A cardiotomy and venous blood reservoir comprising: a housing assembly forming a main chamber; a cardiotomy inlet port fluidly connected to the main chamber; a venous inlet port; a downtube defining an upstream region, a downstream region, and a lumen extending therethrough, wherein: the upstream region extends from the venous inlet port, the downstream region extends from the upstream region and terminates at a downstream end located within the main chamber, a diameter of the lumen increases along at least a portion of the downstream region to the downstream end; and a bowl disposed within the main chamber and forming a floor surface facing the downstream end, the floor surface defined by: an annular shoulder segment circumferentially surrounding and radially spaced from the downstream end, when the shoulder segment is spatially located above the downstream end, an intermediate segment extending radially inwardly and downwardly from the shoulder to a bottom face opposite the shoulder, the bottom face being spatially located below the downstream end, characterized in that a protrusion extending radially inwardly and upwardly from the bottom face to a center, wherein the center is aligned with the lumen and spaced below the downstream end. a housing assembly forming a main chamber; a cardiotomy inlet port fluidly connected to the main chamber; a venous inlet port; a downtube defining an upstream region, a downstream region, and a lumen extending therethrough, wherein: the upstream region extends from the venous inlet port, the downstream region extends from the upstream region and terminates at a downstream end located within the main chamber, a diameter of the lumen increases along at least a portion of the downstream region to the downstream end; and a bowl disposed within the main chamber and forming a floor surface facing the downstream end, the floor surface defined by: an annular shoulder segment circumferentially surrounding and radially spaced from the downstream end, when the shoulder segment is spatially located above the downstream end, an intermediate segment extending radially inwardly and downwardly from the shoulder to a bottom face opposite the shoulder, the bottom face being spatially located below the downstream end, characterized in that a protrusion extending radially inwardly and upwardly from the bottom face to a center, wherein the center is aligned with the lumen and spaced below the downstream end. the upstream region extends from the venous inlet port, the downstream region extends from the upstream region and terminates at a downstream end located within the main chamber, a diameter of the lumen increases along at least a portion of the downstream region to the downstream end; and a bowl disposed within the main chamber and forming a floor surface facing the downstream end, the floor surface defined by: an annular shoulder segment circumferentially surrounding and radially spaced from the downstream end, when the shoulder segment is spatially located above the downstream end, an intermediate segment extending radially inwardly and downwardly from the shoulder to a bottom face opposite the shoulder, the bottom face being spatially located below the downstream end, characterized in that a protrusion extending radially inwardly and upwardly from the bottom face to a center, wherein the center is aligned with the lumen and spaced below the downstream end. an annular shoulder segment circumferentially surrounding and radially spaced from the downstream end, when the shoulder segment is spatially located above the downstream end, an intermediate segment extending radially inwardly and downwardly from the shoulder to a bottom face opposite the shoulder, the bottom face being spatially located below the downstream end, characterized in that a protrusion extending radially inwardly and upwardly from the bottom face to a center, wherein the center is aligned with the lumen and spaced below the downstream end.