The Body's Framework and Engine
Your body's ability to stand up, walk, run, and jump is all thanks to the teamwork between two incredible organ systems: the skeletal system and the muscular system.
The Skeletal System: The Framework
Your skeleton is much more than just a frame for your body. It has several major functions:
1.Support: It provides a rigid framework that supports the body and gives it its shape.
2.Protection: It protects your vital internal organs. The skull protects the brain, the ribs protect the heart and lungs, and the vertebrae protect the spinal cord.
3.Movement: Bones act as attachment points for muscles. They work together as a system of levers to produce movement.
4.Blood Cell Production: A soft tissue inside many bones, called bone marrow, is where new red and white blood cells are made.
5.Storage: Bones store important minerals, especially calcium and phosphorus.
A joint is a place where two or more bones meet. Some joints are fixed (like in the skull), but most are movable, allowing for a wide range of motion.
The Muscular System: The Engine
The muscular system is responsible for all the movement in your body. There are three types of muscle tissue:
1.Skeletal Muscle: This is the muscle that is attached to your bones. You have voluntary control over these muscles, meaning you can choose to move them. They are what allow you to walk, lift, and talk. Under a microscope, they appear striped, or striated.
2.Smooth Muscle: This muscle is found in the walls of internal organs like the stomach, intestines, and blood vessels. You have involuntary control over these muscles, meaning they work automatically without you having to think about it. They are responsible for processes like digestion and regulating blood pressure. They are not striated.
3.Cardiac Muscle: This muscle is found only in the heart. It is involuntary and striated. Its job is to pump blood throughout your entire life without ever getting tired.
How Movement Happens
Muscles can only pull, they cannot push. Therefore, skeletal muscles must work in antagonistic pairs. This means that when one muscle contracts (pulls), the other muscle in the pair relaxes.
Example: Bending your arm. Your biceps muscle on the front of your upper arm contracts, pulling your forearm up. At the same time, your triceps muscle on the back of your arm relaxes.
Example: Straightening your arm. Your triceps contracts, pulling your forearm down, and your biceps relaxes.
Two types of connective tissue are crucial for this system:
Tendons: Tough, flexible cords that connect muscle to bone.
Ligaments: Tough, fibrous bands that connect bone to bone at a joint, providing stability.