Obtain and cook enough chicken pieces to provide one or more different bones any size or shape to each group of students. You also may have students bring leftover cooked chicken bones from home. OR use the long bones prepared for the activity, "The Skeleton. It always is a good idea to have students wash hands before and after any lab activity. Point to your arm or leg and ask students to think about characteristics that might be important for large arm or leg bones.
Tell students they will be conducting an investigation that will provide clues about the structure of long bones in humans and other vertebrates. Specifically, they will be comparing the relative abilities of solid and hollow cylinders to support external weights.
Ask, Is a hollow cylinder or a solid cylinder able to support more weight, relative to its own weight? Each group should conclude its explorations by calculating the ratio of weight supported to cylinder weight for each kind of cylinder.
Did either cylinder hold more weight than you expected? Which cylinder had a higher ratio of weight supported? Did you expect this result? Ask students to think about which type of cylinder hollow or solid might make a better bone. Have students record their predictions about the structure of long bones hollow or solid. Have the Materials Managers pick up one or more bones for their groups. Have students observe the outsides of the bones with and without a magnifier, and draw an exterior view of a bone in the space provided on their sheets.
Using a small saw, hammer or poultry scissors, cut or break open the bone s for each group. Students will observe that the bones have hard walls and a central space filled with a soft substance marrow.
Ask students to compare the structure of the bone to the hollow and solid cylinders. Ask, Which cylinder does the bone most resemble? Help students to conclude that the relatively hollow design of real bones allows them to be light, but still strong enough to do their jobs. The process continues until the bones finish growing.
The epiphyseal plate then calcifies and the bones cannot grow longer. Making bones grow in diameter is more straightforward — the body simply adds more bone tissue on top of old bone. To prevent bones from becoming too dense and heavy during growth, osteoblasts add bone tissue to the outer layer of bone tissue while osteoclasts remove some tissue from the inside of bones.
Bones stop growing in length during puberty. In fact, your bones stop growing altogether at about age Bone density and strength, however, continue to change during the course of your lifetime. They can heal and repair themselves in case you break one. Bones undergo a constant renovation that somewhat resembles a construction zone, with osteoclasts carrying sections of old bone away while osteoblasts and osteocytes patch the newly created holes with fresh material.
Bones are strong but they can break. Bones go through four basic stages of recovery after a fracture. A fracture hematoma, or blood clot, develops first. The blood clot stabilizes the bone and prepares it for healing. The hematoma then turns into a soft callous that deposits calcium to help heal the bone. Osteoclasts and osteoblasts turn the soft callous into a bone callous. A hard shell develops over the fracture to protect and stabilize the bone as it heals.
Keeping your bones strong can reduce your risk for fractures. As many as half of all women and one-quarter of all men will fracture a bone at some time because of osteoporosis, according to the Arthritis Foundation. Osteoporosis is a condition that causes bones to become weak and brittle. Fortunately, you can take steps to keep your bones strong and reduce your risk for fractures. Eat a healthy diet. Focus on foods that contain calcium and vitamins C, D, and K.
Low-fat dairy foods, fish, fruits and vegetables are good sources of these nutrients. Quit smoking. Smokers have lower bone mass and a higher risk for fractures as compared with non-smokers. Reduce alcohol and soda intake. Limit alcohol intake to seven drinks per week for women and ten drinks weekly for men. Soda may reduce bone density. Replace soda with milk or calcium-fortified fruit juice.
Exercise regularly and maintain a healthy weight. Being too heavy or too thin increases the risk for osteoporosis. Weight-bearing exercises, such as walking or strength training, strengthen bones by stimulating the production of bone cells. 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.
Some joints open and close like a hinge such as knees and elbows , whereas others allow for more complicated movement — a shoulder or hip joint, for example, allows for backward, forward, sideways, and rotating movement. Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. Search KidsHealth library. Bones are made up of two types of bone tissues: Compact bone is the solid, hard outside part of the bone.
It looks like ivory and is extremely strong. Holes and channels run through it, carrying blood vessels and nerves. Cancellous pronounced: KAN-suh-lus bone , which looks like a sponge, is inside compact bone. It is made up of a mesh-like network of tiny pieces of bone called trabeculae pronounced: truh-BEH-kyoo-lee. This is where bone marrow is found. How Do Bones Grow?
Bone contains three types of cells: osteoblasts pronounced: AHS-tee-uh-blastz , which make new bone and help repair damage osteocytes pronounced: AHS-tee-o-sites , mature bone cells which help continue new born formation osteoclasts pronounced: AHS-tee-o-klasts , which break down bone and help to sculpt and shape it What Are Muscles and What Do They Do?
Humans have three different kinds of muscle: Skeletal muscle is attached by cord-like tendons to bone, such as in the legs, arms, and face. Skeletal muscles are called striated pronounced: STRY-ay-ted because they are made up of fibers that have horizontal stripes when viewed under a microscope. These muscles help hold the skeleton together, give the body shape, and help it with everyday movements known as voluntary muscles because you can control their movement.
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