Dr. Mujahid Khan

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

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

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

Related to the vertebral artery and vein and the sympathetic trunk

On the left side, the medial border is related to the thoracic duct

Related to the emerging branches of the cervical plexus, the roots of the brachial plexus, and the third part of the subclavian artery

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

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

Origin: Transverse processes of lower cervical

vertebrae

Insertion: Second rib

Action: Elevates second rib, laterally flexes and

rotates cervical part of vertebral column

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

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

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

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) 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)

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

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

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

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