embryology Flashcards
ventral dorsal cranial caudal lateral sagittal coronal
front back top/head bottom/ tail end slide across horizontally slice down the front slice straight down
what are the two types of methods to test for pregnancy and how do they different
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
what is the rate of brith defects in the Uk
1 in 44
when is the most vulnerable time for human broth defects
pre-natal - embryonic period around week 5
what is the most vulnerable system in foetus
CNS is sensitive during the whole gestation
what percentage of genetic defects are due to mitosis or meiosis
18%
what are some example of birth defects
downs syndrome, trisomy 21, extra chromosome 21, growth retardation, intellectual retardation
what percentages of birth defects are -
environmental
unknown
both
environ - teratogens
unk - 50%
both - 25%
what is TORCH
Toxoplasmosis Other - syphilis/parovirusB19 Rubella Cytomegalovirus (CMV) Herpes
what is toxoplasmosis and what causes it
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
what is rubella and what causes it and how does it affect the baby
infection passes over placenta in first 3 months
could have MMR vaccine
in the foetus it causes cloudy cornea, intellectually disability - microcephaly
how does cytomegalovirus
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
how does herpes affect the foetus
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
what is the ZV, how does zika virus effect a baby
can be got by mosquito - causes fever-rash-joint pain but could be asymptomatic
in the foetus it causes microcephaly and severe cognitive deficiencies
what was thalidomide and what is it used for now
developed in germany which was prescribed for morning sickness
now used to treat leprasy/HIV in brazil
caused shortened limbs in foetus
what is foetal alcohol syndrome
lots of alcohol consumption has been linked to foetal prenatal and postnatal growth retardation, intellectual disability, impaired motor ability and coordination
how does radiation affect the mum and the foetus
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
what are the effects of diabetes mellitus
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)
how do folic and deficiencies affect the mother and the foetus
malformations in the CNS, supplements reduce risks by 60%
in foetus neural tube defects, spina bifida, anencephaly (absence of major portion of the brain)
what is gameteogensis
production of spermatozoa or ovum
what does mitosis produce vs meiosis
mitosis = diploid cell meiosis = haploid cell
what happens during fertilisation
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
where does fertilisation most commonly occur
in the ampulla of the uterine tubes
what sweeps the oocyte into the uterine tube
fibrillae
what occurs during the acrosome reaction
- 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
what happens to the zygote cells directly after fertilisation
no change in size but there is rapid cell division but the blastomeres get smaller
what is a morula
occurs around day 4 and is 16-32 cells large
what happens to the cells on day 5
they become a blastocyst
what are the cells called on the inner vs the outer of the blastocyst
inner cell mass = embryoblasts
outer cell mast is the placenta (trophoblasts)
describe the formation of the blastocyst
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)
describe how the blastocyst implants onto the endometrium
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
what do cytotrophblasts differentiate in to and what do they form
differentiate into synctiotrophblasts as get further away from the support layer around the embryo blasts
what do syntiotrophoblasts do
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
what role do syncytioblasts have in protection
they allow prevention of the immune response against blastocyst from the mother
why do syncsytioblasts have multiple nuclei
develop due to breakdown of cell membranes which makes the gaps even smaller so that immune cells cannot get through to the embryo
what do embryoblasts differentiate into
hypoblasts and epiblasts which make the embryo proper
when does transformation into the bilaminar disk occur
one week after fertilisation
what two layers make the bilaminar disk
epiblasts and hypoblasts
how is the dorsal and ventral axis established
epiblasts are dorsal and the hypoblasts are ventral
which axis does the zygote develop to the uterine lining
dorsal
how does the amniotic cavity form
forms as small fluid filled cavity in epiblast between epiblast and cytotrophoblasts - small but grows over a few week
what is the inner membrane of the cytotrophoblast cells called during full implantation
heusers membrane
what is the role of cytotrophoblasts and syncytiotrophoblasts in full implantation
cyto - grown into the support layer
sync - surround everything
during the process of full implantation how does the nutrition of the foetus change is source
