Embryonic overview Flashcards
when is the embryonic period
weeks 3-8. most susceptible to teratogens
When is embryo organogenesis?
weeks 3-8
what is complete and incomplete situs inversus?
- complete: all organs are mirror images
2. incomplete: only affects single organ
What is the primary cause of sirenomelia?
incomplete mesoderm production of the embryo at the caudal region
What is a sacrococcygeal teratoma caused from?
failure of primitive streak to disappear at the end of 4 weeks.
The notochord is derived from what embryonic cell layer?
mesoderm
After neurulation the notochord remains to become what structure in adults?
nucleus pulposus of the intervertebral discs
The lateral embryonic folding is required to produce what structures?
the lateral folding helps to form the gut tube. The parietal mesoderm encapsulate quickly which forces some of the yolk sac out and allows the portion that does become captured, to form the gut tube. lined with visceral mesoderm
What structure is still intact after the lateral folding takes place? Helps hold the gut tube in place.
dorsal mesentery, which later will assist with holding the abdominal organs “in place”
When does lateral folding occur?
week 4.
The cephalocaudal folding also takes place during week four, but produces what?
- places embryo into a fetus, and forms sections such as fore-/mid-/hindgut
The surface ectoderm will give rise to what structures?
- nails, epidermis, hair.
The neuroectoderm gives rise to what structure?
ear, eye, nose sensory epithelium
The neural tube formation provides what structures?
- CNS
2. neural crest cells–> PNS
What are the mesodermal embryonic derivatives?
- neuroectoderm
- paraxial mesoderm
- intermediate mesoderm
- lateral plate mesoderm (splanchnic)
- lateral plate mesoderm (somatic)
What does the paraxial mesoderm give rise to?
- first becomes somites, which then become dermotomes, sclerotomes, and myotomes.
- give rise to muscle, connective tissue (dermis), and skeleton
What does the intermediat mesoderm give rise to?
kidney, ureter, urethra, urinary bladder,
What does the lateral plate mesoderm give rise to?
connective tissues and muscles
What does the endoderm give rise to?
epithelial lining of the GI and respiratory, and bladder and urethra.
What significant things happens during fetal period 9-12?
- slow head growth
- ossification
- RBC production moves from liver to spleen
What should be visualized by week 12?
external genitalia
What is unique of fetal weeks 13-16?
- lengthening body
- hair on scalp
- eye movement
What is unique of weeks 17-20?
- limb movement
- vernix caseosa is held in place by lanugo, to protect fetus
- testes descend
What is unique of 21-25 weeks?
weight gain, and surfactant secretion into lungs.
What is the earliest that a fetus could be born and potentially survive?
21 weeks, up to this point the lungs have not had time to develop
Which develop first finger or toe nails?
finger during week 21-25. toe nails follow at 25-30 weeks
When does RBC formation shift from the spleen to bone marrow?
week 28
When is pupillary light relfex present in fetus?
30-35 week
What method can be used early in pregnancy for determining the fetus status, but has high risk of introducing problems?
chorionic villi sampling
Of the two methods to assess fetal status, which one is less threatening to the life of the fetus?
amniocentesis.
*can’t be sampled as early as chorionic villi sampling.
