A robust understanding of body systems is elusive for many students. For instance, musculoskeletal structures and mechanisms often remain abstract and difficult for students to truly understand, even when teachers provide visual representations and accurate anatomical and physiological information. This article (1) presents a lesson for teaching about the musculoskeletal system by having students develop and build a physical model of an arm and (2) describes how teachers can use this experience to promote a deep understanding of the role of muscles, ligaments, and tendons in movement. This concrete learning experience and resulting arm model establishes a foundation for developing a more robust understanding of anatomical, physiological, and general biological principles. This lesson sequence also embeds questions that overtly draw students' attention to important features of scientific models, which is an important nature of science issue appearing in the Next Generation Science Standards. The instructional sequence has been utilized as the foundation of an entire musculoskeletal unit in an elective anatomy and physiology course for ninth grade students, and it can easily be adapted for use in a middle school life science class or a general high school biology course.