Abstract
The opportunity to encounter and appreciate the range of human variation in anatomic structures—and its potential impact on related structures, function, and treatment—is one of the chief benefits of cadaveric dissection for students in clinical preprofessional programs. The dissection lab is also where students can examine unusual anatomic variants that may not be included in their textbooks, lab manuals, or other course materials. For students specializing in physical medicine, awareness and understanding of muscle variants has a practical relevance to their preparations for clinical practice. In a routine dissection of the superficial chest muscles, graduate students in a human gross anatomy class exposed a large, well-developed sternalis muscle. The exposure of this muscle generated many student questions about M sternalis: its prevalence and appearance, its function, its development, and its evolutionary roots. Students used an inquiry protocol to guide their searches through relevant literature to gather this information. Instructors developed a decision tree to assist students in their inquiries, both by helping them to make analytic inferences and by highlighting areas of interest needing further investigation. Answering these questions enriches the understanding and promotes “habits of mind” for exploring musculoskeletal anatomy beyond simple descriptions of function and structure.
Highlights
The opportunity to encounter and appreciate the range of human variation in anatomic structures—and its potential impact on related structures, function, and treatment—is one of the chief benefits of cadaveric dissection for students in clinical preprofessional programs
We demonstrate this approach, taking advantage of the opportunity presented by an unusual anatomic feature—a large, unilateral M sternalis—to illuminate the various biologic processes that contribute to the appearance and function of the musculoskeletal components of adult human anatomy
After answering the first question on exposing M sternalis—“What is it?”—the question is often, “What does it do?” when the muscle is activated and develops tension, is there any change in the position of skeletal elements located between its attachments? Students in our gross anatomy lab apply a standard template when studying all skeletal muscles to relate the function of a muscle with its location and attachments (See Table 2), and this can be applied to any muscle that presents in their dissections
Summary
“No two bodies are exactly alike.” We repeat this adage in every anatomy class; but students rarely observe significant anatomic variation directly, unless they have access either to advanced imaging or cadaveric dissection. Gross Anatomy), one group of students carrying out routine dissection of the thorax exposed a well-developed and relatively large M sternalis, which they discovered was not included in the reference materials and dissection guides used in the course This discovery prompted both a high level of excitement and an opportunity to use this excitement to promote a deeper understanding of adult musculoskeletal morphology. Geographic populations, and the lower rates in the earlier reports may result from the tendency to These latter studies suggest some variations in prevalence among regional geographic populations, collect data fromsubjects of western European ancestry. Eisler confirms this with his survey of and the lower rates in the earlier reportsprevalence may result was from under the tendency to collect reports from Europe, where reported. Often a crossing over clavicle to attach(Figure to the 1; contralateral clavicle (Figure 1; Gruber [19])
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