Describe the process of inhalation and exhalation in mammals
Inhalation and exhalation are the processes of breathing, which are essential for mammals to take in oxygen and remove carbon dioxide from the body. Here is a description of this process:
1. Inhalation:
- The first step of breathing is inhalation, where the diaphragm, a dome-shaped muscle located at the base of the lungs, contracts and flattens out, while the external intercostal muscles between the ribs contract, lifting the rib cage.
- As a result of these muscular contractions, the chest cavity expands, increasing its volume, and lowers the air pressure inside the lungs.
- Due to the decrease in air pressure within the lungs, the air from the atmosphere, rich in oxygen, rushes in through the nose or mouth, and then passes through the trachea (windpipe) and bronchi.
- The bronchi further branch out into smaller tubes called bronchioles, which end in tiny air sacs called alveoli.
2. Gas Exchange in the Alveoli:
- The walls of the alveoli are very thin and surrounded by a dense network of capillaries. This ensures efficient gas exchange between the respiratory system and the bloodstream.
- Oxygen molecules in the inhaled air diffuse across the alveolar walls and enter the capillaries, where they bind with hemoglobin in red blood cells to be transported throughout the body.
- At the same time, carbon dioxide, a waste product produced by the body's cells, diffuses out of the capillaries into the alveoli.
3. Exhalation:
- Exhalation is the process of breathing out, which occurs as a passive recoil rather than an active muscular effort, unlike inhalation.
- As the diaphragm and external intercostal muscles relax, the chest cavity returns to its original size, and the air pressure within the lungs increases.
- The increased air pressure forces the now carbon dioxide-rich air to be expelled out of the lungs through the bronchioles, bronchi, trachea, and eventually through the mouth or nose.
- The exhaled air is then released into the atmosphere, completing one cycle of inhalation and exhalation.
Overall, the process of inhalation and exhalation allows mammals to constantly exchange oxygen and carbon dioxide, ensuring the body receives the necessary oxygen for cellular respiration and effectively removes waste carbon dioxide.