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

Origin:  Inferior half of nuchal ligament and spinous processes of superior 6 thoracic vertebrae Insertion:  Lateral aspect of mastoid process and lateral third of superior nuchal line Action:  Laterally flexes and rotates head and neck to same side, extend head and neck

 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, and 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