Axial Skeleton- Spine and Thoracic Cage

VERTEBRAL COLUMN (26 bones) Extends from the skull to the pelvis and forms the vertical axis of the human skeleton. The column is composed of many vertebrae, which are separated from one another by cartilaginous intervertebral disks and are held together by ligaments. Its function is to protect your spinal cord. The curvature of the spine helps it to absorb shock and pressure much better than if the spine were straight. This curvature also provides better balance by better distributing the weight of the skull over the pelvic bones.

A typical vertebra has: -body- the thick anterior portion of the vertebrae which supports the weight -pedicles- stalk of vertebra posterior to body -spinous process- most posterior process to which muscles attach -transverse process- extends laterally and provides an attachment point for muscles -superior articular process- articulate with a superior vertebra and function to resist twisting of the spine -vertebral arch- a bony ring made by the pedicles and spinous process which forms the vertebral foramen through which the spinal cord passes

Cervical vertebrae (7) -#1 is called the atlas- distinct in that it lacks a spine and body. It articulates with the skull at a joint that allows the head to nod yes. -#2 is called the axis- it is distinct in that it lacks a spine and contains a modified body (the dens) which rotates with the atlas at a joint allowing the head to nod no. -cervical vertebrae are smaller than other vertebrae, and are the only vertebrae that contain transverse foramina, through which pass vertebral arteries and veins.

Thoracic vertebrae (12) -Contain rib facets which are articular surfaces for ribs. Their spines are longer than cervical vertebrae and their bodies are larger.

Lumbar Vertebrae (5) Bodies are the heaviest and largest of the vertebrae, they lack transverse foramina and rib facets.

Sacrum (1) -Composed of 5 fused vertebrae. -Note the sacral foramina, through which nerves and blood vessels pass. -Many nerves pass through the sacral canal and sacral hiatus.

Coccyx (1) -composed of 4 fused vertebrae

THORACIC CAGE (25 bones) Surrounds the thoracic and upper abdominal cavities The rib cage is essential for protecting your heart and lung, providing a place for your shoulder bones to attach, and it aids in the breathing process.

THORACIC CAGE (25 bones) Ribs (24) -True ribs- upper 7 pairs, attach directly to the sternum through their costal cartilage -False ribs- pairs 8-12, do not attach directly to the sternum -Floating ribs- pairs 11-12, no cartilaginous attachments to the sternum

THORACIC CAGE (25 bones) Sternum or breastbone (1 bone) -manubrium- superior portion -body- middle portion -xiphoid process- inferior portion that projects downward