Which statement best describes red and yellow marrow histology?

• A. Red marrow contains hematopoietic tissue producing blood cells
• B. Yellow marrow adipose tissue
• C. Red marrow stores fat
• D. Yellow marrow hematopoietic tissue

Answer: (A)

Red marrow is the site where blood cell production happens. Histology shows hematopoietic cells at various stages of development embedded in a loose reticular framework with many blood sinusoids, all sitting in the trabecular spaces of cancellous bone. This tissue includes precursors for red blood cells, white blood cells, and platelets, highlighting its primary role in forming blood cells. Yellow marrow, by contrast, is mainly adipose tissue that stores fat, and red marrow can be reactivated to red marrow under certain conditions, but in typical histology it is the hematopoietic tissue that defines red marrow. That makes the statement describing red marrow as containing hematopoietic tissue producing blood cells the best fit.