Biomedical Engineering Reference
In-Depth Information
tenet of Christian morality. What makes human beings morally special entities deserving a
unique type of respect? Christianity answers in terms of the doctrine of ensoulment. This
doctrine holds that only human beings are divinely endowed with an eternal soul. Accord-
ing to Christian ethics, the soul makes humans the only beings with intrinsic value. Kant's
secular version of the doctrine of ensoulment asserts that human beings are morally unique
and deserve special respect because of their autonomy. Autonomy is taken by Kant to be
the capacity to make choices based on rational deliberation. The central task of ethics then
is to specify what human conduct is required to respect the unique dignity of human
beings. For most Kantians, this means determining what limits human beings must observe
in the way they treat one another, and this, in turn, is taken to be a matter of specifying each
individual's fundamental moral rights.
These two ethical schools of thought, therefore, provide some rationale for moral judg-
ments. However, when there is no clear moral judgment, one is faced with a dilemma.
In medicine, moral dilemmas arise in those situations that raise fundamental questions
about right and wrong in the treatment of sickness and the promotion of health in patients.
In many of these situations, the health professional usually faces two alternative choices,
neither of which seems to be a satisfactory solution to the problem. For example, is it more
important to preserve life or to prevent pain? Is it right to withhold treatment when doing
so may lead to a shortening of life? Does an individual have the right to refuse treatment
when refusing it may lead to death? All these situations seem to have no clear-cut impera-
tive based on our present set of convictions about right and wrong. That is the dilemma
raised by Kant:
What ought I do?
CASE STUDY: STEM CELL RESEARCH
At the moment of conception—that is, when a sperm penetrates an egg—the process of fertili-
zation occurs. The formation of an embryo is initiated. Once the sperm enters the egg, there is
an immediate opening of ion channels, which depolarizes the plasma membrane of the cell and
prevents other sperm from fusing with it. DNA replication then begins, and the first cell division
occurs approximately 36 hours later. As the process continues, the cell begins to experience cleav-
age, where the cells repeatedly divide, cycling between the S (DNA synthesis) and M (mitosis)
phases of cell division, essentially skipping the G
1
and G
2
phases, when most cell growth
normally occurs. Thus, there is no net growth of the cells, merely subdivision into smaller cells,
individually called blastomeres.
Five days after fertilization, the number of cells composing the embryo is in the hundreds, and
the cells form tight junctions characteristic of a compact epithelium, which is arranged around a
central cavity. This is the embryonic stage known as the blastocyst. Within the cavity exists a mass
of cells, which protrude inward. These cells are known as the inner cell mass and become the
embryo. The exterior cells are the trophoblast and eventually form the placenta. It is the cells from
the inner cell mass of the blastocyst, however, that, when isolated and grown in a culture, are
identified as embryonic stem cells.
It is important to note that if cell division continues, determination and differentiation happen.
Differentiation occurs when a cell begins to exhibit the specific attributes of a predestined
specialized cellular role. Determination is related to differentiation but is somewhat dissimilar.
