Respiration in human beings is a complex process that involves the exchange of gases between the atmosphere and the body. This process is essential for the survival of all living beings, as it provides the necessary oxygen for the body to carry out its functions and removes the waste product, carbon dioxide.

The process of respiration can be divided into two main parts: external respiration and internal respiration.

External Respiration:

External respiration refers to the exchange of gases that occurs in the lungs between the atmosphere and the blood. The following steps take place during external respiration:

1. Breathing: Breathing is the process of inhaling air into the lungs and exhaling air out of the lungs. During inhalation, the diaphragm and the intercostal muscles contract, which causes the volume of the thoracic cavity to increase, and air is drawn into the lungs. During exhalation, the diaphragm and the intercostal muscles relax, which causes the volume of the thoracic cavity to decrease, and air is pushed out of the lungs.

2. Diffusion: Once air enters the lungs, the oxygen molecules diffuse from the alveoli into the capillaries surrounding the alveoli. At the same time, carbon dioxide diffuses from the capillaries into the alveoli.

3. Transport: The oxygen molecules that have diffused into the blood are transported by the red blood cells to the body's tissues. Similarly, the carbon dioxide that has diffused into the blood is transported by the red blood cells back to the lungs to be exhaled.

Internal Respiration:

Internal respiration refers to the exchange of gases that occurs between the blood and the body's tissues. The following steps take place during internal respiration:

1. Diffusion: Once the oxygen-rich blood reaches the body's tissues, the oxygen molecules diffuse from the red blood cells into the tissue cells. At the same time, carbon dioxide diffuses from the tissue cells into the blood.

2. Utilization: The oxygen molecules that have diffused into the tissue cells are used by the cells to produce energy through a process called cellular respiration. The waste product, carbon dioxide, is a byproduct of this process and is transported back to the lungs to be exhaled.

In summary, respiration in human beings is a complex process that involves the exchange of gases between the atmosphere and the body. External respiration occurs in the lungs, where oxygen is diffused into the blood and carbon dioxide is diffused out of the blood. Internal respiration occurs in the body's tissues, where oxygen is diffused into the tissue cells and carbon dioxide is diffused out of the tissue cells. This process is essential for the survival of all living beings and is controlled by the respiratory system.