Musculoskeletal system: Structure and function

Musculoskeletal system is involved in almost every aspect of our lives as it shapes our bodies and makes all the movements possible, like getting up, walking, and playing sports.

It consists of many different bones and other structures that, together, provide a solid framework for the body, called the skeleton.

Bones get their strength from storing calcium and phosphate, but they can also release them into the body for other organs to use. By working together, bones and muscles form the joints that are responsible for the movement of the body.

Now, when we look at the skeleton, we can see that there are several types of bones: four to be precise. In the arms and legs, there are long bones that bear the load of the body and enable extremity movement.

In the wrists, hands, ankles, and feet, there are short bones that enable more delicate and skillful movement. Then, looking at pelvis, shoulder blades, cranium and rib cage, we can see that they contain flat bones that mainly protect vital organs, like the brain, lungs and heart.

Inside these flat bones, there is a red bone marrow, which produces blood cells, like red and white blood cells and platelets.

Finally, bones of the face and the spine are irregular bones of various shapes that enable flexibility and a variety of movement.

Okay, so the place where two or more bones come together is called the joint. Joints provide range of motion, from the fixed joints of the skull that do not move at all to the shoulder joint that provides a variety of motion.

In order for the joints to function properly, the ends of the bones are covered with the connective tissue called the cartilage that prevents the bones from rubbing against each other and acts as a shock absorber.

A connective tissue wraps around the joint like a capsule and forms a joint cavity. The inner side of this cavity is covered with a synovial membrane that produces synovial fluid: a substance that lubricates the joint surfaces to make movement smoother.

Lastly, in order for the joints to be stable, there are strings of strong connective tissue called ligaments that bind ends of the bones over the joint capsule.

Moving on from the bones and joints, let's look at the main driving force of the motion, which are the muscles. There are 3 types of muscles: skeletal muscles control voluntary actions, like moving your fingers; smooth muscles control involuntary actions, like contractions of the intestine; and cardiac muscles make the heart contract.

Skeletal muscles are also known as striated muscles because, when looked at under a microscope, their fibers are arranged in stripes.

When the muscle contracts, it shortens in length and pulls the bones closer to each other to provide movement. Skeletal muscles attach to bones on the different sides of the joints via the tight, strong connective tissue known as tendons.

Muscles can also attach to other surrounding muscles that have similar functions via a special, thin tendon called the aponeurosis. This helps keep the muscles in a bundle that helps each other muscle produce more stable motion.