A bone marrow aspiration assembly (10, 610) comprising: an outer cannula assembly (12, 612) including an outer handle (16, 616) and an outer cannula (18, 618) defining a first passageway and including a plurality of first openings (72a, 72b, 72c) between a first end (58, 680) and a second end (60, 682) of the first passageway, the plurality of first openings arranged in distal, intermediate, and proximal groups, each group including a first outer array (74a, 76a, 78a) of slots radially spaced apart 180° from a second outer array (74b, 76b, 78b) of slots, the first outer arrays of each of the distal, intermediate, and proximal (78 a) groups are not radially aligned, and the second outer arrays of each of the distal, intermediate, and proximal groups are not radially aligned; an inner cannula assembly (14, 614) including an inner handle (90, 702) and an inner cannula (92, 704) defining a second passageway and configured to be received within the first passageway, the inner cannula (92, 704) includes a plurality of second openings (134a, 134b, 134c) between a first end (120, 760) and a second end (122, 762) of the second passageway; and a flexible seal mounted to the inner handle (90, 702) and positioned such that the seal contacts the outer cannula assembly (12, 612) when the inner cannula assembly (14, 614) is in cooperation with the outer cannula assembly (12, 612) to create a substantially airtight seal therebetween; wherein the inner cannula (92, 704) is longitudinally and axially movable relative to the outer cannula (18, 618) to simultaneously selectively align at least one first opening (72a, 72b, 72c) with at least one second opening (134a, 134b, 134c) to permit aspiration of bone marrow therethrough and to misalign at least one of another first opening (72a, 72b, 72c) and at least one of another second opening (134a, 134b, 134c) to restrict aspiration of bone marrow therethrough. an outer cannula assembly (12, 612) including an outer handle (16, 616) and an outer cannula (18, 618) defining a first passageway and including a plurality of first openings (72a, 72b, 72c) between a first end (58, 680) and a second end (60, 682) of the first passageway, the plurality of first openings arranged in distal, intermediate, and proximal groups, each group including a first outer array (74a, 76a, 78a) of slots radially spaced apart 180° from a second outer array (74b, 76b, 78b) of slots, the first outer arrays of each of the distal, intermediate, and proximal (78 a) groups are not radially aligned, and the second outer arrays of each of the distal, intermediate, and proximal groups are not radially aligned; an inner cannula assembly (14, 614) including an inner handle (90, 702) and an inner cannula (92, 704) defining a second passageway and configured to be received within the first passageway, the inner cannula (92, 704) includes a plurality of second openings (134a, 134b, 134c) between a first end (120, 760) and a second end (122, 762) of the second passageway; and a flexible seal mounted to the inner handle (90, 702) and positioned such that the seal contacts the outer cannula assembly (12, 612) when the inner cannula assembly (14, 614) is in cooperation with the outer cannula assembly (12, 612) to create a substantially airtight seal therebetween; wherein the inner cannula (92, 704) is longitudinally and axially movable relative to the outer cannula (18, 618) to simultaneously selectively align at least one first opening (72a, 72b, 72c) with at least one second opening (134a, 134b, 134c) to permit aspiration of bone marrow therethrough and to misalign at least one of another first opening (72a, 72b, 72c) and at least one of another second opening (134a, 134b, 134c) to restrict aspiration of bone marrow therethrough.