Map the mammalian heart
Describe the external and internal structure of the mammalian heart and trace one-way blood flow.
Section 8.3 · The heart
AS Level; Cambridge International Biology 9700, 2028–2030. Written practice is self-checked; microscope recognition, biological drawing and supervised practical competence require practical work, while human subject-teacher review remains pending.
Before you begin
- Know that mass transport moves substances between exchange surfaces and cells, and that diffusion occurs down a concentration or partial-pressure gradient.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What separates the right and left sides of the heart?
What you will learn
- Identify the four chambers, septum, valves and major vessels
- Describe the external and internal organisation of the heart
Build the explanation
The mammalian heart has a right and left atrium above a right and left ventricle. The septum separates the two sides. The vena cava enters the right atrium; blood passes through the atrioventricular valve to the right ventricle and leaves through the pulmonary artery. Pulmonary veins enter the left atrium; blood passes through the left atrioventricular valve to the left ventricle and leaves through the aorta. Semilunar valves lie at the exits to the pulmonary artery and aorta. Coronary arteries on the heart surface supply the cardiac muscle.
Apply it carefully
Orient diagrams from the body's left and right, not the viewer's. The right side may appear on the left of an anterior-view drawing. Follow valves as one-way gates between chambers and at artery exits. A diagram is simplified; identify only the structures that the question asks for and do not treat a schematic as a scale drawing.
Pause and explain
Which chamber receives blood from the pulmonary veins?
Worked example
Which chamber pumps blood into the aorta?
Show the worked solution
- Follow the systemic route.
- The aorta leaves the left ventricle.
Answer The left ventricle.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Trace blood from the vena cava through the heart to the pulmonary artery.
Give me a hint
Include the valve between each chamber and the vessel exit.
Compare my reasoning
- Vena cava → right atrium → atrioventricular valve → right ventricle.
- Right ventricle → semilunar valve → pulmonary artery.
Blood enters the right atrium from the vena cava, passes through the right atrioventricular valve to the right ventricle, then passes through the pulmonary semilunar valve into the pulmonary artery.
Look for these in your work
- Chambers in order
- Valves included
- Pulmonary artery exit correct
A heart is shown from the front. The viewer's left chamber has the thickest ventricular wall. Which ventricle is this, and why can orientation be confusing?
Give me a hint
Distinguish anatomical left from the viewer's left.
Compare my reasoning
- It is the anatomical left ventricle.
- In an anterior view, anatomical right and left are opposite the viewer's sides.
It is the anatomical left ventricle. In a front-view diagram, the body's right side appears on the viewer's left, so use labels or orientation markers rather than guessing from the page.
Look for these in your work
- Anatomical chamber identified
- View orientation explained
Explain how the septum and valves support separate, one-way pulmonary and systemic pathways.
Give me a hint
State what each structure separates or controls.
Compare my reasoning
- The septum separates right and left sides.
- Valves prevent backflow and the chamber/vessel sequence directs blood through each circuit.
The septum keeps the right and left sides separate. Atrioventricular and semilunar valves open and close with pressure changes to limit backflow, so blood passes through the pulmonary and systemic pathways in the correct direction.
Look for these in your work
- Separation role stated
- Valve role stated
- Pathway direction linked
Common mistakes
- Reversing the body's sides in a front-view diagram
- Putting pulmonary veins into the right atrium
- Treating valves as pumps
What can you explain now?
What separates the right and left sides of the heart?
Compare with the explanation
The septum
The septum prevents the two sides' blood from mixing in the normal heart.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Make it stick
Trace blood through all four chambers and name the valves and vessels at each transition.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.