Muscles and Bones

Muscles and Bones

The skeletal system

• Support- This is the main function of the skeleton- to support our bodies. It gives shape to the body and holds your vital organs in place. Without a skeleton we would be like jelly.
• Protection- The skeleton protects important internal organs. The skull protects the brain, the pelvis protects the reproductive system and the ribs protect the heart and lungs.
• Movement- The skeleton helps our bodies to move by a system of joints and by providing a base for the muscles to attach to.
• Red blood cells- (to carry oxygen) and white blood cells (to protect against infections) are produced in the bone marrow of some bones.
• The skull protects the brain; Ribs protect the heart and lungs; muscles attach to bones
• Red bone marrow produces RBC's, WBC's and platelets. Found in the spine, ribs, pelvis, skull and the spongy material at the ends of long bones.

Bones and Biomechanics

• A bone is a living tissue built by osteoblasts.
• Compact Bone- hard and strong
• Spongy Bone - Light weight
• BIOMECHANICS
• This is the study of how muscles and bones work together.
• Muscles are only able to contract so they must work in pairs to move bones back and forth.
• Tendons binds muscle to bone
• Ligament binds bone to bone
• Ends of bones are covered in cartilage to reduce friction

Why do we need muscles?

• Muscles play a major role in the body. They produce movement, maintain posture, stabilise joints, help blood to circulate and generate heat.
• There are three main types of muscle: Skeletal Muscle; Smooth Muscle and Cardiac Muscle
• Voluntary muscle is attached to the skeleton (we have 600 skeletal muscles) This helps maintain posture, prevent joints dislocating and your facial expression.
• Smooth muscle is a voluntary muscle -does it all the time. Found in the walls of hollow organs, e.g. blood vessels, stomach and intestines.
• Cardiac muscles are involuntary and are found in the walls of the heart and constantly contracts and relaxes, it never rests or fatigues.
• Muscles work by contraction, i.e. getting shorter. They contain mainly mitochondria for energy release. When a muscle contracts, it pulls on the bone, and the bone can move if its part of a joint. Muscles can only pull and cannot push Muscles are only able to contract so they must work in pairs to move bones back and forth. As one muscle in the pair contracts the other relaxes. E.g. to raise the arm, the biceps contract and the triceps relax. In pairs these are called antagonistic muscles.
• For example, to lower the arm the triceps contract and the biceps relax.