Weeks 2 & 3 Development Flashcards Preview

Anatomy > Weeks 2 & 3 Development > Flashcards

Flashcards in Weeks 2 & 3 Development Deck (57):
1

describe week 2

-implantation completed
-trophoblast differentiates into 2 layers
-embryoblast forms 2 layers
-extraembryonic mesoderm splits into 2 layers
-2 cavities form

2

day 8- trophoblast differentiated

-cytotrophoblast
-syncytiotrophoblast

3

day 8- embryoblast differentiates:

-hypoblast
-epiblast

4

day 8, the _____ forms

amniotic cavity

5

amnioblasts are...

epiblast cells adjacent to cytotrophoblast

6

During day 9, ____ migrate peripherally forming the _____

hypoblast cells; exocoelomic (heuser) membrane

7

the exocoelmic membrane and the hypoblast forms lining of _____

exocoelmic cavity (also called primitive yolk sac or primary umbilical vesicle)

8

During day 9, _____ fills in tiny space in _____

fibrin coagulum; endometrial wall

9

During day 9, _____ appear in syncytium of _____

vacuoles; embryonic pole

10

during day 9, fuse form _____ called the _____

lacunae; lacunar stage

11

During days 11 and 12...

-trophoblast characterized by lacunar spaces in the syncytium; forms intercommunicating network
-Cells of syncytiotrophoblast erode endothelial lining of maternal capillaries; sinusoids
-syncytial lacunae become continuous with sinusoids
-establishes uteroplacental circulation

12

during days 11 and 12, blastocyst is completely _____

embedded in stroma

13

During days 11 and 12, new cells appear between inner surface of ____ and outer surface of _____, forming the _____

cytotrophoblast; exocoelomic cavity; extraembryonic mesoderm

14

days 11 and 12 the cells lining the primary umbilical vesicle form a layer of _____ that surrounds the _____ and ______

extraembryonic mesoderm; amniotic cavity; primary umbilical vesicle (yolk sac)

15

days 11 and 12, large cavities known as the _____ form in _____ and will eventually fuse

extraembryonic coelomic spaces; extraembryonic mesoderm

16

days 11 and 12...

-large cavities form in extraembryonic mesoderm
-form extraembryonic cavity (aka chorionic cavity)
-chorionic cavity surrounds amnion and umbilical vesicle except at connecting stalk

17

the extraembryonic mesoderm lining cytotrophoblast and amnion is _____

extraembryonic somatic mesoderm

18

the extraembryonic mesoderm covering the yolk sac

extraembryonic splanchnic mesoderm

19

day 13

-trophoblast characterized by primary villi
-hypoblast produces cells that form secondary yolk sac (aka definitive yolk sac); exocoelomic cysts in the extraembryonic coelom (chorionic cavity)

20

during day 13, the _____ forms

chorionic cavity

21

extraembryonic mesoderm lining inside of cytotrophoblast

chorionic place

22

_____ will develop into the umbilical cord with development of blood vessels

connecting stalk

23

chorionic cavity surrounds ____ and _____ except at _____

amnion; umbilical vesicle; connecting stalk

24

at the end of week 2, a thickening develops in a region of the ____ where the cells become _____ in shape (this is known as the _____)

hypoblast; columnar; prechordal plate

25

the prechordal plate indicates the future site of the ____

mouth

26

recap of week 2

-implantation completed
-uteroplacental circulation established
-embryoblast develops into bilaminar disc
-amniotic and chorionic cavities form
-extraembryonic mesoderm forms
-primary and secondary yolk sacs form

27

week 3

-formative of primitive streak and node
-gastrulation occurs
-formation of notochord
-establishment of body axes
-growth of the embryo

