Lecture 1 Flashcards by Taylor Walker

where does fertilization occur?

ampulla of uterine tube

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after the 2 cell stage, the zygote goes thru a series of mitotic divisions, increasing the number of cells that get smaller and smaller, called ____

blastomeres

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process by which blastomeres form a compact ball of cells segregated into inner and outer cells that communicate via gap junctions

compaction

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16 cell stage of the embryo, approx. 3 days after fetizilation

morula

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internal portion of morula that eventually becomes the embryo

inner cell mass of morula

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outer cell layer surrounding the blastocyst from which placental tissues are derived
(outer cell mass of morula forms the this fetal contribution to the placenta)

trophoblast

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stage of embryogenesis at the time of implantation where outer trophoblast cells form a fluid-filled sphere with a small group of embryoblast cells, the inner cell mass, at one pole
(compaction of the blastomeres by forming tight junctions allows fluid to be pumped into the center of the morula, which results in formation of the ______)

blastocyst

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if pregnancy, ______ secretes hCG that maintains corpus luteum, which makes progesterone to support pregnancy

syncytiotrophoblast

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two layers that make up trophoblast during the second week of development

cytotrophoblast

syncytiotrophoblast

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proliferative inner layer of trophoblast that makes cells
inner layer of mononucleated cells
cells divide and migrate into syncytiotrophoblast-eventaully fuse and lose individ cell membranes

cytotrophoblast

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outer multinucleated layer of the trophoblast that serves to invade the endometrium of the uterus and production of hormones
forms syncytium
outer multinucleated zone w/o distinct cell boundaries

syncytiotrophoblast

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two layers of the germ disc (made by inner cell mass–embryoblast–at one pole of blastocyst) during the second week of development

epiblast

hypoblast

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cavity that forms during second week of development

dorsal (back) side

amniotic cavity

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cavity that forms during second week of development

ventral (front) side

yolk sac

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ventral (bottom) layer of embryoblast with small cuboidal cells adjacent to the blastocyst cavity
contributes to formation of the yolk sac and extraembryonic mesoderm but not to tissues of the embryo

hypoblast

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dorsal (top) layer of embryoblast comprising the bilaminar germ disc during the second week of development
all tissues of the embryo are derived from this
layer of embryoblast with high columnar cells adjacent to amniotic cavity

epiblast

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epiblast cells adjacent to the cytotrophoblast

amnioblasts

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what is the origin of the amniotic sac?

small cavity in the epiblast enlarges to form amniotic cavity

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what is the origin of the yolk sac?

a thin membrane is formed at the embryonic pole, most likely from hypoblast cells, and lines the inner surface of the cytotrophoblast
the membrane + the hypoblast forms the exocoelomic cavity and creates the primitive yolk sac

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what forms the extra embryonic mesoderm?

new cells derived from yolk sac cells appear between the inner surface of the cytotrophoblast and the outer surface of the primitive yolk sac, eventually forming the EE Mesoderm

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what fills the space between the trophoblast externally and the amnion/yolk sac internally?

extra embryonic mesoderm

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large cavities develop in the EE Mesoderm and (once confluent) form the ______, which surrounds the yolk sac and the amniotic cavity except where the connecting disc connects the germ disc to the trophoblast
space formed between the extraembryonic mesoderm lining the cytotrophoblast (somatic-parietal- EE mesoderm) and the splanchnic-visceral- EE Mesoderm that surrounds the yolk sac and embryo
Eventually be obliterated by expansion of the amniotic cavity and fusion of the amnion with the chorion

chorionic cavity

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what are the two types of extra embryonic mesoderm, and what do they line?

extra embryonic somatic mesoderm - lines cytotrophoblast and amnion (body cavity)
extra embryonic splanchnic mesoderm - lines yolk sac (organs)

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cells of the cytotrophoblast proliferate locally and penetrate into the ______, forming cellular columns surrounded by syncytium. Together, this forms the _____.

syncytiotrophoblast

primary villi

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process that occurs during the 3rd weeks of development establishes all 3 germ layers begins w/ formation of primitive streak on surface of epiblast

gastrulation

name all 3 germ layers

ectoderm mesoderm endoderm

elevated region around the craniel end of the primitive streak that is known as the "organizer" regulates important processes like laterality and formation of the notochord

primitive node

cells of the epiblast migrate toward the ______ and, once they arrive detach and slip underneath it

primitive streak

what gene controls invagination of the epiblast?

