Lecture 2 Flashcards
Embryonic development proceeds from 0 to ____ weeks
eight (8)
Fetal development continues from 9 to ____ weeks
thirty-eight (38)
Where does fertilization occur?
In the Ampulla Region of the fallopian (uterine) tube
When does each ovary produce an egg?
Ovaries alternate between the left and the right to each produce eggs bimonthly
Mature eggs are released from _____ that form on the surface of the ovary
blisters
The cilia inside of the fallopian tube sweep thin ____ and ___ towards the _____.
mucus; fluid; uterus
Of the 200-300 million spermatozoa deposited in the female reproductive tract, only ___ to ___ reach the oocyte in the ampulla
300 to 500
What is the smallest cell in the human body?
A sperm cell
What is the lifespan of a sperm cell swimming thru the female reproductive tract?
Days
What is the protective cellular layer surrounding the oocyte?
Corona radiata
What is the name of the protective glycoprotein “shell” under the corona radiata?
zona pellucida
What are the two layers that surround the egg?
Corona radiata (outer); zona pellucida (inner)
The corona radiata can be described as ______ and ______, while the zona pellucida is a _______ membrane.
porous, sticky; gelatinous
What is the name of the lysozome at the tip of the sperm cell?
acrosome
What is inside an acrosome?
Lytic enzymes that can break down proteins.
Enzymes released from the acrosome trigger the ______ reaction. These enzymes also trigger the _____ reaction, which is a rapid, calcium mediated change in the _____ _____.
Acrosome (reaction). Zona reaction (happens very fast); zona pellucida.
What is the major function of the acrosome reaction? What is a major function of the zona reaction?
To break open a sperm entry point in the zona pellucida. To prevent additional sperm from entering (polyspermy)
How many chromosomes will be in an embryo formed by two sperm entering one egg? Is such an embryo viable?
Sixty-nine (69) chromosomes. Such an embryo would be (almost always) non-viable.
When does an oocyte complete its Meiosis II? When does a spermatozoa complete its Meiosis II?
The oocyte completes its Meiosis II after fertilization. The spermatozoa complete Meiosis II even before fertilization.
Initially, a pronucleus is _______. However, before the first cell division the pronuclei swell and each ______ its DNA.
haploid (1n); duplicate
How many hours after fertilization does a deep furrow appear on the zygote and gradually cleave the cytoplasm into two parts?
30 hours
Is the first cleavage of the zygote a mitotic or meiotic division?
Mitotic. Mitosis occurs from here on
What is each cell of the 2-, 4-, and 8-cell stage called?
Blastomere
What is a solid ball of sixteen (16) blastomeres called?
Morula
Does the overall size of the embryo change before it becomes a blastocyst?
The overall size of the embryo remains relatively constant.
What is the Latin translation of a Morula?
A little mulberry
How many days does it take for an embryo to become a morula?
About 3 days
What role does the cytoskeleton play in the early stages of a embryonic cell division?
The cytoskeleton generates the force to pull and push the cells apart.
What protein is the cytoskeleton primarily composed of?
Actin, in the shape of fibers such as microfilaments, intermediate filaments, and microtubules.
Where can actin fibers of the cytoskeleton attach to on the dividing blastomeres?
Can attach to myosin proteins on the blastomeres. Cell junctions such as desmosomes, plaque anchors in the cell membrane.
Early blastomeres are ______-potential. Splitting these cells can produce fully functional ______ twins.
Pluri(-potential). Identical
With each mitotic division, blastomeres become smaller or bigger?
Smaller
After what stage does compaction take place in an embryo?
8-cell stage
What is compaction?
The development of many tight junctions that maximize contact between cells.
Why is compaction important?
Compaction develops the gap junctions and surface cell receptors that allow cells to communicate with each other and begin to coordinate the process of differentiating the embryonic cells into embryonic tissues.
What are cytokines?
Cytokines are molecules released by cells for cell-signaling to self (autocrine) or to nearby cells (paracrine)
What is the main difference between a morula and a blastocyst?
A morula is a solid ball of cells, while a blastocyst is fluid-filled (or cystic)
What is the inner cell mass of the blastocyst called?
Embryoblast
What will the embryoblast develop into?
What will the trophoblast develop into?
What will the fluid-filled inner cavity develop into?
Embryo.
Placenta.
Primary (Primitive) yolk sack.
What are the three (3) layers of the uterus?
Perimetrium (outer)
Myometrium (thick middle layer of smooth muscle)
Endometrium (inner mucosa consisting of a glandular epithelium, richly vascular connective tissue)
Where does the blastocyst normally stick to?
First to the endometrial mucus and then implants into the endometrial tissue.
The blastocyst implants into the endometrial tissue through ______ growth.
Invasive
Trophoblasts cells extend into the ________, like plant roots extend into soil.
Endometrium
Trophoblasts cells are not just squeezing their way into the endometrium, they are actually ________
phagocytotic
The underlying vascular connective tissue of the endometrial surface is known as the endometrial _______.
stroma
A _______ is a mass of cells that are poorly separated from each other.
