Gastrulation, Neurulation (wk 3) Flashcards Preview

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Flashcards in Gastrulation, Neurulation (wk 3) Deck (78):
1

Gastrulation is the beginnings of

Morphogenesis

2

What occurs during gastrulation?

Changes to the bilaminar disc
- appearance of the primitive streak
-development of the notochord and prechoridal plate
-differentiation into 3 germ layers
- trilaminar embryonic disc

3

Once the trilaminar disc is formed, what is the embryo referred to as

A gastrula
(Week 3 development)

4

Germ Layers (3):

Ectoderm
Mesoderm
Endoderm

5

Ectoderm

Surface ectoderm-epidermis
Neuroectoderm - CNS, PNS, retina

6

Mesoderm

Skeletal and smooth muscle, CT., most of cardio system, blood cells, bone marrow, reproductive and excretory organs

7

3 parts of the mesoderm

Paraxial = somites
Intermediate = genitourinary systems
Lateral = body walls

8

Endoderm

Epithelium of respiratory and GI systems, including glands

9

Primitive streak is what

A thickened linear band of epiblast

10

The primitive streak begins where

Caudally in the median plane of the embryonic disc

11

The primitive streak is formed by what

A migration of epiblast cells to the median plane of the embryonic disc

12

What happens when the primitive streak elongates

The cranial end enlarges to form the primitive node and the primitive groove

13

The primitive groove ends in a small depression which is called the

Primitive pit

14

Epiblast cells migrate through the primitive groove to become the

Endoderm and mesoderm

15

All of the primitive stuff together forms the embryo’s

Craniocaudal axis

16

Cells from the deep surface of the primitive streak forms the embryonic connective tissue known as

Mesenchyme

17

Mesenchyme forms many types of cells:

Fibroblasts
Chondroblasts
Osteoblasts

18

The primitive streak decreases in size and becomes an insignficant structure where

In the sacrococcygeal region of the embro (wk 4)

19

The prechordial plate forms when
What is it?
What is it the site of?

Day 14
Endodermal cells in a localized area that form a thickened circular area
This is the site of the mouth

20

Notochordal process forms when

Day 16-17
Mesenchymal cells form a cord called the notochordal process

21

As the notochordal process grows cranially it develops a lumen called

The notochordal canal

22

The notochordal process continues to grow until

It reaches the prechordal plate

23

What does the notochord provide

Defines the axis of the embryo
Gives it rigidity
Serves as the basis for development of the axial skeleton

24

The future site of the vertebral bodies form around what

The notochord
The notochord deteriorates as the vertebral bodies form
Remains as the nucleus pulposus

25

What induces neural plate formation

The notochord

26

How does the mesoderm and endoderm form?

Epiblast cells pass through the primitive streak

Triggered by embryonic growth factors

27

3 types of mesoderm:

Paraxial =somites
Intermediate = genitourinary systems
Lateral = body walls

28

Oropharyngeal membrane is formed how?
What does it prevent?
Future site of?

Formed from the prechordal plate

The endoderm and ectoderm fuse

Prevents the notochordal process from continuing cranially

Future site of the mouth

29

The cloacal membrane forms where and is the future site of what?

Forms caudally to the primitive streak

Site of future anus

30

Cardiogenic area is what?

Premordium of the heart

31

Allantosis appears when?
Shape?
Involved with?
Forms what?

Appears approx day 16

Sausage shaped - extends from caudal wall of umbilical vesicle to the connecting stalk

Involved with early blood formation

Forms the early urinary bladder

The vessels become unbilical arteries and veins

32

The neural plate forms from the thickening of what?

Forms the?

The notochord growth induces the embryonic ectoderm thickens forming the neural plate

Forms the CNS - neuroectoderm

33

Neural grove forms when, how, and what?

Day 18

Neural plate opens in center

Neural folds form on each side of grove

Beginning of the brain!

34

Neural tube begins forming when?

End of week 3

Neural folds come together and fuse

Folic acid plays a part in this

35

Neural crest cells fuse to form what

The neural crest between the neural tube and ectoderm

36

Somites begin forming when?

How?

Forms what?

Begin forming end of week 3

The paraxial mesoderm begins dividing into paired cube shaped bodies called somites - around the neural tube

Starts in the occipital region

Forms most of the axial skeleton - associated with musculature and dermis

37

Each somite is innervated by what?