FGF8

after invagination, cells that displace the hypoblast form the ____ one of the three basic germ layers that form the gut and its derivatives

endoderm

one of the three basic germ layers that form blood vessels, bones, connective tissue, etc. cells that lie b/w the endoderm and epiblast

mesoderm

one of the three basic germ layers that forms skin, CNS, PNS, hair, etc. cells that remain in the epiblast after invagination

ectoderm

during neurulation, _______ cells invaginating in the primitive node move forward cranially in the midline until they reach the prochordal plate

pronotochordal cells

pronotochordal cells become intercalated in the hypoblast so that for a short time, the midline consists of two cell layers that form the ______.

notochordal plate

during neurulation, the hypoblast is replaced by endoderm cells moving in at the primitive streak. Cells of the notochordal plate proliferate and detach from the endoderm to form a solid cord of cells called the _____

definitive notochord

what underlies the neural tube nad serves as the basis for the axial skeleton?

definitive notochord

end of the notochord that forms first

cranial (head) end

the notochord/prenotochordal plate extends cranially to the _____ and caudally to ______

cranially to prochordal plate | caudally to primitive pit

the the point where the primitive pit forms an indentation into the epiblast, the __________ temporarily connects the amniotic and yolk sac cavities

neurenteric canal

what is the organizer during gastrulation?

the node

what does the node organize?

laterality? | established both before and during gastrulation

during week 1 of fertilization, maternal and paternal pronuclei fuse and blastomeres divide to form a _____, or 16 cell stage embryo

morula

formed during day 4-5 after fertilization formed by compaction of blastomeres by formation of tight junctions fluid pumped into center of morula consists of fluid filled cavity and an inner cell mass

blastocyst

inner cell mass of the blastocyst

embryo

fetal contribution to placenta during week 1 post fertilization

trophoblast

trophoblast connects to uterine epithelium and expresses _____, which are carbohydrate binding proteins to bind to carbo receptors in the uterine epithelium

selectins

the maternal immune system switches from _____ to _____ to protect the embryo, increasing her risk of infection and changes in manifestation of autoimmune disease

cell mediated to humoral (antibody mediated)

how are MS and RA affected during pregnancy?

improved

how is systemic lupus erythematosis affected during pregnancy?

worsens

trophoblast forms placental tissue, but with no embryo express only paternal genes probably arise from fertilization of an enucleated egg followed by duplication of the paternal chromosomes to restore a diploid number secrete high concentrations of hCG may become invasive/malignant (choriocarcinomas)

hyatidiform moles ("molar pregnancy")

what layer in the uterus regenerates the endometrial glands for the next cycle?

basal layer of the epithelium

where are the two most common sites for ectopic pregnancies?

``` uterine (fillopian) tubes - 95% rectouterine pouch (Douglas' pouch)--most common site in abdomen ```

the synctyiotrophoblast will continue invading the maternal tissue until eventually reaching _____ at around 12-14 days

maternal blood vessels | Note: Maternal and embryonic circulation are separate

the embryoblast differentiates into....

epiblast | hypoblast

the epiblast differentiates into ____ and creates amnion

amnioblast

the hypoblast leads to the ___

yolk sac

what two cavities form after the embryoblast differentiates into the embryoblast and hypoblast?

