Did you know that whenever you turn your head, you are using a pivot joint? In this lesson, you will learn about the types of joints in your body and specifically about how pivot joints function and where they are located.
What are Joints?
Did you turn your head today? Or perhaps you used your wrist to twist the lid off of a bottle? Both of these actions, and many more, would be impossible without pivot joints. Pivot joints allow rotation, and although you have many joints in your body, there are only three pivot joints. They are located in your neck, your wrist, and your elbow. To really understand how pivot joints work, let's first take a minute to learn about how all joints function.
Joints are junctions between bones that allow your bones to grow and enable your body to move when your muscles contract. Without joints, you wouldn't be able to move at all! There are many joints in your body, and some allow more types of movement than others. Some of the largest joints, such as the knee, hip, shoulder, and wrist, actually contain several smaller joints that work together to permit you to have a wide range of motion.
General Types of Joints
In your body, there are three general types of joints. They're classified according to how much motion they allow.
Fibrous joints are between bones that are in close contact and do not move much at all. This is the type of joint between the bones in your skull.
Cartilaginous joints connect two bones with cartilage in between them. Cartilage is a little bit flexible, so these joints allow a small amount of motion, but not very much. The joints that connect your ribs to your sternum (in the center of your chest) are cartilaginous. This allows the chest to expand and contract a little bit as you breathe.
Finally, the major joints in your body, like the knee, hip, wrist and neck, are synovial joints. A synovial joint includes two or more bones that are covered with slippery cartilage at each end and is enclosed by a capsule that secretes a very slippery fluid that lubricates the joint called synovial fluid. Pivot joints are one type of synovial joint.
What is a Pivot Joint?
Pivot joints are joints that allow bones to rotate. In a pivot joint, a cylinder shaped bone rotates inside another bone or ligament that forms a ring around it. To see how a pivot joint functions, just turn your head from side to side! In your neck, there's a pivot joint between your skull and the top vertebrae that allows your head to turn.
This is not the only pivot joint in your body, however. The two bones in your forearm are called the radius and ulna, and at the elbow, there is a pivot joint between these two bones that allows you to rotate your forearm. There's another pivot joint between these two bones at the wrist. Both of these joints together allow you to rotate your hand without moving your upper arm.
To try this, hold your hand out with the palm facing upward and then turn your hand so it faces towards the ground. Congratulations! You just used the pivot joints in your forearm!
Joints are junctions between bones that allow your body to move. Fibrous joints allow very little motion, cartilaginous joints allow a small amount of motion, and synovial joints allow a wide range of motion. A pivot joint is a type of synovial joint that rotates. Two examples of pivot joints in your body are the pivot joint in your neck that allows your head to rotate and the pivot joints between the radius and ulna that rotate your forearm.
The structure of a pivot joint
- There are three types of joints in the human body: fibrous joints, cartilaginous joints, and synovial joints
- Pivot joints are a type of synovial joint and allow for rotation
- There are only three pivot joints in the body: the neck, forearm, and wrist
At the end, you should be able to complete these tasks:
- Name the three types of joints and summarize their functions
- Identify the three pivot joints in the human body
- Explain how a pivot joint functions and its purpose