Skeletal System

Science, Grade 6


Table Of Contents: Skeletal System

1. Functions of the Skeletal System
Your body has a total of 206 bones, which are attached to your muscles with tendons. The bones of your body have several important functions. They provide support for your body position and movement so you can walk upright. Bones protect vital organs such as your brain and your heart. Bones also help manage and store minerals and even create new blood cells.
2. The Axial Skeleton
The axial skeleton includes the skull, spine, ribs and sternum, which total 80 bones. These bones anchor the body and have limited flexibility. For example, the only bone of your skull which can move freely is your jawbone.
3. The Appendicular Skeleton
The highly movable, flexible regions of your body are called your appendicular skeleton. This includes your shoulders and your hips and the limbs attached to them. The 126 bones in this part of your skeleton help you turn and twist in many directions and support a wide range of movement for your arms and legs.
4. Bone Structure
Your bones may feel hard, but they are constantly changing. Bone is a very dynamic tissue with two key properties that combine to provide strength and support to your body. The outer, smooth part of bone is made up of compact bone. It looks hard to the naked eye and is densely packed tissue. The inner structure of bone is called spongy bone. This bone tissue provides great strength, especially at the ends of bones, because of its honeycomb type structure.
5. Bone Formation
Most bones in the body begin as softer cartilage molds that grow and are slowly replaced by bone tissue rich in calcium that makes the tissue stronger and more rigid. Our bony skeleton and overall body size grows under the control of growth hormone, released by our pituitary gland, most rapidly during adolescence and late teen years. Growth and shaping of bone structure, however, continues throughout our entire life under the effects of gravity and other physical forces.
6. Common Bone Fractures
Some of the most commonly fractured bones include the radius (at your wrist) and clavicle (your collarbone). Fractures can be simple, where the bone has not separated, or they can be compound, where the broken bone piece or pieces pierce the skin and require both resetting of the bone and repair of the skin. If a broken bone is held motionless for some time, as in a plaster cast for weeks, it can be repaired by natural remodeling processes within the bone tissue.
7. Types of Joints Between Bones
The places where your bones meet are called joints. There are three types of joints in the human body. Fixed joints don’t move, such as the places where skull bones meet. Some joints are slightly movable, such as the joints between the bones in your spine. Other joints are freely movable (synovial), such as the knee and elbow and other joints in your arms and legs.
8. Freely Moving Joints - Synovial Joints
There are several types of synovial, or freely moving, joints in the human body. Along the spine and in the arms and legs, synovial joints allow a wide range of motions to support how we move around our environment. Ball and socket joints are the most movable and are found in the shoulder and the hip. Condyloid joints, seen in the wrist and ankles, have more limitations in how they move and are not quite as flexible as ball and socket joints. Hinge joints, which only allow limited movement of flexion and extension, are located in the knee, the elbow and between bones of the fingers and toes.
9. Sprains and Strains
Sprains and strains sound alike and many people don’t understand the difference. But your musculoskeletal system does. Sprains occur at joints and strains happen to muscles. A sprain occurs when one or more of the bones at a joint are pushed too far in a direction they are not positioned to go. For example, when you sprain your ankle, you put weight on your ankle at an unstable angle or position and the bones are sprained. A strain occurs when a muscle is pulled or stretched more than it can support or bear. Both are painful indicators that the human body has limits in motion.
10. Taking Care of Your Bones
Since bones are so important to our everyday lives, it is important to take care of them. Making sure the substance of bones remains intact will go a long way toward keeping bones healthy. That means you must consume enough calcium and protein in your diet to keep bones strong. Routine exercise prevents bone tissue from breaking down with lack of use.