Embryology 1 Flashcards
What is a fetus?
an orgnaism that breathes no air, does not use the digestive tract and lives in a sterile environment
what is a newborn?
an air-breathing organism with a functional GI tract that quickly becomes a colonized by microbial flora
what does the ovaries produce?
oocytes, progesterone and estrogen
what are oocytes?
female haploid gametes
what is another name for the Uterine tube?
fallopian tube
what does the uterine tube receive from the ovaries?
oocytes
where is the site where sperm fertilizes the oocyte?
Uterine tube
Where is the site where the embryo develops
uterus
where is the site where the placenta and membranes develop
uterus
what is a placenta?
site where the maternal and embryonic vasculatures exchange substances
what does unique mean
crossing-over between maternal and paternal chromatids during prophase I to end up with “mixed” chromatids
what does “mixed” mean
some paternal, some maternal genes
where does fertilization occur?
in the ampulla of the uterine tube
what does ovulation mean?
release of a secondary oocyte from ovarian follicle
the ovulated secondary oocyte together with zona pellucida, is externally covered with what
cumulus oophorus
cumulus oophorus will rearrange and form what?
corona radiata
what happens when the zona pellucida is penetrated by a sperm cell and “injects” its genetic material?
it becomes impenetrable and other sperm cells cannot penetrate
what are cells that surround the oocyte, found outside of the zona pellucida?
corona radiata
what are gametes?
a haploid germ cell
what are sperm?
gamete from testes
what are oocytes?
gamete from ovaries
what is fertilization?
fusion of the pronucleus of the 2 gametes
what is the zona pellucida?
protein coat that surrounds an oocyte as well as the early embryo
what is a zygote?
a fertilized, diploid oocyte, has not yet divided
what is an embryo?
multicellular organism, prior to fetal stage (period from fertilization - end of week 7)
what is a fetus?
multicellular organism, from end of embryonic stage to birth
what is a neonate?
newborn
what is extraembryonic
cells from during development that do not become part of the neonatal organism, but involute or contribute to the fetal membranes
what is morula?
approximately 16-cell stage (12-32 cells) of an embryo, no blastocoel
what is blastocyst?
a spherical mass of cells that is composed of a trophoblast that surrounds a fluid cavity (blastocoel) and an inner cell mass (embryoblast)
what is cleavage?
cell division in the early embryo -> each division does not increase the size of the embryo, instead each division results in a smaller and smaller cells
what is a blastomere
a cell that is totipotential and is present during very early develop, product of cleavage
what does totipotential mean
a cell that can become any cell
what does implantation mean?
occurs when an embryo contacts and then becomes surrounded by the endometrium of the uterus
what is a trophoblast
layer of cells on the outside of the sphere (blastomere)
what are embryoblast (inner cell mass)
surrounded by the trophoblast, these cells develop into the embryo
what is blastocoel?
the fluid filled cavity within the sphere
T or F: the epithelial cells of the uterine tube are equipped with cilia that “wave” in a single direction
true
ciliary movement increases by what?
as progesterone levels increase
when does progesterone secretion peak?
shortly after ovulation
what are the important roles early in development for the zona pellucida
- barrier that ensures that only one sperm fertilizes an oocyte
- porous - allows communication between the embryo and the maternal reproductive structures
- protects the embryo from immunologic defenses
- acts as a signal to help with differentiation of trophoblast cells
- prevents premature implantation of the embryo
- prevents the blastomeres from dissociating
what happens when the embryo implants too early?
it could result in an ectopic pregnancy
what day will the embryo “hatch” out of the ZP
day 6
what are the small apical processes on the endometrial epithelium that contacts with the trophoblast of the blastocyst
pinopods
once the trophoblast contacts the endometrial epithelium and invades, it forms two layers which are? which one is inner and which one is outer?
cytotrophoblast - inner layer
synctiotrophoblast - outer layer
what are the important functions of synctiotrophoblast?
