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HHP 1150 Unit 1
Embryology: embryonic period
| Question | Answer |
|---|---|
| Give an overview of the embryonic period | -the time where there is increasing complexity -gastrulation, neurulation, folding, organogenesis (weeks 3-8) -begins with establishment of primitive streak and ends with the main organ systems developed |
| define gastrulation | -main process of embryonic period -cells from the epiblasts migrate to form the primary germ layers -bc of this, embryonic disc goes from bilaminar (epi and hyp) to trilaminar (3 layer) |
| define primitive streak as well as the primitive node and pit. What does this streak indicate? | -streak in epiblast wall facing disk, indicates that gastrulation has begun. -node is the cephalic end if the streak. The pit is a depression in the node formed by migrating epiblast cells |
| What indicates that the pre-embryo structure is now an embryo? | -once all three germ layers have been formed. |
| define invagination. | inward movement of cells from epiblast layer through primitive streak between epiblast and hypoblast layers, becoming the mesoderm. |
| Describe gastrulation, AKA how the three germ layers form. | -begins w primitive streak formation -> invagination (migration from epi) -> mesoderm formed bt epi and hyp -other epi cells displace hypoblast cells and become endoderm -cells remaining in epi become ectoderm |
| where do the cells of the three germ layers originate from? | epiblast |
| what tissues do the ectoderm, mesoderm, and endoderm cells form? In directional terms, where are the three layers | ecto- nervous system and skin. superficial meso- muscle and bone, intermediate endo- inner linings, deep |
| define neurulation | -begins with appearance of notochord (derived from mesoderm) -the formation of the neural tube (spinal cord, beginning of nervous system) from underlying ectoderm cells |
| define embryonic disc folding. explain why folding starts to occur | -folding of trilaminar disc so that endo is inside meso, inside ecto. -early week 3, disc is flat :. called embryonic disc -later week 3, embryo grows faster than space it resides :. must fold to continue growth |
| What two types of folding does the embryo undergo? | cephalocaudal folding and transverse folding |
| explain cephalocaudal folding | head and tail fold, brings heart (initially above mouth) down to chest |
| explain transverse folding | lateral folding so that left and right sides of embryo curve toward midline |
| define organogenesis | once the disc has folded, organ systems begin to develop. by end of embryonic period, most basic organ forms have been developed |
| define teratogens. | agents that interfere with the development of organs and thus can cause congenital malformations (AKA birth defects) |
| Relationship between time of exposure to teratogens and embryo malformation | -Weeks 1-2: the blood is not shared yet so exposure to teratogens are no possible. -W3-7: there is major development :. major morphological abnormalities can occur -W9-38: there is fine tuning :. functional defects and minor morphological abnormalities |
| Before learning that it is a teratogen, Thalidomide was used to treat morning sickness in pregnant women. How would this affect the child at birth? | Morning sickness most often occurs between weeks 3 and 5, which is a time of sensitive development of the embryo. The embryo exposed to Thalidomide would have major morphological abnormalities. Specifically, fucked up limbs |
Created by:
kellyyrosse
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