BONES OF THE SPINE

Introductory Information

• The spine is a stack of 3333 bones called vertebra held together by ligaments and muscles.

• Between each vertebra, there is a fibrocartilage discdisc, which is made mostly of protein and water.

The bones are divided into 5 sections:

• CervicalCervical Spine Spine = the most superior group, a.k.a. the neck; contains 7 vertebrae

• ThoracicThoracic Spine Spine = the chest; contains 12 vertebrae

• LumbarLumbar Spine Spine = the low-back; contains 5 vertebrae

• SacralSacral Spine Spine = Contains 5 vertebrae which are fused together into one structure called the sacrum.

• CoccygealCoccygeal Spine Spine = Contains 4 vertebrae which are fused together into one structure called the coccyx (that’s your tailbone)

Spinal Curvatures:• When viewed laterally, the

spine has 44 curvatures:

• An anterior, or convex, curve called a lordosis is seen in the cervicalcervical and lumbarlumbar spine.

• A posterior, or concave, curve called a kyphosiskyphosis is seen in the thoracicthoracic and sacro-coccygeal spine.

Spinal Curvatures:

• What can cause an increase or decrease in the spinal curvature?

• It depends on shifts in the body’s center of gravity (e.g. with pregnancy, weight gain, weight loss, or trauma).

• Function of the spinal column = to maintain the body in an upright position with the brain located over the body’s center of gravity.

Bones of the Spinal Column

• All vertebrae have: 1.1. A vertebral bodybody.

2.2. 2 Transverse ProcessesTransverse Processes (TP)= lateral bony projections that serve as a source for ligamentous and muscular attachment.

3.3. Spinous ProcessSpinous Process (SP) = a posterior bony process that serves as a source of ligamentous and muscular attachment.

4.4. Vertebral ForamenVertebral Foramen = where the spinal cord and nerve roots pass.

Bones of the Spinal Column

5.5. Superior and inferior articulating facetsarticulating facets = where the vertebra articulates with the vertebrae above and below.

6.6. LaminaLamina = forms the posterior portion of the vertebral foramen.

7.7. PediclesPedicles = form the lateral sides of the vertebral foramen.

8.8. Intervertebral ForamenIntervertebral Foramen (IVF) = located between each vertebra and allows the nerve branches from the spine to pass through.

9.9. Pars InterarticularisPars Interarticularis = the bony area between the superior and inferior articulating facets

Bones of the Spinal Column

Cervical Vertebrae:• How many cervical vertebrae are

there?

• There are 7, numbered from top to bottom (C1-C7).

• What do all cervical vertebrae have?

1. A bifid (split) spinous process

2. A transverse process foramen

• What passes through the foramen?

• The blood vessels for the cervical spine (particularly the Vertebral Artery)

Cervical Vertebrae:• AtlasAtlas = the 1st cervical vertebra

• Has no vertebral bodybody.

• Has 2 large articular facets that provide a surface where the skullskull and the spinal column articulate.

Cervical Vertebrae:• AxisAxis = the 2nd cervical vertebra

• The atlas slides over the axis, and rests on 2 large superior articulating surfaces.

• DensDens (a.k.a. Odontoid Process) = a large bony process between the 2 articular surfaces of the axis.

• C77 = has a very long spinous process (most easily palpated).

Thoracic Vertebrae:• How many thoracic vertebrae are

there?

• There are 12.

• What is special about the SP’s of Thoracic Vertebrae?

• Thoracic vertebrae have longer and more vertically inclined spinous processes.

Costal FacetsCostal Facets = articulating surfaces on the anterior lateral aspects of the transverse processes and the superior and inferior portions of the posterior lateral aspects of the vertebral bodies that provide the articulation for the 12 pairs of ribs with the 12 thoracic vertebrae.

Lumbar Vertebrae:• How many lumbar vertebrae

are there?

• There are 5.

• What is special about them?

• They are the largest vertebrae.

• What do lumbar vertebrae not have?

• They have no transverse process foramen or costal facets on their bodies.

Sacral Vertebrae:• The 55 sacral vertebrae are separate at birth.

• The bones eventually fuse together to form a large triangular-shaped bone known as the sacrumsacrum.

• The 2 large articular surfaces formed on the lateral aspects of the sacrum are where the spinal columncolumn articulates with the bones of the pelvispelvis.

Coccygeal Spine:

• The 44 coccygeal vertebrae are separate at birth.

• The bones eventually fuse together to form the coccyxcoccyx, a.k.a. your tailbonetailbone.

The Intervertebral Disc (IVD)

• The IVD is a cartilaginous disc made of mostly water and protein.

• There is one disc between each pair of vertebrae (except for C1 and the skull, and any of the sacral or coccygeal vertebrae).

• Purpose:

1. A spacer to allow nerve roots to pass from the spinal column to other body structures.

2. Shock absorption for the spinal column.

• Parts of the Disc:

• Nucleus Pulposus = the inner portion of the disc; consists of soft, pulpy, elastic tissue.

• Annulus Fibrosis = the other portion of the disc; cosists of fibrous tissue.

• Parts of the Disc:• Nucleus Pulposus = the inner portion of

the disc; consists of soft, pulpy, elastic tissue.

• Annulus Fibrosis = the other portion of the disc; consists of fibrous tissue.

The Intervertebral Disc (IVD)