Bicarbonate buffer system. Human blood contains large amounts of carbonic acid, which is a weak acid, and bicarbonates, a strong base. If blood pH falls below 6.8 or rises above 7.8, one can become sick or die. This bicarbonate buffer system help maintain blood pH at 7.4. The bicarbonate neutralizes excess acids in the blood while the carbonic acid neutralizes excess bases.
Answer: Regulate the movement of materials in and out of the cell
Explanation:
The cell membrane of animal cells is a thin membrane that lines the entire cell surface, and it is a selectively permeable membrane, thus, allowing the entry of useful materials into the cell and exit of waste products out of the cell.
Answer:
Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
Stars start their lives as clouds of dust and gas. Gravity draws these clouds together. A small protostar forms, powered by the collapsing material. Protostars often form in densely packed clouds of gas and can be challenging to detect.
"Nature doesn't form stars in isolation," Mark Morris, of the University of California at Los Angeles (UCLS), said in a statement. "It forms them in clusters, out of natal clouds that collapse under their own gravity."
Smaller bodies — with less than 0.08 the sun's mass — cannot reach the stage of nuclear fusion at their core. Instead, they become brown dwarfs, stars that never ignite. But if the body has sufficient mass, the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium. The star turns on and becomes a main sequence star, powered by hydrogen fusion. Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star.
How long a main sequence star lives depends on how massive it is. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. (This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time.)
Explanation:
I hope this helped!
Atria is a large part of the heart so too big for cells; arteries & veins lead away or to the heart.
Capillaries are the smallest vascular structures that allow materials to be exchanged easily between cells.
Answer:
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Explanation:
Trepanation is used to treat health problems associated with intracranial diseases, epileptic seizures, migraines and mental disorders by relieving pressure.
