Embryology Flashcards
What is a malformation?
Primary structural defect from localized error in morphogenesis; abnormal formation of tissue or organ.
*most common defect
What is dysplasia?
Abnormal organization of cells into tissues (ex. cleft lip)
What is deformation?
Alteration in shape or structure of a structure or organ that has differentiated normally (ex. clubbed foot)
What is a disruption?
Structural defect resulting from destruction of structure that had formed normally before the insult
What generally occurs in week 1?
- embryo has been fertilized
- divides and travels through fallopian tube
- cleaves and forms morula
- implantation in wall of uterus
Which part of the embryo works its way into the wall of the uterus?
Trophoblast
What generally occurs in week 2?
“the week of 2’s”
- trophoblast -> 2 layers (syncytiotrophoblast, cytotrophoblast)
- embryoblast -> 2 layers (epiblast, hypoblast)
- two cavities (amniotic, yolk sac)
What is the first sign of gastrulation?
Primitive streak
What occurs in week 3, day 15/16?
formation of the trilaminar disc (gastrulation – differentiate ectoderm/endoderm/mesoderm)
What occurs in week 3, day 16?
migration of cells from the epiblast (primitive streak)
- mesenchymal cells come down and populate space between epiblast and hypoblast (replace cells in hypoblast to form three layers)
- development of left/right/cranial/caudal orientation
What occurs in week 3, day 18?
formation of the notochord
- ectoderm begins to form neural groove
- neurulation - neural fold and tube from neural crest
What occurs in week 3, day 20-21?
zipping up of the neural tube
What occurs in week 4, day 24-28?
Neural tube closes and neural crest cells separate from tube
-aided by folate supplementation in pregnant women
What occurs in week 3, day 18-19?
Formation of mesoderm
What occurs in week 3, day 21?
Lateral plate of mesoderm splits into parietal and visceral mesoderm of body cavities.
Paraxial mesoderm will form somites.
