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
What are the 3 germ layers that give rise to all of the cell types in the body?
ectoderm, mesoderm, endoderm
During gastrulation, does the primitive streak grow towards the tail or towards the head?
head
What is the source of cells that enter the primitive streak?
epiblast
What structure is at the leading edge of the primitive streak, and helps to direct the differentiation of migrating cells?
primitive node
Along the primitive streak, epiblast cells proliferate, detach, and move inward into the space between the ___ and the ___
epiblast, hypoblast
During gastrulation, the first inward moving cells displace and invade the hypoblast forming the ____. The cells that follow, fill the space between the epiblast and hypoblast and form the ____. The remaining epiblast cells are the ___. (Which germ layers?)
endoderm, mesoderm, ectoderm
Which molecule controls inward cell migration during gastrulation? Which cells produce this?
Fibroblast growth factor 8 (FGF8). It is produced by the primitive streak cells.
Which germ layer gives rise to the epidermis?
ectoderm
Which germ layer gives rise to enamel?
ectoderm
Which germ layer gives rise to the mouth lining?
ectoderm
Which germ layer gives rise to the nervous system?
ectoderm
Which germ layer gives rise to muscle?
mesoderm
Which germ layer gives rise to bone?
mesoderm
Which germ layer gives rise to the dermis?
mesoderm
Which germ layer gives rise to blood cells?
mesoderm
Which germ layer gives rise to the spleen?
mesoderm
Which germ layer gives rise to lymphatic tissues?
mesoderm
Which germ layer gives rise to the heart?
mesoderm
Which germ layer gives rise to blood vessels?
mesoderm
Which germ layer gives rise to the lungs?
mesoderm
Which germ layer gives rise to most of the urogenital systems?
mesoderm
Which germ layer gives rise to the lining of the gastrointestinal tract and the organs attached to it?
endoderm
Ectoderm, mesoderm, and endoderm all contribute to different types of which category of tissues?
connective tissues
What is mesenchyme? What kind of tissues it is particularly important for?
Undifferentiated embryonic connective tissue. muscle and bone
Is mesenchyme a differentiated connective tissue?
no, it is undifferentiated
____ is the part of the mesenchyme derived from neural crest cells of the ectoderm
ectomesenchyme
What kind of ectodermal cells is ectomesenchyme derived from?
neural crest cells
The dorsal lip of the blastopore in amphibian embryos is equivalent to the ___ ____ in mammalian embryos.
primitive node
By what point in development are the body axes established? When are they refined?
morula stage. During gastrulation
1) ____ and ____ are genes that direct mesoderm differentiation into the notochord and somites essential for establishing the anteroposterior axis.
2) The cells of which structure trigger expression of these genes?
1) chordin, noggin
hint: notoCHORD - CHORDin
2) primitive node
The primitive streak is initiated and maintained by expression of what gene?
nodal
hint: primitive NODe(AL) is the leading edge of the primitive streak
(T/F) Cells of the primitive node never express genes for inhibitory proteins
False
Chordin and Noggin are genes that direct mesoderm differentiation into the ____ and ____ essential for establishing the anteroposterior axis.
notochord and somites
Cells at the anterior end of the embryo secrete factors that inhibit the nodal gene. This allows that tissue to develop into what structure?
The head
1) What genes are regulated by nodal at the posterior end of the embryo?
2) What is the purpose of these genes?
1) transforming growth factor β (TGF β) and bone morphogenic protein 4 (BMP4)
2) They stimulate dorsal-ventral differentiation of the mesoderm into the body wall and organs like the kidneys and blood
____ is a transcription factor that inhibits mesoderm differentiation and permits development of the anterior part of the embryo into the head.
goosecoid
If the transcription factor goosecoid is over-expressed in an organism, what would be the expected result?
two or more heads
Cells of the primitive node invade inward and migrate anteriorly along the midline and form a solid rod of cells called the ___.
notochord
Cells of the primitive node invade ____ (outward/inward) and migrate anteriorly along the midline and form a solid rod of cells called the notochord.
inward
The notochord has an inductive effect on surrounding tissues, influencing the development of which classes of tissues?
nervous, muscle, connective
The notochord serves as the basis for development of the ___ skeleton and segments become the core of the ____ discs.
axial, intervebretal
1) As the notochord is formed, what two membranes are formed, respectively, at the cranial and caudal ends of the embryo?
2) Respectively, what structures do each of these membranes correspond to?
3) a) The membranes consist of tightly adherent layers of which 2 germ layers? b) Which germ layer is missing in between them?
1) buccopharyngeal membrane (hint: bucco = mouth, pharyngeal = throat) and cloacal membrane
2) mouth and anus
3) a) ectoderm and mesoderm. b) mesoderm
In which week of embryonic development does neurulation occur?
week 3
Neurulation:
1) In 3rd week of embryonic development, the notochord has an inductive effect on the overlying ectoderm, causing the ectoderm to thicken and form the ____ _____.
2) The process of neurulation begins with the formation of the __________ that makes up the neural plate.
3) By the end of the 3rd week, the lateral edges of the plate become more elevated and form neural ___ withs a depression between them called the neural ___.
4) The neural folds grow towards each other and meet at the midline where they fuse together forming the neural ____.
1) neural plate
2) neuroectoderm
3) folds, groove
4) tube
For which nervous system is the neural tube the basis of development?
central nervous system (CNS)
1) Mesoderm on either side of the neural tube organizes into paired segments called ___.
2) What are 5 body structures that these segments develop into?
1) somites
2) dermis, muscle, tendon, bone of the body wall and limbs
(mnemonic: Doug Made Two Bright Lanterns)
What two conditions result from regional failures of the neural tube to close? What is the failure in each condition?
Anencephaly- the rostral (head) end of the neural tube fails to close
Spina Bifida- the sacral (bottom) end of the neural tube fails to close
The neural tube induces the development of pairs of somites on either side of the neural tube that will eventually develop into ____, ____, and ____ of the trunk and limbs.
dermatomes (connective tissue of the dermis), myotomes (muscle and tendon), and sclerotomes (bones)
Which germ layer forms the neural tube?
ectoderm
As the neural folds grow together to form the neural tube, the cells on the lateral edge form the neural ___.
crest
What kind of cells develop into melanocytes and hair follicles in the epidermis?
neural crest cells
What kind of cells develop into cartilage and bone of the face and skull
neural crest cells
What kind of cells develop into odontoblasts?
neural crest cells
What kind of cells develop into dorsal root ganglia of the spinal cord?
neural crest cells
What kind of cells develop into sympathetic ganglia?
neural crest cells
What kind of cells develop into parasympathetic ganglia of the gastrointestinal tract?
neural crest cells
What kind of cells develop into Schwann cells and glial cells?
neural crest cells
What kind of cells develop into meninges?
neural crest cells
What kind of cells develop into the adrenal medulla?
neural crest cells
What kind of cells develop into C cells of the thyroid gland?
neural crest cells
What do odontoblasts produce?
dentin of the teeth
Important dental derivatives of ectoderm (figure on 510-2 slide 54):
1) surface ectoderm –> mouth ____ —> tooth ____
2) neural crest cells –> facial ___ + ___ of teeth
1) epithelium, enamel
2) cartilage, dentin
What is the name of the syndrome that is caused by abnormal neural crest cell migration?
treacher collins syndrome (mandibulofacial dysostosis)
(T/F) The fetal period of development is the most susceptible to teratogens.
FALSE, the embryonic period is the most susceptible to teratogens.
A ____ is an agent such as a drug, virus, or radiation that can cause malformations in an embryo or fetus.
teratogen
