Objective To characterize ossified bone marrow blood vessels and confirm the presence of ossified particles (OSP) in humans and rodents.

Methods Human bone marrow blood vessels were processed for scanning and transmission electron microscopy. Whole blood samples were collected from younger (26‐39 years; n = 6) and older (55‐63 years; n = 6) volunteers and male Fischer‐344 rats (1 month, n = 7; 6 months, n = 7; 12 months, n = 7; 18‐months, n = 6; 24 months, n = 8). OSP in the whole blood samples were sorted and imaged with microscopy to determine diameter, circularity, and solidity. Additionally, the chemical composition of OSP was determined via elemental analysis.

Results SEM revealed two types of ossified bone marrow blood vessels: that is, “transitioning” and “ossified.” OSP were adhered to the surface of transitioning vessels and theoretically gain access to and circulate within the blood. The majority of OSP were ≤15 μm in diameter, but many were of sufficient size to serve as emboli (ie, >15 μm).OSP were predominately oblong in shape and several had jagged tips and edges.