Chapter 17.1b The Skeletal System

Joints Our motion is possible because of joints. Joints are anyplace where 2 or more bones come together. The bones making up a joint should have a thin layer of cartilage so they do not rub against each other. Ligaments are a tough band of tissue that holds bones in place at the joint. Many joints are held together with more than one ligament. Muscles are able to move bones by moving joints.

Immovable Joints Immovable joints allow little or no movement. For example bones in your skull and pelvis are immovable joints.

Movable Joints All movement requires movable joints. There are several types of movable joints – pivot, ball and socket, hinge, and gliding. Pivot joint – one bone rotates in a ring of another bone that does not move. (turning your head) Ball and socket joint – a bone with a rounded end that fits into a cuplike cavity on another bone. (shoulder) Hinge joint – joint has back and forth movement like hinges on a door. (Knee) Gliding joint – one part of a bone slides over another bone. (Wrists and ankles)

Moving Smoothly If we did not have cartilage between our bones the ends of the bones would rub together and wear away at the joints. The cartilage reduces friction and allows bones to slide more easily. You have disk between your vertebrate in your back that are pads of cartilage. They cushion and prevent injury in your spinal cord.

Common Joint Problems Arthritis is the most common joint problem – there are several different types that damage joints. It can cause pain, stiffness, and swelling of joints. Osteoarthritis – when cartilage breaks down because of years of use. Rheumatoid arthritis – the body’s immune system tries to destroy its own tissues.