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42 Cards in this Set
- Front
- Back
Describe the stages of cleavage once an oocyte has been fertilized.
Where does cleavage occur? What becomes of the zona pellucida? |
Zygote
2-cell 4-cell 8-cell Morula Blastula (hatches from zona pellucida) Occurs in uterine tube |
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Difference between morula and blastula?
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Morula = solid ball of cells
Blastula = Hollow ball of cells |
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What becomes of the embryoblast cells in the blastula?
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Become embryo
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What eventually becomes of the trophoblasts in the blastula?
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Will become extraembryonic membranes (placenta); provides nutrition
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Which side of the blastula adheres and embeds into the uterus?
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Bare Zone; side nearest embryoblast
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What is the outer layer of the oocyte called? What becomes of it?
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Zona pellucida
It is shed by blastula before it adheres and embeds into uterus |
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How is the oocyte able to enter the uterus from the body cavity? Describe its path.
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Carried into ovary and uterine tube by peritoneal fluid; beating cilia of uterine tube pass it along into the uterus.
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What is the normal site of blastula implantation?
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Endometrium
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What cells do trophoblasts differentiate into? What is the purpose of these cells?
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Trophoblast becomes syncytiotrophoblast and cytotrophoblasts
Syncytiotrophoblast forms syncytium (multinucleate cells without cell borders) which erode endometrial glands and blood vessel walls Cytrotrophoblast maintain single cell layer around blastula, namely around bare zone |
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What part of the uterus sheds during menstruation?
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Endometrium
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What event in blastula implantation marks completion of implantaion?
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Uterine epithelium encloses embryo within uterine wall
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What is an ectopic pregnancy?
Where can ectopic pregnancies occur? Which is most common? |
Ectopic pregnancy: blastula implants in incorrect site
Can be in: 1) Ovary 2) Body Cavity (mesentary) 3) Uterine Tube (MOST COMMON; AKA TUBAL PREGNANCY) 4) Cervix |
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What becomes of embryoblast cells once implantation is complete?
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Embryoblast cells spread apart to separate blastula cavity into two distinct cavities: Amniotic Cavity, and Yolk Sac
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What cell layer is the amniotic cavity derived from?
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Epiblast
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What cell layer is the yolk sac derived from?
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Hypoblast
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What do the cells of the primitive streak become?
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Leave embryo to becomes extraembryonic mesoderm (contribute to placenta!)
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How does the chorionic cavity arise?
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Gaps in extraembryonic mesoderm open to form chorionic cavity
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What structure forms the umbilical cord?
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Connecting Stalk
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What structures comprise the chorion?
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Syncytiotrophoblast
Cytotrophoblast Extraembryonic Mesoderm |
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Explain the dual origin of the placenta.
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Fetal contribution: Chorion
Maternal contribution: Decidua |
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What is the decidua?
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Decidua = maternal portion of placenta; consists of endometrium, endometrial glands
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How does the embryo receive nutrition prior to formation of umbilical vessels?
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Via diffusion
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How does the allantois form? What does it become?
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Forms as an extension of urogenital sinus, later becomes urachus, which becomes median umbilical ligament
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How does weeping bellybutton arise?
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Patent Urachus:
Failure of urachus to fill in lumen to form median umbilical ligament leaves open canal between bellybutton and urachus. Known as weeping bellybutton (leakage of urine out through umbilicus). |
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What blood vessels allow for early diffusion in embryonic development? What do these vessels become?
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Allantoic BV's (become umbilical vein and artery)
Vitelline BV's (become SMA and IMA) |
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Where do umbilical blood vessels arise from? Where do t hey go?
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Umbilical vessels grow out along allantois and into chorionic villi
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What is the purpose of chorionic villi? Fetal or maternal contribution?
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Chorionic villi proliferate under decidual basalis to interact with maternal blood for exchange.
Fetal contribution |
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What becomes of the uterine cavity?
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Decidual capsularis expands to meet decidual parietalis and in process obliterates uterine cavity.
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What becomes of the chorionic cavity?
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Amnion expands to cover umbilical cord and obliterates chorionic cavity in its expansion
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What is the fetus suspended in?
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Amniotic fluid
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Does fetal blood ever mix with maternal blood? How does exchange occur between the two?
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No, fetal blood remains in capillaries in chorionic villi. Intervillous space is filled with maternal blood; bathes chorionic villi.
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What is the relative oxygen content of maternal blood in the intervillous space? How does this fetal uptake of oxygen?
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Blood in intervillous space is partially oxygenated. Fetal hemoglobin has higher affinity for oxygen than maternal hemoglobin and is unaffected by partial oxygenation of blood.
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