Neurulation and Folding Flashcards
(103 cards)
1
Q
what is neurulation
A
the developmental process that establishes CNS in developing embryo
2
Q
what does neurulation start with?
A
the development of the notochord
3
Q
What is neural induction?
A
when the definitive notochord secretes molecules that induces proliferation and differentiations of ectodermal cells above the notochord, giving rise to the neural plate and neuroectoderm
4
Q
what is the neural plate formed from?
A
thickening of the overlaying ectoderm
5
Q
where does the neuroectoderm extend from?
A
extends cranially from the primitive node and overlays the paraxial mesoderm laterally.
6
Q
what does the ectoderm differntiate into?
A
neuroectoderm and surface ectoderm
7
Q
what does the neural folds form from?
A
cells at the lateral edge of the neural plate proliferating
8
Q
where does the neural groove form?
A
between the neural folds (midline)
9
Q
How does the neural tube form?
A
from the gradual fusion of the neural folds at the dorsal midline due to continuing cell proliferation
10
Q
Explain what happens to the ectoderm as the neural tube forms?
A
The neural folds continue to grow and fold, and neural crest is formed at the lateral edges, and all of the other ectoderm = surface ectoderm
11
Q
where does neural tube fusion begin to occur? in what direction does it continue?
A
in the future cervical region of the embyro; continues to move cranially and caudally
12
Q
How does the neual tube communicate to the amnionic cavity?
A
via rostal and caudal neuropores
13
Q
When is neural tube close complete?
A
week 4
14
Q
Once the neural tube fusion is complete, which ends is broader, cephalic or caudal?
A
cephalic end is more broad
15
Q
What are the three expanded regions (brain vesicles) of the cephalic end?
A
- proencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
16
Q
what does the proencephalon give rise to?
A
telencephalon and diencephalon
17
Q
what does the rhombencephalon give rise to?
A
metencephalon and myelencephalon
18
Q
what type of cells histologically are found in the neural tube?
A
pseudostratified neuroepithelium (lies between the two basal membranes)
19
Q
WHat are the three zones that develop within the neural tube?
A
- ventricular zone
- intermediate zone
- marginal zone
20
Q
what types of cells are found in the ventricular zone?
A
proliferating neuronal progenitor cells
21
Q
what type of cells are found in the intermediate zone?
A
migrating neuroblasts
22
Q
what type of cells are found in the marginal zone?
A
azons of the developing neurons
23
Q
what gives rise to all of the neurons and glia of the CNS?
A
neuroepithelium of the neural tube
24
Q
what does the neural tube represent after it is closed?
A
the developing central nervous system
25
what happens to the neural crest cells once the neural tube fusion is initated?
they lose contact with the neuroectoderm, undergo epithelial-mesenchymal transformation, and migrate dorsally and ventrally within the embyro
26
what is the final destination of the neural crest cells originateing at the trunk?
two routes:
1. dorsal route = skin -- become melanocytes of skin and hair follicles
2. ventral route = give rise to organs (dorsal root ganglia, sympathetic trunk ganglia, parasympathetic ganglia, para-aortic ganglia, chromaffin cells of suprarenal medulla, and schwann cells)
27
when do the neural crest cells originiating in the cephalic region of the embryo leave the neural crest?
BEFORE neural tube closure
28
when do the neural crest cells originiating in the trunk region of the embryo leave the neural crest?
migrate AFTER neural tube fusion
29
what is the final destination of the neural crest cells originiating in the cephalic region?
```
head region; primarily to the developing pharyngeal arches
give rise to the craniofacial skeleton,
CT of face and ventral neck,
cardiac outflow tract
odontoblasts and cementoblasts of the teeth
sensory neurons
glia of cranial ganglia
melanocytes
```
30
where do sensory neurons of the cranial ganglia arise from?
nerual crest cells of the head region and ectodermal placodes
31
what do the most rostal neural folds of the telencephalon give rise to?
neuroepithelial cells that form ectodermal placodes; NOT neural crest cells
32
where do motor neurons of the cranial ganglia arise from?
neural tube
33
what are ectodermal placodes
condensation of ectodermal cells within the surface ectoderm adjacent to the nueral tube;
34
what is the function of the ectodermal placodes?
development of sensory organs, hypophysis, teeth, and cranial ganglia
35
what does the olfactory placode give rise to?
sensory epithelium of the nose
36
what does the optic placode give rise to?
vesicles that become the lenses of the developing eyes
37
what does the otic placode give rise to?
labyrinth of the inner ear
38
what placodes give rise to the ameloblasts of the teeth?
placodes located on the frontonasal, maxillary, and mandibular processes
39
what doe the placodes located on the lateral regions of the pharyngeal arches (trigeminal, genticulate, petrosal,nodose placodes) give rise to?
sensory neurons of the cranial ganglia
40
what does the adenohypophyseal placode give rise to?
adenohypophysis
41
where is the adenohypophyseal placode located?
rostal to the buccopharyngeal membrane
42
what does the embryo look like at the end of gastrulation?
a flat trilaminar disk
43
What is embryo folding defined by?
differential growht of the cephalic, caudal, and lateral regions of the embryo during the FOURTH week of develoment resulting in an embryonic disk that has a cylindrical shape
44
In what week does the embryo folding occur?
FOURTH
45
Where does most of the embyronic folding take place? why?
on the flexible outer rim of the embryonic disk because the central region is rigid because the notochord and adjacent somites are there
46
What is saggittal folding?
folding in the head-to-tail direction (sagittal head and sagittal tail folding)
47
what is transverse folding?
folding in the side-to-side (lateral) direction
48
When does neurulation, cephalocaudal and lateral folding take place in relation to one another?
at the same time!
