osteoclast- resorption; promotes active erosion of bone minerals
Bone growth( Ossification)
Types of Joints in the Human Body
The point where two or more bones meet is called a joint. The joints of the skull are known as sutures ( top, left ). Sutures do not have a wide range of movement. Instead, they allow for growth and very limited flexibility. Hinge joints ( top, right ) allow for movement in one plane. The hinge joints of the elbow and knee, for example, bend up and down. Two flat-surfaced bones that slide over one another make up a gliding joint ( bottom, right ). Gliding joints, such as those in the wrist and the foot, provide for limited movement. Ball-and-socket joints ( bottom, left ) allow for the greatest range of motion. The ball-and-socket joints of the shoulder and hip, for example, can rotate in a complete circle.
Clinical applications Common Fractures In a greenstick fracture, the bone does not break all of the way through. Fractures are called simple, or closed, when the bone breaks but the skin does not. A compound, or open, fracture is when the broken bone tears through the skin, introducing the dangerous possibility of infection. The area around a break swells and discolors, but some fractures can be detected only by X ray. The weakened bones of the elderly are especially susceptible to fractures.
A slipped disk, or disk prolapse, occurs when an intervertebral disk, one of the cartilage disks that separates and cushions the bones of the spinal column, pushes against the spinal cord. The result of injury or age-associated degeneration, slipped disks can cause severe and even disabling pain. Most slipped disks occur in the lower back, but the bones of the upper back are also vulnerable. Depending on severity, doctors may prescribe painkillers, bed rest, or surgery to treat slipped disks.