Transport in Animals: Question 7
Syllabus 9.2
A student dissects a mammalian heart in a biology class. After cutting the heart open along its long axis, the student sees four separate internal spaces, flaps of tissue between some of these spaces, and a thick wall of muscle running down the middle of the heart, separating its left and right sides completely.
(a) State the general name given to the two upper chambers of the heart, and the general name given to the two lower chambers. [2]
(b) State the function of the valves found between the atria and the ventricles. [2]
(c) Explain why it is important that the muscular wall between the left and right sides of the heart has no holes in it. [2]
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Worked solution
Part (a): Naming the chambers
The heart has four chambers. The two smaller upper chambers are called the atria (one atrium on each side), and the two larger, more muscular lower chambers are called the ventricles (one ventricle on each side).
Part (b): Function of the atrioventricular valves
The flaps of tissue the student sees between the atria and the ventricles are the atrioventricular valves. Their function is to prevent the backflow of blood from the ventricles into the atria when the ventricles contract. Without these valves, some blood would be forced back the wrong way instead of being pumped forwards out of the heart.
Part (c): Why the septum must have no holes
The thick muscular wall running down the middle of the heart is the septum, and it completely separates the left side of the heart from the right side. The left side always contains oxygenated blood and the right side always contains deoxygenated blood. If the septum had a hole in it, these two types of blood would mix, so the blood leaving the left ventricle for the rest of the body would have a lower oxygen content than it should. This would make the delivery of oxygen to body tissues less efficient, undermining the whole point of having a double circulation that keeps oxygenated and deoxygenated blood apart.
Final answers
- (a) Upper chambers: atria; lower chambers: ventricles.
- (b) Atrioventricular valves prevent backflow of blood from the ventricles into the atria.
- (c) A hole would let oxygenated and deoxygenated blood mix, lowering the oxygen content of blood sent to the body and reducing the efficiency of oxygen delivery.