aiMOOC

The human circulatory system and the heart - Science Year 6

QR-Code

Introduction

How does blood travel from the body to the lungs and back to the body? Connect a muscular pump, a network of vessels and the blood moving through them. Follow a complete route instead of memorising disconnected labels.

Success criteria. Name the main parts of circulation, explain the heart's role, label a simplified four-chamber diagram, trace both linked circuits and interpret a supplied pulse dataset with a limitation.

The diagrams are explanatory models and the measurements below are fictional. Analyse them without taking or sharing personal health measurements. No pulse number in this course is a diagnostic boundary or a ranking of learners.

Connect the pump, the vessels and the transported blood

Three parts working together. The heart is a muscular pump. Blood vessels form the routes, while blood carries substances through those routes. Working body tissues receive oxygen and nutrients, and blood also carries substances away, including carbon dioxide produced by cells.

These roles are connected but different. The heart does not manufacture oxygen. The lungs exchange gases with the blood. Digestion and absorption provide many nutrients, while circulation transports absorbed substances. Drawing arrows between the roles helps explain the system rather than turning the heart into a box that does everything.

Four chambers, two linked sides. The right atrium and left atrium receive blood entering their respective sides. The right ventricle pumps towards the lungs; the left ventricle pumps towards the body. A dividing wall, the septum, separates the two sides. Valves help prevent backflow during the pumping cycle.

Read the actual source diagram. The cutaway labels right atrium and right ventricle on the viewer's left, and left atrium and left ventricle on the viewer's right. The labels use the person's own right and left. An anatomical drawing is not a mirror instruction to rename the chambers.

Locate the aorta, vena cava, pulmonary arteries and pulmonary veins using their labels. The diagram also includes valve and wall details. For the main assessment, identify the four chambers and the named major connections; memorising every small label is not required.

Artery and vein are direction words. An artery carries blood AWAY from the heart. A vein carries blood TOWARDS the heart. A pulmonary artery still counts as an artery even though it carries blood with relatively less oxygen from the heart to the lungs. Pulmonary veins return blood with relatively more oxygen from lungs to heart.

Colour is a model convention. Red and blue commonly distinguish oxygen-rich and oxygen-poor routes in a heart diagram. Human blood is not blue: less-oxygenated blood is a darker red. Use names, directions and written oxygen descriptions so an explanation does not depend on colour vision or a coloured printout.

Capillaries provide exchange sites. Small vessels connect the arterial and venous sides of each circulation. At body capillaries, substances can move between blood and surrounding tissues. At lung capillaries, blood gains oxygen and releases carbon dioxide. A simplified route shows these exchange locations without drawing every microscopic vessel.

A pump analogy and its limit. A water pump and pipes can model pressure-driven movement through a route. They do not show living heart muscle, blood components, valves in full detail or gas exchange across tiny vessel walls. State which relationship the analogy explains and which part needs a biological explanation.

Check your concept map. Connect heart to pumping, vessels to directed routes, blood to transport, lungs to gas exchange and body capillaries to tissue exchange. Correct the claim 'the heart fills the lungs with blood instead of air': air travels through airways, while blood flows through vessels beside the air spaces.

Trace a complete route through heart, lungs and body

Use direction before oxygen content. Start with blood in body capillaries after exchange with tissues. It returns towards the right side of the heart, travels to the lungs, returns to the left side and is pumped out again. The same circulation repeats; the blood is not used up after one visit to a muscle.

The table gives a simplified healthy adult-style circulation model appropriate for this introductory route. It omits smaller branches, the liver's additional routing and the heart muscle's own blood supply.

From	To	Main relationship
Body capillaries	Body veins	Blood returns after exchange with tissues
Body veins	Right atrium	Veins carry blood towards the heart
Right atrium	Right ventricle	Blood moves into the lower right chamber
Right ventricle	Pulmonary arteries	Blood is pumped away towards the lungs
Pulmonary arteries	Lung capillaries	Blood reaches the lung exchange vessels
Lung capillaries	Pulmonary veins	Blood returns after gaining oxygen
Pulmonary veins	Left atrium	Veins carry blood back towards the heart
Left atrium	Left ventricle	Blood moves into the lower left chamber
Left ventricle	Aorta and body arteries	Blood is pumped away towards body tissues
Aorta and body arteries	Body capillaries	Blood reaches the tissue exchange vessels

Explain both circuits. Right ventricle to lungs and back to left atrium is the pulmonary circulation. Left ventricle to body tissues and back to right atrium is the systemic circulation. The two sides work together in a continuous system; one is not switched off while the other takes its turn.

