A patient with osteoporosis is at increased risk for fractures. Which bone is most commonly affected by osteoporosis-related fractures?

A. Striated muscle:Striated muscle refers to muscle with a banded appearance and includes skeletal and cardiac muscle; it is not the typical involuntary muscle of hollow organs.
B. Cardiac muscle:Cardiac muscle is involuntary and striated but is specific to the heart rather than the walls of most hollow organs.
C. Smooth muscle:Smooth muscle is non-striated, involuntary, and forms the walls of hollow organs (for example blood vessels, the gastrointestinal tract, and the bladder).
D. Skeletal muscle:Skeletal muscle is striated and under voluntary control, primarily attached to bones for movement.

A. Endosteum:The endosteum lines internal bone surfaces and participates in bone remodeling but is not the primary site of hematopoiesis.
B. Red bone marrow:Red bone marrow is the active marrow where hematopoiesis (production of blood cells) occurs in adults, located in pelvis, vertebrae, ribs, sternum, and proximal long bones.
C. Periosteum:The periosteum covers the outer bone surface and provides vascular supply and osteogenic cells for bone growth and repair, not the main hematopoietic site.
D. Yellow marrow:Yellow marrow is rich in fat and predominantly serves as an energy store; it can revert to red marrow in severe blood loss but is not the usual site of active hematopoiesis