before full implantation nutrients where provided by diffusion from the uterine gland but now trophoblastic lacunas form within the syncytiotrophoblast cells which hold nutrients
during full implantation a blood supply is formed but from where
uteroplacental circulation forms from the maternal capillaries
scar tissue forms after full implantation on the lining of the uterus what is this called
coagulation plug
describe the process of uteroplacental circulation creation during full implantation
syncytiotrophoblasts erodes the wall of maternal capillaries and blood leaks into the trophoblastic lacunas
when does uteroplacental circulation occur
occurs 4 weeks after last period which may cause some spotting and may be mistaken as a period if unaware of pregnancy
what is the extraembryonic mesoderm
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
what is formed inside the extraembryonic cavity
chorionic cavity
what happens on day 1-3
cleavage - zygote cells divide - blastomere is smaller. 8 cells
what happens on day 4
morula formed (16-32 cells) inner mass = embryoblast - embryo proper outer cell mass trophoblast - placenta
day 5
blastocyst
trophoblast - thin layer
embryoblast - compact mass
day 6
blastocyst hatching + initiate implantation
zona pellucida - blastocyst hatches
implants uterine wall - endometrium
day 7
syncytiotrophoblasts invaginate uterine lining = implantation
finger like projections
enzymes break down lining
day 8
amniotic cavity in epiblast
day 9
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
day 10-11
syncytiotrophoblasts erode maternal capillary walls - uteroplacental circulation
initially uterine gland provides nutrients
extra embryonic mesoderm developing
day 11-12
yolk cells -> extraembryonic mesoderm
extraembryonic mesoderm covers amniotic cavity
day 12-13
extraembryonic mesoderm -> chorionic cavity
embryonic mesoderm falls between hypoblast cells (huessers membrane) + cytotrophoblasts
day 13
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
day 14
connecting stalk -> suspends amniotic cavity and secondary yolk sac
connect embryo - uterine lining encompassed in placenta - form umbilical cord
day 14-15
primitive streak - start of gastrulation
production of left and right axis
ventral and dorsal
cranial and caudal end
day 15
definitive endoderm - epiblast cells move to primitive streak and insert into hypoblast (replacing them)
day 16
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
day 17
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
19-20
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
day 22
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
day 25
fusion anterior neuropore (cranial end)
froms brain
day 28
fusion posterior neuropore (caudal end)
froms spinal cord
2 embryonic folding: lateral and cranio-caudal in 4th week
describe how HcG is made and why it is important in pregnancy
syncytiotrophoblasts secrete hCG
helps maintain endometrium and may play a role in maternal immunotolerance
good indicator of pregnancy via immunoassay from urine
what is ectopic pregnancy
give some examples
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)
what is placenta previa
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
where do most ectopic pregnancies occur
80% occur in the uterine tube
what can ectopic pregnancy be confused for
if in right uterine tube can be mistaken for appendicitis
what is lithopedion
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)
what is hydatidifrom mole
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
what is situs invertus why can it be bad or harmless
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
what is kartenger syndrome
cilia swept in the wrong direction causing cells to grow on the wrong side of the body
what does the mesoderm
ectoderm
endoderm form
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
what is sirenomelia
gastrulation finishes early - insufficient mesoderm formed in caudal region of embryo causing abnormalities of lower limbs and uterogenital system
legs stuck together
what is sacrococcygeal teratoma
too much mesoderm forms - most common tumour in the new-born.. 80% occur in females - good prognosis after resection
what is spina bifida
it is abnormal indication of sclerotomes
vertebral arch not formed - tuft of hair grows in the back where there is not spinal cord
what is meningocele vs myelomenigocele
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
what induces neuraltion and what is it
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
why is folic acid good in pregnancy
reduces chances of spina bifida by 50-70%
what is anencephaly
failure of he anterior neuropore to fuse - fore brain does not form so cognition, memory, speech, vision, hearing is affected
usually causes still birth
what is rachischisis
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
what is neurofibromatosis
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
what is ectopia cordis
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
what is gastroschisis
lateral fold fail to fuse in abdominal region - intestine outside the body wall