Follow oxygen at the exchange sites. Blood entering lung capillaries has relatively less oxygen. It gains oxygen there and returns through pulmonary veins with relatively more. At body tissues, oxygen moves from blood to cells that use it. The returning blood still contains some oxygen: 'oxygen-poor' does not mean empty of all oxygen.

The original British Heart Foundation animation How does a healthy heart work? supports chamber and flow reasoning. Pause to find a labelled atrium, a ventricle and a pulmonary vessel. Compare its model with the complete native route above; colours and animated size are explanations, not exact measurements of a person's heart.

A worked route card. A card starts at the right ventricle. Its next named vessel is the pulmonary artery, then lung capillaries, then pulmonary veins, then left atrium. It does not jump directly to the body arteries or cross the septum into the left ventricle.

An unfamiliar starting place. Start instead at the left atrium and finish at the right atrium. The route goes through left ventricle, aorta/body arteries, body capillaries and body veins. Choosing a different starting point does not reverse any arrows. Check the result against each actual connection in the table.

Repair two common errors. A route 'right ventricle → body arteries' skips the lungs and the left heart in this model. A rule 'every artery carries oxygen-rich blood' fails at the pulmonary artery. Correct both by using the complete directed route rather than remembering a colour.

Your labelled diagram. Draw or describe the four chambers, lungs, body capillaries and major connecting vessels. Add arrowheads and name where oxygen enters the blood. A numbered route table with clear spoken or written explanations is an accessible alternative to a drawing.

Interpret pulse evidence without turning it into a diagnosis

A pulse is evidence of pumping, not the whole system. Heart contractions create pressure changes in arteries. Pulse rate is normally expressed in beats per minute, abbreviated bpm. It describes how often a pulse is counted, not the volume of blood pumped by each beat, the blood's oxygen percentage or a person's complete health.

A supplied fictional record. One model observation sequence counts pulses for thirty seconds at each stage. These values are invented for learning and are not data from a real pupil.

Stage	Count in 30 seconds	Calculated rate in bpm
Before the activity	40	80
Immediately afterwards	58	116
After 2 minutes of rest	46	92
After 4 minutes of rest	41	82

Thirty seconds is half a minute, so doubling each count estimates the corresponding per-minute rate. Forty becomes eighty; fifty-eight becomes one hundred and sixteen. Counting for thirty seconds and multiplying by four would overstate the rate.

Describe the actual pattern. The model rate rises from 80 to 116 bpm, an increase of 36. It then falls to 92 and 82 bpm during rest. The final value is close to, but not exactly, the starting value. Do not say the table records an identical return to baseline.

Connect observation to mechanism. During activity, working muscles generally need oxygen delivered and carbon dioxide removed more rapidly. Heart rate can increase as part of the response. The table is consistent with that explanation, but by itself it does not measure oxygen delivery, the amount pumped per beat or long-term fitness.

A useful measurement limit. Missing one pulse in a thirty-second count changes the calculated rate by two bpm. The rate may also change during the counting interval, and different observation timing can affect comparisons. A single before/after sequence cannot establish a person's lifelong health or show that one classmate is fitter than another.

An anomalous copied value. Suppose a transcription shows 580 pulses in thirty seconds where the original record shows 58. First check the source record and counting interval. Do not call the higher number a real observation or use it to diagnose a condition when the evidence identifies a copying error.

Plan a fairer comparison on paper. Keep counting duration, activity description, observation timing and recording method consistent. Use repeated observations and record uncertainty. Real supervised school activities must follow the teacher's established arrangements and each learner's circumstances; this course can be completed using only the supplied data.

