Final answer:
Viable cells found in the amnion are mostly fetal cells, including a type known as non-embryonic stem cells that can differentiate into various cell types. These cells are collected for analysis from the amniotic fluid through amniocentesis to assess the baby's genetic health.
Step-by-step explanation:
If amnion has viable cells, the kinds of cells present are primarily fetal cells that can include a special type of stem cells known as non-embryonic stem cells (also referred to as amniotic stem cells). These stem cells have the capacity to differentiate into various cell types such as brain, liver, and bone cells. The amnion forms an integral part of the protective layers around the developing embryo, filled with amniotic fluid, which also contains fetal cells that can be used for genetic testing. The amniotic cavity is created at the beginning of the second week of development from the epiblast, which is the upper layer of the embryonic disc. This evolution of the extraembryonic membranes allows less dependence on water for development and enabled the branching out into drier environments, important in the history of amniotes. During a procedure known as amniocentesis, amniotic fluid analysis can be performed, which provides vital information on the genetic health of the baby since the fluid contains these fetal cells.