Question

Diaphragm is a thin muscular membrane that separates the abdominal cavity from the thoracic cavity. When the diaphragm of man is completely dome-shaped it shows
A. End of expiration and beginning of inspiration
B. Beginning of expiration and of inspiration
C. Increased rate of breathing
D. Decreased rate of breathing

Answer 1

Hint: The diaphragm is the major muscle organ responsible for breathing in humans. It is located below the lungs. During inhalation the diaphragm contracts and flattens while upon exhalation the diaphragm comes back into its relaxed state with a dome-like shape.

Complete step by step answer: Breathing is a process in which air moves in and out of the lungs by facilitating the exchange of gas with the internal environment. The mechanism of breathing takes place by two processes: inspiration and expiration. During inspiration the diaphragm and the external intercostal muscles contract. The chest is flattened during this process. It creates a vacuum and the lungs are filled with air. Expiration is a process in which the diaphragm and intercostal muscles relax and the diaphragm is back to its dome shape. During this process, the air is exhaled out of the lungs. The more pressure inside the lungs makes it rush the air outside. So, basically breathing is a process in which oxygen is inhaled and carbon dioxide is exhaled out. So, now it is clear that when the diaphragm is in dome shape the person is about to inspire and it is the end of expiration.
Hence option A is the right answer.

Note: Breathing and respiration are both different processes. Breathing involves inhalation and exhalation of oxygen and carbon dioxide respectively whereas respiration is a process in which energy is generated by oxidizing the complex organic substances required to carry out various life processes. Breathing is a simple process as compared to respiration which is a complex process.