A careful conclusion. 'In this fictional record, pulse rate increased after the activity and declined during rest. The change fits increased circulatory demand, but one model sequence cannot establish long-term fitness.' That connects a claim, numerical evidence, scientific reasoning and a limitation.

Final evidence. Submit a labelled circulation diagram or complete route table, explain the separate roles of heart, vessels and blood, and interpret the pulse record. Use at least three scientific terms accurately. Include a corrected misconception and one limit of the diagram or measurements. A successful digital explanation demonstrates reasoning, not observed practical pulse-taking skill.

Interactive Tasks

Quiz: Test Your Knowledge

What is the heart's main role in the circulatory system? (Pumping blood through the vessel network) (!Manufacturing all the oxygen in the lungs) (!Digesting all food directly inside its chambers) (!Replacing blood vessels with airways)

Which description defines an artery? (A vessel carrying blood away from the heart) (!Any vessel coloured red on a diagram) (!Only a vessel carrying blood towards the heart) (!A vessel that always has oxygen-rich blood)

Where does blood from the right ventricle go next in the route? (Into pulmonary arteries towards the lungs) (!Directly into the aorta towards the body) (!Across the septum into the left ventricle) (!Into the digestive tract as swallowed food)

Which vessels return oxygen-rich blood from lungs to heart? (Pulmonary veins) (!Pulmonary arteries) (!The aorta) (!The body veins before the right atrium)

What happens at lung capillaries in this model? (Blood gains oxygen and releases carbon dioxide) (!Blood becomes blue because oxygen disappears) (!The heart makes food particles there) (!Every blood vessel ends permanently)

Why does the diagram's right atrium appear on the viewer's left? (Right and left refer to the person whose heart is shown) (!The labels always use the viewer's own body sides) (!The heart contains only one side) (!The diagram proves all hearts have reversed anatomy)

What is the rate for fifty-eight counted pulses in thirty seconds? (One hundred and sixteen beats per minute) (!Fifty-eight beats per minute) (!Two hundred and thirty-two beats per minute) (!Twenty-nine beats per minute)

What does the final fictional pulse value show? (Eighty-two bpm which is close to but not equal to the initial eighty) (!An exact return to eighty bpm) (!A permanent fitness ranking for the learner) (!The amount of oxygen in every blood cell)

What is a limitation of one pulse sequence? (It cannot establish long-term health or fitness) (!It contains no numbers that can be compared) (!It proves heart rate never changes) (!It measures all vessel branches directly)

What do blue regions in the explanatory heart drawing mean? (A convention for a relatively lower-oxygen route rather than blue human blood) (!All human veins contain blue liquid) (!The region has no blood or oxygen at all) (!The source is an exact photograph of tissue colours)

Memory Game

Heart	The muscular pump moving blood
Artery	A vessel carrying blood away from the heart
Vein	A vessel carrying blood towards the heart
Capillary	A small exchange vessel
Atrium	An upper heart chamber receiving incoming blood
Ventricle	A lower heart chamber pumping blood out
Pulse rate	The counted pulse frequency expressed per minute

Drag and Drop

Right ventricle	Pumps towards the lungs through pulmonary arteries
Left ventricle	Pumps towards the body through the aorta
Lung capillaries	Exchange gases with blood at the lungs
Body capillaries	Exchange substances between blood and tissues
One pulse sequence	Limited evidence requiring a cautious conclusion

Crossword Puzzle

HEART	The muscular circulatory pump
ARTERY	A vessel defined by movement away from the heart
VEIN	A vessel returning blood towards the heart
ATRIUM	An upper receiving chamber
VENTRICLE	A lower pumping chamber
CAPILLARY	A tiny vessel used for exchange

LearningApps

Optional extra practice. Choose an appropriate activity with your teacher. If the external collection is unavailable, use the native activities and independent tasks in this course.

Cloze Text

Open Tasks

Easy

Five role labels: Label heart, blood vessels, blood, lungs and body capillaries. Explain each role in one sentence.
Four chambers: Find both atria and both ventricles in the source drawing. Explain the person-versus-viewer orientation.
First pulse conversion: Convert the first two thirty-second pulse counts to per-minute rates. State the time conversion.
Direction classification: Explain artery and vein using direction. Give the pulmonary artery as a counterexample to the oxygen-only rule.

