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Embryology Flashcards

1
Q

what does the embryonic period encompass

A

all of
organogenesis

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2
Q

what period of development is most susceptible to disruption and disorder?

A

organogenesis

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3
Q

development of the CNS entails several coordinated _________ and ________ ______

A

molecular and anatomical changes

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4
Q

what entails several molecular and anatomical changes

A

development of the CNS

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5
Q

embryology definition

A

study of initial development of an embryo

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6
Q

study of initial development of an embryo is

A

embryology

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7
Q

all organ systems are developed by how many weeks?

A

8 weeks

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8
Q

what happens by week 8 of development?

A

all organ systems are developed

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9
Q

after 8 weeks the remainder of gestation is referred to as

A

the fetal period

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10
Q

what is the fetal period?

A

after 8 weeks of development

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11
Q

Describe the first 5 initial events

A

fertilisation - zygote is formed
division of the early embryo - cleavage
after around 3 days embryo is now MORULA
by 4 days - BLASTOCOEL develops and the embryo is now a blastocyte
5 Days - EMBRYOBLAST/inner cell mass is distinct

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12
Q

describe events 6-10

A

hatching occurs day 6/7 - from ZONA PELLUCIDA
day 8-9 blastocyte IMPLANTATION
HYPOPLAST and EPIBLAST cells divide into 2 growing lumens (amniotic cavity and YOLK SAC)
Interface of 2 cell tyes is called - BILAMINAR GERMINAL DISC and becomes the fetus
GERMIAL DISC is where GASTRULATION OCCURS

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13
Q

where does gastrulation occur

A

germinal disc

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14
Q

what is the interface between 2 cell types called?

A

bilaminar germinal disc

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15
Q

what is the bilaminar germinal disc

A

interface between 2 cell types

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16
Q

what is gastrulation

A

generation of the 3 germ layers which derive all embryonic structures

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17
Q

what is the generation of the 3 germ layers that derive all embryonic structures called?

A

gastrulation

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18
Q

describe initial events 11-14

A

Gastrulation occurs along PRIMITIVE STREAK in a caudal to cranial orientation
cells from epiblast invaginate into primitive streak to form ENDODERM and MESODERM - 3 layers form
Led by primitive node
Primitive node also allows for formation of Notochord that orchestrates formation of neural tube

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19
Q

what does primitive node determine

A

anterior-posterior access

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20
Q

where does gastrulation occur

A

along primitive streak in caudal to cranial direction

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21
Q

What does notochord orchestrate

A

formation of neural tube

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22
Q

what orchestrates formation of the neural tube

A

notochord

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23
Q

what are the 3 germ layers

A

ectoderm, mesoderm and endoderm

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24
Q

what does ectoderm form

A

epidermis, epithelial lining of mouth and anus, cornea and lens of eye, nervous system, adrenal medulla

