Term
| The 2 cell zygote undergoes cleavage. What is cleavage? |
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Definition
| Division to increase number of cells without an increase in size. |
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Term
| What are early cells in the zygote called? |
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Definition
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Term
| How many cells are in the morula stage? |
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Definition
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Term
| Which embryonic stage undergoes compactation? What does compactation do? |
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Definition
| The morula undergoes compactation which divides them into an inner and outer cell mass. |
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Term
| What happens when the morula enters the uterine cavity? |
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Definition
| The fluid filled blastocyst cavity is formed, the whole complex is called the blastocyst, and the inner cell mass becomes the embryoblast while the outer cell mass becomes the embryoblast |
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Term
| About how long after fertilization does the blastocyst attach to the posterior uterine wall? |
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Definition
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Term
| What do the trophoblast cells at the embryonic pole of the blastocyst proliferate to become? What is their function? |
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Definition
| syncytiotrophoblasts, which are able to invade the uterine lining. |
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Term
| Where does the embryo typically implant? |
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Definition
| Superior and lateral uterine walls |
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Term
| What part of the blastocyst eventually becomes the placenta? The embryo? |
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Definition
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Term
| What happens with the embryoblast immediately after implantation? |
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Definition
| cells differentiate and organize into 2 layers. cells on the future dorsal side of the embryo (near uterine wall) become epiblast or primary ectoderm while cells on the ventral side become the hypoblast (endoderm). Hypoblast+epiblast=bilaminar germ disc |
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Term
| What is happening at around 8 days post-fertilization? |
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Definition
| embryo penetrates further into uterine wall. High proliferation in syncytiotrophoblast and cytotrophoblast. proteolytic enzymes in cytotrophoblast degrade endometrial tissue. |
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Term
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Definition
| cells of the epiblast split in middle to form amniotic cavity, some hypoblasts converge away from the bilaminar disc to form primary yolk sac |
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Term
| What happens to the primary yolk sac? |
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Definition
| On day 12, a second wave of cells migrates ventrally to form the secondary (definitive) yolk sac, which closes the primary yolk sac. The primary sac moves to the abembryonic pole and eventually disappears |
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Term
| What is the name of the stalk that encloses the definitive yolk sac and bilaminar germ disc? |
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Definition
| connecting stalk (eventually becomes umbilical cord) |
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Term
| At what region of the embryo is the primitive streak located? The buccopharyngeal membrane? |
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Definition
| caudal end of the embryo; cranial end of embryo *cranial extent of gastrointestinal tract |
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Term
| What 3 components make up the primitive streak? |
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Definition
| primitive pit, primitive groove, primitive node |
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Term
| What is the cloacal membrane? |
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Definition
| It defines the caudal extent of the gastrointestinal tract |
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Term
| How are the 3 definitive germ layers formed? On which days does this occur? What is this process called? |
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Definition
| Epiblasts xform into undifferentiated mesenchymal cells that invade hypoblast, replacing it with definitive endoderm. 2nd wave of migrating cells forms a new layer, definitive mesoderm. Remaining epiblasts become definitive ectoderm. Occurs at day 14-16. This is called gastrulation. |
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Term
| What is the embryo called immediately following gastrulation? |
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Definition
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Term
| How do the notochordal process and the heart form? |
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Definition
| mesodermal cells migrate laterally and cranially. cells cranial to the primitive pit that remain in midline become the notochordal process |
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Term
| How does the notochord form? |
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Definition
| notochord develops from notochordal process. It looses its lumen and becomes a solid tube. it also converts ectoderm overlying it into neuroectoderm, forming the neural tube |
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Term
| How does the notochord influence the growth of the neural plate? |
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Definition
| induction of neural plate cells by the notochord cause its growth into neuroectodermal cells. |
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Term
| What are the different parts of the neural plate? |
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Definition
| neural fold, neural groove, and neural crest |
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Term
| What part of the neural plate becomes the neural crest? The neural tube? |
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Definition
| neural crest; neural folds |
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Term
| What do the neural crest cells become? |
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Definition
| dorsal root and autonomic ganglia |
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Term
| What are the last portions of the neural tube to close? |
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Definition
| cranial and caudal neuropores |
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Term
| What are some of the causes of inneffective closure of the neuropores? What results from this? |
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Definition
| gene mutations or teratogenic mechanisms; congenital defects or malformation of spinal cord/brain |
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Term
| What happens to the mesoderm lateral to the neural tube? Why is this patterning significant? |
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Definition
| mesoderm organizes into somites. segmental pattern serves as a template that is important in development of musculo-skeletal and nervous system interrelationships |
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Term
| How does the 3 dimensional embryo form? What body parts are translocated in this process? |
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Definition
| cranial, caudal, lateral folding of the germ disc; septum transversum, cardiogenic region, and distal hindgut |
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Term
| Why does the embryo come together in the midline during the process of lateral folding? |
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Definition
| growth and development of neural tube, heart, gastrointestinal tract, and decrease in size of the yolk sac |
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Term
| What is the septum tranversum? What does it separate? How do these two regions communicate |
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Definition
| developing diaphragm; separates the intraembryonic coelom into thorax and abdomen, called at this stage the pericardial and peritoneal cavities. They communicate through the pleuroperitoneal canals |
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Term
| What eventually closes the pleuroperitoneal canals? |
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Definition
| the pleuroperitoneal membranes grow out bilaterally from the posterior body wall towards the septum transversum and then fuse |
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Term
| What happens when the pleuroperitoneal membrane fails to fuse with the septum transversum or fails to form? |
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Definition
| An opening in diaphragm results where abdominal contents can enter thoracic cavity, called congenital diaphragmatic hernia. stomach and small intestines compromise developing lungs and compress the heart |
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