Axial Skeleton: Vertebrae and Thorax Function of the vertebral column (spine or backbone): 1) 2) 3) Composition of Vertebral column The vertebral column is formed by 33 individual vertebrae (some of which are fused): cervical vertebrae thoracic vertebrae lumbar vertebrae one sacrum formed by fusion of 5 sacral vertebrae one (or two) coccyx formed by fusion of (usually) 4 coccygeal vertebrae Curvature Function The four curves function to: Abnormal Spinal Curvatures Scoliosis- Kyphosis- 1
Lordosis- Structures of the vertebrae A typical vertebra has the following structural features: i.body ii. vertebral arch, which consists of: a. two pedicles b. two laminae iii.7 processes: a. two transverse processes b. one spinous process (spine) c. two superior articular processes with facets d. two inferior articular processes with facets Vertebrae Common Features: body (centrum)- vertebral arch- pedicle- lamina- vertebral foramen- transverse processes- spinous process- superior & inferior articular processes- As a consequence of the above structural features, each vertebra has a 2
There are unique structural features in each of the vertebrae in the cervical (e.g., atlas, axis), thoracic, and lumbar regions of the spine A typical vertebrae consists of two essential parts: Anterior- Posterior- The vertebral arch consists a pair of pedicles & laminae vertebral arch supports seven processes 4 articular, 2 transverse, 1 spinous When the vertebrae are articulated w/ each other the bodies form support for head & trunk vertebral foramina form a canal for spinal cord Between every pair of vertebrae are 2 holes: the intervertebral foramina, one on either side, for the transmission of the spinal nerves & blood vessels Differences between vertebrae: Atlas: Axis- Cervical Thoracic Lumbar Cervical Vertebrae- C1 - C7 neck region of spine 1st two cervical vertebrae have important functions: C1 (Atlas) -has no body - 3
- C2 (Axis) -- - - Cervical Vertebrae- C1 - C7 *spinous processes- short & divided into 2 branches *transverse processes contain foramina (unlike thoracic & lumbar) Thoracic Vertebrae- T1 - T12 larger than cervical vertebrae body - -has 2 costal facets (articulating surfaces) spinous process- - lever for muscle attachment transverse process- vertebral foramen- intervertebral foramina- decreases incidence of nerve compression range of motion- limited because of rib articulations & long spinous processes 4
Lumbar Vertebrae- L1 - L5 5 unfused larger vertebrae support most of the weight of the body body- blocklike, massive bean shape spinous process- horizontal points straight back vertebral foramen- pedicles- intervertebral foramina- nerve compression is more common Sacrum- 5 fused vertebrae articulations: 1. superiorly with L5 2. inferiorly with coccyx 3. ala with coxal bone (ilium) (sacroiliac joint)-forms posterior wall of pelvis median sacral crest- formed by fused spinous processes sacral canal- canal continues inside vertebral canal terminates via a larger opening Sacral hiatus-large opening vertebral canal posterior sacral foramina- nerves pass thru 5
Coccyx Bony Thorax protects thoracic cavity: heart & lungs Sternum- Manubrium Body Xiphoid Process Ribs- 12 pairs typical ribs #3-9 head- 2 facets seperated by a crest articulates with: neck- connects head to shaft shaft- thin, flat, curved Bones of the Rib cage ( thorax) The skeletal portion of the thorax (chest) is a cage formed by several bones. The thoracic cage surrounds and protects organs in the thoracic cavity and upper abdominal cavity as well as providing support for the bones of the pectoral girdles and upper limbs. Sternum, which consists of (three) major regions and major surface markings: a. (upper portion) b. (main portion) c. (lower portion) Other structures: costal notches which occur where the costal cartilage attaches jugular notch formed at the superior end of the manubrium clavicular notch where the clavicle articulates 6
The ribs The rib cage has 12 pairs of ribs, each pair attached posteriorly to the thoracic vertebra. Anteriorly, the first 7 pairs are attached to the sternum by individual costal cartilage. These ribs are known as The remaining 5 pairs ( ribs 8,9,10, 11 & 12) are known as Because the last 2 pairs (11& 12 ) do not attach at all to the sternum they are called Ribs articulations- True Ribs- superior seven rib pairs False Ribs- inferior five rib pairs - Floating Ribs- inferior two rib pairs Rib Structures: 1) neck- 2) angle 3) body- 4) head - 5) tubercle- 7