4 mistakes learners make with the heart and circulation, each one named and explained.
Blood passes through the heart twice on every circuit, once to the lungs and once to the rest of the body.
You say an artery is a vessel carrying oxygenated blood, so the pulmonary artery has to be a vein.
Nearly every artery you meet first does carry oxygenated blood, so the pattern gets learned as the definition.
Question. Does the pulmonary artery carry oxygenated or deoxygenated blood?
A common answer. oxygenated, because it is an artery
The answer. deoxygenated, and it is still an artery
Why. An artery is defined by carrying blood away from the heart, whatever is in it.
Away from the heart is an artery. The pulmonary pair are the exceptions that prove it.
You trace blood from the heart to the body and back to the heart, and never send it to the lungs.
One loop is the simplest picture, and the heart is drawn as a single pump.
Question. How many times does one drop of blood pass through the heart in one full circuit?
A common answer. once
The answer. twice
Why. Once on the way to the lungs and once on the way to the body, which is why the heart has four chambers.
Count the chambers. Four exists because there are two circuits to drive.
You call the movement of water into a cell diffusion, or describe active transport as going from high to low concentration.
All three move substances across a membrane, and two of them happen without any help.
Question. Glucose is absorbed from the gut into the blood when the blood already holds more of it. What is this?
A common answer. diffusion
The answer. active transport
Why. Moving against the concentration gradient needs energy, which is what makes it active.
Check the direction against the gradient first. That decides which of the three it is.
You say villi and alveoli increase the surface area, without saying what that does to the ratio.
Surface area is the phrase the mark scheme rewards, so it gets said on its own.
Question. Why do alveoli make gas exchange efficient?
A common answer. because they increase the surface area
The answer. because many tiny sacs give a large surface area for a small volume
Why. It is the surface area to volume ratio that matters, not surface area by itself.
Always finish the sentence: large surface area to volume ratio.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.