IGCSE›Cambridge IGCSE Biology›Mind mapsCirculatory SystemsCambridge IGCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsThe systemBlood vessels, a heart pump and valvesEnsures one-way flow of bloodValves stop backflowSingle circulationFound in fishHeart passed through once per circuitHeart → gills → body → heartBlood loses pressure in the gillsDouble circulationFound in mammalsHeart passed through twice per circuitPulmonary circuit: heart to lungs and backSystemic circuit: heart to body and backSeptum keeps the two sides separateCirculationblood transportWhy double?Blood re-pressurised after the lungsFaster oxygen delivery to tissuesOxygenated and deoxygenated blood kept apartSupports high metabolic rate and activityValvesFlaps open for forward flowFlaps close against backflowIn the heart and in veinsNo valves in arteriesExam tipsSay blood passes through the heart twiceName both circuits: pulmonary and systemicFish: gills come before the body