Exam category: Procedures → all three (Head/Spine/Pelvis, Thorax/Abdomen, Extremity)
Why it matters: Every order and report you read names bones, positions, and projections with these terms, and position, projection, and view are not interchangeable.
Two vocabularies meet in this module. The first names the bones themselves: what a long bone is made of, how bones are grouped, and what the bumps and holes on them are called. The second names what you do to the patient: position, projection, planes, and oblique naming. You need the first to read an anatomy question, and the second to read an order. Everything here exists so that any technologist reading an order knows exactly what to do, and any technologist reading a report knows exactly which structure is meant.
The adult skeleton has 206 named bones. It splits into two divisions:
| Division | What it contains | Count |
|---|---|---|
| Axial | Skull, vertebral column, ribs and sternum. The body's central column. | 80 |
| Appendicular | Upper and lower limbs plus the shoulder and pelvic girdles that hang them on. | 126 |
The two divisions account for every named bone, so any two of these three numbers give you the third.
Sesamoid bones sit outside the axial and appendicular divisions. These are small oval bones that form inside a tendon, usually near a joint. They are not counted in either division, with one exception: the two patellae, which are the largest sesamoid bones in the body and are counted. Other common ones sit at the base of the first toe and near the base of the thumb.
Memory cue — 206, split 80/126. Axial is the axis, the central column: skull, spine, ribs, sternum. Appendicular is the appendages and the girdles that attach them. Sesamoids are extra, and the patellae are the exception that counts.
Answer this to keep going. 17 more sections unlock below.
Sesamoids sit near the thumb, at the base of the first toe, and at both knees (the patellae). Which of these enter the 206-bone count?
Section 1 of 18. Answer the check to keep going.