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systemic embryology and congenital malformations Flashcards

1
Q

what happens in gastrulation?

A

formation of the trilaminar germ disc from bilaminar germ disc

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2
Q

what does the ectodermal germ layer give rise to?

A

organs and structures that maintain contact with outside world
forms the neuroectoderm that leads to formation of neural tube
neural crest cells
pituitary glands
sensory epithelium of ear, nose and eye
epidermis of skin and integumentary structures
enamel of teeth
orla and proctodeal epithelium

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3
Q

what is the process that forms neural tube?

A

neurulation

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4
Q

what are integumentary structures?

A

hair, nails, sweat glands and mammary glands

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5
Q

what is the proctodeal

A

anal canal

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6
Q

what are the parts of the mesoderm?

A

paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm

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7
Q

what does the paraxial mesoderm form?

A

segmental blocks - somitomeres - neuromeres in head region and associated with neural plate

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8
Q

what do neuromeres do?

A

contribute to mesenchyme in head

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9
Q

what is a mesenchyme?

A

connective tissue

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10
Q

formation of somites

A

from the occipital region down the somitomeres form segmented pairs of blocks of mesoderm - somites on either side of developing neural tube

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11
Q

when does the first pair of somites arise?

A

20th day of development

new somites appear craniocaudally at 3 pairs/ day

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12
Q

how many pairs of somites?

A 
at end of 5th week 42-44 pairs have been formed 
4 occipital 
8 cervical
12 thoracic
5 lumbar
5 sacral 
8-10 . coccygeal 
can be used to determine age of embryo
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13
Q

role of intermediate mesoderm

A

contribute in formation of structures of the urogenital system - primordial germ cells, gametes and gonads

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14
Q

lateral plate mesoderm

A

splits into parietal and visceral layers

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15
Q

what is the parietal layer

A

somatic
lines the body cavity walls
with overlying ectoderm forms lateral body wall

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16
Q

what does the lateral plate mesoderm form?

A 
dermis of skin in body wall 
limb bones
connective tissue of limbs
sternum
costal cartilage
limb muscles 
body wall muscles 
lining of peritoneal, pleural and pericardial cavities and secrete serous fluid
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17
Q

what forms the blood cells and vessels?

A

lateral plate mesoderm

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18
Q

what forms the wall of the gut tube?

A

mesoderm of visceral layer and endoderm

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19
Q

what does the endoderm formed?

A

epithelial lining of GI tract, respiratory tract, urinary bladder, urethra, tympanic cavity and auditory tube
parenchyma of thyroid, parathyroid, liver and pancreas

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20
Q

what is parenchyma

A

the functional tissue of an organ distinguished from supportive/ connective tissue

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21
Q

where is smooth muscle derived from?

A

mesoderm

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22
Q

morphogenesis

A

form-shaping process in an embryo, controlled by fundamental cell behaviours that result in differential tissue growth

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23
Q

what are cellular behaviours?

A

changes in cell shape, size, position, number, migration and adhesivity

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24
Q

formation of birth defects

A

interference with differential tissue growth in an embryo that could be caused by genetic mutation, teratogen exposure or a combination of both

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25
what is the word for formation of birth defects?
dysmorphogenesis
26
normogenesis
individuals who develop within close range of abstract norm in form and function
27
structural birth defects
involved both malformations and deformation resulting from abnormal development
28
other words for birth defects
congenital malformations, congenital anomaly | describe structural, behavioural, functional and metabolic disorders present at birth
29
malformations
consist of primary morphologic defects in an organ or body part and result from disturbance of developmental events or processes directly involved in formation of a particular structure
30
what causes malformations?
environmental and or genetic factors acting independently or together
31
what are environmental factors called?
teratogens
32
deformation
consist of secondary morphologic defects that are imposed upon an organ or body part due to mechanical forces over a prolonged period - indirect effect
33
example of malformation
neural tube defects
34
example of deformation
clubfeet due to compression in amniotic cavity due to insufficient amniotic fluid
35
insufficient amniotic fluid
oligohydramnios
36
destructive processes
morphological alterations of already formed structures due to destructive processes
37
examples of destructive processes
produced by amniotic bands - cleft lip, toe and finger amputations
38
malformation syndrome
when dysmorphogenesis occurs as a pattern of well characterised multiple primary malformations appearing together in a predictable fashion in one or more tissues due to a specific underlying single or common cause
39
downs syndrome
trisomy 21
40
symptoms of downs syndrome
``` flat facial feature with a small nose reduced muscle tone - hypotonia upward/ downward slant to eye enlarge tongue that sticks out single deep crease across centre of palm hyperflexibility of joints ```
41
examples of malformation sydrome
fetal alcohol syndrome/ fetal alcohol spectrum disorder
42
symptoms of fetal alcohol syndrome
short palpebral fissure lengths smooth philtrum thin upper lip brain damage
43
what is a teratogen?
any factor or agent that causes birth defect or congenital malformation or congenital anomaly
44
what determines the capacity of an agent to produce birth defects
genotype of conceptus and maternal genome developmental stage at the time of exposure to teratogens dose and duration of exposure to a teratogen
45
mechanism of teratology
action of a teratogen is the specific ways in which it acts on developing cells and tissues to initiate abnormal embryogenesis may involve inhibition of specific biochemical or molecular process or pathway
46
pathogenesis
the abnormal developmental processes that result in dysmorphogenesis may involve cell death, decreased cell proliferation
47
what are the manifestations of abnormal development?
death malformation growth retardation functional disorders
48
gastrulation
stage in embryonic development at beginning of the third week and is highly sensitive stage for teratogenic insult
49
what cells are damaged by teratogens
ingressing epiblastic cells whose fate has already been determined at or before the time of gastrulation
50
examples of errors in gastrulation
``` holoprosencephaly caudal regression syndrome e.g. sirenomelia situs inversus laterality sequences sacrococcygeal teratomas ```
51
holoprosencephaly
high doses of alcohol during gastrulation may kill cells of the anterior midline of the germ disc leading to deficiency of midline in craniofacial structures small forebrain merged lateral ventricles eyes are close together
52
caudal dysplasia
mesodermal insufficiency in caudal most region of embryo which contributes to formation of lower limbs, urogenital system and lumbosacral vertebrae
53
what is caudal dysplasia associated with
maternal diabetes in humans
54
situs inversus
condition with transposition of viscera in thorax and abdomen
55
laterality sequences
not complete situs inversus but are predominantly bilaterally either left or right sided can cause polysplenia, asplenia or hypoplastic spleen they are likely to have heart defects
56
sacrococcygeal teratomas
where remnants of the primitive streak persist in the sacrococcygeal region to form tumours
57
assessing health of unborn
maternal serum screening - maternal serum alpha-feto-protein plus
58
MSAFP
``` maternal serum alpha-feto protein plus measures: maternal serum alpha-feto protein human chorionic gonadotropin unconjugated estriol inhibin-A ```
59
maternal serum alpha-feto-protein
produced by fetal liver - level increases steadily during pregnancy
60
hCG
produced by placenta, levels peak at week 14 and dropping after
61
unconjugated estriol
produced by placenta
62
inhibin-A
produced by fetus and placenta
63
what does high maternal serum AFP suggest?
neural tube defects
64
what does high maternal hCG and inhibin-A levels and low estriol suggest
downs syndrome

Physiology 2 (20 decks)

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