What is the seventh organ to exist

The stomach

Explanation:

As the main organ in the body that is the most important for body function, in the first place there would be the brain. After that, there are the lungs, the liver, the bladder, the kidneys, the heart, and the seventh organ to exist there is the stomach.

There are also 11 organ systems which are skeletal, integumentary, muscular, lymphatic, respiratory, digestive, endocrine, nervous, cardiovascular, urinary, and reproductive systems.

The stomach is referring to the digestive system of the body.

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frequency is the answer