About This File
The dorsal (thoracic) spine forms the middle portion of the vertebral column extending below the seventh cervical vertebra to above the first lumbar vertebra. The dorsal spine is formed by twelve vertebral bodies. The vertebrae forming the dorsal spine are unique in shape as they are the only vertebral bodies articulating with ribs.
The lumbar spine represents the mid-lower segment of the vertebral column and is composed of five adjacent vertebrae. They are convex anteriorly to form a lumbar lordosis. The lumbar spine facet joints allows limited movements and rotation.
The sacrum is the lower most segment of the vertebral column and also forms the posterior wall of the bony pelvis. The sacrum is formed by five fused sacral vertebrae.The sacrum is formed by fusion of five sacral vertebrae has three surfaces, a base and an apex. The body of the first segment is large and is similar to lumbar vertebra whereas the bodies of the next bones get progressively smaller, are flattened from the back, and curved to shape.
The sacrum articulates with four other bones – iliac bones on either side, L5 above and coccyx below. It is tilted forward and curved with anterior concavity and posterior convexity allowing greater room for pelvic cavity. The curvature of sacrum varies in individuals.
This model shows segment of the heart, the aorta and sacro-iliac joints.