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IMS > embryology > Flashcards

embryology Flashcards

1
Q 
ventral 
dorsal 
cranial 
caudal 
lateral 
sagittal 
coronal
A 
front
back 
top/head 
bottom/ tail end 
slide across horizontally 
slice down the front 
slice straight down
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2
Q

what are the two types of methods to test for pregnancy and how do they different

A

1) menstraual age
check from a woman last menstral cycle - three equal trimesters
2) fertilisation age - more accurate
there is a two week difference between last menstrual age and fertilisation age

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3
Q

what is the rate of brith defects in the Uk

A

1 in 44

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4
Q

when is the most vulnerable time for human broth defects

A

pre-natal - embryonic period around week 5

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5
Q

what is the most vulnerable system in foetus

A

CNS is sensitive during the whole gestation

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6
Q

what percentage of genetic defects are due to mitosis or meiosis

A

18%

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7
Q

what are some example of birth defects

A

downs syndrome, trisomy 21, extra chromosome 21, growth retardation, intellectual retardation

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8
Q

what percentages of birth defects are -
environmental
unknown
both

A

environ - teratogens
unk - 50%
both - 25%

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9
Q

what is TORCH

A 
Toxoplasmosis
Other - syphilis/parovirusB19
Rubella 
Cytomegalovirus (CMV)
Herpes
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10
Q

what is toxoplasmosis and what causes it

A

infection via parasite, cat faeces, under cooked meat - it is usually asymptomatic
in the foetus there is inflammation of retina and eye, hearing loss - hydrocephaly (fluid in brain pushes soul apart) microcephaly - brain forms smaller than usual

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11
Q

what is rubella and what causes it and how does it affect the baby

A

infection passes over placenta in first 3 months
could have MMR vaccine
in the foetus it causes cloudy cornea, intellectually disability - microcephaly

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12
Q

how does cytomegalovirus

A

virus that crosses placenta - infection via bodily fluid - usually asymptomatic
in foetus inflammation of retina, enlarged spleen or liver - mineral deposits on the brain eg calcium, microcephaly

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13
Q

how does herpes affect the foetus

A

herpes simplex and herpes zoster, varicella zoster = chicken pox - most dangerous between 13-20 weeks/ just before birth/ two days postpartum
causes skinless and scarring, limb hypolasia, microcephaly, visual defects

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14
Q

what is the ZV, how does zika virus effect a baby

A

can be got by mosquito - causes fever-rash-joint pain but could be asymptomatic
in the foetus it causes microcephaly and severe cognitive deficiencies

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15
Q

what was thalidomide and what is it used for now

A

developed in germany which was prescribed for morning sickness
now used to treat leprasy/HIV in brazil
caused shortened limbs in foetus

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16
Q

what is foetal alcohol syndrome

A

lots of alcohol consumption has been linked to foetal prenatal and postnatal growth retardation, intellectual disability, impaired motor ability and coordination

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17
Q

how does radiation affect the mum and the foetus

A

causes cell death or chromosome changes, CNS most affected - in first trimester
in the foetus causes microcephaly, mental and cognitive disabilities, haemopoiteic malignancies and leukaemia

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18
Q

what are the effects of diabetes mellitus

A

causes cellular structural defects, changes in cellular physiology
in the foetus it causes macrosomia (enlarged baby), ventricular septal defects (within heart), spina bifida (neural tube defect), renal agenesis (failure of mature kidney formation)

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19
Q

how do folic and deficiencies affect the mother and the foetus

A

malformations in the CNS, supplements reduce risks by 60%

in foetus neural tube defects, spina bifida, anencephaly (absence of major portion of the brain)

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20
Q

what is gameteogensis

A

production of spermatozoa or ovum

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21
Q

what does mitosis produce vs meiosis

A 
mitosis = diploid cell
meiosis = haploid cell
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22
Q

what happens during fertilisation

A

fusion of the male and female gamete to form zygote
there is capacitation of sperm (matured by secretions from vagina and cervix)
there is the acrosome reaction - breaks down the wall of the ovum causing the formation of a zygote
then there is fusion of the pronuclei

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23
Q

where does fertilisation most commonly occur

A

in the ampulla of the uterine tubes

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24
Q

what sweeps the oocyte into the uterine tube

A

fibrillae

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25
Q

what occurs during the acrosome reaction

A
  • Capacitated sperm pass through corona radiate (outer ovum), acrosome releases enzymes which allow sperm to penetrate zona pellucida, sperm penetration initiates cortical reaction which prevents other sperm penetrating the same ovum, zona pellucida becomes impenetrable
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26
Q

what happens to the zygote cells directly after fertilisation

A

no change in size but there is rapid cell division but the blastomeres get smaller

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27
Q

what is a morula

A

occurs around day 4 and is 16-32 cells large

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28
Q

what happens to the cells on day 5

A

they become a blastocyst

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29
Q

what are the cells called on the inner vs the outer of the blastocyst

A

inner cell mass = embryoblasts

outer cell mast is the placenta (trophoblasts)

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30
Q

describe the formation of the blastocyst

A

embryoblast cells form compact mass inside
trophoblast cells for thin outer layer and fluid is taken in forming a cyst
this occurs via osmosis (one of the two methods)

