{"schemaVersion":1,"id":"en-hub-systemes","type":"hub","pillar":"body","locale":"en","translationGroupId":"hub-systemes","slugPath":"body/systems","title":"The systems of the body","shortTitle":"Systems","summary":"Seventeen pages describing not parts but workings: what commands, what carries, what transforms, what protects. None has a 3D scene, and each says why.","level":"beginner","estimatedMinutes":4,"synonyms":["body systems","nervous system","brain","circulation","breathing","digestion","immunity"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"A structure occupies a place; a system performs a function. "},{"kind":"link","value":"Pectoralis major","href":"/en/body/muscles/pectoralis-major","external":false},{"kind":"text","value":" can be located, felt and shown. The nervous system sits nowhere in particular: it runs through everything."}]},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"These seventeen pages describe workings rather than parts. They were written by the same rule as the rest of the corpus — each because a word kept appearing without ever being described — and they share a constraint the "},{"kind":"link","value":"Body","href":"/en/body","external":false},{"kind":"text","value":" pillar displays rather than works around: "},{"kind":"strong","value":"none has a 3D scene"},{"kind":"text","value":"."}]},{"id":"b3","type":"heading","level":2,"text":"What commands","anchor":"what-commands"},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"The nervous system and what it produces. These eight pages read in order, from general to particular, and the "},{"kind":"link","value":"from an intention to a movement","href":"/en/pathways/from-an-intention-to-a-movement","external":false},{"kind":"text","value":" pathway strings them together."}]},{"id":"b5","type":"list","ordered":false,"items":[[{"kind":"link","value":"The nervous system","href":"/en/body/systems/the-nervous-system","external":false},{"kind":"text","value":" — central and peripheral, and the part that works without the will."}],[{"kind":"link","value":"The neuron","href":"/en/body/systems/the-neuron","external":false},{"kind":"text","value":" — a signal that never varies in size, only in rate."}],[{"kind":"link","value":"The neuromuscular junction","href":"/en/body/systems/the-neuromuscular-junction","external":false},{"kind":"text","value":" — where the command becomes contraction, and why relaxing costs energy."}],[{"kind":"link","value":"The brain","href":"/en/body/systems/the-brain","external":false},{"kind":"text","value":" — its map, its real neuron count, and where they actually are."}],[{"kind":"link","value":"Motor control","href":"/en/body/systems/motor-control","external":false},{"kind":"text","value":" — why a fast movement is launched rather than steered."}],[{"kind":"link","value":"Proprioception","href":"/en/body/systems/proprioception","external":false},{"kind":"text","value":" — the sense that knows where the body is without looking."}],[{"kind":"link","value":"Balance","href":"/en/body/systems/balance","external":false},{"kind":"text","value":" — three independent pieces of information the brain must reconcile."}],[{"kind":"link","value":"Pain","href":"/en/body/systems/pain","external":false},{"kind":"text","value":" — the difference between the signal sent and the experience lived."}]]},{"id":"b6","type":"heading","level":2,"text":"What carries","anchor":"what-carries"},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"Five pages on what circulates, and on the two networks that handle it."}]},{"id":"b8","type":"list","ordered":false,"items":[[{"kind":"link","value":"The heart","href":"/en/body/systems/the-heart","external":false},{"kind":"text","value":" — two circuits in series, and what training actually improves."}],[{"kind":"link","value":"Blood and circulation","href":"/en/body/systems/blood-and-circulation","external":false},{"kind":"text","value":" — everything happens in the capillaries; the rest is plumbing."}],[{"kind":"link","value":"The lungs","href":"/en/body/systems/the-lungs","external":false},{"kind":"text","value":" — an exchange costing no energy, and the fact that breath is not what limits."}],[{"kind":"link","value":"The lymphatic system","href":"/en/body/systems/the-lymphatic-system","external":false},{"kind":"text","value":" — the return network, with no pump."}],[{"kind":"link","value":"The kidneys","href":"/en/body/systems/the-kidneys","external":false},{"kind":"text","value":" — a regulator, not a waste filter."