Standard

Complete circulation route: Construct a labelled diagram or route table covering both linked circuits, every connection and the return to the starting region.
New starting point: Trace from left atrium to right atrium without reversing any arrow. Explain the exchange location passed.
Pulse pattern and limit: Describe all four supplied rates, calculate the rise and explain why the final value is not identical to baseline. State one limitation.
Correct a model error: Repair the right-ventricle-to-body shortcut and the claim that blue diagram regions show blue human blood.

Advanced

Evaluate a pump analogy: Explain one useful relationship and two limits of a pump-and-pipes model compared with living circulation.
Measurement uncertainty: Explain how one missed pulse in thirty seconds changes the calculated rate. Suggest consistent timing and repeat observations in a paper plan.
Transcription versus observation: Compare the copied 580 with the original 58 count. Identify the evidence-supported correction without diagnosing anyone.
Complete scientific explanation: Use a route, numerical evidence and at least three scientific terms to explain circulatory response to activity. Include a limit and an accessible alternative to drawing.

Learning Check

Main parts and roles: Submit labelled parts and a connected explanation.
Complete directed route: Trace both linked circuits with labelled arrows.
Direction and oxygen: Explain pulmonary vessels and where gas exchange occurs.
Actual pulse calculations: Interpret the complete fictional table.
Evidence and misconception: Explain a response, check the copying error and name a limit.
Unfamiliar route and complete explanation: Trace from left atrium and assess an original response.

Worked checks and assessment guidance

Heart pumps; vessels provide directed routes; blood transports substances. Lungs exchange gases and body capillaries exchange with tissues. The heart does not manufacture oxygen or digest food. Four chambers are right atrium, right ventricle, left atrium and left ventricle.
Body capillaries → body veins → right atrium → right ventricle → pulmonary arteries → lung capillaries → pulmonary veins → left atrium → left ventricle → aorta and body arteries → body capillaries. Start elsewhere if desired but preserve every directed connection.
Pulmonary arteries carry relatively oxygen-poor blood away from the right ventricle towards the lungs. Pulmonary veins return relatively oxygen-rich blood towards the left atrium. Artery/vein depend on direction; colour is a model convention and oxygen-poor blood is not completely oxygen-free.
Thirty-second counts 40, 58, 46, 41 correspond to 80, 116, 92, 82 bpm. Initial rise is 36 bpm. Rates then fall during rest; final 82 is two above initial 80, not an identical return. One missed pulse changes a doubled thirty-second estimate by 2 bpm.
Increased muscle demand is consistent with a faster circulatory response, but this sequence does not measure oxygen delivery or long-term fitness. The original 58 versus copied 580 identifies a transcription error. Repeat timing consistently; no diagnosis or learner ranking follows from the supplied fictional values.
Left atrium → left ventricle → aorta and body arteries → body capillaries → body veins → right atrium. Require labels, arrowheads or a clear table, at least three accurate scientific terms and a specific model or measurement limitation. Digital work does not establish observed pulse-taking competence.

Learning evidence

Keep a labelled four-chamber diagram or full directed route, a five-role concept map, all pulse conversions and a claim–evidence–reasoning conclusion with a limitation. Preserve corrected misconceptions. No personal measurements or fitness comparison are required.

OER and Wikipedia

Checked 12 November 2026. Department for Education: science programmes of study, Year 6 animals including humans, informs main parts, functions and evidence-based explanation.

NHLBI: How blood flows through the heart and British Heart Foundation: How your heart works support the chamber sequence and lung/body routes. This is an introductory model, not personal medical assessment.

Original embedded British Heart Foundation: How does a healthy heart work? supports the labelled circulation model. It remains at its publisher and is not described as Commons-licensed.

Route tasks, fictional counts, calculations, counterexamples and feedback are original. Diagrams are unchanged, use the person's right/left and explanatory colours, and omit many smaller routes. No exact physiological size or clinical range is inferred from screen images.

Heart diagram-en.svg, ZooFari, CC BY-SA 3.0. Unchanged.

Circulatory System en.svg, LadyofHats, Mariana Ruiz Villarreal, Public domain. Unchanged.