What is the general timing of human development?
Day 0 fertilization week 1 preimplantation week 2-3 early development and gastrulation week 3-8 embryonic period week 9-38 fetal period
How does the fertilized egg develop to the implantation stage?
oogenesis during embryonic dev-->oocytes-->fertilization-->formation of blastocyst (32 cell stage-->implantation (penetration of endometrial epithelium)
What is the trophectoderm?
Part of the blastocyst that will become the placenta
What is the inner cell mass of blastocyst?
will give rise to embryo proper and extraembryonic material
From where does the amnion and amnionic cavity arise?
-inner cell mass -fluid accumulation between cells of inner cell mass forms the cavity -the amnion is the roof of the amniotic cavity
From where does the chorion and chorion cavity arise?
-chorionic cavity forms between layers of extraembryonic mesoderm and encloses embryonic disc ,yolk sac, and amnion
Draw basic version of embryo in second week of development, including: embryonic disc, amniotic cavity, yok sac, connecting stalk, chorionic cavity, and placenta.
What is gastrulation?
When bilamniar embryonic disc converts into trilaminar disc, forms ectoderm, mesoderm, and endoderm. 3rd week.
How does the notochord influence development?
The notochord directs the inductive events in 3, 4 th week that causes ectoderm to become neural plate.
What is derived from the neural crest?
peripheral nervous system, melanocytes, smooth muscle in cardiovascular outflow, craniofacial derivaties.
What is derived from tne neural tube?
What is the function of the yolk sac?
-functions in metabolism and embryo/maternal transport.
What is the oropharyngeal membrane?
anterior end of embryo, marks the positinon of future mouth. where mesoderm doesn't penetrate between ectoderm and mesoderm.
What is the cloacal membrane?
marks position of future anus.
What does the intermediate mesoderm give rise to?
Most of the urogenital system
What does the lateral mesoderm give rise to?
It is divided into the somatic and splanchnic mesoderm. Somatic-->body wall, visceral-->splanchnic organs
What does ventral folding accomplish?
-Brings heart and septum transversum to thorax
-repositions caudal end and umbilicus
-defines foregut, midgut, hindgut
-partitions embryonic coelom into pericardial adn peritoneal cavities by septum transversum
What does lateral folding accomplish?
-flat-->radial 3 layer embryo
-coelomic cavity becomes body cavity
-forms the lateral and ventral body wal
How is the plerual cavity of the lungs created?
-pleuropericardial folds extend inward and fuse with tissue surrounding ventralateral side of esophagus as lungs grow
-results in separation of pleural and pericardial cavities.
-phrenic nerves are brought inward as the folds extend inward