4.1.3 Internal Organs⭐内脏

The heart pumps blood to all parts of the body through a system of arteries and veins.

It's located in the chest, between the lungs, and it beats about once per second.

The kidneys remove waste and toxins from the blood.

They are bean-shaped organs and are about 10 centimeters long and 6 centimeters wide.

The lungs exchange oxygen from the air with carbon dioxide from the blood.

They expand when inhaling air, and contract when exhaling air.

The stomach is below the heart and is part of the digestive system.

It uses acids to digest food before passing it to the small intestine.

The bladder is a balloon-shaped organ that collects urine from the kidneys.

In an adult, the bladder can hold about half a liter of urine.

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