49
what leads to repositioning of the rostal embryonic structures during embryo folding?
rapid growth of the cranial neural folds rising above the surface of the ectoderm
50
what membranes move to lie ventral and caudal to the developing brain during sagittal head folding?
The septum transversum mesenchyme,
cardiogenic mesenchyme,
rostral part of the intraembryonic coelom,
and buccopharyngeal membrane
51
Following head folding, the _________ becomes the most rostral structure of the developing embryo; followed by the _______, _______, and ______.
the proencephalon = most rostral, followed by the buccopharyngeal membrane, heart, and septum transversum
52
what forms the foregut ending at the stomodeum?
The cephalic end of the ENDODERM folding ventrally and caudally
53
Which folds first, the head or tail (sagittal)?
the head
54
what leads to repositioning of the caudal embryonic structures during embryo folding?
accelerated growth of the caudal neural folds
55
what membranes/structures move ventrally and rostrally during tail-sagittal folding?
the connecting stalk, allantois, and cloacal membrane
56
where do the connecting stalk and allantois lie after sagittal tail folding?
they lie rostral to the cloacal membrane and next to the yolk sac
57
what forms the hindgut?
the caudal end of the ENDODERM folding ventrally and rostrally
58
What forms the midgut?
the portion of the gut lying between the foregut and hind gut and still connected to the yolk sac
59
what are a majority of the cells in the septum transversum destined to be?
mesenchyme of the developing liver; later on they also become parts of the epicardium, central portions of the diaphragm, and the esophageal mesentery
60
What happens to the yolk sac during sagittal tail folding?
1. gets pushed out of the embryo proper
| 2. remains connected to the embryo via vitelline duct that opens into the midgut
61
what forms the umbillical cord?
the vitelline duct, associated with allantois and the connecting stalk
62
What does the Intraembryonic coelom form form?
differntiation of the lateral plate mesoderm during 3rd week of development
63
what shape does the intraembryonic coelom have at week3
horseshoe - like shape with its ends pointing caudally
64
What is the intraembryonic coelom surronded by dorsally? ventrally?
dorsally: somatopleure
ventrally: splanchnopleure
65
On what side of the embryo does the intraembryonic coelon communicate with the extraembrionic coelom?
Both sides!
66
What happens during head fodling in transverse embryonic folding?
repositioning of the rostral portion of the intraembryonic cavity ventral to the developing heart; (folding of the rostral portion of the "horseshoe" toward the midline), giving rise to the pericardial cavity
67
How does the pericardial cavity form?
from the developing heart descending into the
68
what separates the pericardial cavity from the rest of the intraembryonic coelom (and from the peritoneal cavities)?
septum transversum extending dorsally on each side of the developing gut
69
What are the peritoneal cavities represented by during the transverse folding of the embryo?
two tubular spaces lying on each side of the developing gut
70
the somatopleure and splanchnopleure grow ____ toward the midline and finally fuse everywehre along the midline except for the ______.
ventrally; small opening at the midgut level
71
where is the amnionic cavity located? what does it envelop?
surrounds the embryo, forms amnion, envelops the umbillical cord (and embryo)
72
What is the intraembryonic coelom divided into during transverse folding?
into the pericardial cavity and peritoneal cavity; which are connected by the pericardioperitoneal canal
73
what connects the gut to the yolk sac?
vitelline duct
74
What leads to the formation of the definitive foregut, midgut, and hindgut?
the midline fusion of the splanchnopleure
75
what are the definitive foregut, midgut, and hindgut, surrounded by?
visceral mesoderm
76
what is formed by the fusion of the somatopleure?
the ventral body wall
77
what is the ventral body wall covered in?
the surface ectoderm (internally)
78
What are the main outcomes of the embryo folding?
1. formation of the gut
2. maturation of the intraembryonic coelom
3. formation of the septum transversum
4. segmentation of the intraembryionic coelom into pericardial and peritoneal cavities
5. formation of the ventral body wall
6. formation of the umbilical cord
79
what is the origin of the epidermis on the trunk?
surface ectoderm
80
what is the origin of the dermis on the trunk?
mesoderm
81
what is the origin of the epidermis on the head and neck?
surface ectoderm
82
what is the origin of the dermis of the head and neck?
neural crest
83
what is the origin of the lens
ectodermal placodes
84
what is the origin of the epithelium of the iris and ciliary body + muslces ?
neuroectoderm
85
what is the origin of the retina?
neuroectoderm
86
what is the origin of the stroma of the iris and ciliary body?
neural crets
87
what is the origin of the inner layer of the tympanic membrane?
endoderm
88
what is the origin of the intermediate layer of the tympanic membrane?
mesoderm
89
what is the origin of the external layer of the tympanic membrane?
surface ectoderm
90
what is the origin of the inner ear
extodermal placodes
91
what is the origin of the epithelium of tympanic cavity and audiotry tube
endoderm
92
what is the origin of the middle ear ossicles and muscles?
neural crest
93
what is the origin of the external ear?
surface ectoderm
94
what is the origin of the main body of the thyroid gland?
endoderm
95
what is the origin of the parafollicular cells of the thyroid gland?
neural crest
96
what is the origin of the adenohypophysis?
ectodermal placodes
97
what is the origin of the neurohypophysis?
neuroectoderm
98
what is the origin of the chromaffin cells on the adrenal gland medulla?
neural crest
99
what is the origin of the adrenal gland cortex?
mesoderm
100
what is the interembryonic coelom lined by internally once the extraembryionic splanchnopleuric and somatoplueric mesoderms are fused? externally?
internally: visceral mesoderm
externally: somatic mesoderm
101
what is the function of the umbillical cord?
connects the embryo to the placenta
102
what is the gut covered by internally? externally?
internally: embryonic endoderm
externally: visceral mesoderm
103
up until what point are neural crest cells produced?
up until the diencephalon
