Abnomralities in human development Flashcards
What are the 3 main classes of causes of maldevelopment?
Genetic-30%
Environemental-15%
Multifactorial-55%
Are twins considered mal-development? What is chimersim?
Changes in the amount of conceptuses or fetus that develop-twins, triplets, chimerae
identical-one conceptus forms 2/3 inner cells forming 2/3 babies
Chimersim-2 genetically distinc conceptuses combine very early to form one individual–very rare=> often cause mixture of responses on skin and other (Blashko’s lines
Cojoined twins-siamese twins-extend of conjoining determines outcome-more in the middle, worse it is (usually due to twins not seperating properly
What are the maldevelpment changes that can affect cells?
distribution or chr changes can lead to issue (even smallest changes)
Cellular-
-mosaicism-non disjunction of chr during duplication-differences between cells within 1 person-depends of how few affected cells there are=eg: heterochromia (must predate day 22), 3 color turtoise shell cats (only in female)
-Distribution bewteen cells of inner cell mass and placenta-some studies suggest defective cells are moved to placenta, normal cells stay in inner cell mass (meaning one can be normal and the other not)
-Chimerism
What are the maldevelpment changes that can affect chromosomes ? Exemples of too many?
Too many, too few, or translocation
=> all will give rise to syndromes
too many can be XY linked-kleinfeters (XXY), XXXY, XXX (not too severe), XXXX (more severe), XYY (variable outcomes) => shows how well X chr inactivation works (but cant inactivate them all-as more X=more severity)
Ausotomsal-only 3 viable with birth
Downs-heart issues, Edwards (Chr18)-very few after 2 weeks, Patau (13)-usually die within a year
-Chr not in usual environement and control will be different
in other misscarriages, all other trisomies have been found-not viable and baby is lost. EXCEPT Chr1 trisomy never been detected (too serious?)
(same with too little)
mosaics/partial extra chr material-less severe symtpoms than in completes trisomes
Too few-XY or autosomal
XY
Exemple of too few chr syndromes? And translocations?
Too few-XY or autosomal
XY-only viable is XO -turners syndrome
autosomal-no complete loss are viable
partial loss syndromes do exist-
translocation
XY linked-can be officially XX but has bit of Y carried on-XX male
Autosomal-linked most commonly with tumour developments (lymphomas, leukemias, sacromas-as the new piece of CHr is now being controlled by different TF)
What are the maldevelpment changes that can affect genes?
Mutations (gain or loss of function-but what gene it is detemrines function), or altered expression
eg; KIT receptor-loss some function-heart shaped patch of white skin on abdomen and head
Holt-Oram syndrome-TBX5 (TF)-heart hands deffects->atrial septation defects (no formation of 4 chambers-large heart)-and range of hand abnormality (long thumbs-like finger–can differ between right/left hand)
Achrondroplasia-FGFR3-dwarfism type–dramatic shortening of long bones of body-rest is in proportion–defect in conversion of cartilage to bone during development and lengthening after
What are birth defects?
congenital malformation-not genetic teratology or dysmorphology-change in pattern of development 3% of pregagncies of serious defects 20% of deahts 15%
What are teratogens?
Infections agents-rubella (cataracts, glaucoma, heart defects, deafness)
Physical agents-Xrays
Chemical agents-legal/illegal drugs, alcohol-Thaliomide, lithium
alcohol (one week late shouldnt affect children much)
When do most birth defects later on?
early-but depends on organ
heart-3-5 weeks
palate-before 9
ears-all the way through
What is polydatyly? Main causes? When?
Extra fingers-sometimes well formed, sometimes fused. Or thumb appearing/duplication of pattern of hand (2hands + fusion in middle)
happens between day 35 and day 45
day 35-pad no limb
44-hand forms and fingers start to grow
group of cells-ZPA-control digit development (if extra-mirror hand)
Sonic Hedgehog-Shh-polarising factor/pattern development
What is cleft life and palate? causes? When?
Split in lip, no sepration bewteen nose cavity and mouth
Head development happens in 2 halves-eyes are very side of head, nose middle-two seperate nose that arrive to center around 10 weeks
Tissue seperating it in middle is lost in controlled ways-> pulls eye and nose
Formation of cleft during that-and theyre filled in slightly later-palate fuse in the middle
easily repairable in babies-not even scars-because babies heal better and well
What is spina bifida? causes? When develop?
Twining of spin-looks like spine in two parts
Protrusion of tissue at bottom of spine (can happen above or two areas)
Understanding-can just contain ECF, or have neuronal tisuse (follows the protusion out). can have hair at this area-little development
no bone under protusion-neural tissue controls bone formation
surgey can only help anatomical problem-not neurological
cause-very early -day22
Neural tube fueses-and if improper, spina bifida (28 weeks)-will not fuse after
Folic acid in diet decrease indicence by 70%
need to be given very early-3 months/cycle before conception-when egg is forming and gathering nutrients-but cant always plan for that (if you know ur pregnant its too late)
what is anencephaly?
Lack of hear/brain
stem and face is fine, but the rest is not-lack anything else
folci acid also benefits–top of spinal chord hasnt formed properly (anterior neuropore at top needs to fuse)
What is the effects of thalidomide in birth defects?
drug for morning sickness-taken 1st 3rd of pregnancy
Limbs affected, deformed eyes, heart, alimentary, urinary tract
has uses in leprosy and cancer treatment
about day 28
Inhbits blood vessels development-so in budding limbs trying to grow-lead to cell death and can grow out->no limbs. (or partial loss) –also why other tissues can be affected
upper limbs absence is most common-rest of body anatomy fine
also why used against cancer
What is respiratory distress syndrome? Causes? When in development?
not quite development-lung surfactant issues
increases in last 3 weeks
1% of births
premature babies often have that-especially if way too early (100%)
one injection of glucocoriticoid can do the trick-especially in premature
NO surfactant-very high tension-and when baby breaths, just cant and dies
functional issues not anatomical issues
