U3 S11

Collagen is a protein which makes up most of the connective tissue in bone. The collagen allows bones to be flexible enough to withstand knocks and bumps.

• oMarrow is a soft tissue found in bones.
• oRed marrow is where platelets and red and white blood cells are produced. It is the center of flat bones such as ribs.
• oYellow marrow stores fat. It is found at the center of long bones such as the femur.

Long bones lengthen at their ends, in the growth plates. Bone cells called osteocytes move into the cartilage, hardening it and changing it into bone.

Growth plates are areas of cartilage that continue to make new cells.

Bones are connected to each other at joints by ligaments. Fixed joints, like the ones in the skull, allow little or no movement. Movable joints allow more movement of the bones.

Shoulders and hips are ball-and-socket joints. They are movable joints that allow one of the bones of the joint to rotate in a large circle.

Wrists and ankles are gliding joints. They are movable joints that allow much flexibility in many directions.

Knees and elbows are hinge joints. They are movable joints that allow bones to move back and forth like a door.

A sprain is an injury to a ligament from stretching a joint too far. The tissues in a sprained ligament can tear and the joint becomes swollen and painful to move.

Osteoporosis is a disease that causes bone tissue to become thin. The bones become weak and break more easily. Having much calcium in your diet can help prevent this disease.