In fetal life, the lungs are not expanded, so most of the blood from the right ventricle is shunted from the pulmonary artery to the aorta through the patent ductus arteriosus. With a few breaths the lungs expand, and blood flows from right ventricle to pulmonary artery into the lungs. Withdrawal of circulating prostaglandin from the mother plus bradykinins released from the expanding lung of the infant cause the ductus to close over a few minutes to hours. The closed ductus remains as the ligamentum arteriosum.
Answer:
The primary means for transmitting messages between the brain and the rest of the body is the <u>spinal cord</u>.
Explanation:
The spinal cord is the main pathway of the nervous system. The impulses are transmitted to the brain through bundles of ascending nerve fibers, while the descending fibers transmit impulses in the opposite direction. Signals are transported to and from different parts of the body along the fibers of the pair of spinal nerves, which form intersections with the spinal cord through their dorsal and ventral roots; the sensory and motor fibers converge in the gray matter of the medulla.
<span>d. only the fittest of sperm and egg combinations will survive.
Others are external fertilization:
</span>a. all of the sperm will fertilize eggs.
b. sperm and egg will be released simultaneously.
c. the number of sperm and eggs produced will be equal.
<span>e. sperm will be protected until they can unite with the eggs.</span><span>
</span>
Answer:
The answer is B.
Explanation:
If warmer temperatures last longer there will be no need for the white fur