Schematic of 2 platelet production mechanisms and MK membrane structures in bone marrow. Bone marrow MKs release platelets via 2 distinct mechanisms: (1) Proplatelets: long and irregularly shaped cytoplasmic protrusions that extend from the surface of MKs into sinusoids. Proplatelets can undergo further fragmentation prior to being converted into circulating platelets; and (2) Membrane buds: platelet-sized membrane protrusions directly released from the MK surface into sinusoids. Budding MKs are more frequently detected (70%-80%) in the bone marrow than proplatelets (2%). Buds are membrane structures distinct from MK membrane blebs and MVs. Buds contain typical platelet granule proteins (VWF) as well as internal CD41 (integrin α_IIbβ₃) and filamentous actin, all of which are absent in blebs and microvesicles. Created using BioRender.com.