Lecture 8- Early embryology 1

Question 1

how does one become a multicellular body?

Answer 1

• growth
• morphogenesis
• specialisation

Question 2

morphogenesis

Answer 2

development of form and structure

Question 3

from fertilisation to birth (3 stages)

Answer 3

pre-embryonic
embryonic
fetal

Question 4

pre-embryonic

Answer 4

weeks 1-2

Question 5

embryonic

Answer 5

3 to 9

Question 6

foetal

Answer 6

9 to 38

Question 7

pregnancy weeks is calculated from

Answer 7

date of last menstrual period

Question 8

where does fertilisation take place

Answer 8

ampulla of the fallopian tubes

Question 9

fertilised oocyte is called a

Answer 9

zygote

Question 10

where is the ideal place for the embryo to implant

Answer 10

posterior uterine wall

Question 11

pre-embryonic weeks (1-2) weeks involves

Answer 11

1. cleavage
2. compaction
3. Implantation begins

Question 12

cleavage occurs

Answer 12

within 30h of fetilisation (day 2)

Question 13

what is cleavage

Answer 13

first mitts division resulting in two blastomeres of equal size

Question 14

zona pellucida

Answer 14

forms around zygote and morula

Question 15

morula formed when

Answer 15

32 cells within structure

Question 16

cells in the morula are said to be

Answer 16

totipotent

Question 17

totipotent

Answer 17

potential to become any cell

Question 18

compaction

Answer 18

formation of first cavity in morula (blastocoel)

Question 19

during compunction which structure is formed

Answer 19

blastocyst

Question 20

before compaction all cells are

Answer 20

totipotent

Question 21

after compact cell become

Answer 21

pluirpotent

Question 22

pluripotent

Answer 22

capacity to become many cells

Question 23

during blastocyst formation what happens

Answer 23

o Cell differentiation starts

• Trophoblasts- outer layer
• Inner cell mass- foetus

Question 24

after compaction/ blastocyst formation the blastocyst

Answer 24

hatches (day 5) from zone pellucid

- can now enlarge and interact with uterine surface

Question 25

when doe implantation begin

Answer 25

day 6-7

Question 26

how many cells in conceptus at the beginning of implantation

Answer 26

around 100 cell - of these 8 will make the embryo - the rest will become fatal membrane

Question 27

what happens to the outer cell mass in week2

Answer 27

outer cell mass differentiates into syncytiotrophoblast and cytotrophoblast

Question 28

what happens to the inner cell mass

Answer 28

becomes bilaminar disk | - epiblast and hypoblast

Question 29

epiblast

Answer 29

structure which the amniotic cavity grows from

Question 30

hypoblast

Answer 30

cavity which the primitive yolk grows from

Question 31

by the end of the 2nd week

Answer 31

conceptus has implanted the embryo and its two cavities (amniotic and yolk sac) will be suspended by connecting stalk within a supporting sac (chorionic cavity)

Question 32

chornionc cavity

Answer 32

support the conceptus

Question 33

connecting stalk

Answer 33

connect the embryo to the uterine wall

Question 34

syncytiotrophoblast

Answer 34

s the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother.

Question 35

cytotrophblast

Answer 35

is the inner layer of the trophoblast. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo

Question 36

chorionic villus

Answer 36

basic structural unit of metaneral- fetal exchange | - maternal blood flow within placenta (supports embryo)

Question 37

primitive yolk sac membrane Is pushed away from cytotrophoblast layer by

Answer 37

an acellular extra embryonic reticulum

Question 38

embryonic reticulum gets converted to

Answer 38

extraembyronic mesoderm by cell migration

Question 39

by the end of week 2 the maternal sinusoids will have

Answer 39

invaded the synncytiotrophoblasts | - Lacunae become continuous with sinusoilds

Question 40

when the lacunae become continuous with sinusoids

Answer 40

uteroplacenta circulation begins

Question 41

near the end of week2 what forms

Answer 41

a secondary yolk sac

Question 42

the secondary yolk sac is also called

Answer 42

the definitive yolk sac- pinches off from the primitive yolk sac

Question 43

connecting stalk is the

Answer 43

future umbical cord

Question 44

bleeding by the end of week 2 can be confused with

Answer 44

menstrual bleeding

Question 45

50% of zygotes are

Answer 45

lost within the first 2-3 weeks

Question 46

how many diagnosed pregnancies will miscarry

Answer 46

15%

Question 47

how many women suffer recurrent miscarriagee

Answer 47

1%

Question 48

aminiotic sac

Answer 48

Formed from spaces within the epiblast

Question 49

blastocoele

Answer 49

first cavity- formed as a result of compaction

Question 50

primitive yolk sac

Answer 50

exoelomic cavity - formed by hypoblast lining blastocoele

Question 51

secondary yolk sac

Answer 51

aka definitive yolk sac | - formed within primitive yolk sac

Question 52

extraembryonic coelom

Answer 52

aka chronionic cavity | - formed from space within the extracembryonic reticulum and mesoderm

Question 53

assisted reproductive technique

Answer 53

oocyte are fertilised in vitro and allowed to divide to the 4 or 9 cells take

Question 54

what is transferred into the women uterus

Answer 54

the morula

Question 55

benefits of assisted reproductive techniques

Answer 55

A cell can be safely removed from the morula and tested for conditions prior to transfer of the embryo into the mother

Question 56

ectopic pregnancy

Answer 56

implantation at site other than uterine body - peritoneal or ovarian - life threatening emergency

Question 57

Placenta praevia

Answer 57

implantation in inferior uterine segment - can cause haemorrhage - requires C-section