1. Vertebral Column/Thoracic Cage
Chapter 7
Vertebral Column/Thoracic Cage

2. Vertebral Column Location: General Structure: Functions:
Forms the vertical axis of the skeleton
General Structure:
Composed of vertebrae
Vertenrae are separated by masses of fibrocartilage called intervertebral discs
Each intervertebral disc is connected to one another by ligaments
Functions:
Supports the head and trunk
Protects the spinal cord, which passes through the vertebral canal (formed by openings in the vertebrae)

3. Vertebral Column Number of bones in an infant skeleton:
Number of bones in an adult skeleton:
26 bones
Five bones are fused into the sacrum
Four bones are fused to form the coccyx (tailbone)

4. Vertebral Column Curvatures: Thoracic curvature Sacral curvature
Concave anteriorly
Primary curve
Sacral curvature
Cervical curvature
Convex anteriorly
Secondary curve
Develops when a baby begins to hold up its head
Lumbar curvature
Secondary curvature
Develops when a child begins to stand

5. Typical Verterbra Body Drum-shaped
Forms the thick, anterior portion of the bone
Longitudinal rows of bodies support the weight of the head and trunk

6. Typical Vertebrae Intervertebral discs Separate adjacent vertebrae
Fastened to the roughened upper and lower surfaces of the vertebral bodies
Soften forces (such as from walking and jumping) that might fracture the vertebrae or injure the brain

7. Typical Vertebra Anterior longitudinal ligaments
Join adjacent vertebrae on the anterior surface
Posterior longitudinal ligaments
Join adjacent vertebrae on the posterior surface

8. Typical Vertebrae Vertebral Foramen
Opening through which the spinal cord passes

9. Typical Vertebrae Vertebral Arch Surrounds the vertebral foramen
Formed by:
Pedicles
Two short stalks that project posteriorly from each vertebral body to form the sides of the vertebral foramen
Spinous process
Posterior projection formed by the fusion of two plates called laminae
Serves as an attachment for various ligament sand muscles

10. Typical Vertebrae Transverse process
Projects laterally and posteriorly between the pedicles and laminae
Serves as an attachment for various ligament sand muscles

11. Typical Vertebrae Superior articulating process
Projects upward from each vertebral arch
Has cartilage-covered facets by which each vertebrae is joined to the one above it
Inferior articulating process
Projects downward from each vertebral arch

12. Typical Vertebrae Intervertebral foramina
Formed by aligning notches on the lower surfaces of the vertebral pedicles
Provide passageways for spinal nerves that pass between adjacent vertebrae and connect to the spinal cord

13. Cervical Vertebrae Seven vertebrae that form the neck
Smallest of the vertebrae
Have the densest bone tissues

14. Cervical Vertebrae Special features:
Transverse processes have transverse foramina, which serve as passageways for arteries leading to the brain
Spinous processes of the 2nd through 6th cervical vertebrae are forked (bifid) to provide attachments for muscles
Spinous process of the 7th cervical vertebra is longer and called the vertebra prominens

15. Cervical Vertebrae
1st cervical vertebra is called the atlas and supports the head
Hardly has a body or spine
Appears as a bony ring with two transverse processes
Has two kidney-shaped facets on its superior surface that articulate with the occipital condyles
2nd cervical vertebra is called the axis
Has a toothlike process called the dens, or odontoid process that projects upward and into the ring of the atlas
As the head turns from side to side the atlas pivots around the dens

16. Thoracic Vertebrae 12 vertebrae below the cervical vertebrae
Special features:
Transverse processes project posteriorly at sharp angles
Spinous processes are long and pointed and slope downward
Bodies have facets on each side that articulate with ribs
Beginning with the third thoracic vertebra, each vertebra increases in size to bear the increasing load of body weight

17. Lumbar Vertebrae 5 vertebrae in the small of the back Special Features
Have larger and stronger bodies than vertebrae above them as they have to support more weight
Have thinner transverse processes that project laterally
Have short thick spinous processes that project posteriorly and nearly horizontally

18. Sacrum
Consists of 5 vertebrae that gradually fuse together between the ages of 18 and 30
Forms the posterior wall of the pelvic cavity

19. Sacrum Special Features:
Spinous processes are fused to form a ridge of tubercules called the median sacral crest
Joined to the coxae of the pelvis at its auricular surfaces by fibrocartilage of the sacroiliac joints
The upper anterior margin of the sacrum (or the first sacral vertebra) is called the sacral promontory
Posterior sacral foramina are located to the sides of the tubercules and allow nerves and blood vessels to pass through
Vertebral foramina of the sacral vertebrae form the sacral canal which opens at the tip of the sacrum (called the sacral hiatus)
Opening exists because the laminae of the last sacral vertebrae are not fused
Four pairs of anterior sacral foramina are located on the ventral surface and allow passageways for nerves and blood vessels

20. Coccyx
Tailbone
Usually consists of 4 vertebrae that fuse by the 25th year.
Cushions the force of sitting
Attached to the margins of the sacral hiatus by ligaments

21. Thoracic Cage
Includes the ribs, the thoracic vertebrae, the sternum, and the costal cartilages (attach ribs to sternum)
Functions:
Support the shoulder girdle and upper limbs
Protect the viscera in the thoracic and abdominal cavities
Play a role in breathing

22. Ribs
Usual number is 24 (one pair attached to each of the 12 thoracic vertebrae)
Some people can develop extra ribs associated with the cervical or lumbar vertbrae
True ribs (vertebrosternal ribs)
First seven rib pairs
Join the sternum directly by costal cartilage
False ribs (vertebrochondral ribs)
Remaining five pairs
Cartilages of the upper three pairs of false ribs join the cartilage of the 7th rib
The last two pairs have no attachment to the sternum, so they are called floating ribs (or vertebral ribs)

23. Ribs
A typical rib has a long slender shaft which curves around the chest and slope downward
An enlarged head is located at the posterior end and articulates with a facet on the body of its own vertebra and the next highest vertebra
Neck of the rib is flattened, lateral to the head, where ligaments attach
A tubercle that is close to the head of the rib articulates with the transverse process of the vertebra

24. Ribs
Costal cartilages are composed of hyaline cartilage and are attached to the anterior ends of the ribs (and contour in line with them toward the sternum)

25. Sternum
Breastbone
Flat elongated bone located along the midline in the anterior portion of the thoracic cage
Develops in three parts:
An upper manubrium
The manubrium usually remains as a separate bone until middle age or later when it fuses to the body of the sternum
A middle body
A lower xyphiod process that projects downward
The xiphoid process begins as a piece of cartilage, slowly ossifies, and fuses to the body of the sternum by middle age
The sides of the manubrium and the body are notched where they articulate with costal cartilage
The manubrium also articulates with the clavicles by facets on its superior border