So What Is the Density?
Biomedical engineers must know the density of healthy human bones in order to help people.Copyright (top) 2014 Jplee0203, Wikimedia Commons; (bottom) 2007 Henry Vorderbruggen, U.S. Navy, Wikimedia Commons http://commons.wikimedia.org/wiki/File:Bone_Density.jpg
http://commons.wikimedia.org/wiki/File:US_Navy_071010-N-7157V-001_Hospital_Corpsman_3rd_Class_Katelyn_Wisnoski,_assigned_to_Naval_Hospital_Bremerton,_performs_a_bone_density_test_at_a_Breast_Cancer_Awareness_Event_at_Bangor_Fitness_Center.jpg
Students review what they know about the 20 major bones in the human body (names, shapes, functions, locations, as learned in the associated lesson) and the concept of density (mass per unit of volume). Then student pairs calculate the densities for different bones from a disarticulated human skeleton model of fabricated bones, making measurements via triple-beam balance (for mass) and water displacement (for volume). All groups share their results with the class in order to collectively determine the densities for every major bone in the body. This activity prepares students for the next activity, "Can It Support You? No Bones about It," during which they act as biomedical engineers and design artificial bones, which requires them to find materials of suitable density to perform as human body implants.
Biomedical engineering focuses on technological advances that improve human health care. Implants are human-made medical devices that replace missing biological structures or support damaged biological structures; these devices must be able to provide the same function as the body parts they replace. Implants that are made of materials foreign to the body (such as metals and plastics) must mimic the key properties of the original body tissue. In order to design implants, devices and procedures that help patients with broken bones, biomedical engineers must know the different densities of human bones. When biomedical engineers create implant models, they first research the problem and collect data, such as the material properties of biological and artificial tissues. In this activity, students make laboratory measurements and use math to calculate the densities of the bones they have researched.
After this activity, students should be able to:
- Calculate the density of various bones in the human body.
- Name the 20 major bones of the human body and identify where in the body they are located.
- Use water displacement to find the volume of irregularly shaped objects.
- Use a triple beam balance and a graduated cylinder to determine the density of objects.