510-02 Introductory Embryology Flashcards
When does embryonic development occur? Fetal development?
Embryonic development occurs for 8 weeks after fertilization. Fetal development occurs during weeks 9-38
What does crown rump length measure?
growth of the embryo
Fertilization of the oocyte by sperm usually takes place in the ___ region of the uterine tube.
ampulla
After fertilization, what sweeps the zygote towards the uterus?
the ciliated lining of the Fallopian tube
What is an ectopic pregnancy?
When implantation occurs in the uterine tube or outside the uterus
Is an ectopic pregnancy viable?
no
What is the protective cellular layer surrounding the oocyte that many spermatozoa bind to?
corona radiata
What is the protective glycoprotein “shell” under the corona radiata?
zona pellucida
The tip of each spermatozoan contains a vesicle of enzymes called the ___
acrosome
Acrosomal enzymes are released after sperm binds to the ___ ____, trigerring the” ___ reaction.” This reaction allows the sperm to penetrate the ____.
zona pellucida, acrosome, oocyte
What is the purpose of the zona (cortical) reaction? What is its mechanism?
The Zona (cortical) reaction prevents polyspermy. It is rapid, calcium-mediated change in structure of zona pellucida, preventing other sperm from entering.
(T/F) The oocyte finishes its second meiotic division before a spermatozoon enters the oocyte?
False, the oocyte finishes its 2nd meiotic division AFTER a spermatozoon enters the oocyte
After 2nd meiotic division, one daughter cell is significantly smaller than the other.
1) What is this cell called?
2) What is the larger cell called and
3) where are its chromosomes contained?
1) second polar body
2) definitive oocyte
3) female pronucleus
During pronuclear stage, do the male and female pronuclei in the zygote initially contain haploid (1n) or diploid (2n) DNA?
Haploid (1n)
How many pairs of maternal and paternal chromosomes are produced in preparation for 1st cell division?
2 maternal pairs and 2 paternal pairs
1) In how many days after fertilization does morula form?
2) How many cells does morula contain?
3) What are each of these cells called?
1) 3 days
2) 16 cells
3) blastomeres
(T/F) The overall size of the embryo remains relatively constant through these cell divisions.
True, the overall size of the embryo does not change as the number of cells increases
(T/F) The blastomere cells become larger with each mitotic division during cleavage.
False, they become smaller as the number of cells increases yet the size of the embryo remains constant
After the 8 cell stage, the blastomeres undergo ____. They do this by developing many ___ junctions that maximize the contact between the cells.
compaction, tight
When does compaction occur in the blastomeres?
After the 8 cell stage
During compaction, why do blastomeres develop many tight junctions?
To maximize the contact between cells
Why do the inner cells of the blastula differentiate differently than the outer cells?
They receive more communication from other cells via gap junctions.
Autocrine vs Paracrine regulation
autocrine: cell captures its own cytokine
paracrine: cytokine is captured by a nearby target cell
What does the primary yolk sac contain? Does it contain yolk in humans?
water, no
Why do humans not need to make yolk?
humans use placenta to nourish embryo
The solid morula absorbs fluid into inner cavity, forming the _____. The fluid accumulation inside the morula segregates cells to different parts of the embryo, allowing for the development of the 3 ___ ____.
blastocyst, germ layers
1) The inner cell mass of the blastocyst is called the ____ and will develop into the ____.
2) The cells surrounding the blastocyst are called the ___ and these cells will develop into the _____.
1) embryoblast, embryo
2) trophoblast, placenta
What is the fluid filled inner cavity of the blastocyst?
the primary yolk sac
What are the three layers of the uterus (from outer to inner)?
perimetrium, myometrium, endometrium
Which layer of the uterus does the blastocyst implant into?
endometrium
During blastocyst implantation, the cells of the ____ grow like roots into the uterine endometrium.
trophoblast
The cells of the embryoblast differentiate into the ____ and the ____. What is this important for?
epiblast and hypoblast. This sets up the anatomy for differentiation of the embryonic tissues and of the embryonic membranes.
1) As the trophoblast grows into the endometrial stroma, it forms 2 layers. The inner layer is the ____ and the outer layer is the _____.
2) In which one of these layers does each cell have a definite boundary? 3) In which one are all cells in one big mass?
1) cytotrophoblast, syncytiotrophoblast
2) cytotrophoblast
3) syncytiotrophoblast
Under some conditions, cells merge together and all of the cell contents are contained within a common plasma membrane. This produces a multinucleate cell called a ____
syncytium
A ____ syncytium occurs when cells are joined with so many gap junctions that the cytoplasm is functionally joined. The actions of these cells are _____ synchronized.
functional, electrochemically
The epiblast forms 1) ____ and the 2) ___ _____. The hypoblast develops into the 3) ____ ___.
1) ectoderm
2) amniotic cavity
3) yolk sac
When does the primitive yolk sac become the secondary (definitive) yolk sac?
In a 13 day blastocyst, when the extraembryonic mesoderm proliferates and surrounds the chorionic cavity around the primitive yolk sac.
What are the 3 layers that form the chorion?
1) extraembryonic mesoderm that lines the chorionic cavity
2) cytotrophoblast
3) syncitiotrophoblast
1) What hormone is produced by the chorion?
2) By what point of development are there detectable amounts of this hormone produced?
3) What is its purpose?
1) Human Chorionic Gonadotropin (hCG)
2) By the end of the 2nd week
3) hCG diffuses into the mother’s blood and keeps the corpus luteum in the ovary alive and producing progesterone + estrogen needed to maintain the uterus in a pregnant state
Exchange between maternal and placental blood is facilitated by interdigitating ___ ___. These contain embryonic capillaries and __ ___.
trophoblast villi, intervillous spaces
Are the intervillous spaces of the trophoblast villi fed by embryonic or maternal blood vessels?
maternal
A connecting stalk of extraembryonic mesoderm links the embryoblast to the ___. When embryonic blood vessels grow in the connecting stalk, it becomes the ___ ___.
chorion, umbilical cord
____ is the process that establishes the ectoderm, mesoderm, and endoderm
gastrulation