early human development Flashcards
list the three phases of fertilization
- penetration of the corona radiata
- penetration of the zona pellucida
- fusions of sperm cell membranes and oocyte
what triggers the formation of fertilisation membrane, which is impenetrable to sperm?
sperm entry which triggers cortical granule release
what is the term given to the fusion of the male and female pronuclei?
zygote
from a zygote what happens during cleavage?
cleavage is a period of rapid cell division (no size increase)
zygote –> morula (16+ cells)–> blastocyte
what gives rise to the emrbyo?
inner cell mass
what happens to remaining cells which form the trophoblasts?
contribute to placenta
where are embryonic cells derived from?
inner cell mass of blastocyts
once the blastocyst has hatched from the zona pellucida what happens next?
embryo interacts directly with the endometrial lining of the uterus
where is the correct implantation site?
body of uterus
what happens to the embryo by days 9-12?
the synctiotrophoblast has extended and by erosion contacts maternal blood supply
- amniotic cavity is present
- definitive yolk sac
- chorionic cavity
what is gastrulation?
formation of the germ layers
the cells migrate through the primitive streak and two layers become one, name the three layers
ectoderm - nervous system and skin
mesoderm - muscle, bone and internal organs
endoderm - gut
what is the first step in the formation of a neural tube?
an area of the ectoderm is induced to form neural tissue (day19/20)
list the derivatives of the neural crest
- scwhann cells and meninges
- dorsal root ganglia
- autonomic ganglia
- odontoblasts
- melanocytes
- chromaffin cells
- bones and connective tissue of craniofacial structures
pharyngeal arches development
arch 1 - day 22
arch 2 and 3 - day 24
arch 4 and six day 29
