special topics

Question 1

what does embryogenesis achieve?

Answer 1

patterning - cells acquire identity in space and time (know where & when to grow)
major axis defined - anterior/posterior, dorsal/ventral
rudiments of major organs
3 germ layers defined
major process of development is similar for all organisms

Question 2

fertilisation - place, how

Answer 2

fallopian tube
sperm travels:
corona radicata –> zona pellucida –> plasma mem of secondary oocyte –> cytoplasm of secondary oocyte

Question 3

cleavage and formation of blastocyst/blastula + implantation (start)

Answer 3

day 1 - cleavage of zygote --> 2 cells. Fallopian tube
day 2 - 4 cell stage
day 4 - morula (lots of cells)
day 5 - blastocyst IN UTERUS
cells divide but no change in volume
blastocyst structure:
trophoblast = outer layer (--> placenta)
embryo blast = inner cell mass (-->baby)
blastocyst cavity = inside 
implantation
day 6= B implants into endometrium wall (sticky outer layer - comes out of  zona pellucida)

Question 4

development of trophoblast and bilaminar embryonic disc

Answer 4

TROPHOBLASTS
give rise to placenta - chorionic villi = fetal part of placenta. important for nutrients and waste
2 types - cyto and syncytio
enzymes that allow fertilised egg to implant
produce hormone - pregnancy test
BILAMINAR EMBRYONIC DISC - day 8
2 cells differentiate in inner cell mass –> epiblast (give rise to ectoderm) and hypoblast (give rise to endoderm)
epi = top layer (closest to wall) etc.

Question 5

gastrulation

Answer 5

formation of third germ layer - meso
amniotic cavity and yolk sac in blastula
formation of primitive streak - invagination of ectoderm (amniotic cavity) from posterior to anterior forms the mesodermal layer
afterwards = organogenesis

Question 6

embryonic folding

Answer 6

day 22 to 28
folding of head and tail end, lateral folding –> tube with ectoderm on the outside and endoderm in the inside (meso in between)

Question 7

stem cells, types

Answer 7

once cells differentiated then LIMITED division - this is why we have stem cells
stem cells divide to form 1 daughter (–> differentiate) + 1 daughter retaining stem cell properties - GROWTH, RENEWAL, REPAIR
decreasing development potential as more daughters formed (daughter = limited differentiation)
TOTIPOTENT - zygote. gives rise to all embryonic & placenta tissue, all cell types of body
PLURIPOTENT - cells in inner mass. give rise to all cells types in body
MULTIPOTENT - all cell types in particular tissue or organ
NULLIPOTENT/UNIPOTENT - only one particular tissue, no other cell types

Question 8

clinical application of stem cell (skin stem cells)

Answer 8

3-4 weeks renewal
keratinocyte (unipotent) stem cells –> differentiated keratinocytes –> divide & move up until dead cells on surface
edit keratinocyte cells (so they’re LONG LASTING) to repair genetic defects in patients