lecture 1 - development of the cns Flashcards
(81 cards)
1
Q
when is the pre-embryonic period?
describe organ system development at this point.
A
- weeks 1-2
- no distinct organ systems
2
Q
when is the embryonic period?
describe organ system development at this point.
A
- weeks 3-7
- most of the body systems develop during this period (CNS, heart, arms, legs, ears, eyes, teeth, palate, external genitalia) - means its the most ! tetragenic !
3
Q
when is the fetal period?
describe organ system development at this point.
A
- weeks 8-38
- continuation of development of organ systems from embryonic period (except heart, arms, legs) as the baby grows in size
4
Q
what is fertilization? where does it most commonly ocur?
A
sperm joins egg - ampulla of uterine tubes, travles to endometrium where it implants
5
Q
what is fusion?
A
makes zygote
6
Q
what is cell cleavage?
A
zygote –> morula
7
Q
what is a morula? when does it typically form?
A
- 16 cell mass
- day 4
8
Q
what is blastulation?
A
morula –> blastula
9
Q
what are blastomeres?
A
divisions of genetic material
10
Q
what is a blastula? when does it typically form?
A
- 100 cell mass
- day 5-8
11
Q
is blastulation before or after implantation?
A
before
12
Q
what is occuring (in more detail) during blastulation?
A
- embryoblast and trophoblast differentiation (simultaneously)
- formation of blastomere cavity in the centre of the blastomere
13
Q
the trophoblast goes on to become what?
A
the placenta
14
Q
the embryoblast goes on to become what?
A
the fetus
15
Q
what is the trophoblast composed of?
A
cytotrophoblasts and syncytiotrophoblasts
16
Q
are cytotrophoblasts mono- or multi-nucleated?
A
mono
17
Q
are syncytiotrophoblasts mono- or multi-nucleated?
A
multi
18
Q
describe the cytotrophoblasts
A
surrounds primitive yolk sac, then embryo
19
Q
describe the syncytiotrophoblasts
A
froms through movement, fuses with maternal sinusoids to form trophoblastic lacunae (part of blood supply to embryo)
20
Q
what do the cytotrophoblasts connect?
A
embryo to mom via blood
21
Q
what do the syncytiotrophoblasts connect?
A
mom to embryo
22
Q
whar does the embryoblast develop into?
A
bilaminar disc
23
Q
describe the development of the embryoblast into the bilaminar disc
A
- starts at day 9
- day 12: embryoblast splits into:
- – epiblast (surrounds amniotic cavity – embryo proper)
- – hypoblast (surrounds exocoelomic cavity – yolk sac/allantois)
24
Q
what is gastrulation?
A
blastula –> gastrula
25
what is a grastrula?
multilayered and multidemensional cell structure
26
what does gastrulation establish? what does this mean
- the cranio-caudal axis
| - first time we have direction in the fetus
27
where does gastrulation occur?
at the bilaminar disc
28
what marks the begining of gastrulation?
the primitive streak
29
describe gastrulation
- as the primitive streak advances, the primitive node forms, which eventually turns into the primitive pit
- along the primitive streak, the epiblast begins to undergo ingression through the primitive pit
30
During ingression, invaginating cells have four destinations - what are they?
(i.e., what is formed during gastrulation?)
1. ectoderm
2. mesoderm
3. endoderm
4. notocord
31
where do invaginating cells for the ectoderm end up?
remain in epiblast
32
what will the ectoderm become?
NS, epidermis, hair, nails, teeth, and sensory epithelium of eyes/ears/nose
33
where do invaginating cells for the mesoderm end up?
between the former hypoblast and the epiblast
34
what will the mesoderm become?
muscles, bone, cartillage blood, bvs, notocord
35
where do invaginating cells for the endoderm end up?
replacing the hypoblast
36
what will the endoderm become?
lining of GI and respiratory tracts, accessory digestive organs, urinary organs, endocrine glands
37
describe the notocord as a destination of invaginating cells
- some ascend to oropharyngeal membrane
- most form fetal primitive backbone (for structural integrity), which eventually develops into the nucleus pulposus (which is gelatenous tissue btween the discs in the adult back)
38
neurulation spans which days of development?
