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Answer:
D. Alveoli
Explanation:
Functionally, the respiratory system is separated into a conducting zone and respiratory zone:
Conducting zone consists of the nose, pharynx, larynx, trachea, bronchi, and bronchioles. These structures form a continuous passageway for air to move in and out of the lungs.
Respiratory zone is found deep inside the lungs and is made up of the respiratory bronchioles, alveolar ducts, and alveoli. These thin-walled structures allow inhaled oxygen (O2) to diffuse into the lung capillaries in exchange for carbon dioxide (CO2).
The respiratory zone begins where the terminal bronchioles join a respiratory bronchiole, the smallest type of bronchiole, which then leads to an alveolar duct, opening into a cluster of alveoli.
Answer:
The cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells. The first man to witness a live cell under a microscope was Anton van Leeuwenhoek, who in 1674 described the algae Spirogyra. Van Leeuwenhoek probably also saw bacteria.
Explanation:
