Bones

Bone serves many important functions. Bones support the body, protect underlying organs, and provide a movable skeleton against which the muscles can work. In addition, bone forms all the cells of the blood, plus takes part in calcium and acid-base balance, and storage of trace elements (such as zinc) needed by cells elsewhere. bone as the most lasting parts of the body, bones are traditionally used for ‘mortal remains’. The longest bone is the femur (thigh bone), which accounts for a quarter of one's stature; the smallest bone is the stapes — one of the tiny ossicles in the middle ear which transmits the vibrations from the ear drum to the inner ear. There are over 200 bones in the adult skeleton. They can be divided into two principal types: the long bones such as the femur, tibia, and humerus, which develop principally from within a cartilaginous framework, and the flat bones such as the skull, bones of the pelvis, and scapula, which develop within membranes of fibrous tissue.

Myelofibrosis

Myelofibrosis is a disorder of the bone marrow, in which the marrow is replaced by scar (fibrous) tissue. Bone marrow is the soft, fatty tissue inside your bones. Stem cells are immature cells in the bone marrow that give rise to all of your blood cells. Your blood is made of:
1. Red blood cells (which carry oxygen to your tissues)
2. White blood cells (which fight infection)
3. Platelets (which help your blood clot)
Scarring of the bone marrow means the marrow is not able to make enough blood cells. Anemia, bleeding problems, and a higher risk of infections may occur.
As a result, the liver and spleen try to make some of these blood cells. This causes these organs to swell, which is called extramedullary hematopoiesis.
The cause of myelofibrosis is unknown. There are no known risk factors. The disorder usually develops slowly in people over age 50.
Diseases such as leukemia and lymphoma may also cause bone marrow scarring. This is called secondary myelofibrosis.