Human embryonic development Flashcards
what is the pre-embryonic period
fertilisation of egg to end of 3rd week of development
what is embryonic period
and what is formed
organogenesis - 4-8 weeks the three germ layers are formed ectoderm mesoderm endoderm main organs established sometimes this period includes pre embryonic stage so first 8
what is the fetal period
beginning of 3rd month to brith
period of maturation
no general agreement of beginning or end of this period
in what weeks of development if the embryo not susceptible to any harmful substance
2 weeks
when is the embryo most sensitive
1st trimester - congenital malformations
gametogenesis
production of male and female gametes or sec cells from primordial germ cells via meiotic division in the gonads
spermatogenesis
oogenesis
principle goals of gametogenisis
Gametogenesis reduces the chromosome number of the games fro diploid ( 23 paris- 46) to haploid ( 23 unpaired)
Gametogenesis results to an enhanced genetic variability in the gametes through a random recombination of genetic materials on homologous maternal and paternal chromosomes
Spermatogenesis does not start in the male until puberty - occurs in the seminiferous tubules of the testes
Oogenesis starts from fetal life in the female - occurs in the ovary and ocmpleted at puberty
what is a stem cell
undifferentiated cell that has ability to form specialised cell types - either embryonic or adult stem cells. Embryonic stem cells are pluripotent while adult stem cells are multipotent
what cell
ability to form all mature cell types in the body except placenta and extraembryonic cells. ( can form blood ) It cannot form a whole organism
pluripotent cell
ability to form more than one closely related mature cell types in the body but not as varied as pluripotent eg cord blood, bone marrow stem cells from erythrocyte , leukocyte and platelet - only form blood related cells
what cell
multipotent
has ability to form all differentiated cell types in the body including the placental and extraembryonic membrane cells. It could from a whole organism eg a zygote and first few generations of Blastomeres - form whole
what cell
totipotent
where does fertilisation occur
ampullary region of the uterine tube ( oviduct)
Phase 1 - penetration of the corona radiata
Phase 2 - penetration of the zona pellucida
Phase 3 - fusion of the oocyte and sperm cell membranes
are the 3 phases of what
fertilisation
what is capacitation
a sperm conditioning process within the female reproductive tract ( uterine tube) in prep for fertilisation in the ovum. Involves epithelial interactions between the sperm and the mucosal surface of the uterine tube. Only capacitated sperm can pass through the corona cells and undergo the acrosome reaction
what is the acrosome reaction
sperm with zona pellucida of oocyte - release of enzymes to penetrate cona pellucida
when the sperm makes contact with the plasma membrane of the oocyte this leads to release of lysosomal enzymes from the cortical granules in the plasma membrane doing what
makes it impenetrable for the rsperm - protection of polyspermy
principle goal of fertilisation
restore diploid
how could male infertility result
quantity or quality of sperm ejaculated
what is cleavage
repeated mitotic division of the zygote resulting in increased number of cells
daughter cells generated termed blastomeres
Zygote - morula
Bilaminar embryonic germ disc
epiblast and hypoblast(primitive endoderm) evolved from emrbyoblast
what is the embryonic germ disc
cluster of embryonic cells from blastocyst
where is the primitive streak found and what does it start
caudal end of epiblast
gastrulation
Defines all major body axes of the developing embryo - cranial - caudal axis , medial lateerla axis and left and right axis and dorsal and ventral axis is all established as a results of formation of primitive streak
what is gastrulation
process of epiblast cells movement through primitive streak transforming bilaminar germ disc into the trilaminar germ disc - then 3 primary germ layers
ectoderm ( epiblast )
mesoderm ( grey cells)
endoderm ( hypoblast)
when does gastrulation commence
15ht day with formation of primitive streak
what is a congential malformation due to error of gastrulation
caudal dysplasia e.g. sirenomelia - legs fused together
dextrocardia - heart on right instead of left
situs inversus - major visceral organs are reversed or mirrored from their normal positions
organogenesis
formation of the primary germ layers and major organs
this layer gives rise to organs and structure that maintain contact with outside world
forms the neuroectoderm which forms the neural tube and neural crest cells and pituitary
sensory epithelium for the ear
epidermis of the skin
enamel of teeth
oral and anal canal epithelium
what layer?
