abnormalities of human devleopment Flashcards
causes of maldevelopment
mostly due to many factors, but a third due to genetics
identical twins vs chimaerism
one conceptus forms 2 sets of genetically identical cells vs 2 genetically different conceptuses combine to form one person
define conceptus
everything that develops from zygote, including embryo
what are conjoined twins
where there is only partial separation of inner cell mass
what is mosacism (non-disjunction)
chromosomes not distributed evenly
distribution of cells in baby and placenta
cells can distribute so that placenta is abnormal, but baby is not
eye colour- chromosome, most common colour, and when differentiation ccours
chr15, brown, and day 22, so any abnormality must occur BEFORE day 22
kleinfelters- chromsomes and main effect
XXY= less fertility
what determines survival in downs
heart issues
edwards syndrome- chr and severity
18, very few are born
patau’s syndrome- chr and severity and how common
13, most die before- rarest out of the 3
turners syndrome, and is YO viable
XO- female, short and infertile- NO
any autosomal conditions of too few chromsomes
no ie loss of any autosomal chromsome= certain death
XY linked translocation
XX male- where should be girl, but partial translocation of Y chromosome= male
autosomal translocation effects
leads to tumours, as chromosomes control cell growth
what occurs in holt oram syndrome- mutation and structures affected
mutation in TBX5 T.F= heart (division of atria issue) and hand defects
achondroplasia- mutation and effect
FGFR3 mutation (increased function)= less cartilage converted to bone= short limb bones
teratogens- define and examples
agents that disrupt development of fetus- infectious agents like HSV/HIV, physical like Xrays, and chemical like alcohol/lithium- heart/CNS/lungs vulnerable earlier
polydactyly
extra finger- abnormality occurs at around day 25
what factor controls limb development
sonic hedgehog
cleft lip/palate- cause and treatment
lip/palate separated, as they form from two separate halves of the face- can be treated easily
spina bifida- types
bulge of tissue from spine outside body- contains either only CSF (meningocele) or neural tissue (myelomeningocele)
effect of surgery on spina bifida
helps with anatomical issues, but functional issues ie below lesion often can’t be repaired
cause of spina bifida including time
spine forms a tube- if tube not sealed ie neurulation, leads to a hole at around day (called neuropore0 21-28=
key nutrient decreasing incidence in spina bifida
folic acid- give 3 months before pregnancy (as egg takes 3 months)
anencephaly- day and cause
defect in brain development due to formation of anterior neuropore ie at top of spine around day 22
thalidomide- structures affected and cause including day
causes deformed limbs (especially upper)/eyes and heart- affects blood vessels, thus cells of limb bud die= limbs affected- day 28
use of thalidomide
still used in leprosy+ cancer (as blood vessels affected)
respiratory distress syndrome- effect and treatment
babies has no lung surfactant (develops in last trimeser)= lungs can’t expand: injection of glucocorticoids
facial devleopment
facial structures develop on side of head, then move to middle-
