Question

4. Which of the following structures is NOT part of the respiratory system?
a. Alveoli b. Bronchus c. Heart d. Trachea​

Answer 1

Heart is not a part of respiratotory system. It is the part of circulatory system.

Other all are the part of respiratory system.

Alveoli - Site of exchange of gases.

Bronchule - Branches which come out of the bronchi.

Trachea - The wind pipe.

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Answer 2

The structure which is not a part of the respiratory system is (c) Heart.

Explanation:  

• The alveoli is the site where the exchange oxygen and carbon dioxide takes place between blood and alveoli during the process of breathing in and breathing out.

• A bronchus is a passage or airway in the respiratory system that conducts air into the lungs. It is the further extension of Trachea.

• The heart is a muscular organ the size of a fist that is found directly behind and slightly to the left of the breastbone. The circulatory system includes the heart, which pumps blood through a network of arteries and veins.

• The trachea or windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing air to travel through.

Hence, The structure which is not a part of the respiratory system is (c) Heart.