1 individual spinal nerve

39

Somites differentiate into 2 regions:

Sclerotome - ventraomedial part, form axial skeleton

Dermomyotome - dorsolateral part w/ 2 regions

40

Myotomes and dermatomes of the same somite are innervated by what

The same spinal nerve

41

Myotomes differentiate into two regions:

Epaxial - muscle innervated by dorsal primary rami, deep muscles of the back

Hypaxial - muscle innervated by ventral primary rami, all other muscles

42

Each individual spinal nerve separates into what

Dorsal and ventral primary rami just outside of the IFV

43

Lateral mesoderm forms the

Body walls

44

Lateral mesoderm differentiation causes the development of the

Intraembryonic coelom

- small coelomic spaces in lateral mesoderm and cardiogenic mesoderm forming a single horseshoe shaped cavity

45

Development of the intraembryonic coelom divides the lateral mesoderm into 2 layers called:

Somatopleure - the somatic or parietal

Splancnopleure - splanchnic or visceral

46

When does the circulatory system begin?

Beginning of wk3

47

When does uteroplacental circulation begin

Wk 5

48

Angiogenesis begins where?
When?

Begins in the extraembryonic mesoderm of the umbilical vesicle, chorion, connecting stalk

Wk3

49

Mesnechymal cells differentiate into

Angioblasts

50

Angioblasts form clusters known as

Blood islands

51

Angioblasts flatten to form what

Primitive endothelial cells

52

The mesenchymal cells that surround the primordial endothelial blood vessels differentiate into what

The muscular and connective tissue elements of the vessels

53

Vasculogenesis is the formation of

New vascular channels by assembly of individual cell precursors (angioblasts)

54

Primordial blood cells develop from hematopoietic progenitor that form from specialized endothelial cells of vessels called

Hemangioblasts - located on the umbilical vesicle and allantois

55

What is hematogenesis

When does it begin

Where does it begin

Blood formation

Week 5

Beginning in liver, then in spleen, bone marrow, lymph nodes

56

Mesenchymal tissue in cardiogenic area forms what

Heart and great vessels

57

Primitive heart tube contains what and forms what

Contains endothelium-lined channels = endocardial tubes

Fuse to form a primordial heart tube

58

How does the primordial cardiovascular system form?

The tubular heart joins with blood vessels in the embryo, connecting stalk, chorion, and umbilical vesicle

59

What is the first organ system functioning?

At end of week 3 the blood is circulating and heart is beating

60

Trancus arterious

Premordium of the aorta and pulmonary trunk

61

Bulbus cordis

Forms the primitive ventricle and part of the aorta

62

Sinus venosus

Premordium of the SCV IVC some coronary veins and atria

63

Development of chorionic villi

Early wk 3

Mesenchyme grows into the primary villi

Forms a core of loose connective tissue

This is secondary villi

64

When do primary chorionic villi appear?

At end of second week

Cytrotrophoblastic cells produce cellular extensions that grow into the overlying syncytiotrophoblast forming it

65

What happens to mesenchymal cells in the secondary villi?

They differentiate into both capillaries and blood vessels

66

When capillaries become visible the villi are called

Tertiary chorionic villi

67

The capillaries fuse to form

Arteriocappillary networks

68

The capillary network is connected to the embryonic heart by vessels that differentiate from what

The mesenchymne of the chorion and connecting stalk

69

Lacunae does what

The maternal blood flows into it

Oxygen and nutrients are passed to the embryo tissues over the surface of synchytiotrophoblast

70

Oxygenated blood passes into the lacunae from what

The spiral endometrial arteries in the endometrium

71

Deoxygenated blood is removed from the lacunae through what

Endometrial veins

72

When is fetal blood flow established

End of 3rd week

73

Heartbeat is present at day what

21-22

74

When can the heartbeat be detected

During 4th week

75

Cytotrophoblastic shell is formed by what?

Cytotrophoblastic cells of the chorionic villi

76

Main stem chorionic villi

Attach the villi to the endometrium

77

Branch chorionic villi grow from

The sides of the main stem chorionic villi

78

Most of the exchange of material between blood of the mother and the embryo takes place through

the walls of the branch chorionic villi

79

2 regions of the dorsolateral part, aka the dermomyotome

Myotome - myoblast - form muscle

Dermatome - fibroblast - form dermis