Answer:
The reason why only 3 out of the 22 possible autosomal trisomies are seen in newborns, is because the rest of them are chromosomal abnormalities not compatible with life and thus an spontaneous abortion occurs. The embryos suffering from these trisomies do not survive for more than a few weeks in the uterus, so the miscarriage often goes unnoticed for the mother as she may not have realized she was pregnant.
The only trisomies that are allow fetuses to be born are: Patau Syndrome (trisomy 13), Edwards Syndrome (trisomy 18), and Down Syndrome (trisomy 21). Out of these three, people with Down Syndrome have the largest life expectancy.
Yes it is absolutely true that each lung is fed oxygen by a separate bronchus. There are actually two lungs and two bronchi. Each of the two lungs are safeguarded by the two ribcages as
they are placed within the rib cages. The lungs actually consists of elastic
sacs that contract and expand for taking in and releasing air. This way oxygen
is passed into the blood and carbon dioxide is taken out from the blood and
passed out. This is also the main function of the lungs.