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31
Q

describe how the blastocyst implants onto the endometrium

A

blastocyst hatches and initiates implantation days 5-6
implants onto the uterine wall as wants to get nutrients
the zona pellucid comes off before implantation

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32
Q

what do cytotrophblasts differentiate in to and what do they form

A

differentiate into synctiotrophblasts as get further away from the support layer around the embryo blasts

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33
Q

what do syntiotrophoblasts do

A

they implants into the uterine layer via fingerlike projections which bury into uterine lining and break it down via enzymes - this allows us to get nutrients

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34
Q

what role do syncytioblasts have in protection

A

they allow prevention of the immune response against blastocyst from the mother

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35
Q

why do syncsytioblasts have multiple nuclei

A

develop due to breakdown of cell membranes which makes the gaps even smaller so that immune cells cannot get through to the embryo

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36
Q

what do embryoblasts differentiate into

A

hypoblasts and epiblasts which make the embryo proper

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37
Q

when does transformation into the bilaminar disk occur

A

one week after fertilisation

38
Q

what two layers make the bilaminar disk

A

epiblasts and hypoblasts

39
Q

how is the dorsal and ventral axis established

A

epiblasts are dorsal and the hypoblasts are ventral

40
Q

which axis does the zygote develop to the uterine lining

A

dorsal

41
Q

how does the amniotic cavity form

A

forms as small fluid filled cavity in epiblast between epiblast and cytotrophoblasts - small but grows over a few week

42
Q

what is the inner membrane of the cytotrophoblast cells called during full implantation

A

heusers membrane

43
Q

what is the role of cytotrophoblasts and syncytiotrophoblasts in full implantation

A

cyto - grown into the support layer

sync - surround everything

44
Q

during the process of full implantation how does the nutrition of the foetus change is source

A

before full implantation nutrients where provided by diffusion from the uterine gland but now trophoblastic lacunas form within the syncytiotrophoblast cells which hold nutrients

45
Q

during full implantation a blood supply is formed but from where

A

uteroplacental circulation forms from the maternal capillaries

46
Q

scar tissue forms after full implantation on the lining of the uterus what is this called

A

coagulation plug

47
Q

describe the process of uteroplacental circulation creation during full implantation

A

syncytiotrophoblasts erodes the wall of maternal capillaries and blood leaks into the trophoblastic lacunas

48
Q

when does uteroplacental circulation occur

A

occurs 4 weeks after last period which may cause some spotting and may be mistaken as a period if unaware of pregnancy

49
Q

what is the extraembryonic mesoderm

A

wall of cells formed around the whole of the embryo outside of the hypoblasts but inside of the cytotrophoblasts - it continues to develop until it covers the whole amniotic cavity to form a new layer of connective tissue derived from the you sac

50
Q

what is formed inside the extraembryonic cavity

A

chorionic cavity

51
Q

what happens on day 1-3

A

cleavage - zygote cells divide - blastomere is smaller. 8 cells

52
Q

what happens on day 4

A 
morula formed (16-32 cells)
inner mass = embryoblast - embryo proper
outer cell mass trophoblast - placenta
53
Q

day 5

A

blastocyst
trophoblast - thin layer
embryoblast - compact mass

54
Q

day 6

A

blastocyst hatching + initiate implantation
zona pellucida - blastocyst hatches
implants uterine wall - endometrium

55
Q

day 7

A

syncytiotrophoblasts invaginate uterine lining = implantation
finger like projections
enzymes break down lining

56
Q

day 8

A

amniotic cavity in epiblast

57
Q

day 9

A

hypoblast cells migrate and encase blastocyst cavity leading to formation of primary yolk sac
syncytiotrophoblasts covers whole outside blastocyst
trophoblastic lacuna = nutrients
coagulation plug = scab heal uterine lining

58
Q

day 10-11

A

syncytiotrophoblasts erode maternal capillary walls - uteroplacental circulation
initially uterine gland provides nutrients
extra embryonic mesoderm developing

59
Q

day 11-12

A

yolk cells -> extraembryonic mesoderm

extraembryonic mesoderm covers amniotic cavity

60
Q

day 12-13

A

extraembryonic mesoderm -> chorionic cavity

embryonic mesoderm falls between hypoblast cells (huessers membrane) + cytotrophoblasts

61
Q

day 13

A

second wave of hypoblasts -> secondary yolk sac
second wave push primary yolk sac out of way - remnants left
there are now three cavities from left to right
amniotic cavity
primary yolk sac
chorionic cavity

62
Q

day 14

A

connecting stalk -> suspends amniotic cavity and secondary yolk sac
connect embryo - uterine lining encompassed in placenta - form umbilical cord

63
Q

day 14-15

A

primitive streak - start of gastrulation
production of left and right axis
ventral and dorsal
cranial and caudal end

64
Q

day 15

A

definitive endoderm - epiblast cells move to primitive streak and insert into hypoblast (replacing them)

