Understanding your spine and how it works can help you better understand some of the problems that occur from aging or injury.
Many demands are placed on your spine. It holds up your head, shoulders, and upper body. It gives you support to stand up straight, and gives you flexibility to bend and twist. It also protects your spinal cord.
2. Cervical Vertebrae
âĸ The cervical spine is much more mobile than the thoracic or lumbar
regions of the spine.
īą Typical Cervical Vertebra (C3-C7)
The bodies of these four vertebrae are small, and transverse diameter is greater than anterio-posterior and
height dimensions.
īą Atypical Cervical Vertebrae (C1-C2)
C1
ī§ The Atlas, C1, is the topmost vertebra, and along with the Axis; forms the joint connecting the skull and
spine.
ī§ Its chief peculiarity is that it has no body, and this is due to the fact that the body of the atlas has fused
with that of the Axis.
C2
ī§ The Axis, C2, forms the pivot upon which the Atlas rotates. The most distinctive characteristic of this
bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body.
ī§ The body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper
and front part of the third vertebra
3.
4. There are 26 muscles in the neck-10 pairs of 2 and 2 sets of 3,
to be precise.
- Sternocleidomastoid
- Scalene
- Platysma
- Digastric
- Omohyoid
- Sternohyoid
- Sternothyroid
- Mylohyoid
- Stylohyoid
- Geniohyoid
- Thyrohyoid
5. Sternocleidomastoid Muscle
īļOrigin: upper border of manubrium sterni and medial third of upper surface
of clavicle.
īļInsertion: mastoid process and lateral third of superior nuchal line.
īļNerve supply: Spinal accessory nerve (motor) and C2,3 (proprioceptive).
īļAction:
īŧBoth muscles extend the atlanto-occipital joint and flex the other cervical
intervertebral joints.
īŧOne muscle turns the head to make the face looks upward and to the
opposite side.
īŧOn fixation of the insertion, the muscle act as accessory muscle of inspiration
6.
7. Trapezius Muscle
īļOrigin: Medial third of superior nuchal line, external occipital protuberance,
ligamentum nuchal, 7th cervical spine all the thoracic spines.
īļInsertion: lateral third of clavicle, acromion process and spine of scapula.
īļNerve supply: Spinal accessory nerve (motor) and C3,4 (proprioceptive).
īļAction:
īŧ muscles extend the neck.
īŧ Upper fibers of one side lateral flex the neck.
īŧ Upper fibers elevate the shoulder.
īŧ Middle fibers retract the shoulder.
īŧ Lower fibers depress the shoulder.
8.
9. Platysma Muscle
īļOrigin: deep fascia of the upper part of
thorax (covering pectoralismajor and
deltoid).
īļInsertion: lower border of the mandible.
Mentalis
Depressor labii inferioris
Depressor anguli oris
īļNerve supply: Cervical branch of facial
nerve.
īļAction: Depression of the mandible.
10.
11. Splenius Capitis Muscle
īļOrigin:
1.Lower part of ligamentum nuchae.
2.Upper four thoracic spines.
īļInsertion: mastoid process and outer part of
superior nuchal line.
īļNerve supply: segmental innervation from the
dorsal rami of spinal nerves
īļAction: Extension of the neck.
12.
13. Levator scapulae muscle
īļOrigin: Transverse processes of upper four cervical vertebrae.
īļInsertion: Upper part of medial border of scapula.
īļNerve supply: C3,4 and dorsal scapular nerve (C5).
īļAction: Elevation of scapula.
14. Scalenus Medius Muscle
īļOrigin: Transverse processes of
lower six cervical vertebrae (2-7).
īļInsertion: Upper surface of the
first rib.
īļNerve supply: Segmental from
the ventral rami of cervical
nerves.
īļAction: Elevation of first rib and
lateral flexion the neck.
15. Scalenus anterior muscle
īļOrigin: Transverse processes of typical
cervical vertebrae (3-6).
īļInsertion: Scalene tubercle of the first
rib.
īļNerve supply: Segmental from the
ventral rami of 4th, 5thand 6thcervical
nerves.
īļAction: Elevation of first rib and lateral
flexion the neck
16. Thoracic Spine
âĸ 12 thoracic vertebra
âĸ Vertebral body is heart shaped.
âĸ Presence of demi-facets on the sides of each vertebral body â these
articulate with the heads of the ribs
âĸ Presence of costal facets on the transverse processes â these articulate with
the tubercles of the ribs. They are present on T1-T10 only.
âĸ The spinous processes are long
âĸ The superior facet articulates with the head of the adjacent rib, and the
inferior facet articulates with the head of the rib below
âĸ T2- T9 is a typical vertebra these facets are demi-facets.
17. Atypical Vertebra
ī§ T1 â Superior facet is not a demi facet, as this is the only vertebrae
to articulate with the 1st rib.
ī§ T10 â A single pair of whole facets is present which articulate with
the 10th rib. These facets are located across both the vertebral
body and the pedicle.
ī§ T11 and T12 â Each have a single pair of entire costal facets,
which are located on the pedicles.