Biological causes of osteoporosis. The major functions of bones are to:. Provide structural support for the body Provide protection of vital organs Provide an environment for marrow where blood cells are produced Act as a storage area for minerals such as calcium. Bones are made of two tissue types:. Compact bone: also known as cortical bone, this hard-outer layer is strong and dense Cancellous bone: also known as trabecular bone, this spongy inner layer network of trabeculae is lighter and less dense than cortical bone.
Bones are composed of:. Osteoblasts and Osteocytes: these are bone forming cells Osteoclasts: these are bone resorbing cells Osteoid: this is the non-mineral, organic part of the bone matrix made of collagen and non-collagenous proteins Inorganic mineral salts deposited within the matrix. Bone Cells. Cells in our bones are responsible for bone formation, resorption, maintenance and re- modelling: Osteoblasts: These cells are derived from mesenchymal stem cells and are responsible for bone matrix synthesis and its subsequent mineralization.
In the adult skeleton, the majority of bone surfaces that are not undergoing formation or resorption i. Osteocytes: These cells are osteoblasts that become incorporated within the newly formed osteoid, which eventually becomes calcified bone.
However, by age 65, women and men tend to lose bone tissue at the same rate. Although men do not undergo the equivalent of menopause, production of the male hormone testosterone may decrease, and this can lead to increased bone loss and a greater risk of developing osteoporosis. Osteoporosis is preventable for many people. Prevention is important because although there are treatments for osteoporosis, a cure has not yet been found.
A comprehensive program that can help prevent osteoporosis includes:. Would you like to order publications on bone disorders to be mailed to you? Visit our online order form. What Is Bone? Without all the bones of the foot working together, it would be impossible to balance properly.
The bones in the feet are arranged so the foot is almost flat and a bit wide, to help you stay upright. So the next time you're walking, be sure to look down and thank those toes! Fixed joints are fixed in place and don't move at all. Your skull has some of these joints called sutures, remember? One of these joints is called the parieto-temporal say: par-EYE-ih-toh TEM-puh-rul suture — it's the one that runs along the side of the skull.
Moving joints are the ones that let you ride your bike, eat cereal, and play a video game — the ones that allow you to twist, bend, and move different parts of your body. Some moving joints, like the ones in your spine, move only a little.
Other joints move a lot. One of the main types of moving joints is called a hinge joint. Your elbows and knees each have hinge joints, which let you bend and then straighten your arms and legs. These joints are like the hinges on a door.
Just as most doors can only open one way, you can only bend your arms and legs in one direction. You also have many smaller hinge joints in your fingers and toes. Another important type of moving joint is the ball and socket joint. You can find these joints at your shoulders and hips.
They are made up of the round end of one bone fitting into a small cup-like area of another bone. Ball and socket joints allow for lots of movement in every direction. Make sure you've got lots of room, and try swinging your arms all over the place.
Have you ever seen someone put oil on a hinge to make it work easier or stop squeaking? Well, your joints come with their own special fluid called synovial fluid say: SIH-no-vee-ul that helps them move freely.
Bones are held together at the joints by ligaments say: LIH-guh-mints , which are like very strong rubber bands. Protect those skull bones and your brain inside!
When you use a skateboard, in-line skates, or a scooter, be sure to add wrist supports and elbow and knee pads. Your bones in these places will thank you if you have a fall! If you play sports like football, soccer, lacrosse, or ice hockey, always wear all the right equipment. And never play on a trampoline. Many kids end up with broken bones from jumping on them. Broken bones can eventually heal, but it takes a long time and isn't much fun while you wait.
Strengthen your skeleton by drinking milk and eating other dairy products like low-fat cheese or frozen yogurt. They all contain calcium, which helps bones harden and become strong. Be active! Another way to strengthen your bones is through exercise like running, jumping, dancing, and playing sports. Reviewed by: KidsHealth Medical Experts. Larger text size Large text size Regular text size. It's time to look at all your bones — the adult human body has of them!
The movements that muscles make are coordinated and controlled by the brain and nervous system. The involuntary muscles are controlled by structures deep within the brain and the upper part of the spinal cord called the brain stem. The voluntary muscles are regulated by the parts of the brain known as the cerebral motor cortex and the cerebellum ser-uh-BEL-um. When you decide to move, the motor cortex sends an electrical signal through the spinal cord and peripheral nerves to the muscles, making them contract.
The motor cortex on the right side of the brain controls the muscles on the left side of the body and vice versa. The cerebellum coordinates the muscle movements ordered by the motor cortex.
Sensors in the muscles and joints send messages back through peripheral nerves to tell the cerebellum and other parts of the brain where and how the arm or leg is moving and what position it's in.
This feedback results in smooth, coordinated motion. If you want to lift your arm, your brain sends a message to the muscles in your arm and you move it.
When you run, the messages to the brain are more involved, because many muscles have to work in rhythm. Muscles move body parts by contracting and then relaxing. Muscles can pull bones, but they can't push them back to the original position. So they work in pairs of flexors and extensors. The flexor contracts to bend a limb at a joint. Then, when the movement is completed, the flexor relaxes and the extensor contracts to extend or straighten the limb at the same joint.
For example, the biceps muscle, in the front of the upper arm, is a flexor, and the triceps, at the back of the upper arm, is an extensor. When you bend at your elbow, the biceps contracts. Then the biceps relaxes and the triceps contracts to straighten the elbow. Joints are where two bones meet.
They make the skeleton flexible — without them, movement would be impossible. Joints allow our bodies to move in many ways.
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