I.

Introduction

Bone Marrow, soft, pulpy tissue that fills the cavities of bones, occurring in two forms, red and yellow. One of the largest tissues in the body, bone marrow accounts for 2 to 5 percent of an adult’s weight. Red marrow, present in all bones at birth, serves as the blood manufacturing center. As an infant matures, most of the red marrow in the shaft of long bones, such as the arm and leg bones, is gradually replaced by yellow marrow. Yellow marrow is composed primarily of specialized fat cells.