Download Embryology and Stem Cells

Human Embryology
Begins with the fertilization of an egg
by a sperm. A fertilized egg is called a
zygote.
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 The fertilized egg divides into two cells and then
into four cells. These are embryos at the 2-cell
and 4-cell stage.
 The embryo will continue to divide until it forms
a solid
ball of 64 cells called a morula. Human
embryology is just like the embryology of all
other animals until the morula stage. Cells in the
morula stage are totipotent
stem cells.
What is a stem cell?
 A cell in the body whose job has not yet
been determined.
What is meant by totipotent?
 a cell with the “total” potential to develop into
 a new individual. They can become ANY cell in
the body.
 The morula will then hollow out forming a
blastula.
 Four days after fertilization, hatching occurs.
 The blastula emerges from the hardened zona
pellicula (ZP).
 Four to six days after fertilization, cells within the
Blastula will become differentiated into two types
of cells, 1) embryonic stem cells 2)and
trophoblasts.
 inner cell mass (ICM) contains the 40 embryonic
stem cells that will become the fetus and
amniotic sac. The trophoblasts will become the
placenta.
 These cells of the blastula are pluripotent.
What is meant by pluripotent?

They can become ALMOST ANY cell in the
body.
Pluripotent stem cells differentiate into
4 Main Branches
 1.
HSC- Blood Stem Cells
(all blood cells)
 Erythorocytes
 Neutrphils
 Basophil
 Thrombocytes
Lymphocytes
Eosinophils
Moncytes
2. MSC- Mesenchymal Stem Cells
 Bone cells
 Tendon cells
 Adipose cells
Cartilage cells
Muscle cells
Marrow cells
3. ESC- Endodermal Stem Cells
 3. ESC – Endodermal Stem Cells
(digestive tract & lungs)
 Esophagus
Pancreas
 Liver
Intestines
 Stomach
Lungs
4. NSC- Neural Stem Cells
 (brain and nerve cells)
 Neurons
 Glial cells
Oligodendrocytes
Astrocytes
 These four major branches will differentiate into
 210 types of specialized somatic (body) cells.
 On day 49, about eight weeks after
fertilization, the embryo becomes a fetus
which contains fetal stem cells. Fetal stem
cells are also pluripotent.
 Stem cells from the placenta and adult stem cells are
multipotent.
 What is meant by multipotent?
 a cell with “much” potential to develop into
different cells. They can become A LIMITED
RANGE of cells in the body.