Muscles of the Neck

The cutaneous muscle is absent in the region of the neck. The cervical muscles of neck may be divided into two groups- ventral cervical and lateral cervical

Ventral cervical group

These muscles lie below and lateral to the cervical vertebrae and are for the most part found around the trachea. They are

1. Sterno-cephalicus
2. Sterno-thyro-hyoideus
3. Omo-hyoideus
4. Scalenus
5. Rectus capitis ventralis major (Longus capitis)
6. Rectus capitis ventralis minor (Rectus capitis ventralis)
7. Rectus capitis lateralis
8. Intertransversales colli (Intertransversari cervicis)
9. Longus colli

Sterno-cephalicus

• This muscle consists of two divisions -sterno-mandibularis and sterno-mastoideus.
• Origin: 
  • The two divisions arise together from the manubrium sterni and first costal cartilage.
  • On either side the muscles are very close together at their origin and at the lower third of the neck and from the middle of the neck, they diverge.
  • The sterno-mandibularis is the superficial division and it forms the lower boundary of the jugular furrow.
  • The deep division is the sterno-mastoideus.
  • It covers the oesophagus, trachea, and carotid structures and crosses under the superficial division at the upper third of the neck.
• Insertion:Superficial division is inserted to the anterior border of the masseter muscle and the angle of the jaw; the deep division is common with the rectus capitis ventralis major to the mastoid process, and the basilar tubercles.
• Action: Together to flex the head and the neck and acting singly to incline head and neck laterally.
• Blood supply: Common carotid artery.
• Nerve supply: Spinal accessory nerve.

Sterno-thyro-hyoideus

• This is a long, slender muscle situated on the ventral face of the trachea.
• Origin: Manubrium sterni.
  • The two side muscles are very close together at their origin and cover trachea at the lower third of the neck. About the middle of the neck, each muscles divide into two bands-the thyroid and hyoid bands which diverge from those of the opposite side from the upper third of the neck. Hence in the upper third of the neck, the ventral face of the trachea is not covered by any muscle. The thyroid band is the larger and the lateral of the two bands.
• Insertion:Thyroid band is inserted to the thyroid cartilage of the larynx and the hyoid band to the body of the hyoid and lingual process.
• Action: To depress the hyoid, larynx, and tongue during deglutition .
• Blood supply: Carotid artery.
• Nerve supply: First and second cervical spinal nerves .

Omo-hyoideus

• This is small triangular muscle extending from the neck at its ventro-lateral aspect in an oblique direction upward and forward to the hyoid bone.
• Origin: Transverse processes of the third and fourth cervical vertebrae.
  • This muscle passes under the deep face of the brachio-cephalicus and sterno-mastoideus obliquely forwards and inwards laterally over the sterno-mastoideus or passes through the latter and passes forwards in company with the hyoid band of the sterno-thyro-hyoideus.
• Insertion:Body of the hyoid bone.
• Action: To retract the hyoid and root of the tongue.
• Blood supply: Carotid artery.
• Nerve supply:  Second cervical spinal nerve.

Scalenus

• This muscle is situated partly in the posterior part of the cervical region and partly on the antero-lateral part of the thorax. It is made up of two division-dorsal and ventral between which emerge the roots of the brachial plexus.
• Origin:
  • The dorsal part-scalenus dorsalis arises from the transverse processes of the fourth to the seventh cervical vertebrae.
  • The ventral part- scalenus ventralis arises from the transverse processes of the fourth to the sixth cervical vertebrae.
  • The dorsal part is covered by the serratus thoracis.
  • The roots of the phrenic nerves traverse the ventral part. The brachial vessels cross its ventral edge.
• Insertion:The dorsal part into the fourth rib; ventral part to the anterior border of the first rib.
• Action: To flex the neck or incline it laterally. If the neck is fixed, acts as an inspiratory muscle.
• Blood supply: Vertebral and intercostal arteries.
• Nerve supply: Cervical spinal nerves.

Rectus capitis ventralis major (Longus capitis)

• This muscle extends from the neck to the basi occipital.
• Origin: Transverse processes of the 2 nd to 6 th vertebrae.
• Insertion:Basilar tubercle.
• Action: To flex the head or incline it laterally.
• Blood supply: Vertebral and occipital arteries.
• Nerve supply: Cervical spinal nerves.

Rectus capitis ventralis minor (Rectus capitis ventralis)

• This is a small muscle placed partly above, partly below and external to the preceding (This muscle and the next should be examined in a median sagittal section of the head).
• Origin: Ventral surface of the exterior of the wing of atlas.
• Insertion:Basilar tubercle.
• Action: To flex the occipito-atlantal joint.
• Blood supply: Occipital artery.
• Nerve supply: First cervical spinal nerve.

