Embryology Flashcards
what are the three trimesters called?
weeks 0-3: conceptus/embryo
weeks 3-8: embryonic period
weeks 9-40: petal period
what is gametogenesis?
formation of gametes, consisting of mitosis and meiosis, leading to genetic variation
what is oogenesis?
formation of female gametes
what is spermatogenesis?
formation of male gametes
what happens during fertilisation?
union of gametes, formation of zygote: diploid, single cell embryo, sex determination
what happens during cleavage?
period of rapid mitotic cell division
many daughter cells called blastomeres
up to 8 cell stage blastomeres are thought to be totipotent
no increase in size, formation of morula (16 cells) then blastocyst (days 1-4)
what happens during gastrulation?
formation of the germ layers (week 3): ectoderm, mesoderm, endoderm
what happens during organogenesis?
formation of organs and systems, basis of these in place by the end of embryonic period, continues to develop through foetal period
what happens during foetal period?
growth and weight gain (mainly grows in second trimester and adds weight in the third), tissue mature and become functional, overt sexual differentiation, bone laid down and connections made in CNS
what does induction mean?
ability of one cell type to cause another to differentiate
what are primary processes from zygote to human?
cell division, differentiation, cell attachment, apoptosis, induction, cell migration
what are secondary processes from zygote to human?
axis formation/polarity (cells need to know where they are in relation to each other and the embryo), folding and rotation (gives embryo 3D from, allows formation of complex structures)
two controls of development?
genetic - gene expression tightly regulated in time and space
epigenetic - preferential expression of either the maternal or paternal copy of the gene
what does sperm bind with in a human specific interaction?
zona pellucida glycoprotein (ZP3)
what is released from the sperm head?
acrosomal enzymes
what are the two sperm entry tiggers?
completion of meiosis 2
release of cortical granules by oocyte
what is mosaicisom?
individuals with two of more cell lines with different chromosome complements
what is a morula?
16+ blastomeres, cells confined within zone pellucid
what happens with compassion of the morula?
to maximise available space by coming into closer contact with each other and begin cell junctions
when and where does implantation occur?
day 6, on the posterior or anterior uterine wall
what does a trophoblast divide into?
cytotrophoblast = made of individual cells syncytiotrophoblast = single multinucleated cell
what two layers does the embryo split into?
epiblast = dorsal surface of the embryo
hypoblast = ventral surface of the embryo
forming the amniotic cavity
what happens after the embryo has been organised into two layers?
implantation is complete and closure by fibrin coagulum, vacuoles appear in the synctiotrophoblast and unite to form lacunae. formation of two cavities: amniotic cavity (epiblast) and primitive yolk (hypoblast)
what happens on day 9?
blastocyst embedded in the endometrium
lacunae formation
what happens on day 15?
gastrulation
