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Y2 LCRS Reproduction, Development and Ageing > complications of development > Flashcards

complications of development Flashcards

1
Q

3 types (and prevalence) of mal-development

A

genetic (30%), environmental (15%), multifactorial (55%)

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2
Q

examples of categories of mal-development

A

eye mosaic (different coloured eyes), cleft lip/palate, trisomy 18 (weeks to months survival), trisomy 13, polydactyly, chimerism, thalidomide

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3
Q

chain of development

A

change in numbers of conceptuses or foetuses that develop

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4
Q

examples of gross changes in numbers of conceptuses or foetuses that develop

A

twins, triplets (very early split of fertilised eggs from identical), chimaera (2 genetically distinct conceptuses which combine very early in development and form one individual with no reaction to different genetically distinct cells; example is Blaschko’s lines)

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5
Q

extreme between multiple pregnancies

A

conjoined twins caused by incomplete inner cell mass separation

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6
Q

what determines outcome of conjoined twins

A

extent of joining

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7
Q

what else can change development and gene expression

A

distribution and content of cells and chromosomes

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8
Q

3 patterns of cellular distribution

A

mosaicism (non-disjunction), distribution of cells between inner cell mass and trophectoderm (placenta), chimerism

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9
Q

what is mosaicism (non-disjunction)

A

differences between cells within one individual (if most cells are normal, then impact is modest)

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10
Q

describe distribution of cells between inner cell mass and trophectoderm

A

abnormal cells will move into placenta (easier process), normal cells will move to embryo (more difficult process), so genetics of infant and placenta are different

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11
Q

what is chimerism

A

fused multiple zygotes

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12
Q

example of mosaicism

A

heterochromia (different coloured eyed)

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13
Q

what is eye colour gene chromosome

A

15

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14
Q

when does eye differentiation begin and significance

A

day 22 post-fertilisation (so chromosomal problem must predate this to cause heterochromia)

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15
Q

3 types of chromosome problems and outcome

A

too many, too few (aneuploidy), translocations; all give rise to syndromes

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16
Q

common chromosomal syndromes caused by too many chromosomes (XY linked)

A

Kleinfelter’s syndrome (XXY) and other more severe forms, including XYY

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17
Q

what happens to X chromosome in females (XX)

A

one is inactivated in females

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18
Q

effect on severity of increasing number of X chromosomes in too many chromosome abnormalities

A

more severe

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19
Q

common chromosomal syndromes caused by too many chromosomes (autosomal)

A

Down’s syndrome (chromosome 21; heart problems determine survival), Edward’s syndrome (chromosome 18; live <2 weeks), Patau’s syndrome (chromosome 13; most die before birth)

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20
Q

exception trisomy chromsome which has never been detected in miscarriage or birth

A

chromsome 1, as it carries so many genes (largest chromosome) that defect prevents implantation and is lost immediately

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21
Q

symptoms of mosaic or partial extra chromosomal material compared to complete trisomies

A

less severe

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22
Q

common chromosomal syndrome caused by too few chromosomes (XY linked)

A

Turner’s syndrome (X0; female, short stature, infertile); Y0 is not viable

23
Q

common chromosomal syndromes caused by too many chromosomes (autosomal)

A

no complete losses are viable, but partial chromosome loss syndromes are possible

24
Q

what are translocations

A

altered distributions of chromosomes

25
Q

example of XY linked translocation

A

XX male as XY translocation

26
Q

what are autosomal translocations linked with

A

development of tumours e.g. lymphoma, leukaemia, sarcoma

27
Q

what affects function of gene product

A

altered expression (e.g. more/less key regulator), or mutations in gene (key regulator, receptor etc.)

28
Q

3 examples of gene defects

A

piebaldism (KIT), Holt-Oram syndrome affecting heart and hands (TBX5), achondroplasia (gain of function mutation in FGFR3 - switched on permanently)

29
Q

what happens to heart and hand in Holt-Oram syndrome (variable in effects even on same person e.g. both hands affected differently)

A

overlarge heart as atrial septation defects, correct number of digits on hand but abnormalities (e.g. thumb)

30
Q

what happens in achondroplasia

A

defects in conversion of cartilage to bone and lack of bone growth (especially large bones, such as humerus and femur)

31
Q

organism size vs number of genes, and therefore what contributes to how our bodies work

A

don’t correlate, so microbiome has large effect

32
Q

2 other terms which mean the same as birth defect

A

congenital malformation, congenital abnormality

33
Q

define birth defect

A

change in pattern of development (teratology or dysmorphology)

34
Q

define teratogen

A

any agent that can disturb the development of an embryo or fetus (usually most vulnerable in early stage, with some exceptions)

35
Q

3 types of teratogen

A

infectious agents, physical agents, chemical agents

36
Q

6 systems which can be affected by teratogens

A

limbs and digits, urogenital, heart, CNS, face, lungs

37
Q

describe polydactyly and when it occurs

A

nothing stands out except additional digit; forelimb bud appears at day 27/28, and hindlimb bud at day 29: limb grows out from lateral plate mesoderm rapidly under control of special signalling regions and is fully formed by day 56, so abnormality between day 27 and day 56

38
Q

what controls pattern of digits development

A

sonic hedgehog is polarising factor for limb development, mediating ZPA cells

39
Q

facial development: where do eyes, ears and nose originate from before migrating to correct place (by week 10)

A

eyes on side of face, ears part way down legs, nose where eyes

40
Q

what forms and are filled in during facial development, and what is the outcome if not filled in

A

clefts; cleft lip and palate (early surgery after birth and healing process much more rapid)

41
Q

what is spina bifida

A

twinning of soft tissue in spine (variable protrusion of tissue (CSF or spinal tissue) from spine external to body) - anatomically corrected by surgery but nerve damage less easily repaired

42
Q

what directs formation of spinal bone

A

nervous tissue, as where this doesn’t develop, bone overlying it doesn’t form

43
Q

what causes spina bifida and when

A

poor sealing of neural tube (neuralation failure), forming gap which tissue leaves by (day 22/23), so problem present within 4 weeks of pregnancy

44
Q

what can cause poor sealing of neural tube, causing spina bifida

A

folic acid deficiency

45
Q

when should folic acid be given

A

ideally 3 months before pregnancy (during which egg matures before fertilisation), or more

46
Q

what is anencephaly

A

defect in skull and brain development during day 22/23, with female babies affected more commonly than male

47
Q

what can cause anencephaly

A

folic acid deficiency (similar to spina bifida)

48
Q

when does limb development occur

A

days 24-56

49
Q

what were the variable consequences of thalidomide (drug for morning sickness, so taken during first trimester)

A

limbs affected (upper limbs > lower limbs), as well as deformed eyes and hearts, deformed alimentary and urinary tracts, blindness and deafness

50
Q

what is thalidomide used for now

A

some leprosy and cancer treatments (mess up blood vessel development)

51
Q

effect of thalidomide on blood vessels in limbs

A

affects rapidly developing blood vessels, causing cell death in developing limb bud so couldn’t grow out properly

52
Q

when does thalidomide affect limb development

A

days 25-28

53
Q

what does respiratory distress syndrome cause, and when does this affect

A

malfunctioning lungs with no surfactant, affecting premature infant between 24-31 weeks

54
Q

preventions of respiratory distress syndrome in premature infant

A

injection of glucocorticoid

Y2 LCRS Reproduction, Development and Ageing (10 decks)

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