The average adult has about 216 bones forming the support structures of his body. Muscles, ligaments and tendons, as well as your nervous system, provide the movement of the skeleton. Among all of these bones, three major bone structures are essential for human survival and movement. They are the skull, vertebrae and pelvis. These make up the core of the skeletal system.
Cranial
Your skull is made up of 22 bones that are fused together to protect your brain and brain stem. Except for the jawbone, the skull bones are connected by sutures, which are fibrous joints that allow some elasticity in the skull. Eight bones form the neurocranium, which protects the brain and brain stem, and fourteen bones form the splanchnocranium, the bones of your face.
Vertebrae
Your spine, also known as a vertebral column, is the major supporter of your body and protects the spinal cord. It is made up of 33 individual vertebrae, a sacrum, and the coccyx (tailbone). Between each of the vertebrae is an intervertebral disc---which is made up of fibrocartilage---that allows some degree of movement in the spine. Your spine moves in three planes of motion: sagittal (forward and backward), frontal (side to side), and transverse (rotation at various angles).
Your spine is divided into five sections, which are named according to region and position. The cervical spine (seven vertebrae) makes up the neck portion, consisting of the atlas (C1) that moves and rotates the head and the axis (C2).
The thoracic spine (twelve vertebrae) serves as a connection point for your ribcage, which protects your heart.
The lumbar spine (six vertebrae) has the largest segments of the spine. The lumbar spine absorbs the most amount of pressure in your body.
The sacrum is made up of five fused vertebrae and is also the part of your pelvis.
The coccyx is the remnant of the tail, but it also serves as the attachment point for various muscles, tendons and ligaments.
A normal, healthy spine should have slight curves like the letter S in all sections of the spine that provides shock absorption, flexibility, and stability.
Pelvis
The pelvis is made up of eight fused bones that support your upper body when standing and sitting. It also protects parts of the urinary tracts and internal reproductive organs and provides attachments for external reproductive organs, muscles and connective tissues in the area.
According to Anthony Carey of Function First in San Diego, your pelvis plays a major role in body positions, stabilization and posture. When your pelvis is tilted forward from the top, it causes hyperextension in the lumbar spine, which causes the buttocks to lift up. If the pelvis is tilted back, it causes the spine to flex forward, hunching your shoulders in the process. If the pelvis is rotated excessively in one direction, the spine will compensate the rotation by turning to the opposite direction of the pelvic rotation.
References
- "Principles of Human Anatomy"; Gerard Tortora; 2003
- "Pain-Free Program"; Anthony Carey; 2005
- "Athletic Body in Balance"; Gray Cook; 2003
