Basics Of Embryology 1 Flashcards
_______ is a specialized process of cell division that only occurs in the germ line.
What does “germ line” mean?
Meiosis
Sex cells
What does mitosis yield?
2 diploid 2N daughter cells.
What does meiosis yield?
4 haploid, 1N, offspring
In males, how does meiosis occur?
Cell divisions are equal and 4 identical spermatozoa are created
In females, how does meiosis work?
The cell divisions are unequal, yielding a single massive haploid locate and 3 small, nonfunctional, haploid polar bodies.
Day 0 of development
Fertilization, pronuclear stage
Haploid sperm fuses with the haploid egg
When the sperm fuses with the egg, the result is a..
Zygote (diploid)
Day 1 of Development
Cleavage, within 1st 24 hours.
2 cell phase
Rapid series of mitotic cell divisions
Cleavage
Daughter cells within a zygote during cleavage
Blastomeres
Day 2 of development
4 cell phase
Day 3 of development
8 cell phase, and undergo compaction.
What is compaction?
It means the blastomeres become adhered to one another by tight junctions. During Day 3, and the 8 cell stage,
Day 4 of development
Embryo consists of 16 to 32 cells, also known as a morula (latin for blueberry lol)
What is a morula?
16 to 32 cells in day 4 of embryo development
When the blastomeres segregate to the center of the morula during compaction, these centrally placed blastomeres are now called:
Embryoblasts
Blastomeres now placed at the periphery of the morula during compaction is called…
Trophoblasts
The inner cell mass of the morula gives rise to the
Embryo proper
The trophoblast is the primary source of the fetal component of the..
Placenta. Aka the periphery cells
What is blastocoel?
A large cavity within the morula
When is the blastocyst formed?
Day 5/96 hours
When the inner and peripheral cells are differentiated into a cavity and a singled layered epithelium.
When does the morula reach the uterus? What happens then?
Between 3 and 4 days of development.
Implantation occurs very soon after, when the blastocyst adheres itself to the uterine lining.
What is decidual reaction?
When the cells of the endometrial stroma respond to the progesterone secreted by the corpus luteum and differentiate into metabolically active, secretory cells called DECIDUAL CELLS
When do cells of the embryoblast begin to differentiate into two epithelial layers?
Even before implantation occurs
By day 8, the embryoblast consists of a distinct external later of columnar cells called the _________ and an internal layer of cuboidal cells called the __________
Epiblast
Hypoblast or primitive endoderm
The resulting two-layered embryoblast is called the:
Bilaminar embryonic disc or bilaminar blastoderm
First new cavity to form during the 2nd week that appears on day 8 as fluid begins to collect between cells of the epiblast and trophoblast
Amniotic cavity
When is the embryo completely implanted into the uterine endometrium?
By nine days.
The migrating hypoblast cells merge to form a second cavity called the…
Primary yolk sac
When is the extraembryonic mesoderm formed?
In the middle of the second week/days 10 to 11
One days 12 to 13, what forms within the extraembryonic mesoderm?
The chorion.
On day 13 what happens to the primary yolk sac?
It breaks up and is reduced to a collection of vesicles at the abembryonic end of the chorionic cavity
By the end of the 2nd week, what happens between the definitive yolk sac and the primary yolk sac?
The bilaminar embryonic disc with its dorsal amnion and its ventral yolk sac is suspended within the chorionic cavity by a think connecting stalk
With splitting of the extraembryonic mesoderm into two layers, the amnion, yolk sac, and chorion all become 2 layer structures.
Chorion and amnion consist of ________ and _________
Yolk sac consists of _________ and __________
Ectoderm and mesoderm
Endoderm and mesoderm
Extraembryonic mesoderm forming the outer layer of the yolk sac is a major site of….
Hematopoiesis (blood formation)
What is meckels diverticulum?
When the yolk sac fails to disappear before birth and persists in the form of a digestive tract anomaly
