Respiratory System — Set 4

Correct Answer: A. 16%

Inhaled air contains about 21% oxygen, while exhaled air still contains about 16% oxygen. The body does not extract all the oxygen from the air in a single breath. This is why mouth-to-mouth resuscitation is effective in emergencies.

Correct Answer: D. Difficulty breathing at high altitudes

Mountain sickness occurs because atmospheric pressure and oxygen concentration decrease at high altitudes. The body may experience headache, fatigue, and breathlessness as it struggles to get enough oxygen. Over time, the body adapts by producing more red blood cells.

Correct Answer: C. pH and CO2 concentration

The correct answer is 'pH and CO2 concentration'. The Bohr effect states that hemoglobin's oxygen-binding affinity is inversely related to acidity and CO2 levels. In tissues with high CO2, hemoglobin releases oxygen more easily. This ensures that active tissues receive the oxygen they need for metabolism.

Correct Answer: C. Esophagus

The esophagus belongs to the digestive system and serves as the passage for food to the stomach. The other three structures are essential components for the conduction and exchange of air. They are all located within the thoracic cavity or neck.

Correct Answer: C. 6000 mL

The correct answer is '6000 mL'. Total lung capacity is the maximum amount of air the lungs can hold after a full inspiration. For an average adult male, this volume is approximately 6 liters. Factors like age, height, and fitness levels can influence this capacity.

Correct Answer: A. Nitrogen

Nitrogen makes up nearly 78% of the Earth's atmosphere. While we inhale it, the body does not use it for respiration, and it is exhaled in the same amount. Oxygen, the gas we use, makes up only about 21% of the air.

Correct Answer: C. Diaphragm

Inhalation is an active process that begins with the contraction of the diaphragm and external intercostal muscles. This contraction expands the chest cavity, lowering the internal air pressure. Air then flows into the lungs from the higher-pressure atmosphere outside.

Correct Answer: D. Difficulty in exhaling air

The correct answer is 'Difficulty in exhaling air'. Emphysema damages the elasticity of the alveoli, making it difficult for the lungs to push air out. Patients often feel they cannot get all the air out of their lungs, leading to 'air trapping'. This results in a barrel-shaped chest and chronic fatigue.

Correct Answer: C. Four

A hemoglobin molecule contains four iron-containing heme groups. Each of these heme groups can bind to one molecule of oxygen. Therefore, a fully saturated hemoglobin molecule carries four oxygen molecules.

Correct Answer: A. Trachea

The trachea is a 10-12 cm long tube that serves as the main airway to the lungs. It is called the windpipe in common language to distinguish it from the food pipe. It is held open by rings of hyaline cartilage.