The<unk>  is the main or mid section (shaft) of a  long bone. It is usually filled with Yellow Cartilage, which is made mostly of adipose (fat). This provides some protection to shaft when presure is applied. Yellow marrow also contains white blood cells, which is important in the body's defense against disease.
Diaphysis
Epiphysis
Megaureter
Third spacing of fluids
Nephrostomy
Pneumoperitoneum
Hemoperitoneum
Metaphysis