Sisäänhengityksen

Sisäänhengitys, also known as inhalation or inspiration, is the process by which air is drawn into the lungs. It is the first phase of breathing, the fundamental respiratory act that supplies the body with oxygen and removes carbon dioxide. This process is largely involuntary, meaning it occurs automatically without conscious thought, though it can also be controlled voluntarily to a certain extent.

During inspiration, the diaphragm, a large dome-shaped muscle located at the base of the chest cavity, contracts and flattens. Simultaneously, the external intercostal muscles, located between the ribs, contract, pulling the rib cage upward and outward. These muscular actions increase the volume of the thoracic cavity. As the volume of the thoracic cavity increases, the pressure inside the lungs, known as intrapulmonary pressure, drops below the atmospheric pressure. This pressure difference causes air to flow from the higher pressure outside the body into the lower pressure within the lungs.

The air enters the body through the nasal cavity or mouth, passes through the pharynx, larynx, and trachea, and then travels down the bronchi into progressively smaller airways called bronchioles, finally reaching the alveoli in the lungs. It is in the alveoli, tiny air sacs, where the crucial exchange of gases takes place: oxygen from the inhaled air diffuses into the bloodstream, and carbon dioxide from the blood diffuses into the alveoli to be exhaled.