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Course: MCAT > Unit 3

Lesson 1: Chemical and physical sciences practice passage questions

Blood flow in the arteries


An adult patient is admitted to the hospital after complaining about heart problems. The doctor treating the patient thinks that there may be a problem with the patient’s main pulmonary artery. The main pulmonary artery (MPA) is a short and wide tube shaped artery that carries deoxygenated blood from the heart to the lungs. See Figure 1 for details.
Figure 1. A diagram of the heart. The main pulmonary artery is indicated by the red box.
Tests are run to determine the dimensions of the patient’s (MPA) as well as the constant speed with which blood flows through the patient’s MPA. The results of the tests are shown in in the following table, along with values for a normal adult.
Table 1. Results of the MPA test compared to normal values.
MPA parameterPatient's valuesNormal values (for adult)
MPA length6.0cm5.0cm
MPA radius2.0cm3.0cm
Speed of blood through MPA40cm/sec60cm/sec
In an effort to improve the patient’s blood flow to the lungs, a physician performs an angioplasty to dilate the radius of the MPA. In the first step of the process, the surgeon inserts a special catheter into the heart. The physician immediately follows this by inserting a deflated balloon into the vessel. She pumps the balloon with air, and in doing so enlarges the MPA. Finally, she inserts a permanent metal stent into the vessel wall to support the new expansion.
How long does it take a blood cell to completely pass through the entire length of the main pulmonary artery of the patient?
Choose 1 answer: