The rib cage curves around the heart and lungs. What skeletal function is shown by this body example?

A helmet covers the outside of the head, but the skull already surrounds the brain. What skeletal job does the skull perform?

When a student sits upright, the stacked vertebrae of the spine keep the trunk from collapsing. Which skeletal function is being used?

The pelvis and femurs bear much of a person's weight while standing. What job of the skeleton does this evidence best show?

At the knee, the femur and lower-leg bones meet so the leg can bend and straighten. What skeletal function is shown at this joint?

A doctor treats a patient by replacing the red marrow inside the patient's bones. Which bone function is the doctor trying to restore?

To bend an elbow, the biceps contracts while the triceps relaxes. What does this evidence show about moving bones?

During a soccer kick, the quadriceps shortens across the knee and the lower leg swings forward. What caused the bone movement?

A student straightens an elbow when the triceps contracts and the biceps relaxes. Why must another muscle work after the biceps bends the elbow?

During a calf raise, the calf muscle lifts the heel by working on the heel bone. What principle of muscle movement is shown?

When standing still, back and abdominal muscles make small contractions that keep the spine balanced over the pelvis. What are the muscles doing?

A shoulder muscle crosses the shoulder joint and shortens to lift the upper arm bone. Why does crossing a joint matter?

A tough band connects the calf muscle to the heel bone so contraction can move the foot. Which structure is described?

At the knee, a tough band connects the femur to the tibia and helps stop the bones from sliding apart. What structure is this?

The ends of bones in a joint are covered with smooth, flexible tissue that reduces rubbing during motion. What is that tissue called?

The elbow is the place where upper-arm and forearm bones meet, letting the arm bend. What term names that meeting place?

A thin layer of synovial fluid fills the space between the bone ends in the knee joint. What role does this fluid play?

After six weeks in a cast, a student's forearm muscle is smaller and weaker. Which explanation best fits the evidence?

After two months of stair training, a runner's quadriceps can lift the same load more times than before. What explanation matches the data?

Astronauts can lose bone mineral density in low gravity, so they do resisted exercise in space. What does this evidence show about bones?