}]]},{"id":"b9","type":"heading","level":2,"text":"What transforms","anchor":"what-transforms"},{"id":"b10","type":"list","ordered":false,"items":[[{"kind":"link","value":"The digestive system","href":"/en/body/systems/the-digestive-system","external":false},{"kind":"text","value":" — a tube whose inside is, technically, outside the body."}],[{"kind":"link","value":"The endocrine system","href":"/en/body/systems/the-endocrine-system","external":false},{"kind":"text","value":" — a slow, diffuse network with no designated recipient."}]]},{"id":"b11","type":"heading","level":2,"text":"What protects","anchor":"what-protects"},{"id":"b12","type":"list","ordered":false,"items":[[{"kind":"link","value":"The skin","href":"/en/body/systems/the-skin","external":false},{"kind":"text","value":" — barrier, sensor, and above all radiator."}],[{"kind":"link","value":"The immune system","href":"/en/body/systems/the-immune-system","external":false},{"kind":"text","value":" — a defence that recognises before it fights."}]]},{"id":"b13","type":"heading","level":2,"text":"Why none of these pages has a scene","anchor":"why-none-of-these-pages-has-a-scene"},{"id":"b14","type":"callout","tone":"limit","title":"Three reasons, and each page says which","content":[[{"kind":"text","value":"Body Lab's scenes derive from four anatomical sources: the skeleton, the muscles, the joints and the regions of the body. None of these systems appears among them — but not for the same reason, and running the three together would give a blanket excuse where the project owes an account."}],[{"kind":"strong","value":"The source does not contain the tissue"},{"kind":"text","value":": nerves, vessels, lungs, heart, glands, skin."}],[{"kind":"strong","value":"The scale is beyond a mesh's reach"},{"kind":"text","value":": neuron, neuromuscular junction, proprioceptive receptors, capillaries, alveoli."}],[{"kind":"strong","value":"The data exists, but under a non-commercial licence"},{"kind":"text","value":": the digestive system and the kidneys belong to the visceral system of the atlas used, which the project cannot take up."}],[{"kind":"text","value":"The Body hub announced at launch that these systems would not be covered. The position has changed on one point: being unable to show does not require saying nothing, provided the absence is declared."}]]},{"id":"b15","type":"heading","level":2,"text":"Where to start","anchor":"where-to-start"},{"id":"b16","type":"paragraph","content":[{"kind":"text","value":"The "},{"kind":"link","value":"from an intention to a movement","href":"/en/pathways/from-an-intention-to-a-movement","external":false},{"kind":"text","value":" pathway follows a single movement, from the decision through to recovery, crossing nine of these pages in order. It is the most continuous read."}]},{"id":"b17","type":"paragraph","content":[{"kind":"text","value":"Otherwise "},{"kind":"link","value":"the nervous system","href":"/en/body/systems/the-nervous-system","external":false},{"kind":"text","value":" is the widest door: it links all the others."}]},{"id":"b18","type":"shapierAction","actionId":"pathway-energy-recovery","label":"Follow the Energy and Recovery pathway","description":"Putting these workings to use for training and recovery happens in Shapier; Body Lab only describes how these systems work.","webTarget":"https://shapier.app/en/parcours/energie-recuperation","appTarget":"shapier://parcours/energie-recuperation"},{"id":"b19","type":"relatedContent","title":"The seventeen systems","targetIds":["en-mechanism-nervous-system","en-mechanism-neuron","en-mechanism-neuromuscular-junction","en-mechanism-brain","en-mechanism-motor-control","en-mechanism-proprioception","en-mechanism-balance","en-mechanism-pain","en-mechanism-heart","en-mechanism-blood-circulation","en-mechanism-lungs","en-mechanism-lymphatic-system","en-mechanism-kidneys","en-mechanism-digestive-system","en-mechanism-endocrine-system","en-mechanism-skin","en-mechanism-immune-system"]}],"relations":[],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02"},"limitations":["This index page describes how a set is organised; the descriptions, their sources and their limits sit on the pages themselves.","None of these pages assesses an individual situation. A sudden disturbance of speech, vision, strength or balance is a medical emergency."],"seo":{"title":"The systems of the body — command, transport, transformation, protection","description":"An index of the seventeen pages on the body's systems: nervous and brain, heart and circulation, lungs, digestion, hormones, immunity, skin, kidneys.","canonicalPath":"/en/body/systems","image":"/og/en/hub-systemes.png"},"app":{"offlineEligible":true},"version":1}