The right answer is vein (it contains blood and has valves).
The infra-cardiac veins of small and medium caliber possess this system of fight against gravity. The valves consist of a dense connective tissue, surmounted by endothelial cells, corresponding to a fold of the intima. They allow blood circulation in the sense organ / heart but prevent venous reflux.
Answer:
<em>The fact that the left ventricle of the heart is thicker than the right ventricle reveals that it pumps blood against a greater resistance. -C.</em>
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Answer:
endoplasmic reticulum
Explanation:
ER is full with proteins than help to synthesize phospholipids in plant cells
Answer:
chloroplasts
Explanation:
photosynthesis takes place inside plant cells in small things called chloroplasts ( mostly found in the mesophyll layer) contain a green substance called chlorophyll
A star’s life expectancy depends on its mass. Generally, the more massive the star, the faster it burns up its fuel supply, and the shorter its life. The most massive stars can burn out and explode in a supernova after only a few million years of fusion. A star with a mass like the Sun, on the other hand, can continue fusing hydrogen for about 10 billion years. And if the star is very small, with a mass only a tenth that of the Sun, it can keep fusing hydrogen for up to a trillion years, longer than the current age of the universe.
