VAN 121: Veterinary Gross Anatomy-II (2+2)

LATERAL CERVICAL GROUP

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

• First layer
  • Trapezius cervicalis
  • Brachio-cephalicus
• Second layer
  • Omo-transversarius
  • Rhomboideus cervicalis
• Third layer
  • Serratus cervicis
• 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

( View the lateral neck region )

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 ( View the first layer of Lateral neck muscles )

• 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 part cleido-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.

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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.

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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.

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Fourth layer  ( View the lateral neck muscles )

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.

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