- invasion into the endometrial stroma and formation of villi
- secretion of human chorionic gonadotrophin (hCG)
what does human chorionic gonadotropin do?
it prevents the shedding of the endometrium by maintaining ovarian secretion of steriod hormones
what is the hormone detected in pregnancy tests?
hCG
as the synctiotrophoblast invades into the stroma, the inner cell mass (embryoblast) differentiates into 2 distinct layers which are?
epiblast and hypoblast
what will line the blastocystic cavity and form the primary yolk sac?
hypoblast
Hypoblast is also known as?
primary endoderm
what is coelom?
a fluid-filled cavity (blastocystic cavity)
what is gastrulation?
the process of forming 3 embryonic germ layers
what are the 3 embryonic germ layers?
ectoderm, endoderm, mesoderm
list the embryonic germ layers from exterior to interior?
ectoderm, mesoderm, endoderm
what does cephalad mean?
towards the head region
what does caudad mean?
towards the tail region
implantation of the embryo is complete at about day what?
day 10
when implantation is complete, stromal cells undergo what? and is now known as what?
decidualization and decidual cells
what do decidual cells do?
they accumulate glycogen and lipids throughout the uterus
- The decidual cells that the syncytiotrophoblast contact undergo apoptosis, releasing stored nutrients needed for embryonic growth
the epiblast enlarges and gives rise to ?
amnioblast
what are ambioblast
cells that surround the developing amniotic cavity
what extends around the entire interior surface of the blastocoel
hypoblast
what cells begin to form and migrate between the hypoblast-derived cells and the cytotrophoblast
extraembryonic mesoderm
blastocoel turns into what?
primary umbilical vesicle/primary yolk sac
what forms the bilaminar disk
hypoblast and epiblast
what is extraembryonic coelom
the cavity between the extra-embryonic mesodermal cells
as the extraembryonic coelom enlarges and develops, it will develop into what?
chorionic cavity
extraembryonic coelom completely surrounds the rest of the embryo everywhere except for?
the junction of the amniotic cavity and the rest of the chorionic sac, this is the connecting stalkw
what later develops into the umbilical cord
connecting stalk
what are the two layers of extraembryonic mesoderm, separated by the fluid in the extraembryonic coelom?
extraembryonic splanchnic mesoderm and extraembryonic somatic mesoderm
what does the extraembryonic splanchnic mesoderm surround
umbilical vesicle
where is the extraembryonic somatic mesoderm?
found just underneath the cytotrophoblast, inner lining of the chorionic sac
what is chorion
the wall of the chorionic sac
what are “little lakes” or lacunar networks
where syncytiotrophoblast contacts endometrial blood vessels, the blood vessel deteriorates and blood pools
what appears at the end of week 2
prechordal plate
what is the prechordal plate?
Thickened area of columnar cells that acts as an organization area, found in the cephalad region of the hypoblast
what does induction mean in this case?
signaling “episodes” by key areas of the embryo that stimulate differentiation and development of local structures
what is the organizer of the head and mouth region, and helps to induce the formation of structures found at the cephalad pole of the embryo
hypoblast
what is the process by which the 3 germ layers of the embryo are established
gastrulation
what are the 3 germ layers
- ectoderm
- mesoderm
- endoderm
during gastrulation, bilaminar embryonic disc becomes what?
trilaminar embryonic disc
at the beginning of the 3rd week, formation of the ?
primitive streak appears
what is the primitive streak
thickened linear band in the median plane of the dorsal aspect of the embryonic disc
where does the primitive streak initiates
the caudal region of the epiblast
cells at the cephalad end of the primative streak proliferate to form a ?
primitive node
a narrow groove develops in the primitive streak called
primitive groove
the primitive groove is continuous with a small depression in the primitive node known as the ?
primitive pit
Cells leave the deep surface of the streak and form ?
mesenchyme
what is mesenchyme
embryonic connective tissue which forms the supporting tissues of the embryo
what forms the intraembryonic or embryonic mesoderm
mesoblasts
cells from the epiblast, as well as from the primitive node and other parts of the primitive streak displace the hypoblast and form what
embryonic endoderm (roof of the umbilical vesicle)
what forms the embryonic ectoderm
cells in the epiblast
