Image from: http://earthhopenetwork.net/forum/showthread.php?tid=706
I. Definition:
= The branch of biology that studies the
formation and early development of living
organisms
 Embryo (implantation to 8 weeks)
 Fetus (after 8 weeks)
Image from: http://www.amazon.com/Nova-Miracle-Life-Lennart-Nilsson/dp/6302895189;
II. Early Embryonic Development
Process:
A. Fertilization
B. Implantation
C. Gastrulation
D. Cell differentiation
Images from: http://en.wikipedia.org/wiki/Fertilisation; http://www.lifenews.com/2011/12/05/pregnancy-begins-at-conceptionfertilization-not-implantation/ http://www.bio.miami.edu/dana/106/106F05_4.html; ;
A. Fertilization:
1. =Egg and sperm come together to
form a fertilized egg (called a …
)
Fertilization
Human Zygote
Click for Video
Images from: http://en.wikipedia.org/wiki/Fertilisation; http://php.med.unsw.edu.au/embryology/index.php?title=Fertilization; http://www.exploratorium.edu/imaging_station/gallery.php?Asset=Zebrafish%20development&Group=&Category=Zebrafish&Section=Introduction
2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage
2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage
b. Soon a solid ball of cells is
formed, called a ....
A scanning electron micrograph of a
human embryo at the eight-cell stage
(day three).
Image from: http://www.biologyreference.com/Co-Dn/Development.html
2. After fert., before implantation . . .
a. The zygote begins to divide
i. First few mitotic cell divisions
are called cleavage
b. Soon a solid ball of cells is
formed, called a .... morula
c. Next, the morula will change
into a fluid filled ball of cells,
called a. . .
Blastocyst in crosssection: Cells of inner cell
mass will give rise to the
gastrula, outer cells will
become apart of the
placenta and other
membranes.
Image from: http://www.medpedia.com/news_analysis/30-The-Patients-Doctor/entries/79401-How-to-improve-the-vitrification-of-blastocysts
FERTILIZATION
1. Zygote
2. Morula
3. Blastula
• Egg and sperm
come together to
form a fertilized
egg
• First few mitotic
cell divisions are
called cleavage
• solid ball of cells
is formed
(the eight-cell
stage - day 3)
• fluid filled ball of
cells called a
blastocyst (day
5)
B. Implantation:
1. The blastocyst will
attach to the
uterine wall.
We call this
attachment
IMPLANTATION
Image from: http://www.implantationbleedinginsight.com/
Implantation
Embryo
C. Gastrulation:
1. The process in
which the cells of
the blastocyst
develop into three
germ layers to
form a . . . .
Image/video from: http://www.youtube.com/watch?v=UgT5rUQ9EmQ/;
Images from: http://biologieprojekt2009.wordpress.com/von-der-zygote-zum-mehrzeller/; http://moodle.urbandale.k12.ia.us/mod/slideshow/view.php?id=1932&img_num=2
Gastrulation (cont) :
2. The formation of 3 germ layers
a. Endoderm
• Inner-most layer
• (digestive tract)
b. Mesoderm
• Middle layer
• (internal organs)
c. Ectoderm
• Outer-most layer
• (skin and nervous system)
Images from: http://www.childrenscolorado.org/wellness/info/kids/21825.aspx; https://marketplace.secondlife.com/p/Beating-Anatomical-Heart-Animation-Sound/833619?id=833619&slug=Beating-Anatomical-Heart-Animation-Sound; http://www.rocketgirls.org/8-steps-for-beautifulglowing-skin-cleanse.html; http://biologieprojekt2009.wordpress.com/von-der-zygote-zum-mehrzeller/; http://www.youtube.com/watch?v=UgT5rUQ9EmQ/;
Checkpoint……….
Embryo Stages
Zygote
Morula
Blastocyst
Gastrula
D. Cell Differentiation
1. Once 3 germ cell layers formed in gastrula,
then . . . Cell differentiation (or giving cells
specific jobs) begins . . .
a. 1st = neurulation
i. Development of nervous system
ii. Occurs soon after gastrulation is
complete
b. Organogenesis = organs start to form
c. Morphogenesis = limbs start to assume
shape
A. Membranes form
to protect and
nourish the
developing embryo.
1 = amnion
membrane forms
the amniotic sac
(fluid filled cushions
embryo)
Image from: http://www.billcasselman.com/dictionary_of_medical_derivations/dmd_eight.htm
2
= chorion forms outer most membrane.
This combined with uterine lining form
the organ called the placenta
Image from: http://bohone.wikispaces.com/Group10
The PLACENTA is a maternal-fetal
organ which begins developing at
implantation of the blastocyst
Image from: http://embryology.med.unsw.edu.au/Medicine/BGDlabplacenta.htm
Birth—3 phases
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
Cervix
Vagina
IV. Stem Cells
= unspecialized cells that have the potential
to differentiate
*Blood,
skin, and
nerve
cells
*Undiff.
cells
found
among
diff. cells
ADULT
*Limited
in what
they can
become
MULTIPOTENT
*Can give
rise to an
entire
organism
*Same as
totipotent
but can’t
create an
entire
organism
PLURIPOTENT
Potential
to give
rise to
any & all
tissue
types of
cells
TOTIPOTENT
4 Types of Stems
*Replenish
dying cells
1. Totipotent Stem Cells
These are the most versatile of the stem cell types. When a sperm cell and an
egg cell unite, they form a one-celled fertilized egg. This cell is totipotent,
meaning it has the potential to give rise to any and all human cells, such as
brain, liver, blood or heart cells. It can even give rise to an entire functional
organism. The first few cell divisions in embryonic development produce more
totipotent cells. After four days of embryonic cell division, the cells begin to
specialize into pluripotent stem cells.
2. Pluripotent Stem Cells
These cells are like totipotent stem cells in that they can give rise to all tissue
types. Unlike totipotent stem cells, however, they cannot give rise to an entire
organism. On the fourth day of development, the embryo forms into two layers,
an an outer layer which will become the placenta, and an inner mass which will
form the tissues of the developing human body. These inner cells, though they
can form nearly any human tissue, cannot do so without the outer layer; so are
not totipotent, but pluripotent. As these pluripotent stem cells continue to divide,
they begin to specialize further.
Source: Brown University, Division of Biology and Medicine—Retrieved 6.7.11 from:
http://biomed.brown.edu/Courses/BI108/BI108_2002_Groups/pancstems/stemcell/stemcellsclassversatility.htm
3. Multipotent Stem Cells
These are less plastic and more differentiated stem cells. They give rise
to a limited range of cells within a tissue type. The offspring of the
pluripotent cells become the progenitors of such cell lines as blood cells,
skin cells and nerve cells. At this stage, they are multipotent. They can
become one of several types of cells within a given organ. For example,
multipotent blood stem cells can develop into red blood cells, white
blood cells or platelets
4. Adult Stem Cells
An adult stem cell is a multipotent stem cell in adult humans that is used
to replace cells that have died or lost function. It is an undifferentiated
cell present in differentiated tissue. It renews itself and can specialize to
yield all cell types present in the tissue from which it originated. So far,
adult stem cells have been identified for many different tissue types
such as hematopoetic (blood), neural, endothelial, muscle,
mesenchymal, gastrointestinal, and epidermal cells.
Source: Brown University, Division of Biology and Medicine—Retrieved 6.7.11 from:
http://biomed.brown.edu/Courses/BI108/BI108_2002_Groups/pancstems/stemcell/stemcellsclassversatility.htm