🩸 Hematology & Oncology🟢 BasicBone Marrow

Bone Marrow: Structure and Response to Disease

The body's blood-cell factory, and the ways it changes when the body needs more cells or when disease invades it.

Key points

Red (active) marrow makes blood cells, while yellow (fatty) marrow is inactive but can turn back into red marrow when demand rises.
In adults, active red marrow is concentrated mainly in the axial skeleton (vertebrae, sternum, ribs and pelvis) and the proximal ends of the femur and humerus.
All blood cells arise from a single pluripotent haematopoietic stem cell that can both renew itself and differentiate.
Under stress such as chronic haemolysis the marrow expands, fatty marrow reverts to active marrow, and blood formation can even restart in the liver and spleen (extramedullary haematopoiesis).
Marrow failure, as in aplastic anaemia, leaves too few of all three cell lines, giving pancytopenia.
When marrow is crowded out by fibrosis or tumour, immature red and white cells are pushed into the blood, giving a leucoerythroblastic picture.

Red marrow makes cells, yellow is spare capacity — under stress yellow turns red and the liver and spleen can pitch in.

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🩸 Hematology & Oncology🟢 BasicBone Marrow

The body's blood-cell factory, and the ways it changes when the body needs more cells or when disease invades it.

Red (active) marrow makes blood cells, while yellow (fatty) marrow is inactive but can turn back into red marrow when demand rises.
In adults, active red marrow is concentrated mainly in the axial skeleton (vertebrae, sternum, ribs and pelvis) and the proximal ends of the femur and humerus.
All blood cells arise from a single pluripotent haematopoietic stem cell that can both renew itself and differentiate.
Under stress such as chronic haemolysis the marrow expands, fatty marrow reverts to active marrow, and blood formation can even restart in the liver and spleen (extramedullary haematopoiesis).
Marrow failure, as in aplastic anaemia, leaves too few of all three cell lines, giving pancytopenia.
When marrow is crowded out by fibrosis or tumour, immature red and white cells are pushed into the blood, giving a leucoerythroblastic picture.

Red marrow makes cells, yellow is spare capacity — under stress yellow turns red and the liver and spleen can pitch in.