~19-28
39
describe day 19 of neurulation
- epiblast begins to thicken cranially, forming the neural plates
- lateral edges of the neural plates elevate, while the midline depresses
40
describe day 20 of neurulation
- neural fold begins to fold dorsally in the middle of the craniocaudal axis forming the neural groove
- folding proceeds both cranially and caudally
41
describe day 22 of neurulation
- neural tube begins to close at the middle
| - fusion proceeds both cranially and caudally
42
describe day 23 of neurulation
neuropores begin to close (last part)
43
when does the cranial neuropore close?
day 26
44
when does the caudal neuropore close?
day 28
45
what happens when the neuropores fail to close?
neural tube defect
46
what (specifically) results when the cranial neuropore fails to close?
anencephaly - born without sections of the frontal lobe, cerebrum, and skull (because it develops around the developing brain)
47
what (specifically) results when the caudal neuropore fails to close?
spina bifida - neural tube doesn't close all the way in the spinal cord - bulges out - can cause movement problems
48
what are neural crest cells?
during neural folding, cells from the neural folds break off and migrate to form other structures
49
what do neural crest cells become?
- dorsal root ganglia
- autonomic chain ganglia
- adrenal medulla
- schwann cells of PNS
- melanocytes
- dermis, sm and adipose of the face
50
breify decsribe the development of the sc
neuroepithelium divides into neuroblasts (primitive nerve cells), forming:
( 1) deep mantle layer (gray matter) (neural tube itself)
(2) superficial merginal layer (white matter)
51
the deep mantla layer can be further subdivided into:
```
alar plate (sensory, dorsal)
basal plate (motor, ventral)
sulcus limitans
```
52
what distinguishes the alar and basal plate?
sulcus limitans
53
the neural tube dilates to form 3 primary vesicles:
prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
54
what are the secondary vesicles of the prosencephalon?
telecephalon, diencephalon
55
what does the telecephalon form?
cerebrum
56
what does the diencephalon form?
thalamus and hypothalamus
57
what are the secondary vesicles of the mesencephalon )?
mesecephalon
58
what does the mesencephalon form?
midbrain
59
wheat are the secondary vesicles of the rhombencephalon?
metencephalon, myelencephalon
60
what does the metecephalon form?
pons and cerebellum
61
what does the myelencephalon form?
medulla oblongata
62
which secondary vesicle forms the lateral ventricles?
telencephalon
63
which secondary vesicle forms the third ventricle?
diencephalon
64
which secondary vesicle forms the cerebral aqueduct?
mesencephalon
65
which secondary vesicle forms the fourth ventricle?
rhombencephalon
66
which secondary vesicle forms the central canal?
mesencephalon
67
what are the 3 spinal flexures?
cephalic, cervical and pontine
68
where is the cephalic flexure?
exists entirely in the mesencephalin
69
where is the cervical flexure?
exists at the end of the vesicles - distinguishes the brain and spinal cord
70
where is the pontine flexure?
distinguishes metencephalon and myelencephalon
71
what is the first flexure to form?
cephalic
72
what is the last flexure to form?
pontine
73
describe the 'C-shape'
- neurons in the neocortex (telencephalon) proliferate, migrate and begin to devlop connections rapidly
- causes C-shape rotation because the skull cannot contain all of these new connections
74
what signals the end of fertilization?
implantation (development of fibrin coagulum)
75
what is the result of increased cortical convolutions?
(gyri and sulci) - increased surface area
76
summarize the events of week 1
- fertilization
- cleavage
- implantation begins
77
summarize the events of week 2
- embryoblast differentiation
- trophoblast differentiation
- implantation is complete - fibrin coagulum
78
summarize the events of week 3
ingression (ectoderm, mesoderm, endoderm, notocord)
79
when does the embryo become asymetric?
week 3
80
summarize the events of week 4
neurulation
81
when, specifically, does brain development occur?
end of the 1st trimester