derivatives of the ectodermal layer
what 3 parts make up the mesoderm germ layer
paraxial
interrmediate
lateral plate
what part of the mesoderm layer forms
somitomeres - in head called neuromeres
and then somites that are either side of the neural tube
paraxial
can the age of the embryo be accurately determined by counting the somites at specific periodicity
yes
what part of the mesoderm layer contributes to formation of structures of urogenital system inducing primordial germ cell gametes and gonads
intermediate mesoderm
what part of the mesoderm layer splits into parietal and visceral
lateral plate mesoderm
which part of the lateral plate mesoderm lines the cavity walls and forms dermis of skin in body wall and connective tissue and costal cartilage and pericardial membrane
parietal
what part of the lateral plate mesoderm forms the gut wall with the endoderm and serous membranes surrounding organs and forms
BLOOD CELLS ADN BLOOD VESSELS
visceral
what germ layer
is the main epithelial lining of the GI and pharynxc
respiratory tract, urinary bladder , urethra and tympanic membrane as well as auditory tube
parenchyma of thyroid and paraT liver and pancreas
endoderm germ layer
what are the walls of the GIT formed from
smooth muscle and the connective tissue derived from mesoderm
morphogenesis
form shaping process of the embryo - changes in cell shape size position number migration and adhesitivtiy
interference with diff tissuegrowth in E resuls in dysmorphogenisis and formation of birth defects
responses due to influence of genetic variation and environmental factros during devleometn - considered a normal
those individuals who develop in close range of abstract norm both in form and function are said to have developed normally - what word describes this
normogenesis
those individuals who develop outside the range are considered to develop abnormally - what word describes this
dysmorphogenesis
what is a malformation
primary morphologic defects in an organ or body part e.g. neural tube due to close of neural folds
syndactly - failure of digits fully separated
caused by teratogens or genetic factors
deformation
2nd morpjoligc defects imposed upon on organ or body part due to mechanical forces over a prolonged period of time
e.g. clubfeet - compression of amniotic cavity as a result of insufficient amniotic fluid
what is a syndrome
when dysmorphognesis occurs as a pattern of well characterised multiple primary malformations in a predictable fashion in 1 or more due to a specific underlying angle or common cause
what problem causes these symptoms flat face small nose reduced muscle tone upwards slant to eyes enlarged tongue that stick out deep single palmar crease hyper flexibility of joints
Downs syndrome
thin upper lip brain damage smooth philtrum short palpebral fissure length symtpks of what
fetal alcohol syndrome
teratogen
factor or agent that causes a brith defect or congenital malformation
factor that determine capacity of teratogen to produce BD
genotype concept and maternal genome
development stage at time of exposure
dose and duration of exposure
pathogensis
abnormally development of a process
when do errors of gastrulation occur
3rd week - epibalstic cells are sensitive
a high dose of alcohol kills midline germ disc causing a deficiency of craniofacial structures what is this Called
holoprosencephaly - eyes close and cleft lip
caudal dysplasia
mesodermal insufficiency which forms lower limns ad urogenital system and lumbosacral vertebrae
situs inversus
transportation of viscera in thorax and abdomen
sacrococcygeal teratomas
remnants of primitive streak persist in that region to form tumours
in maternal serum screening wha protein is detected
alpha- feto protein - produced by the fatal liver - levels increase during pregnancy
need to be combined with more tests due to the fact that high false positive rate
in a neural tube defect what is high that should be normal during gestation
maternal serum AFP
in Down syndrome what hormones are high and low
HCG and INhbin A increased and estriol down
nuchal translucency test
thickness of fluid at the neck - feotus with downs or other heart defects accumulate fluid in back of the neck during 1st trimester
fetal echocardiogrpahy measure what
fetal HR and HB
amniocentesis
analysis of amniotic fluid aspirated from the amniotic cavity 14 -16 weeks of gestation
chronic villus sampling
analysts chronic tissue sample