``` amniotic cavity (dorsal to epiblast) yolk sac (vental to hypoblast) ```

blood vessels in the mesoderm core with most of the cytotrophoblast degenerated and covered by syncytiotrophoblast formed by EE Mesoderm and will connect the EE mesoderm formed around the outside of the amnion and yolk sac, splits into two layers

vessels in the tertiary villi

2 layers of the EE mesoderm

somatic (perietal) - lines body cavity | splanchnic (visceral) - lines organs

cavity between the somatic (perietal) and splanchnic (visceral) layers of the EE mesoderm

chorionic cavity

process of forming the three primary germ layers from the epiblast involving movement of cells through the primitive streak to form endoderm and mesoderm begins during 3rd week after fertilization

gastrulation

germ layer | CNS, PNS, skin, eyes, internal ear, neural crest cells, bones/cartilage of face, some skull

ectoderm

germ layer | blood, bones, connective tissue, urogenital and cardiovascular systems

mesoderm

germ layer | gut, gut derivatives, parenchyma of glands, liver, pancreas, lungs, etc.

endoderm

organizer at the cranial end of the primitive streak

primitive node

gene that comes out of the primitive node | gene expression in the anterior visceral endoderm

SHH (Sonic Hedge Hog)

collection of mesoderm cells lying b/w the oropharyngeal membrane and the cranial end of the notochord some of the first to pass through the primitive streak and are important for forebrain induction using sonic hedgehog (SHH) as a signal molecule

prechordal plate

eventually, the ______ forms the nucleus pulposus in the intervertebral discs

notochord

the ______ axis is established by the anterior visceral endoderm (AVE) secretes genes necessary for head development

cranial caudal axis

head mesoderm | organized by Goosecoid and other genes that regulate BMP-4 protein

dorsal/paraxial mesoderm

protein secreted throughout hte embryonic disc and vantralizes mesoderm, forming intermediate and lateral plate mesoderm antagonized by Goosecoid gene and others expressed by node (members of the transforming growth factor Beta family that serve as signal molecules for many morphogenetic events: dorsaling the CNS, participating in bone formation, etc.)

BMP-4 (bone morphogenetic protein 4)

gene that controls the formation of dorsal mesoderm in regions caudal to the head expressed by node and notochord decrease in this gene could lead to caudal dysgenesis (mermaid syndrome: missing kidneys, fused lower limbs)

Brachyury (T-gene)

master gene for laterality establishes left sidedness upregulated by seratonin, nodal, and FGFs

PITX2

restricts nodal expression to left side

seratonin

transposition of the viscera due to laterality issue usually no other defects complete reversal of left and right-sidedness of the organs in the thorax and abdomen

situs inversus

what forms the villi for placenta?

trophoblast

at the core of cytotrophoblast | covered by sycytiotrophoblast

primary villi

at the core of the EE mesoderm | covered by cytotrophoblast then covered by each other with umbilical vessels to form fetal circulation?

secondary villi

cells that surround the blastocyst cavity and cover the inner cell mass; will form the trophoblast

outer cell mass

cluster of cells segregated to one pole of the blastocyst | entire embryo develops from this

inner cell mass

mesodermal connection that connects the embryo to the placenta contains the allantois and umbilical vessels and will be incorporated into the umbilical cord with the yolk sac (vitelline) stalk (duct)

connecting stalk

groove formed in the epiblast at the caudal end of the bilaminar germ disc stage embryo through which epiblast cells migrate to form endoderm and mesoderm during gastrulation

primitive streak

depression in the primitive node

primitive pit

membrane formed at the caudal end of the embryo from adhesion between epiblast and hypoblast cells later covers the cloaca eventually breaks down to form openings into the urogenital sinus and anus

cloacal membrane (plate)

collection of endoderm cells at the cranial end of the bilaminar disc responsible for inducing the head region through secretion of transcription factors (OTX2, LIM1, and HESX1)

anterior visceral endoderm (AVE)

right and left sides are established during gastrulation in the third week of development patients with defects in sidedness, such that they are primarily bilaterally left- or right-sided have laterality sequences

laterality sequences

Lecture 1 Flashcards

(86 cards)