State two ways in which carbon dioxide is carried in the blood.
Table 4.1 gives the partial pressures of oxygen ($pO_2$) and carbon dioxide ($pCO_2$) at W, X and Y in Fig. 4.1. Using Fig. 4.1 and Table 4.1, describe the exchanges that occur as blood travels from X to Y.
Elastic fibres are found in tissues at the gas exchange surface in the lungs. Describe the roles of elastic fibres in the gas exchange system and in the cardiovascular system.
Scientists in Peru examined how moving from sea level to high altitude affected the composition of blood. Fig. 4.2 shows, for each sampling time: - the mean blood volume per kg of body mass in $\text{cm}^3\,\text{kg}^{-1}$ - the proportions of red blood cells and plasma.
The proportion of mean blood volume made up by red blood cells at sea level is $48\%$. Calculate the percentage of mean blood volume made up by red blood cells at $5$ to $6$ months after living at high altitude. Show your working and give your answer to the nearest whole number.
Describe and explain the results shown in Fig. 4.2.