Cardiovascular System
The tide that never restsSystema cardiovasculare
A closed loop of pump and pipework that carries oxygen, fuel, heat, and signals to every living cell.
- Primary role
- Transports oxygen, nutrients, hormones, and heat
- Scale
- Roughly 100,000 km of vessels
- Every day
- Moves about 7,500 L of blood
Organs in this atlas 1
How it works as a whole
Nothing in the body is more than a fraction of a millimetre from a capillary, and that is the whole design problem the cardiovascular system solves. A single muscular pump drives blood through arteries that divide and divide again until their walls are one cell thick, close enough for oxygen to step across into tissue. The return journey runs at low pressure through veins whose one-way valves and surrounding muscle do the lifting. Two circuits run in series: a short pulmonary loop to the lungs to reload oxygen, and a long systemic loop to everywhere else.
Other key structures
- ArteriesCarry blood away from the heart under high pressure
- CapillariesSingle-cell-thick walls where exchange actually happens
- VeinsReturn blood at low pressure, using valves against gravity
- BloodThe medium itself — cells, platelets, plasma, and dissolved cargo
Connected systems
- Respiratory SystemSends blood to the lungs to exchange CO₂ for oxygen
- Urinary SystemKidneys filter this system's blood and set its pressure
- Nervous SystemAutonomic signals raise and lower heart rate beat to beat
Common conditions
- Hypertension
- Atherosclerosis
- Heart failure
- Deep vein thrombosis
- Anaemia
- Stroke
The through-lineThe heart's own rhythm is intrinsic — it will beat in isolation — but its rate and force are tuned continuously by the nervous and endocrine systems to match whatever the body is doing.
Did you knowLaid end to end, one person's blood vessels would wrap the equator roughly two and a half times.
The path through this system
0 of 11 steps done — read it, walk it in 3D, then be asked about it.
Start: Heart: the lesson
ReadHeart: the lessonStructure and story of the heart, layer by layer.
3 min
Guided walk-throughGuided dissection: heartWalk the heart structure by structure, then cut inward layer by layer.
6 min
Memo cardsHeart memo cardsTurn the cards on the heart — structures, layers, key facts — and grade yourself.
4 min
Multiple choiceHeart quizA multiple-choice round on the heart, reshuffled every time.
4 min
Multiple choiceCardiovascular System quizA quiz pulling from every organ in the cardiovascular system.
3 min
Click on the 3D modelFind the heart structuresClick the named structures directly on the live 3D heart.
5 minLabel the diagramLabelled diagram: HeartThe heart plate with its labels taken off: put each one back on its number, or draw it yourself first.
5 min
Match layersMatch heart layersPair each layer of the heart, outside in, with what it does.
4 min
Match pairsMatch heart structuresPair each structure in the heart with its role.
4 min
Put in orderOrder the heart's blood flowTrace blood through the heart in the order it actually flows.
4 minReadHeart in the clinicWhere the heart shows up in the clinic, and what goes wrong.
3 min