Activity 2F: Classifying Bones

The students will become familiar with the four general groups of bones in the body. Use the color code on the sheet "Bone Classification" for the students to label these bone groups and classify the bones, or use the skeleton that was glued together in Activity 2A. Discuss the following information with the students. You may wish to instruct the students to take notes over this information. The bones are classified into four groups:

Long bones form the levers of our arms (humerus, ulna, radius) and legs (femur, tibia, fibula). Other long bones are in the hands and the feet (metacarpals and metatarsals). They are strong shafts made of compact bone tissue. They have large ends consisting of spongy tissue covered with compact tissue. They are slightly curved enabling them to absorb shock.

Flat bones provide broad surfaces to protect other structures and for anchoring muscles. Examples include skull, some facial bones, shoulder bones (scapula), ribs, breastbone (sternum), and hips (pelvis). Flat bones are broad flat plates of spongy tissue sandwiched between two layers of compact tissue.

Short bones are strong, irregular cubes, made of spongy bone covered with compact tissue. Short bones include the kneecap (patella), wrist (carpals), ankle (tarsals), and fingers and toes (phalanges).

Irregular bones are shaped differently enough that they cannot be grouped with the other three types of bones. The proportion of spongy to compact tissue varies from bone to bone. Vertebrae (spinal bones) and some facial bones are in the category.