Download Visible Embryo Worksheet

Visible Embryo Worksheet
Go to this site http://www.visembryo.com/baby/1.html and complete the
following:
Stage 1
Fertilization begins when a sperm penetrates an oocyte ____________ and it ends with
the creation of the __________. The fertilization process takes about ______ hours.
A sperm can survive for up to ______hours.
The fusion of the oocyte and sperm nuclei marks the creation of the ___________ and
the end of _________________________.
Stage 2
The zygote now begins to _________________, with each division occurring into two cells
called blastomeres. The zygote's first cell division begins a series of divisions, with
each division occurring approximately every ____________ hours. Each blastomere
within the zona pellucida becomes smaller and smaller with each subsequent
division.
When cell division generates about sixteen cells, the zygote becomes a
____________________(mulberry shaped). It leaves the fallopian tube and enters the
uterine cavity ___________________ days after fertilization.
Stage 3
About four days after fertilization, the morula enters the _____________ cavity. Cell
division continues, and a cavity known as a blastocele forms in the center of the
morula. Cells flatten and compact on the inside of the cavity while the zona pellucida
remains the same size. With the appearance of the cavity in the center, the entire
structure is now called a ______________________.
Stage 4
The pressure of the blastocele expanding in the middle of the blastocyst against the
rigid wall of the zona pellucida, creates "hatching" of the ___________________ from the
zona around the sixth day after fertilization.
As the ___________________ enters the uterus free from the zona, the outer layer of
trophoblast cells secrete an __________________ to erode the epithelial lining of the
uterus and allow the ___________________ to implant.
Human chorionic gonadotropin (hCG) is also secreted by the trophoblast cells
stimulating the corpus luteum to continue progesterone production. Progesterone
maintains the ____________ lining of the uterus. Endometrial glands in the uterus had
already begun to enlarge in response to the progesterone stimulated to release by
the corpus luteum ("yellow body") which once surrounded the egg as it grew in the
ovary almost six days prior.
The ______________ is therefore swollen with new blood capillaries and the circulation
between mother and ______________ begins, a process needed for the continuation of
pregnancy.
Stage 5
Trophoblast cells continue to engulf and destroy cells of the uterine lining creating
blood pools and stimulating new capillaries to grow - beginning the growth of the
__________________.
The _________________ inner cell mass differentiates into two layers:
EPIBLAST The top layer of cells (dark blue) which will become the embryo and
amniotic cavity.
HYPOBLAST Lower layer of cells (yellow) which become the yolk sac.
_______________________ ___________________ - implantation sites not in the uterus - can
occur at this time and may continue up to 16 weeks unnoticed. Quick diagnosis can
pharmacologically treat without surgery preserving the site of the pregnancy.
Stage 6
Placenta Formation
Chorionic _____________ "fingers" form in the "placenta" anchoring the embryo to the
__________________. Blood vessels begin appearing first in the "placenta" surrounding
the embryo. The _________________ begins producing hematopoietic or non-nucleated
blood cells.
Stalk Formation
By the end of stage 6a, the embryo is attached to the developing ___________________ by
a stalk later to become part of the umbilical cord.
Gastrulation
In Carnegie Stage 1, the exit of the first polar body through the zona pellucida
determined the gastrulation axis.
Stage 6b begins as a narrow line of cells appear on the surface of the formerly 2
layered embryonic disc. This "primitive streak" marks bilateral symetry in the
embryo and indicates ___________________ has begun - the migration of cells from the
outer edges of the disc into the primitive streak and down creating a new third
layer. The embryo now has endoderm, mesoderm and ectoderm layers.
ECTODERM ___________________________________of the embryonic disc. Will later form:
skin, hair, lenses of the eyes, lining of the internal and external ear, nose, sinues,
mouth, anus, tooth enamel, pituitary and mammary glands, and all parts of the
nervous system.
MEDODERM ________________________________ of the embryonic disc and precursor to the
muscles, bones, lymphatic tissue, spleen, blood cells, heart, lungs, reproductive and
excretory systems.
ENDODERM _________________________________ of the embryonic disc from which will
form the lining of the lungs, the tongue, tonsils, urethra and associated glands,
bladder and digestive tract.
Stage 7
Neurulation
In Stage 6, gastrulation began with the appearance of the primitive streak. In Stage
7, __________________________ continues with the formation of a new cell layer - the
ectoderm - changing the ____________-layered disc into a ____________-layered disc.
