The central nervous system by sending messages from the brain through the nerves that go to your spine.
There are many reasons to why slaves were essential in the colonial economy:
Slaves were generally used more in the south, because large plantations were found there, which meant that the need for large amounts of workers.
Slaves provided cheap labors, and as they were not "citizens" of the US, they were not allowed their rights.
Slaves were also relatively easy to buy and replace, however, their survival rates were not that good after they traveled long distance.
etc.
hope this helps
Answer:
The function of the pleura is to allow optimal expansion and contraction of the lungs during breathing. The pleural fluid acts as a lubricant, allowing the parietal and visceral pleura to glide over each other friction free. This fluid is produced by the pleural layers themselves.
A star is a fusion reactor. Under enormous pressure, resulting from gravity, light nuclei of gases such as hydrogen merge to form helium, and since this process releases energy, the start begins to radiate the excess energy. Later on, helium fusion produces heavier elements, and so on.