Human embryonic development Flashcards by HARRY RICHARDSON

what is the pre-embryonic period

fertilisation of egg to end of 3rd week of development

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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

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what is the fetal period

beginning of 3rd month to brith
period of maturation
no general agreement of beginning or end of this period

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in what weeks of development if the embryo not susceptible to any harmful substance

2 weeks

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when is the embryo most sensitive

1st trimester - congenital malformations

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gametogenesis

production of male and female gametes or sec cells from primordial germ cells via meiotic division in the gonads
spermatogenesis
oogenesis

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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

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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

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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

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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

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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

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where does fertilisation occur

ampullary region of the uterine tube ( oviduct)

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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

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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

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what is the acrosome reaction

sperm with zona pellucida of oocyte - release of enzymes to penetrate cona pellucida

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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

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principle goal of fertilisation

restore diploid

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how could male infertility result

quantity or quality of sperm ejaculated

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what is cleavage

repeated mitotic division of the zygote resulting in increased number of cells
daughter cells generated termed blastomeres
Zygote - morula

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Bilaminar embryonic germ disc

epiblast and hypoblast(primitive endoderm) evolved from emrbyoblast

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what is the embryonic germ disc

cluster of embryonic cells from blastocyst

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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

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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)

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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