Neural crest cells originate at the top of the __________________ tube and migrate
extensively, differentiating into many cell types such as ________________, glial cells,
pigmented cells of the epidermis, epinephrine producing cells of the adrenal gland,
and various skeletal and connective tissues of the head. It appears that the
_____________ of a migrating cell is largely determined by its final _____________________.
Gastrulation
Gastrulation in full force. Cells are ___________________ across the surface of the 2
layered embryonic disc and into the newly formed Primitive Streak. After migrating
through the Primitive Streak, these new cells collect into a new 3rd layer - the
_______________________.
Stage 8
The embryonic area is now shaped like a pear, and the head region is broader than
the tail end.
The ectoderm has thickened to form the ____________ plate. The edges of this plate rise
and form a concave area known as the neural __________________. This groove is the
precursor of the embryo's ________________ system and it is one of the first organs to
develop.
By stage 8, the ______________ cells are already developed and begin to form channels
along side of the epithelial cells forming at the same time.
What is the Sonic Hedgehog (shh) gene and how did it get its name?
Stage 9
Looking at the embryo from the top, the head end is wider than the tail end, with a
slightly narrowed middle.
_________________, which are composed of mesoderm, appear on either side of the
neural groove. The first pair of somites appear at the tail and progress to the middle.
One to three pairs of somites are present by Stage 9.
Every ridge, bump and recess now indicates cellular differentiation.
A _____________ fold rises on either side of the primitive streak. The primitive streak
now runs between one-fourth to one-third of the length of the embryo.
Secondary blood vessels now appear in the chorion/placenta. Hematopoietic cells
appear on the _____________________ simultaneously with endothelial cells which will go
on to form ______________ vessels for the newly emerging blood cells.
Endocardial (muscle) cells begin to fuse and form into the early embryo's two
_________________tubes.
Stage 10
Rapid _________________ growth and change elongates the embryo and expands the
yolk sac.
On each side of the neural tube, between four and twelve pairs of somites can exist
by the end of Stage 10. The cells which become the _____________ appear as thickened
circles just off of the neural folds. The newly differentiated cells of the ears are also
present.
Neural folds are rising and fusing at several points along the length of the neural
tube concomitant with the budding somites which appear to "zipper" the neural
tube _______________. Neural crest cells will eventually contribute to the ___________ and
________________of the embryo.
The two endocardial tubes formed in Stage 9 now fuse in Stage 10. Together they
form one single tube generated from the cells of the "roof" of the nueral tube. The
heart tube takes on an _________________establishing the asymetry of the heart. As the
S-shape forms, _______________ muscle contraction begins.
Stage 11
Thirteen to twenty pairs of ______________ are present and the embryo is shaped in a
modified S curve. The embryo has a bulb-like tail and a connecting stalk to the
developing placenta.
A primitive S-shaped tubal _______________ is beating and peristalsis, the
______________muscle contractions propelling fluids throughout the body, begins.
However, this is not true circulation because blood vessel development is still
____________________________.
At this stage, the neural tube determines the form of the embryo. Although the
primary blood vessels along the central nervous system are now connecting in Stage
11, the central ___________________ system appears to be the most ____________________
system. If twenty somites are present in the embryo, the forebrain is completely
closed.
Stage 12
The embryo curves into a C shape. The arches that form the ____________ and
___________ are now becoming evident under the enlarging _____________________. By the
time the neural tube is closed, both the ___________ and ____________ will have begun to
form. At this stage, the _________________ and _______________ cord together are the
largest and most compact tissue of the embryo.
Valves and septa may appear in the ______________ in Stage 12.
The beginning cells of the ____________ form before the rest of the ______________ system.
Stage 13
The ______________________ epithelium layer begins to differentiate into the future
locations of the liver, _______________, stomach and _____________________.
Stage 14
Head and Neck
The _____________ and ___________ grow rapidly. The mandibular and hyoid arches are
noticeable. Ridges demarcate the three sections of the brain (midbrain, forebrain
and hindbrain).
Thorax
_____________________, the tube through which food is swallowed, forms from a groove
of tissue that separates from the trachea, which is also visible.
Semilunar ____________ begin to form in the heart. Four major subdivisions of the
heart (the trabeculated left and right ventricles, the conus cords and the truncus
arteriosus) are clearly defined. Two sprouts, a ventral one from the aortic sac and a
dorsal one from the aorta, form the pulmonary (sixth aortic) arch.
Right and left lung sacs lie on either side of the esophagus.
Abdomen and Pelvic Regions
Ureteric bud appear. Metanephros, which will eventually form the permanent
_________________, is developing.
Limbs
Upper ____________ elongate into cylindrically-shaped buds, tapering at tip to
eventually form hand plate. Nerve distribution process, i_______________________, begins
in the upper limbs.
There are more stages and other events that happen. We will cover them later but
you should click ahead to see what they are.