Unlike Tibetans, who adapt to high altitudes by breathing more rapidly and maintaining lower hemoglobin levels, Andean populations have evolved a different physiological response to hypoxic environments. In the high altitudes of the Andes, long-term residents possess significantly elevated hemoglobin concentrations, which directly increase the total oxygen-carrying capacity of their blood. However, this physiological adjustment comes with a distinct physical cost. The high concentration of red blood cells causes the blood to become much more viscous, or thicker, than normal. This increased viscosity, in turn, leads directly to elevated pulmonary arterial pressure as the body attempts to circulate the thick blood. Over many years, the cardiovascular system is forced to work much harder to pump this viscous blood through the pulmonary vessels. This persistent overexertion ultimately results in right ventricular hypertrophy, which is the physical enlargement of the heart’s right ventricle. Consequently, while these elevated hemoglobin levels allow Andean residents to successfully perform demanding physical labor in thin air, they also directly predispose these individuals to chronic mountain sickness in later life.
According to the passage, right ventricular hypertrophy in Andean residents is directly caused by which of the following?
- AThe physical enlargement of the right ventricle, which thickens the red blood cells.
- BAn increase in breathing rate that raises the blood's oxygen-carrying capacity.
- The cardiovascular system's persistent overexertion when pumping highly viscous blood.Answer
- DA sudden drop in pulmonary arterial pressure caused by chronic mountain sickness.