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25
what does meso derm form
notochord, skeletal system, muscular system, excretory system, reproductive system, dermis of skin
26
what does endoderm form
epithelial lining of digestive tract and respiratory system, lining of urethra urinary bladder and reproductive system, liver, pancreas, thymus, thyroid
27
what foes notochord form in line with
primitive node
28
what is the notochord in vertebrates
transient but essential
29
what does notochord do
organises surrounding tissues and provides structural support
30
what does notochord secrete
factors which control CNS development from overlying ectoderm
31
what does notochord regulate
left/right asymmetry arterial/venous identity in major vessels aids in the specification of forming somites
32
notochord secretes:
signalling factors which induce specification of the overlying ectoderm to form the neural plate (starts day 18)
33
uneven proliferation causes the formation of:
neural groove and neural folds
34
_____ converge at _____ to form the neural tube
neural folds at the neural plate border
35
neural folds converge at neural plate border to form
neural tube
36
final closures of the neural tube at the ________
caudal and cranial neuropores
37
when does the cranial neuropore close
day 24 of development
38
when does the caudal neuropore close
day 28 of development
39
what gives sheets of cells the ability to specify and develop multiple organ systems, many cell types and all in the correct orientation and order
morphogens and also via a cell's competence for that morphogen signal (external and internal control)
40
what do morphogens do
specifying and developing multiple organ systems, many cell types and all in the correct orientation and order
41
what does notochord induce and via what
induces the floor plate via Sonic HedgeHog
42
what does induction of notochord by SHH allow for
a switch in cadherin expression (E to N) and initiation of inward folding
43
what signals are required for notochord to switch in cadherin expression
Chordin, Noggin and SHH
44
where are the morphogens Chordin and Noggin expressed
in the node at the cranial end of the primitive streak
45
what are Chordin and Noggin morphogens key for
setting the midline of the embryo - determining dorsal/ventral AND left/right axes both of which are required for future brain segmentation
46
after initiation of initial folding, what does the surrounding ectoderm express
opposing morphogens BMPs (4 and 7) and WNTs
47
what doe the opposing morphogens after initial folding allow for
orientation of the roof plate and closure of the neural tube. aid in specification of the now overlying ectoderm - epithelium
48
what population of cells are specified after the closure of the neural tube
neural crest cells
49
what happens after closure of the neural tube
neural crest cells detach from the neural folds and sit dorsal to the roof plate of the neural tube
50
neural crest cells migrate and differentiate into what key structures
Neurons and glia of the PNS Adrenal Medulla Melanocytes Facial cartilage and bone Corneal epithelium Endothelial lining of the aortic arches, endocardial cushion and aorticopulmonary septum
51
as the neural tube starts to close, distinct structures are specified at the _____ end
cranial
52
as the neural tube starts to close, what distinct structures are specified at the cranial end
primary vesicles (week 4)
53
what are the primary vesicles
prosencephalon mesencephalon rhomboencephalon
54
primary vesicles after further specification form:
secondary vesicles
55
what are the secondary vesicles
telencephalon diencephalon mesencephalon metencephalon myelencephalon
56
describe initial formation of vesicles
via tightly orchestrated proliferation events cranial end of the neural tube proliferates before closure even occurs to crease the 3 primary vesicles proliferation of neural tube occurs in restricted space creates 3 bends of neural tube to allow for further specification
57
3 bends in the neural tube called:
Cephalic flexure (ventral) - midway through the mesencephalon Pontine flexure (dorsal) - at the base of metencephalon Cervical flexure (ventral) - separates the myelencephalon from the spinal core
58
when do the flexures in neural tube develop
between primary and secondary vesicle formation - present by week 5
59
what does the telencephalon become
cerebrum
60
neurogenesis meaning
process by which neurons and glia proliferate, migrate and are specified to form the mature brain
61
what is synaptogenesis
synapse formation and organisation occurs
62
what is neural pruning
orchestrated apoptosis
63
what is orchestrated apoptosis known as
neural pruning
64
where is myelination initiated
starts in the cerebellum and the brain stem
65
what is deemed a multipotent neuroepithelial population
neural stem cells
66
what initiates proliferation in the embryonic brain
neural stem cells
67
what doe neural stem cells produce and what do they develop
radial glia that develop into both glia and neurons
68
what are radial glia essential for
development of the embryonic neural network - comprise the ventricular zone
69
what do NSCs divide by to continue what
NSCs divide by both asymmetric and symmetric division to continue self-propagation during development
70
what do NSCs primarily divide into
neurons, astrocytes and oligodendrocytes
71
what is cell specification determined by
spatial patterning (dorsal/ventral) time/chronological local signalling (microenvironment/morphogens)
72
what is a key requirement of the developing brain
migration
73
what are the 2 types of migration
glial mediated - use of radial glia framework somal translocation 0- self propelled
74
what are the 2 directions of migration
radial - radiates out from the centre tangential - moves around or along the neural tube
75
when does formation of synapses start
during fetal life (mid-second trimester) and is intensely built in the first few years of life
76
when does axonal myelination start
late in gestation and is continued throughout adolescence and into adulthood
77
at 12 weeks gestation
brain structures similar to the adolescent/adult brain lack of gyri and sulci in the cerebral cortex
78
what increases cortical volume
sulcation and gyrification
79
what is sulcation and gyrification essential for
increasing cortical volume and allowing for increased cognitive fucntion/processing
80
when are primary sulci initiated and formed
week 12- 28 vast majority of gyri and sulci are formed and defined in second and third trimester
81
how much does grey matter increase per week from week 29
15ml/week
82
how are preterm infants kept
in conditions which prevent overstimulation/ can impact neural development as a result
83
what is one of the most essential pieces of embryology
closure of the neural tube
84
what occurs if neural tube is not closed
neural tube defects
85
what is anencephaly
failure of the cranial neuropore to close
86
what occurs when cranial neuropore fails to close
anencephaly
87
what is telencephalon
absence of major aspects of the brain and skull
88
what is the most common neural tube defect
spinal bifida
89
how does spina bifida occur
when the caudal neuropore fails to close
90
what are neural tube defects linked to
folic acid metabolism
91
mechanism of folic acid preventing neural tube defects?
not fully understood possible role in epigenetic reprogramming which coincides with the time of neural tube formation
92
what is the most severe neural tube defect
craniorachischisis
93
what is Craniorachischisis
both brain and spinal cord are exposed
94
what causes craniorachischisis
multi factorial cause - genetic and environmental disruption. linked with genetic disruption of the folate metabolism pathway seen in cases of trisomy 18
95
describe microcephaly
smaller than normal head circumference due to lack of brain development associated with many exposures to teratogens (ZIKA) genetic links - trisomies usually lack of cerebral cortex development poor neurogeneis, loss of neural stem cells or uncontrolled apoptosis
96
describe holoprocencephaly (HPE)
defect whereby the procencephalon fails segment at the midline failure of segmentation at week 5-6 detected by ultrasound poor prognosis
97
describe variances of holoproencephaly
classifications - lobar, semi-lobar, alobar reflected in facial patterning of fetus- most severe is cyclopia less severe- cleft lip

Embryology (1 decks)

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