65
Q

day 16

A 
three layers 
epiblast cells continue to move down primitive streak - the middle layer between epiblast and definitive endoderm = mesoderm
the cells left behind are the ectoderm 
1 - ectoderm 
2 - mesoderm 
paraxial 
intermediate 
lateral 
3 - definitive endoderm
66
Q

day 17

A

notochordal process - primitive streak degenerates, cranial to caudal
primitive node -> notochordal process -> fuses with endoderm -> notochordal plate
notochordal plate then detaches from endoderm to form solid notochord

67
Q

19-20

A 
neural plate - neural folds caudal 
notochordal signals overlying ectoderm - neuroectoderm - neural plate - lateral edges raised - neural folds 
paraxial -> somites 
sclerotome - bone cartilage 
myotome - skeletal muscle 
dermatome - dermis
68
Q

day 22

A

neural plate -> folds caudal
neural folds fuse (cervical region: cranial - caudal fashion
the neural tube separates from the ectoderm
neural crest cells from lateral edge migrate ventrally and differentiate to form body structures

69
Q

day 25

A

fusion anterior neuropore (cranial end)

froms brain

70
Q

day 28

A

fusion posterior neuropore (caudal end)
froms spinal cord
2 embryonic folding: lateral and cranio-caudal in 4th week

71
Q

describe how HcG is made and why it is important in pregnancy

A

syncytiotrophoblasts secrete hCG
helps maintain endometrium and may play a role in maternal immunotolerance
good indicator of pregnancy via immunoassay from urine

72
Q

what is ectopic pregnancy

give some examples

A

fertilisation and implantation in an abnormal site - occurs in 2% of pregnancies
9% related to deaths of mother
fertilised egg can implant in ampulla, middle or end of uterine tube. Can also escape to abdominal cavity (mesentery)

73
Q

what is placenta previa

A

zygote implants in the uterus but the uterus is too far down so covers the cervix - the support structures develop over the birth canal - therefore the baby has to develop via C section

74
Q

where do most ectopic pregnancies occur

A

80% occur in the uterine tube

75
Q

what can ectopic pregnancy be confused for

A

if in right uterine tube can be mistaken for appendicitis

76
Q

what is lithopedion

A

stone child
if abdominal pregnancy occurs and the foetus dies - when it is too large to be broken down it calcifies (thought to protect mother from necrotic tissue)

77
Q

what is hydatidifrom mole

A

rapid development without any embryonic tissue so only trophoblasts
fertilisation occurs with egg lacking a nucleus
suggests parental genes favour formation of trophoblasts at expense of embryo

78
Q

what is situs invertus why can it be bad or harmless

A

the major in organs in the body are reversed

partial situs inversus causes problems such as dextrocardia, oxygenated blood gos to lungs and deox to body

79
Q

what is kartenger syndrome

A

cilia swept in the wrong direction causing cells to grow on the wrong side of the body

80
Q

what does the mesoderm
ectoderm
endoderm form

A

meso - skeletal muscle, some smooth muscle, heart, blood vessels part of GI, reproductive system
ecto - CNS, spinal cord, epidermis, PNS
endo - epithelial lining of GI tract, glands, rest of urinary system

81
Q

what is sirenomelia

A

gastrulation finishes early - insufficient mesoderm formed in caudal region of embryo causing abnormalities of lower limbs and uterogenital system
legs stuck together

82
Q

what is sacrococcygeal teratoma

A

too much mesoderm forms - most common tumour in the new-born.. 80% occur in females - good prognosis after resection

83
Q

what is spina bifida

A

it is abnormal indication of sclerotomes

vertebral arch not formed - tuft of hair grows in the back where there is not spinal cord

84
Q

what is meningocele vs myelomenigocele

A

failure of vertebral arch to form causing release of meninges causing a hernia bulb protruding out of the back but there is no neural tissue
mylo - neural tissue present outside of the body but can be repaired inside womb at 20 weeks

85
Q

what induces neuraltion and what is it

A

induced by signals from the notochord which causes thickening of overlying ectoderm which gives rise to the neural plate
lateral edges form neural folds which form with the midline to form neural tube
begins around cervical region and continues cranially and caudally
as the folds fuse it separates from the ectoderm
somites forms vertebral arches which will turn into vertebrae

86
Q

why is folic acid good in pregnancy

A

reduces chances of spina bifida by 50-70%

87
Q

what is anencephaly

A

failure of he anterior neuropore to fuse - fore brain does not form so cognition, memory, speech, vision, hearing is affected
usually causes still birth

88
Q

what is rachischisis

A

failure of posterior neuropore to fuse - spinal cord does not form properly causing paralysis - motor and sensory disfunction - neural tube open to environment leads go high chance of infection

89
Q

what is neurofibromatosis

A

genetic condition caused by mutated neurofibromin 1 gene
NF1 is tumour suppressor gene switched off in neurofibromatosis leading to increase cell division - benign tumours of the nervous stem skin and cranial bones

90
Q

what is ectopia cordis

A

lateral folds fail to fure in throaic region leading to heart outside body - breast bone doesn’t form correctly so need protective wear until it does
can have heart outside of the body

91
Q

what is gastroschisis

A

lateral fold fail to fuse in abdominal region - intestine outside the body wall

IMS (20 decks)

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