A long bone, such as those of the limbs, shows both
varieties of bone tissue. When sawn through longitudinally the distribution of
compact and cancellous tissue can be seen. It is divided into a shaft, the
central part, and two extremities or ends of the bone. If the shaft is cut
across, dense bone tissue will be seen and a hollow center called the medullary
cavity, containing yellow bone marrow. If the end of a long bone is cut, the
space in the cancellous tissues will be seen containing red bone marrow. In the
yellow marrow fat cells predominate; in the red marrow red blood cells are very
numerous the red bone marrow is the birthplace of both red and white blood
cells.
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