Rectus capitis lateralis

• This is smaller than the preceding and is under the cover of obliquus capitis anterior.
• Origin: The atlas, lateral to the origin of the obliquus capitis anterior.
• Insertion:Paramastoid process.
• Action: To flex the occipito-atlantal joint.
• Blood supply: Occipital artery.
• Nerve supply: First cervical spinal nerve.

Intertransversales colli (Intertransversari cervicis)

• These are six in number. This occupies the space between the articular and transverse processes of the cervical vertebrae. In general, there is a muscle for each joint. Each muscle has dorsal and ventral parts. Origin and insertions are not recognized.
• Attachment: The dorsal bundles extend from the upper part of the transverse process to the anterior articular process of the preceding vertebra. The deeper part of the ventral bundles extends between the ventral parts of the transverse process. Their superficial fibres unite to form a long muscle-intertransversarius longus-whose anterior attachment is to the lateral border of atlas.
• Action: To flex the neck laterally.
• Blood supply: Vertebral artery.
• Nerve supply: Cervical spinal nerves except the first and the last.

Longus colli

• This is a long muscle extending from the sixth dorsal vertebra to the atlas. It is situated on the ventral aspect of the bodies closely applied against its fellow. It consists of thoracic and cervical parts.
• Origin: Bodies of the first six dorsal vertebrae to the medial surface of transverse process of the cervical vertebrae.
• Insertion:The thoracic part is inserted to the bodies and transverse processes of the last two cervical vertebrae. The cervical part is inserted to the bodies of the cervical vertebrae and the ventral tubercle of atlas.
• Action: To flex the neck.
• Blood supply: Subcostal and vertebral arteries.
• Nerve supply: Cervical and dorsal spinal nerves.

Lateral cervical group

These muscles lie lateral and dorsal to the cervical vertebrae and are arranged in superimposed layers. They are-

1. First layer
   • Trapezius cervicalis
   • Brachio-cephalicus
2. Second layer
   • Omo-transversarius
   • Rhomboideus cervicalis
3. Third layer
   • Serratus cervicis
4. Fourth layer
   • Splenius
   • Longissimus capitis et atlantis
   • Complexus (semispinalis capitis)
   • Multifidus cervicis (semispinalis of the neck)
   • Obliquus capitis anterior (obliquus capitis cranialis)
   • obliquus capitis posterior (obliquus capitis caudalis)
   • Rectus capitis dorsalis major
   • Rectus capitis dorsalis minor

First layer

Trapezius cervicalis

• It is a broad triangular muscle extending along the dorsal midline from the level of atlas to the end of the thoracic region, and covers a part of the shoulder. It consists of cervical and dorsal parts.
• Origin: Ligamentum nuchae and supraspinous ligament from the level of the atlas to the twelfth dorsal vertebra.
• Insertion:The tuberous part of the spine of the scapula and the scapular fascia.
• Action: To elevate the shoulder as a whole. The cervical part draws it forwards and the dorsal part backwards.
• Blood supply: Deep cervical, dorsal and intercostal arteries.
• Nerve supply: Spinal accessory nerve.

Brachio-cephalicus

• This muscle extends from the head, along the neck to the arm. Its upper border is in close apposition with the trapezius and the lower border forms the upper boundary of the jugular furrow. It consists of a dorsal part cleido-occipitalis and a ventral partcleido-mastoideus, the division being indicated by the position of exit of cutaneous branches of the ventral divisions of the cervical spinal nerves.
• Origin: Dorsal part – occipital bone, ligamentum nuchae. Ventral part – mastoid process, wing of atlas and the mandible.
• Insertion:The united portion of the two divisions is inserted along with the anterior superficial pectoral to the anterior edge of the humerus.
• Action: When the head and neck are fixed, to draw the limb forwards and extend the shoulder joint; when the limb is fixed, the two side muscles together extend the head and neck. Each side muscle acting by itself to incline the head and neck to its own side.
• Note: The deep face of the muscle receives at the lower part of the neck a small bright red fasciculus of muscle, which arises from the cartilage of the first rib. This is the vestige of subclavius of man.
• Blood supply: Inferior cervical, carotid and vertebral arteries.
• Nerve supply: Cervical spinal and axillary nerves.

Second layer 

Omo-transversarius

• This muscle extends from the level of the atlas to the shoulder and most part covered by the preceding muscle except at the scapular portion where it is seen as a broad, flat muscular band.
• Origin: Wing of atlas and transverse process of the axis.
• Insertion:Scapular spine and scapular fascia.
• Action: To pull the lower angle of the scapula forwards and upwards and to tense the scapular fascia.
• Blood supply: Superior and inferior cervical arteries.
• Nerve supply: Cervical spinal nerves.