Syncytium. Multiple nuclei and organelles bounded by one outer membrane.
The outer part of the trophoblast is considered a _______.
Syncytium.
What two layers does the embryoblast differentiate into?
Epiblast and hypoblast.
The epiblast will eventually produce all three _____ layers. Initially it forms the ____ layer and the ______ cavity.
germ; ectoderm; amniotic
What does the hypoblast develop into?
Yolk sac
What thee layers of cells are part of the chorion?
- Extraembryonic mesoderm
- Cytrotrophoblast
- Syncitiotrophoblast
The extraembryonic mesoderm creates a loose network between the _______ and the __________.
Embryoblast; trophoblast.
How do primitive streak cells move?
They move like an amoeba in the very loosely held embryologic tissues
What germ layer do the first inward moving epiblast cells that invade and displace the hypoblast become?
endoderm
The cells that follow the first inward moving epiblast cells fill the space between the epiblast and the hypoblast. What are these cells called?
Mesoderm
Cells that do not migrate from the original epiblast become the ________ germ layer
ectoderm
What gene controls inward cell migration? Which cells produce this gene?
Fibroblast growth factor 8 (FGF8). Produced by primitive streak cells
Where do all three germ layers initially come from?
epiblast
What germ layer gives rise to the epidermis, enamel, mouth lining, and the nervous system?
Ectoderm
Lungs arise from which two germ layers?
Meso- and Endo-derm
Muscles and bones come from what germ layer?
Mesoderm
The lining of the GI tract and pharyngeal derivatives such as palatine tonsils, thyroid gland, and parathyroids are derived from which germ layer?
Endoderm
Blood cells, blood vessels, heart, lymphatic tissues, and dermis are derived from what germ layer?
Mesoderm
The digestive organs and the urinary bladder are derived from what germ layer?
Endoderm
The dermis, spleen, and most of the urogenital system are derived from what germ layer?
Mesoderm
What class and type of tissue is mesenchyme?
Undifferentiated embryonic connective tissue
T/F Connective tissues arises from all three germ layers.
True
Mesenchyme is derived from mesoderm. However, neural crestal cells of the ectoderm produce a special mesenchymal tissue called ________.
Ectomesenchyme (mesectoderm)
The dorsal lip of a blastospore in amphibian embryos is equivalent to the ________ ______ in mammalian embryos.
primitive node
When are body axes established in an embryo?
The morula stage.
Development is stimulative, however a lot is ________.
Inhibitory
The primitive node cells produce inhibitory proteins that block excessive growth of the _______ germ layer.
mesoderm
The same inhibitory proteins that block excessive growth of the mesoderm also trigger the expression of genes like chordin and noggin that direct the mesoderm to differentiate into the _______ and _____.
Notochord, somites
What body axis are the notochord and somites essential for establishing?
AP
What gene initiates and maintains the primitive streak?
The nodal gene
The Goosecoid transcription factor inhibits the mesoderm so a ______ could grow.
head
What effect does the over-expression of Goosecoid have on embryos?
The development of multiple heads.
What is formed by the inward invasion cells from the primitive node?
The notochord
What kind of effect does the notochord have on surroudning tissues?
Inductive
The anus is initially formed by the _______ membrane. The mouth by the ___________ membrane.
cloacal, buccopharyngeal
Which germ layer is NOT present in the cloacal and buccopharyngeal membranes?
Mesoderm
What germ layer is the notochord derived from?
Ectoderm
What does the inductive effect of the notochord do to the overlying ectoderm in the third week of embryonic development?
It causes the ectoderm to thicken and form the neural plate
The process of neurulation begins with the formation of neuroectoderm that makes up the ______ _______.
Neural plate
By the end of the third week the lateral edges of the neural plate become more elevated and form neural _____ with depression in between them call the neural _____.
folds, groove
What happens to the neural folds that causes them to form a neural tube?
The grow towards each other and meet at the midline
What is the neural tube a basis of?
The CNS
Where does closure of the neural tube begin? (cranium, middle, or caudal).
In the middle of the embryo and proceeds cranially and caudally
The exposed mesoderm on either side of the elevated neural tube sides organizes into what paired segments?
Somites
What do somites develop into?
Dermis, muscle, tendon, bone of the body wall and limbs
Where does Cerebro-Spinal-Fluid come from?
Plasma filtered out from blood under pressure
Spina bifida can be 100% preventable with the presence of what vitamin?
Folic acid (a B vitamin)
The sequence of neurulation is first the neural _____, then the neural _____, followed by the neural ______, that finally forms the neural tube.
plate, fold, crest
The neural crest is eventually delaminates into neural ______ ______
crest cells.
What is a teratogen?
An agent that can cause malformations in an embryo or fetus.
What are three examples of teratogens?
A drug, virus, radation
When is the risk of developmental malformation highest?
During the embryological stage
