What is the primary function of the lungs?

The primary function of the lungs is to exchange gas between the bloodstream and the environment, which is crucial for maintaining life. This process, known as respiration, allows for the intake of oxygen from the air, which is then transported to the body’s tissues to support cellular functions. Concurrently, carbon dioxide, a waste product of metabolism, is expelled from the bloodstream into the lungs to be exhaled. This gas exchange occurs in small air sacs called alveoli, where oxygen diffuses into the blood while carbon dioxide diffuses out.

The other options, while important bodily functions, do not primarily involve the lungs. Regulating body temperature is mainly managed by the skin and sweat glands. Filtering toxins from the blood is primarily the role of the liver and kidneys. Producing hormones for metabolism is mainly the function of the endocrine system, particularly glands such as the pancreas and thyroid. Thus, the correct answer highlights the lungs' essential role in respiration, which is vital for sustaining life and supporting metabolic processes throughout the body.