Which of the following factors are favourable for the formation of oxyhaemoglobin in alveoli?

The correct option is High pO₂ and Lesser H⁺ concentration.

Oxyhaemoglobin is formed when oxygen binds with haemoglobin in the red blood cells. This process occurs in the alveoli of the lungs, where oxygen is loaded into the blood. The association of oxygen with haemoglobin is primarily determined by the partial pressure of oxygen (pO₂) and is also influenced by other factors such as the partial pressure of carbon dioxide (pCO₂), hydrogen ion concentration (H⁺ concentration or pH), and temperature.

In the alveoli, the conditions are highly favourable for the binding of oxygen to haemoglobin (association). The specific conditions present in the alveoli include:
1. High pO₂: The air in the alveoli is rich in oxygen, leading to a high partial pressure of oxygen, which drives its binding to haemoglobin.
2. Low pCO₂: Carbon dioxide is constantly expired, keeping its partial pressure low in the alveoli.
3. Lesser H⁺ concentration (higher pH): Lower level of carbon dioxide leads to a decrease in hydrogen ion concentration.
4. Lower temperature: The temperature in the alveolar region is slightly lower compared to active tissues.

All these factors (high pO₂, low pCO₂, lesser H⁺ concentration, and lower temperature) shift the oxygen-haemoglobin dissociation curve to the left, promoting the formation of oxyhaemoglobin. Conversely, in the tissues, low pO₂, high pCO₂, high H⁺ concentration, and high temperature favour the dissociation of oxygen from oxyhaemoglobin.

Therefore, among the given choices, the factor combination that favours oxyhaemoglobin formation in the alveoli is high pO₂ and lesser H⁺ concentration.