L18 - development of multicellular organisms Flashcards
what does the sperm cell have to pierce through in order to fertilise the egg
acrosome
what does the inner cell mass of the blastocyst form and what type of cells are they
embryo proper
totipotent
what do outer cells of the blastocyst form
trophectoderm which forms extra embryonic tissues
what is the egg cortical reaction and when does it occur
protective reaction carried out by the egg once its been fertilised which prevents other sperm entering
what happens to intracellular Ca2+ when egg is fertilised
rises
in fertilisation what do Ca2+ waves activate
- membrane biosynthesis
- mitotic spindle restoration
- block polyspermy
- stimulates gene expression
what are the stages of development
- fertilisation
- cleavage (first rounds of division)
- blastula
- gastrulation (formation of 3 germ layers)
what determines zygote body axis
sperm site of entry
what happens during cleavage stage
cell will divide at steady rate but no growth
what are the 3 germ layers
- endoderm
- mesoderm
- ectoderm
what happens during gastrulation
formation of 3 germ layers
what structures does endoderm give rise to
lungs stomach liver intestines endocrine glands
what structures does mesoderm give rise to
kidney heart limbs muscle skeleton reproductive system
what structures does ectoderm give rise to
neural tissue (brain, spinal cord)
skin
skull
what gene regulates eye development
pax 6, expressed in cells where eye will form
