embryology

Question 1

what is embryology

Answer 1

anatomical description of different stages of an embryo

Question 2

what is developmental biology

Answer 2

embryology and the mechanisms involved in regulating embryo development

Question 3

somatic cells vs germ line cells

Answer 3

somatic cells are cells that form the body, so they have a limited life
germline cells are cells for reproduction that are responsible for next generation development = ‘immortal’

Female germ cells = oocytes
Male = sperm

Question 4

three types of mammals

Answer 4

1) monotremes - lay eggs
2) marsupials - short gestation, immature young (kangaroo) , placenta
3) placentals - have placenta and more mature when born (mouse, humans)

Question 5

5 stages of early development

Answer 5

cleavage
compaction
trophectoderm + formation blastocyst
primitive endoderm
implantation

Question 6

define cleavage

Answer 6

cell division without cell growth

Question 7

what are cells called in the 2 to 8 cell stage

Answer 7

blastomeres, which can be removed from the embryo without affecting development. they are totipotent

Question 8

what happens during compaction

Answer 8

blastomeres maximise cell-cell contact to form morula. requires e-cadherin.

Question 9

what is the first differentiation event

Answer 9

cells on surface of morula differentiate into trophectoderm - cells are now restricted in development potential ( pluripotent)

Question 10

before compaction what transcription factor do all cells express + what do they do

Answer 10

oct4 - required for inner cell development (pluripotency of icm cells)
cdx2 - required for trophectoderm

Question 11

how is differentiation of trophectoderm regulated

Answer 11

following compaction cells on outside have higher levels of Cdx2 + cells on inside have higher levels of oct4
cdx2 switches off oct4
oct4 switches off cdx2

Question 12

what happens if cdx2 is blocked

Answer 12

trophectoderm doesn’t develop properly + blastocyst doesn’t form

Question 13

what is the function of the trophectoderm

Answer 13

pump sodium ions inside morula = form blastocyst
hatching from zona pellucida
implantation
maintenance of pregnancy
formation of placenta

Question 14

when about does trophectoderm develop

Answer 14

about day 5 after fertilisation

Question 15

what is the first function of the trophectoderm + what does this cause

Answer 15

pump sodium ions inside the morula, accumalation of na draws wter in osmotically - causes blastocoel to form ( fluid filled cavity)

Question 16

what does ability of trophectoderm to pump na ions depend on

Answer 16

polarisation of ion channels
na pump

Question 17

define cell polarisation

Answer 17

intrinsic asymmetry observed in cells
in shape of cells or how cellular components are organised

Question 18

which way are epithelial polarised

Answer 18

along apical basal axis

Question 19

which are the two types of trophectoderm are present after blastocyst formation

Answer 19

polar trophectoderm = direct contact with underlying epiblast
mural trophectoderm = line blastocoel

Question 20

what enzyme does mural trophectoderm secrete

Answer 20

strypsin = lyses a hole in the zona so blastocyst can escape
mural te gives rise trophoblastic giant cells = terminally differentiated + non-invasive

Question 21

when does polar te differentiate

Answer 21

upon contact with uterine epithelium, into cytotrophoblastic cells ( highly proliferative + responsible for implantation of embryo)