EPA overrides scientists' calls for tougher pollutant limit

The Trump administration on Monday made final its decision to leave limits for a deadly kind of air pollutant unchanged, overriding scientific findings that tougher standards could save tens of thousands of lives yearly.

Organoids produce embryonic heart

There was a time when the idea of growing organs in the lab was the stuff of science fiction. Today, stem cell biology and tissue engineering are turning fiction into reality with the advent of organoids: tiny lab-grown tissues ...

Can we get along? Resilience can help promote civil discourse

For a variety of reasons 2020 has been stressful, frightening, and just plain exhausting. Because of the coronavirus pandemic, some of us have lost loved ones. Many are working from home, and others are unemployed. Wildfires ...

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Heart

The heart is a muscular organ in all vertebrates responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in annelids, mollusks, and arthropods. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart."

The heart of a vertebrate is composed of cardiac muscle, an involuntary striated muscle tissue which is found only within this organ. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during a lifetime (about 66 years). It weighs on average 250 g to 300 g in females and 300 g to 350 g in males.

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