Skeletal System
The skeleton functions to allow for limb movement, locomotion, muscle attachment and leverage points and structural support via a symphony of 206 bones; flat, irregular, long and short. Flat bones are thin, leveled and typically curved, irregular bones are not even or balanced in shape, long bones are longer than they are wide (ex: humerus, femur), and short bones have approximately equal dimensions. Specific landmarks of bone are often referenced during surgery (foramen, lamina, pedicle, posterior fossa, lamina, sphenoid, etcetera.)
The skeleton is separated into two types: The medial axis of the body is known as the Axial Skeleton;
The hyoid bone, ossicles of the ear, ribs, skull, sternum and vertebral column are part of the axial skeleton.
The bones of the the Appendicular Skeleton attach to the axial skeleton; the upper extremities (humerus, radius, ulna, bones of the wrist and hand, manubrium, sternum, xiphoid process, 12 ribs (7 true and 5 false (floating)) and the pectoral girdles (clavicles and scapulae), and the lower extremities (femur, tibia, fibula, bones of the talus and metatarsals) and the pelvic girdle (ilium, ischium and pubic bone).
The hyoid bone, ossicles of the ear, ribs, skull, sternum and vertebral column are part of the axial skeleton.
The bones of the the Appendicular Skeleton attach to the axial skeleton; the upper extremities (humerus, radius, ulna, bones of the wrist and hand, manubrium, sternum, xiphoid process, 12 ribs (7 true and 5 false (floating)) and the pectoral girdles (clavicles and scapulae), and the lower extremities (femur, tibia, fibula, bones of the talus and metatarsals) and the pelvic girdle (ilium, ischium and pubic bone).
The spine has 33 stacked vertebrae bones that structurally support the spinal cord and form the spinal canal. A typical vertebrae has a posterior and medial spinous process, lamina positioned laterally on either side of the spinous process which is adjacent to the vertebral canal which houses the spinal cord, a body which is a large portion positioned anteriorly, an articular process to articulate with vertebrae positioned superiorly and inferiorly and a process on the thoracic vertebrae specifically for articulation with the ribs/a costal facet.
- 7 Cervical (Neck) (Moveable/Flexible Vertebrae)
- 12 Thoracic (Moveable/Flexible Vertebrae)
- 5 Lumbar (Moveable/Flexible Vertebrae)
- 5 Sacral (Fused/Immoveable)
- 4 Coccyx (Fused/Immoveable)
Cervical, thoracic, lumbar, sacral and coccygeal vertebrae all have characteristics that are both similar and individual characteristics that make them unique. It is imperative to understand the fundamental anatomy of the vertebral bodies and how they relate to the functional surgery of the patient.
- C1/Atlas - articulates with the occipital bone at the foramen magnum and with C2. It's characteristic is that it is just a ring, it has no body
- C2/Axis - differs because the body of C1 fuses to the body of C2 at a projetion called the odontoid process
- Cervical - Smaller processes
- Thoracic - have facets for ribs, also have very large and longer spines than the adjacent vertebrae
- Lumbar - Weight bearing, largest bodies of the vertebrae
- Sacrum - Fused
- Coccyx - Fused
Each pair of vertebrae (except C1/C2) is attached by joints, intervertebral discs and a pair of gliding facet joints. Intervertebral disc material (annulus fibrosus & nucleus pulposus) lies between and allows for movement of the bodies of the vertebrae and absorb shock. It is composed of rings of fibrocartilage (very strong); the annulus fibrosis ring, whose core is composed of a soft gelatinous center called a nucleus pulposus, attaches above and below each body. A herniated or "slipped" disc is the nucleus pulposus which comes out of the annulus fibrosis and presses on the nerve roots typically eliciting extreme pain. The discs are also subject to degenerative changes.
From the posterior view, the vertebrae in conjunction appear as a column (vertebral column) which gives form to the back and torso, dexterity and mobility function and flexibility, and spinal cord protection. From the lateral view, it has slight curves at each level. Abnormal curves have specific names;
From the posterior view, the vertebrae in conjunction appear as a column (vertebral column) which gives form to the back and torso, dexterity and mobility function and flexibility, and spinal cord protection. From the lateral view, it has slight curves at each level. Abnormal curves have specific names;
The vertebral bodies have distinct landmarks and can be characterized
There are a number of processes (appendage or outgrowth) arising from vertebral arch
- body; anterior, thick and disc (rounded) shape, the weight bearing part of vertebrae
- lamina; posterior vertebral arch
- pedicle; extend from the body and unite with the lamina
There are a number of processes (appendage or outgrowth) arising from vertebral arch
- transverse processes; point where lamina and pedicle join
- spinous process; projects posteriorly
- superior articular processes; articulates with inferior processes
- inferior articular processes; articulates with superior processes of the vertebra above
- facets; articulating surfaces of articular processes
- intervertebral joints; articulations formed between bodies and articular facets of successive vertebrae
- intervertebral foramen; opening on both sides of column that permits passage of spinal nerves and vessels
- Kyphosis is an accentuated thoracic curve is called kyphosis
- Lordosis is an accentuated lumbar curve is called lordosis
- Scoliosis is a tortuous curve of varying degree and usually in the thoracic region