骨头是如何造血的 How bones make blood

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At any given moment, trillions of cells are traveling through your blood vessels, sometimes cycling the body in just one minute.

Each of these cells has its origins deep in your bones.

Bones might seem rock-solid, but they're actually quite porous inside.

Large and small blood vessels enter through these holes.

And inside most of the large bones of your skeleton is a hollow core filled with soft bone marrow.

Marrow contains fat and other supportive tissue, but its most essential elements are blood stem cells.

These stem cells are constantly dividing.

They can differentiate into red blood cells, white blood cells, and platelets, and send about hundreds of billions of new blood cells into circulation every day.

These new cells enter the bloodstream through holes in small capillaries in the marrow.

Through the capillaries, they reach larger blood vessels and exit the bone.

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