.
5- It contains Sensory fibers for the pleura & peritoneum covering the upper and
lower surfaces of the central part of the diaphragm.