Rhomboideus cervicalis

• This muscle extends from ninth to tenth dorsal vertebra to about the level of the middle of the funicular part of the ligamentum nuchae. It is under the cover of trapezius and consists of cervical (rhomboideus cervicalis) and dorsal (rhomboideus thoracalis) parts.
• Origin: Ligamentum nuchae, and the spines of dorsal vertebrae from the first to about seventh or eighth.
• Insertion:The medial surface of the cartilage of the scapula.
• Action: To draw the shoulder upwards and forwards.
• Blood supply: Superior cervical and dorsal arteries.
• Nerve supply: Fifth, sixth, seventh, eighth cervical spinal nerves.

Third layer

Serratus cervicis

• It is a large, thick muscle extends from the level of the second cervical vertebra to the fifth rib. The posterior part of this muscle is overlapped by the two anterior digitations of the succeeding. It lies partly on the neck and partly on the lateral wall of the thorax.
• Origin: From the transverse process of the second or third cervical vertebra to seventh cervical vertebra and the lateral face of ribs from first to the fifth rib.
• Insertion:The triangular rough area at the dorso-anterior part of the ventral surface of the scapula.
• Action: To pull the scapula towards the neck. Two side muscles acting together to extend the neck and singly inclines the neck to its own side.
• Blood supply: Superior cervical, dorsal and vertebral arteries.
• Nerve supply: Fourth, fifth and sixth cervical spinal nerves and long thoracic nerve.

Fourth layer

Splenius

• It is a triangular muscle.
• Origin: The summits of first three or four dorsal spines.
• Insertion:Occipital, transverse processes of the first three cervical vertebrae in common with the omo-transversarius, cleido-occipitalis and longissimus capitis et atlantis.
• Action: To elevate and extend the head and neck or incline towards the neck.
• Blood supply: Deep cervical artery.
• Nerve supply: Cervical spinal nerves except the first two.

Longissimus capitis et atlantis

• These are two parallel muscular bundles on the deep face of the splenius. The upper most medial part is longissimus capitis and is overlapped by the lower lateral part, the longissimus atlantis.
• Origin: Transverse process of the first two dorsal and the articular processes of the cervical vertebrae except the first two or three.
• Insertion:Mastoid process and wing of atlas.
• Action: Similar to preceding.
• Blood supply: Deep cervical and vertebral arteries.
• Nerve supply: Cervical spinal nerves except the first two.

Complexus (semispinalis capitis)

• This muscle is covered by the splenius and partly by the longissimus capitis et atlantis. It lies lateral to the ligamentum nuchae.
• Origin: Spines of the second, third and fourth dorsal vertebrae, transverse processes of the first ten dorsal vertebrae and articular processes of last five cervical vertebrae.
• Insertion:Occipital bone lateral to the insertion of ligamentum nuchae.
• Action: Chief extensor of the head and to incline it laterally.
• Blood supply: Deep cervical and occipital arteries.
• Nerve supply: Cervical spinal nerves.

Multifidus cervicis (semispinalis of the neck)

• This muscle is made up of oblique bundles, which are placed between the complexus and longissimus capitis et atlantis externally and the lamellar portion of the ligamentum nuchae and the superior division of the cervical portion of the longissimus dorsi internally. It lies over the first thoracic and last five cervical vertebrae.
• Origin: Posterior articular processes of the last five cervical.
• Insertion:Spines and posterior articular processes of preceding cervical vertebrae.
• Action: Extend the head or flex it laterally.
• Blood supply: Deep cervical and vertebral arteries.
• Nerve supply: Cervical spinal nerves, except the first two.

Obliquus capitis anterior (obliquus capitis cranialis)

• This is a quadrilateral muscle situated on the side of the occipito-atlantal joint.
• Origin: Interior edge and ventral surface of the wing of atlas.
• Insertion:Paramastoid and mastoid processes.
• Action: To extend the head on the atlas and flex the head to a side.
• Blood supply: Occipital artery.
• Nerve supply: First cervical spinal nerve.

Obliquus capitis posterior (obliquus capitis caudalis)

• It is thick, quadrilateral muscle situated chiefly over the wing of the atlas and axis.
• Origin: Posterior oblique process and spine of the axis.
• Insertion:Dorsal face of the wing of atlas.
• Action: Rotate the atlas and with it the head to one side.
• Blood supply: Occipital artery.
• Nerve supply: Second cervical spinal nerve.

Rectus capitis dorsalis major

• It is a narrow, elongated muscle lies under the complexus lateral to the funicular part of the ligamentum nuchae and extends from the axis to the occipital bone along the dorsal median line closely applied to the fellow of the opposite side .
• Origin: Spine of the axis.
• Insertion:Occipital bone, near the external occipital protuberance.
• Action: To extend the head.
• Blood supply: Occipital artery.
• Nerve supply: Second cervical spinal nerve.

Rectus capitis dorsalis minor

• This muscle is very small and lies under the preceding.
• Origin: Dorsal arch of the atlas.
• Insertion:Occipital bone between the external occipital protuberance and foramen magnum.
• Action: To assist the preceding.
• Blood supply: Occipital artery.
• Nerve supply: First cervical spinal nerve.