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Flashcards in Embryology Deck (55):
1

2 differences of chick gastrulation vs. frog (other than being flat)

1. endoderm displaces hypoblast
2. Hensen's node closes primitive streak to end gastrulation

2

What does the blastocoel form in the adult?

Nothing (gets filled up)

3

Compare blastula cells in mesolecithal

Asymmetric/different because yolk slows cleavage

4

Describe steps of neurulation

Thick dorsal ectoderm = neural plate
Invaginates, neural groove w/folds on sides
Folds fuse, enclosing neural tube
Epidermal ectoderm grows over top

5

Germ layer origin of chorion

Ectoderm, somatic hypomere mesoderm

6

Name the 4 major extra-embryonic membranes

1. Yolk sac
2. Amnion
3. Chorion
4. Allantois

7

Blastula formation events

Form hollow ball of cells; hole = blastocoel

8

Which organisms have a chorioallantoic placenta?

Most eutherian mammals

9

Morula (def)

symmetric ball of cells

10

Germ layer origin of allantois

Endoderm, splanchnic hypomere mesoderm (from hindgut region)

11

Events of cleavage

Short/no growth phase between cell divisions (division while overall embryo maintains size)

12

Major events of organogenesis

-embryo grows, lengthens
-germ layers further differentiate, work in concert to form complex organs

13

Which direction does Koller's sickle move?

posterior to anterior

14

How do extra-embryonic membranes form?

Lateral germ layers (ectoderm, hypomere mesoderm, endoderm) form folds, grow around embryo

15

Describe blastodisk of macrolecithal egg from dorsal to ventral

epiblast (dorsal, formed first, forms embryo), blastocoel (middle), hypoblast (ventral, forms after, guides cell migration in gastrulation)

16

Where do neural crest cells originate?

In neural folds (during neurulation)

17

Animal pole (def)

thinner, yolk-less end of blastula/gastrula (top in most diagrams, made of ectoderm)

18

Germ layer origin of notochord?

Mesoderm

19

Homoplasty (def)

Structures with a similar appearance

20

What does the archenteron become in the adult?

Gut (blastopore = anus in deuterostomes)

21

What does the posterior marginal zone in the chick embryo become?

Koller's sickle, then primitive streak

22

Shape of macrolecithal-egg embryo

disk

23

What does the neural tube become in adults?

Brain: ventricles
Spinal cord: cerebrospinal fluid canal

24

Function of the yolk sac

extra-embryonic membrane surrounding yolk, forming vitelline vessels to transport nutrients from yolk to embryo

25

Which vertebrates have a yolk sac placenta?

Most methatherian mammals

26

Function of allantois/allantoic membrane

Sequester nitrogenous wastes away from the embryo so it doesn't poison itself

27

Describe epiblast from anterior to posterior

Area opaca -> area pellucida (most of the epiblast) -> posterior marginal zone (thicker, becomes Koller's sickle, then primitive streak)

28

What does the coelomic fold become in the adult?

Muscular diaphragm (mammals only)

29

Mesoderm differentiates into...

Notochord, Epimere, Mesomere, Hypomere

30

What happens to the hypoblast in the chick embryo?

Displaced by endoderm during gastrulation
(Hypoblast: lower layer of blastula, directly dorsal to yolk)

31

Cells migrate into the blastopore through which analogous structures in the frog and chick embryo?

frog: blastopore
chick: primitive streak

32

What does the coelom divide into in all vertebrates? What separates them?

Pericardial & pleuroperitoneal cavities; transverse septum

33

Vegetal pole (def)

Thicker, yolk-filled end of blastula/gastrula (bottom in most diagrams, made of endoderm)

34

Which direction does Hensen's node move?

anterior to posterior

35

How do metatherian mammals form the embryonic placenta?

From yolk sac

36

What is Hensen's node?

Anterior end of the primitive streak

37

Germ layer origin of yolk sac

Endoderm, splanchnic hypomere mesoderm

38

How do complex organs form in the embryo?

Several germ layers work together

39

Which organisms do/don't have an allantois & why?

Anamniotes: no, wastes diffuse into water
Mammals: no, wastes removed by placenta
Sauropsids: yes, can't get rid of wastes

40

Germ layer origin of amnion

Ectoderm, somatic hypomere mesoderm

41

Ectoderm differentiates into...

Neural crest cells, neural plate cells, Epidermal

42

Epimere mesoderm forms... In the 24-hour chick embryo (overall structure name, plus differentiated layers)

somites (little balls); dermatome, myotome, sclerotome

43

What does the pleuroperitoneal cavity divide into in mammals, and what separates it?

Pleural cavity, peritoneal cavity; coelomic fold (becomes muscular -> diaphragm)

44

What is contained in the amnion?

Embryo, amniotic fluid

45

Who has protostome development?

Invertebrates: arthropods, molluscs, insects, etc.

46

How do eutherian mammals form the placenta?

From chorioallantoic membrane

47

3 main events of gastrulation

1. archenteron formation by cell migration into blastocoel
2. germ layer differentiation
3. committed anterior/posterior

48

Function of amnion

Cushion embryo in amniotic fluid, prevent dessication (b/c waterproof)

49

What is the transverse septum & what does it do?

Fold that divides coelom into pericardial & pleuroperitoneal cavities

50

Function of placenta

Exchange gases, nutrients, wastes between mother & embryo

51

Where is the coelom located?

Between the somatic and splanchnic hypomere mesoderm

52

3 differences between deuterostomes & protostomes

1. Cleavage pattern (spiral in protostomes, radial in deuterostomes)
2. End function of blastopore (mouth in protostomes, anus in deuterostomes)
3. Origin of skeleton (protostomes: ectoderm mostly, deuterostomes: mesoderm mostly)

53

How is the primitive streak formed?

Migration of Koller's sickle from posterior to anterior (mnemonic: sickle cuts up to form streak)

54

Describe structure & function of chorion

Membrane fuses w/allantois to form chorioallantoic membrane; allows gas exchange through egg shell via many blood vessels

55

What is the coelomic fold and what does it do?

Divides pleuroperitoneal cavity in mammals into pleural and peritoneal cavities by fusing with transverse septum