Memory tricks for all 206 bones

Most students think bones just provide support — but SMITH reveals four more critical functions. Red bone marrow produces all blood cells (hematopoiesis) — this is why bone marrow conditions like leukemia are so serious. Yellow marrow stores triglycerides. Bones store 99% of the body's calcium and phosphorus — released when blood levels drop.

The cranium is formed by 6 bones — 2 paired (parietal and temporal) and 4 unpaired (frontal, occipital, sphenoid, ethmoid). The sphenoid is called the keystone of the cranial floor — it articulates with every other cranial bone. The ethmoid forms the roof of the nasal cavity and part of the orbit.

14 facial bones total — 6 paired and 2 unpaired. The mandible is the only movable bone of the skull. The maxilla forms the upper jaw and most of the hard palate. The zygomatic forms the cheekbone. The vomer forms the inferior nasal septum. The lacrimal contains the lacrimal sac for tear drainage.

The vertebral column has 33 vertebrae total — 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused). The meal times correspond to typical eating hours — 7am breakfast, noon lunch, 5pm dinner. C3-C5 innervates the diaphragm (phrenic nerve). C4 injury = death. L4-L5 = most common herniated disc location.

Osteogenic cells are stem cells that differentiate into osteoblasts. Osteoblasts BUILD bone — they secrete osteoid (unmineralized matrix). Once surrounded by matrix they become Osteocytes — mature bone cells that MAINTAIN bone. Osteoclasts BREAK DOWN bone (resorption) — giant multinucleate cells. Think: Blast = Build, Clast = Crush.

Joints are classified by structure and mobility. Fibrous joints = immovable (synarthrosis) — skull sutures. Cartilaginous joints = slightly movable (amphiarthrosis) — pubic symphysis, intervertebral discs. Synovial joints = freely movable (diarthrosis) — shoulder, knee, hip. Synovial joints have a joint cavity, articular cartilage, synovial membrane, and synovial fluid.

Bone markings fall into three categories. Processes project outward — tuberosity, crest, trochanter, tubercle, epicondyle, spine. Depressions sink inward — fossa, sulcus, groove, fovea. Openings go all the way through — foramen, meatus, canal, fissure. Knowing the category tells you immediately whether a marking sticks out, sinks in, or opens.

Pathologic fractures occur through diseased bone (osteoporosis, cancer) — minor trauma causes break. Impacted fractures — fragments are driven into each other. Greenstick fractures — incomplete break, one side bends, common in children (green wood analogy). Spiral fractures — twisting force, common in sports, important forensically as possible abuse indicator in children.

The pectoral girdle attaches the upper limb to the axial skeleton. The clavicle (collarbone) is the only bony connection between the arm and the trunk — it acts as a strut. It is the most commonly fractured bone in the body because when you fall on an outstretched hand the force transmits up to the clavicle. The scapula is a free-floating bone protected by muscles.