Beijing's smog woes cast pall over 'green' Winter Olympics

Beijing's air pollution is far below acceptable World Health Organization levels with the Chinese capital a month away from hosting the Winter Olympics –- but environmental data shows its skies have improved dramatically ...

Deciphering the impact of gene loss on biological evolution

A paper in Nature proposes a new evolutionary scenario that helps to better understand the evolution of our phylum and to discover what the ancestor of tunicates—the sister group of vertebrates—were like. Specifically, ...

A heart that beats (almost) like our own

The fruit fly, long the organism of choice for scientists studying genetics and basic biological processes, still harbors some secrets of its own.

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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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