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Computer Science 129
Stem Cells
K. Devlin
Chapter 7
Stem Cells
• There are two types of stem cells
– Embryonic Stem Cells
– Adult Stem Cells
• To figure out where they come from we
need to understand a little embryology
K. Devlin
Chapter 7
Stem Cells
• http://www.youtube.com/watch?v=rN3lep6
roRI
• Watch the above video until part 5 (watch
the first 16 minutes)
K. Devlin
Chapter 7
Stem Cells
K. Devlin
Chapter 7
Stem Cells
• Cells from a morula are considered totipotent –
they can develop into anything embryonic or
extra-embryonic
• Cells from the inner cell mass are called
pluripotent – they can be anything except
trophoblast cells
• Once a cell has differentiated they are
multipotent – ex. Ectoderm can become skin,
brain or nervous tissue – multiple things
K. Devlin
Chapter 7
Stem Cells
K. Devlin
Chapter 7
Stem Cells
• Fertilization occurs in the fallopian tubes of a
woman (uterine tubes)
• When the sperm combines with the ovum, we
have a zygote
• The zygote undergoes cell division and we end
up with a ball of cells called the morula
• The morula develops into a blastocyst with the
inner cell mass inside
K. Devlin
Chapter 7
Stem Cells
• The cells on the outside of the blastocyst are
called trophoblasts. These cells protect the
inner cell mass, which is the developing embryo,
from the mother’s immune system (the mother’s
immune system views the developing embryo as
foreign since half of it is from the father –
actually it is 51% mom and 49% dad because of
the mitochondrial DNA from mom makes it a
little more mom than dad)
K. Devlin
Chapter 7
Stem Cells
• The inner cell mass, which is developed at
around day 7-10, is where scientists harvest
embryonic stem cells
• These cells have not differentiated, or become
determined at this point. When cells become
determined, it is “determined” what they will
become when they grow up.
• The cells will become endoderm, mesoderm or
ectoderm
K. Devlin
Chapter 7
Stem Cells
• The following table indicates the type of
cells that each of the germ layers will
ultimately develop into
K. Devlin
Chapter 7
Stem Cells
Germ Layer
Structures they become
Ectoderm
Epidermis – outer layer of skin
Brain, spinal cord, nerves
Mesoderm
Bones, muscle, dermis-lower layers of
skin, blood, connective tissue,
reproductive tissue, urinary tissue
(basically everything else that is not
from endoderm or ectoderm)
Endoderm
Linings of the guts and associated
organs and linings of lungs and
respiratory tissues
K. Devlin
Chapter 7
Stem Cells
• Once a cell has become determined, or
become a germ layer, they will continue to
develop into those tissue types. You can
not make an endoderm cell become brain
tissue or mesoderm become guts and so
on.
• If a cell is gotten before it is determined, it
can be forced to become any tissue. They
are metabolically more active as well.
K. Devlin
Chapter 7
Stem Cells
• It is no longer legal to make embryos for
the purpose of destroying the embryo to
do stem cell work. Where do scientists get
them then?
– Unused embryos from fertility clinics
– Wharton’s jelly on the placenta
K. Devlin
Chapter 7
Stem Cells
• Use of stem cells from Wharton’s jelly is
ideal since there is no destruction of an
embryo involved.
K. Devlin
Chapter 7
Stem Cells
• What about Adult Stem Cells? Where can
we harvest those?
–
–
–
–
–
–
–
–
K. Devlin
Adipose tissue (fat)
Skin
Spinal fluid
Heart cells
Liver cells
Brain
Bone marrow
Teeth
Chapter 7