28

formative process by which the 3 embryonic germ layers are formed

endoderm, mesoderm, ectoderm all formed by gastrulation

29

endoderm, mesoderm, ectoderm all formed from _____

epiblast

30

gastrulation begins with formation of ______

primitive streak

31

cephalic end of primitive streak =

primitive node which surrounds the primitive pit

32

during gastrulation, epiblast cells migrate towards _____ and slip beneath epiblast, which is called _____

primitive streak; invagination

33

invaginating epiblast cells:

-displace/replace hypoblast cells forming endoderm
-lie between epiblast and endoderm to form mesoderm
-cells remaining in epiblast form ectoderm

34

hypoblast cells are fairly ___ and not ___; the migrating epiblast cells which displace/replace the hypoblast cells are much more ___ and ____; the same goes for the epiblast cells which remain in the epiblast and do not migrate; they will also become more ____ to form the ____

thin; robust; robust; substantial; robust; ectoderm

35

during gastrulation, cells continue to spread ____ and _____; in cephalic direction, pass on each side of _____

laterally; cranially; prechordal plate

36

the prechoral plate is formed between the tip of the ____ and ____

notochord; oropharyngeal membrane (future opening of the oral cavity)

37

during notochord formation, _____ invaginate in the _____ which forms the _____

prenotochordal cells; primitive pit; notochordal process

38

the notochordal process grows cranially from the _____ until it reaches the _____ and acquires a ____, which is known as the ____

primitive node; prechordal plate; lumen; notochordal canal

39

the floor of the _____ fuses with ____ below and it degenerates

notochordal process; endoderm

40

once the floor degenerates, the _____ now has open connection with _____ through what is known as the _____

amniotic cavity; umbilical vesicle; neurenteric canal

41

two other names for extracoelomic cavity

primitive yolk sac and primary umbilical vesicle

42

the notochordal process is basically a hollow tube of _____ which move forward _____ from ____ to _____

prenotochordal cells; cranially; primitive node; prechordal plate

43

remains of notochordal process comprise the _____; this ____ separates from _____, folding in to form the ____

notochordal plate; notochordal plate; endoderm; notochord

44

recap of notochord formation

The ventral floor of the tube fuses with the underlying endoderm and the two layers breakdown, leaving the flattened notochordal plate. (At the level of the primitive pit the yolk sac is transiently communicating with the amniotic cavity thru the neurenteric canal).
The notochordal plate then detaches from the endoderm, into the mesoderm containing space between the endoderm and ectoderm, forming a solid rod = notochord.

45

the cloacal membrane is formed at the _____ of the _____

caudal end; embryonic disc

46

cloacal membrane similar to ______

oropharyngeal membrane

47

yolk sac forms _____ that extends into ______; allantois forms around _____

diverticulum; connecting stalk; day 16

48

allantois in lower vertebrates serves as a reservoir for ____ products of the _____; in humans, it remains ____ but may be involved in abnormalities of _____

excretion; renal system; rudimentary; bladder development

49

beginning of week 3, trophoblast is characterized by _____; _____ covered by _____

primary villi; cytotrophoblastic core; syncytial layer

50

further development of trophoblast: _____ penetrate core of primary villi (secondary villus)

mesodermal cells

51

end of 3rd week, mesodermal cells differentiate into ____ and _____

blood cells; small blood vessels (tertiary villus)

52

capillaries in tertiary villi make contact with capillaries developing in _____ of _____ and in ______; contact established with ______, connecting the ____ and ____

mesoderm; chorionic plate; connecting stalk; intraembryonic circulatory system; placenta; embryo

53

blood vessels arise from blood islands

vasculogenesis

54

blood vessels sprouting from existing vessels

angiogenesis

55

____ cavity enlarges; embryo attached to its _____ by narrow _____

chorionic; trophoblastic shell; connecting stalk

56

connecting stalk will develop into the _____ with development of _____

umbilical cord; blood vessels

57

recap of week 3

-formation of primitive streak and node
-gastrulation occurs
-formation of notochord
-establishment of body axes
-growth of the embryo
-primary to secondary to tertiary villi