The tiny air sacs called alveoli are found in which human organ?

The correct option is Lungs.

Step-by-step Explanation:

1. Structure and Function of Alveoli:
Alveoli are microscopic, balloon-like air sacs located at the very ends of the respiratory tree (branching off from the bronchioles). They serve as the primary site of gas exchange in the human body, allowing oxygen to diffuse into the bloodstream and carbon dioxide to be removed from it.

2. Organ Identification:
These tiny structures are located exclusively within the lungs. A pair of healthy adult human lungs contains roughly 300 to 500 million alveoli, providing a massive surface area for efficient respiration.

3. Analysis of Other Options:
• Kidneys: The functional filtering units of the kidneys are called nephrons, not alveoli.
• Liver: The liver consists of functional units called hepatic lobules containing cells known as hepatocytes.
• Heart: The heart is a muscular organ composed of cardiac muscle cells divided into four chambers (atria and ventricles) designed to pump blood.