# Science: A Field Of Wonder/Musculo-Skeletal System

The musculo-skeletal system constitutes bones, muscles, joints, and connective tissues. Together, these body parts provide the framework for your body, generate your movements, and dictate your grade of flexibility. They comprise roughly sixty percent of your body mass and use up most of your energy. What will happen to humans without the musculo-skeletal system?

## Functions of the Musculo-Skeletal System

The human skeletal system is comprised of individual bones and cartilage that receive a supply of blood and are held together by fibrous connective tissues. Its three main functions are protection, motion, and support. The system protects the body by enclosing the vital organs. It permits movement by responding at certain joints to the activities of skeletal muscles. It supports the body by serving as a framework to which tendons and fascia are attached.
Movements such as walking and running are caused by the coordinated work of joints, bones, and skeletal muscles. Skeletal muscles are also responsible for various facial expressions, eye movements, and respiration. Nearly all movements in the body are the results of muscle contraction.
The bones are the main structures of support and movement. They are made up of hard material to which the skeletal muscles attach. They consist of living cells incorporated within a dense layer of protein and minerals. The main function of the bones is to support the weight of the body. Together with the muscles, the bones maintain good posture and control the movements of the body. Without the skeleton , contracting muscle fibers could not make you stand, sit, walk, or run.
Every bone in the skeleton contains two form of tisses. The compact (firm) bone is somewhat solid and is found on the external surface. The spongy (cancellous) bone is located inside the bone. Bones are made up of sodium, phosphorus, calcium, and other minerals, as well as the protein collagen. Bones originate as cartilage which slowly transforms to bones through a process called ossification.
The bones also store fats, minerals, and lipids in are areas filled with yellow marrow. Red blood cells, white blood cells, and other blood components are produced in the red marrow found in the bones,
The bones protect the different organs of the body. Below are the most important bones in the body and functions:
* The skull protects the brain and forms the shape of our face.
* The ribs shelter the heart, lungs, liver, and spleen.
* The spinal cord which is the passageway for messages between the brain and the body, is protected by the backbone or spinal column.
* The pelvis protects the urinary bladder, intestines, and reproductive organs.

### Muscles and Joints

The human body has more than 600 muscles. Muscles make up 50 percent of a person's body weight. Each muscle is attached by a connective tissue to two or more bones and they tend to function in group or pairs. When an individual muscle contracts, the opposing muscle usually relaxes,
Humans have three different kinds of muscles.
* Cardiac muscles are found in the walls of the heart's chambers. They are involuntary muscles. Their regular, powerful contractions force blood out of the heart as it beats.
* Smooth or involuntary muscles are also made of fibers. These muscles look smooth and are controlled by the nervous system. Examples of smooth muscles are the walls of the stomach and intestines, which helps break up food and move it through the digestive system.
* Skeletal muscles, also know as voluntary muscles, are attached to the bone, mostly in the arms. They are also called striated because they are made up of fibers. These muscles clutch the skeleton together, provide the body shape, and help with everyday movements.
Joints make the skeleton flexible; they occur when two bones meet. Muscles pull on the joints, allowing us to move.
Joints are classified based on the movements they produce.
* Immovable or fibrous joints do not move. For example, the skull is made of bony plates which mush be steady to protect the brain. Between the boundaries of these plates are joints of fibrous tissues. Fibrous joints also grip the teeth in the jawbone.
* Partially movable or cartilaginous joints move a little. The bones in the spinal column are connected by a cartilage. Each of the bones in the spine moves in relation to one another and together, these movements give the its flexibility.
* Freely movable joints are the main joints of the body usually found at the shoulders, elbows, wrists, hips, knees, and ankles. They move in different directions. They are filled with synovial fluid, a lubricant that helps the joints move freely.
There are three kinds of freely movable joints that play a big part in voluntary movement.
* Hinge joints permit movement in one direction, like the knees and elbows.
* Ball-and-socket joints allow free movement, like the hips and shoulders.
* Pivot joints allow a rotating motion, like that of the head moving from side to side.
* Gliding joints allow the bones to glide pass one another in any direction along the plane of the joint, like the wrist and bones of the ankle.
* Saddle joints allow movement in two directions, like the thumb.

### How Joints and Muscles Work

Even when you are not moving, muscles throughout your body are still regularly working. Muscles allow your chest to expand and contract as you breathe. They also enable your heart to beat and your blood vessels to control the pressure and flow of blood through your body.
When you sit, walk, run, laugh, talk, and exercise, your muscles are working to help you do all these activities. The movements your muscles make are controlled and guided by the nervous system. If you want to move any part of your body, your brain sends messages to the muscles. When you run, many muscles have to work in rhythm. Your muscles can pull bones, but they cannot push them back to the original position.

### Connective Tissues

Generally, skeletal muscles are attached to two bones through tendons. Tendons are strong bands of dense regular connective tissues which firmly attach muscles to to bones. When you wiggle your fingers, you can see the tendons move at the back of your hand as they do their job. To produce, motion, they transmit tension from the muscle to the bone.
The fascia is a soft, thin, jelly-like membrane that is merged with the bones, muscles, tendons, nerves, blood vessels, and organs throughout the body. It supports and connects the different body parts.
Bones are fixed firmly to other bones by long, fibrous straps called ligaments. Ligaments make the bones stable and support the joints by holding them in place

## Diseases and Disorders of the Musculo-Skeletal System

Even though bones are strong, they can also break. Muscles can weaken and joints (as well as tendons, ligaments, fascia, and cartilages) can be damaged by injury or disease. Here are some conditions that can affect the muscles, bones, and tendons.
* Arthritis is the inflammation of the joints. People who have it experience swelling and pain in the affected areas, and they often have difficulty in moving.
* Fracture occurs when a bone breaks due to a forceful impact. After a bone fracture, fresh bone cells fill the gap and repair the break.
* Osteoporosis is experienced when the bone tissue becomes breakable, slender, and malleable. The bones break easily and the spine begins to disintegrate and collapse. Exercising regularly and getting plenty of calcium can help avoid getting osteoporosis later in life.
* Scoliosis is a condition which causes the spine to cure abnormally. Every person's spine allows a certain amount of curvature which is necessary for movement and other activities.
* Sprains and strains are caused by the overstretching or the partial tearing of the ligaments. Strains frequently happen when a person takes part in a strenuous activity without preparing the muscles through warm-up exercises. Sprains, on the other hand, are usually the result of an injury, such as the twisting of the ankle or knee.
* Tendinitis is a common sports injury that happens after overusing a muscle. The tendons become swollen, which can be painful.

## Taking care of the Musculo-Skeletal System

* Regular exercise can keep the bones and muscles strong. Walking, jkogging