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58 Cards in this Set

  • Front
  • Back
When is an embryo referred to as a fetus? Why?
After 8 weeks b/c organoogenesis is complete.
Fertilized Cell
Daughter cells that form after fertilization usually 16-32
Collection of blastomeres
Where is the ovum fertilized? Where does it go after fertilization?
Ovum fertilized in ampulla of uterine tube

Travels to the uterus after fertilization
Blastocyst Cavity
Fluid-filled area found in the morula
Term that refers to a morula w/a blastocyst cavity
Outer Cell Layer/Trophoblast
Gives rise to embryonic part of placenta and is in blastocyst
Inner Cell Layer/Embryoblast
Gives rise to whole embryo/embryo proper, forms in blastocyst
Embryonic Pole
Designated side of the blastocyst where the inner cell mass/embryoplast moves
Zona Pellucida
Outer protective layer of the blastocyst lost during dev't

Allows rapid growth to occur
Outer Syncytiotrophoblast
One of the trophoblast differentiated layers, invades uterine wall, produces HCG
Inner Cytotrophoblast
One of the trophoblast differentiated layers, produces new cells
Cell layer that forms after the first week along the embryoblast facing the blastocyst, below epiblast, cells produce extra-embyronic mesoderm
Fertilized Oocyte
What are the 2 layers that the inner cell mass becomes?
1. Epiblast

2. Hypoblast
One of layers formed from the inner cell mass, above hypoblast, gives rise to the fetus
Bilaminar Germ (Embryonic) Disc
Made of the epiblast and hypoblast
Amniotic Cavity
Cavity that forms within the epiblast, filled with amniotic fluid, lined with amnioblasts (specialized epiblast cells)
What ruptures signaling the onset of labor?
Amniotic cavity
Primary Yolk Sac
Below hypoblast layer, contains fluid
Extraembryonic Mesoderm
Loose connective tissue outside the primary yolk sac, vesicles form here
Extraembryonic Coelom
Separates the extraembryonic mesoderm into two layers:

1. Extraembryonic splachnic mesoderm
2. Extraembyronic somatic mesoderm
Where do the epiblast and hypoblast come from?
Inner cell mass/embyroblast
What is the bilaminar germ disc comprised of?
Epiblast and hypoblast
What cavity forms in the epiblast?
Amniotic cavity filled with amniotic fluid
Cells from what layer give rise to the extraembyonic mesoderm?
What is another name for the primary yolk sac?
Exocoelomic cavity
What is the difference b/w the exocoelomic cavity and the extraembyronic coelom?
Exocoelomic cavity = primary yolk sac

Extraembryonic coelom = formed from the extraembryonic mesoderm and separates the mesoderm
Chorionic Cavity
Renamed term for extraembryonic coelum

Enlarges to pinch off primary sac to give rise to the 2ndary yolk sac
Oropharyngeal Membrane
Future mouth, forms at end of bilaminar disc where epiblast + hypoblast cells become attached
Cloacal Membrane
Future anus, forms at end of bilaminar disc where epiblast + hypoblast cells become attached
Primitive Streak
At the caudal (posterior) end of bilaminar disc, depression is called primitive groove
Primitive Node
At the cranial (anterior) end of bilaminar disc, depression is called primitive pit
Epiblast cells migrate through the primitive groove and pit into area underneath (ventral), displacing existing hypoblast cells to form new hypoblast layer (embryonic endoderm)
Embryonic Endoderm
Formed during gastrulation when epiblast cells move ventrally from primitive groove and pit
Intraembryonic Mesoderm
Eventually forms notochord, between the epiblast and hypoblast layers during gastrulation
Embryonic Ectoderm
Cells that stay in the epiblast during gastrulation
How is the notochordal process initiated?
Cells migrate from the epiblast through the primitive pit and move in a cranial (anterior) direction in the mesodermal layer until it reaches the oropharyngeal membrane
____ will form into the notochord?
Notochordal process
How is the neural plate formed?
Formation of notochord induces the overlying ectoderm to thicken leading to formation of the neural plate
Formation of the neural plate leads to formation of a specialized ectoderm referred to as?
Formation of the neural plate, folding of plate into neural folds and closure of folds to form the neural tube
Neural Tube
Forms during neurulation, gives rise to the CNS
Hypoblast cells form what layer?
Embyronic endoderm
Oropharyngeal Membrane
Cranial/Anterior end during gastrulation, future mouth
Cloacal Membrane
Caudal/Posterior end during gastrulation, future anus
Which layer does the notochord arise from?
Intraembryonic mesoderm
The intraembyronic mesoderm differentiates into which 3 layers?
1. Paraxial Mesoderm
2. Intermediate Mesoderm
3. Lateral Plate Mesoderm
Intermediate mesoderm gives rise to?
Urogenital system
Lateral plate mesoderm is involved in what?
Body Folding
How are somites formed?
By paraxial mesoderm differentiation + segmentation
Portion of somite, gives rise to bone and cartilage (forming vertebrae + ribs)
After the neural tube is formed, what happens?
The tube drops beneath the ectodermal layer, closure of the cranial neuropore and then caudal neuropore in a zipper-like fashion
Neural Crest Cells
Along edge of neural folds, detach themselves and migrate to body areas
What does the 2ndary yolk sac become?
GI tract + derivatives
Lateral plate mesoderm divides into which 2 layers?
1. Somatic/parietal layer lining future body wall
2. Splanchnic/visceral layer lining outside of 2ndary yolk sac
GI tract is derived from which structure?
Yolk sac