- Worksheet 1: How the Skeletal System Works
- Worksheet 2: The Protection Function of Bones
- Worksheet 3: Axial Skeleton and Appendicular Skeleton
- Worksheet 4: Axial vs Appendicular Skeleton and the Functions of the Skeletal System
- Worksheet 5: Kinds of Joints
- Worksheet 6: Know Your Bones
- Worksheet 7: Labeling the Skeleton
The skeletal system is made up of the bones and joints in your body, as well as the connective tissue that binds them to each other.
Bones
Adults have 206 bones (although the exact number depends on whether certain bones are counted as one are separately — it’s kind of complicated). Children are born with more than 206 bones but some of them fuse as we grow up.
The smallest bone in the body is the stapes, which is only 2 to 3 millimeters long and is found inside your ear.
The longest bone is the femur or thigh bone.
Your bones have many important functions (jobs):
- They give your body its shape and framework. It holds you up — without your skeleton, you would just be a bunch of organs in a weirdly-shaped bag of skin.
- Your bones work with your muscles so you can move.
- Your bones also store important minerals like calcium.
- Your bones — specifically, the part of the bone called the bone marrow — are also the site where your blood cells are produced.
- Last but definitely not the least, your bones protect many of your most important organs, such as your brain, spinal cord, heart, and lungs.
Joints
The point where two bones meet is called a joint.
There are many types of joints, depending on what they are made of, how much movement they allow, and what kind of movement takes place in them.
When the bones are joined by dense connective tissue that has a lot of collagen fibers , they are called fibrous joints , and there is no movement that happens in them. An example of fibrous joints are those between the plates of your skull, where they are called sutures.
When the bones are joined by a tissue called cartilage , they are called cartilaginous joints . Cartilage is less stiff and so there is a bit of movement that can happen in cartilaginous joints, such as those between the discs of your backbone.
When there is something like a bag of fluid between two bones, they are called synovial joints . They are also known as freely movable joints because they allow a great amount of movement. The fluid in synovial joints is called synovial fluid and it acts like a lubricant to allow smooth and easy movement in the joint. A lot of the joints in your body where movement takes place — such as your knee or your elbow — are synovial joints.
In turn, there are several types of synovial joints , depending on the kind of movement they allow:
- ball and socket joint – such as in the shoulders and hips
- gliding or plane joint – such as in the wrists and ankles
- hinge joint – such as in the knees and elbows
- pivot joint – such as in the neck
- condyloid joint – such as in the jaw and fingers
- saddle joint – such as at the base of the thumb
