Embryology Flashcards
What percentage of birth defects are of known causes?
50%
What is a teratogen? Teratology?
Teratogen: anything that causes a birth defect
Teratology: Science of understanding causes of birth defects.
What are some known teratogens?
Alcohol, Thalidomide.
What is pregenesis?
Developmental pre-conditions enabling successful reproduction.
What are the steps of pregenesis/
- Formation/migration of primordial germ cells
- Cortico-medullary differentiation of gonads (ovaries and testes)
- Increase cell number by mitosis
- Gametogenesis
Where do the primordial germ cell migrate to?
They go into the yolk sac for a period, then come back.
What are teratomas?
Migrating cells that end up in the wrong places, like primordial germ cells.
What is meiosis? What is different in the S phase of mitosis and meiosis?
Meiosis: cell division to generate gametes.
Mitosis S phase, sister chromatids line up. Meiosis S phase, homologous chromosomes line up.
What is spermatogoina? Oogonia?
Spermatogonia: male primordial germ cell.
Oogonia: Female primordial germ cell
What is meiotic nondisjunction?
Failure of paired chromosomes to separate regularly.
What is surrounding the egg after follicle rupture? What does it do?
Sticky cumulus corona radiata. Gives nutrients and helps egg move.
What is capacitiation?
Process which sperm cells undergo in order to reach and penetrate the egg.
What are the barriers the sperm must penetrate?
Corona radiata, Zona Pellucida, Egg plasma membrane.
Acrosome and Cortical reactions are based on what?
Acrosome=sperm
Cortical=egg
Once fertilized the cell is now______ and termed ______.
Diploid, Zygote.
What is cleavage?
Set of mitotic events where each daughter cell is half the size of the parent.
If the zygote undergoes cleavage very early, what can result?
Twins.
What is compaction?
The cleaved cells flatten and create junctions.
What is a morula?
Solid ball of cells.
What is a blasocyst? What is contained in it?
The zygote compacts and creates a hollow center. Inner cell mass and trophoblast.
What is hatching?
Blastocyst escapes the zona pellucida so it can grow.
What cells arise during the second week?
- Trophoblast
2. Inner cell mass
What cells arise from the trophoblast?
Cytotrophoblast, Syncytiotrophoblast.
What cells arise from the inner cell mass and what do they form?
Epiblast: Amnion
Hypoblast: Yolk sac
What happens during blastogenesis week 3?
Formations of 3 layers. Gastrulation.
WHere is the primitive streak?
On the epiblast.
Epiblast cells that migrate between the epiblast and hypoblast become?
Mesoderm
Epiblast cells that migrate to the hypoblast?
Endoderm
Epiblast cells that remain in the epiblast?
Ectoderm
Ectoderm forms?
Epidermis, Nervous system, enamel.
What does the mesoderm form?
Connective tissue, Muscle..
What does the endoderm form?
Guts, respiratory system.
What is important about the notochord?
A signaling machine made of mesoderm.
What happens during week 4?
Neuralation. Neural plate folds to become neural tube.
What is the neural plate?
Ectoderm induced to differentiate into neural tissue.
what are the 3 types of mesoderm? What do they form?
- Somites (paraxial): Muscle, Bone, Connective tissue
- Lateral plate mesoderm: Muscle of body wall, Digestive tract, proximal part of limpts
- Intermediate Mesoderm: Urinary and parts of genital system.
What are the two types of Lateral plate mesoderm?
- Splanchnic, associated with the endoderm.
2. Somatic: Associated with the ectoderm.
Transverse or lateral folding?
Left and right sides of the embryo curve towards the midline.
Cephalocaudal Folding?
Occurs in head and tail regions.
Explain the neural tube closure beginning to end.
- Closure begins midway.
- Anterior cranial neuropore closes
Posterior caudal neuropore closes
what are placodes?
Thickening of ectoderm from signaling of the
nervous system.
What is the Stomadeam? Proctodeam? What is speacial about them?
Stomadeam=future mouth
Proctodeam=Future anus
Only have Ectoderm and endoderm.
What is the Oropharangeal membrane? Proctodeal membrane?
Oro=Membrane that separates oral cavity from the throat.
Proc=Membrane at proctodeam.
