Question 19M.3.SL.TZ1.3
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.3.SL.TZ1.3 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Deduce, Identify | Question number | 3 | Adapted from | N/A |
In 1628, the physician William Harvey described details of the circulation of blood for the first time. In one experiment, he tied a tight bandage around the upper arm of a volunteer to display the blood vessels in the lower arm more clearly. He pressed his finger on the blood vessel at H. At the same time, he pushed the blood in the vessel from H to O with a second finger, removing the blood as shown in the diagram. When the finger at H was released, the blood vessel refilled with blood.
[Source: adapted from William Harvey original plate]
Identify the type of blood vessels shown in the diagram.
[1]
vein/veins
Veins were often identified but arteries almost as frequently.
Deduce what the experiment demonstrated about the circulation of blood.
[2]
a. blood flows towards the heart ✔
b. valves prevent backflow ✔
c. blood flow is unidirectional ✔
The majority of candidates described what was shown in the illustration rather than making a deduction. The most common correct answers were veins taking blood to the heart and flow being unidirectional. Surprisingly, the presence of valves was less often noted.
