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human development > congenital defects and embryology > Flashcards

congenital defects and embryology Flashcards

1
Q

what does congenital mean?

A

present at birth

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2
Q

how many births have some defects? how many of these are minor abnormalities

A

20%

75% of these are minor abnormalities

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3
Q

how many births could be prevented if we knew the cause?

A

half

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4
Q

in how many births is the cause unknown?

A

70%

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5
Q

name some of the causes of birth defects?

A
  • genetic/chromosomal
  • drugs
  • environmental
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6
Q

what drugs can cause birth defects?

A

accutane - anti-acne medication which contains an active form of Vitamin A. Vit A is fat-soluble so can be stored in the fat in toxic levels which can then pass onto the infant

thalidomide - given to women for morning sickness but wasn’t tested properly  caused babies to be born without limb

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7
Q

what environmental factors can cause congenital defects?

A

o Infections agents (rubella – causes eye defects, CMV, Zika – causes microcephaly)
o Environmental agents (alcohol and smoking)

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8
Q

what does a lack of folic acid lead to?

A

birth defects

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9
Q

how can birth defects be prevented using folic acid?

A

prevent if women consume 400 micrograms of folic acid daily, prior (three months) and during the first trimester

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10
Q

why does an embryo have to be implanted into the endometrium by 5 weeks?

A

placenta needs to be formed and developed enough to give you an O2 supply bc embryo is 4mm – the limit of diffusion

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11
Q

when is the embryonic period?

A

between 3 and 5 weeks

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12
Q

when is the fetal period?

A

between 8 weeks and birth

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13
Q

what are major congenital defects defined as?

A

requiring medical/surgical treatment

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14
Q

what are minor congenital defects defined as?

A

anomaly that doesnt require intervention

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15
Q

name some major congenital defects

A 
anencephaly
cleft lip and palate
omphalocele
phocomelia
spina bifida
talipes equinovarus
hypospadias
congenital diaphragmatic hernia
gastroschisis
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16
Q

what is anencephaly?

A

born without a skull

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17
Q

what is omphalocele?

A

intestines, liver and other abdominal organs outside body: failure of return of these contents in 9th week

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18
Q

what is phocomelia?

A

shortened limbs

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19
Q

what is spina bifida?

A

failure of closure of spinal cord and vertebral column

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20
Q

what is talipes equinovarus?

A

club foot

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21
Q

what is hypospadias?

A

urethra detached from penis

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22
Q

what is congenital diaphragmatic hernia?

A

diaphragm goes not close properly allow gastrointestinal contents (intestines) to push into the thorax and prevent proper development of lungs.

23
Q

how can congenital diaphragmatic hernia be treated?

A

simple sutures

24
Q

what is gastroschisis?

A

body wall has not closed so abdominal contents leak outside

25
Q

name minor congenital defects

A

Auricular ear tag, supernumerary nipples, overlapping digits, micropenis
syndactyly, polydactyly, ankyloglossia, cryptorchidism
holoprosencephaly
cleft lip and cleft palate
congenital diaphragmatic hernia

26
Q

what is syndactyly?

A

when fingers are fused together

27
Q

what is polydactyly?

A

having an extra finger

28
Q

what is ankyloglossia?

A

tongue tied

29
Q

what is cryptorchidism?

A

undescended testes

30
Q

how is cryptorchidism corrected?

A

usually spontaneously corrected within 3 months

31
Q

what complications can arise if cryptorchidism isnt treated?

A

Gives 20x increased risk of developing testicular malignancy and can lead to male infertility

32
Q

what is holoprosencephaly?

A

loss of midline structures

33
Q

how can severity of holoprosencephaly differ?

A

o Severity can vary from mild to severe

34
Q

what are the causes of holoprosencephaly?

A

genetic or environmental

35
Q

why is it better to repair a cleft lip/palate in utero?

A

better regenerative capacity in utero and scar tissue doesn’t form bc immune system isn’t fully formed

36
Q

how can a cleft lip/palate be repaired?

A

o Repairs can be done with simple sutures or synthetic patch such as Gor-tex (for large defects)
o In utero repair via laproscopy can allow lungs to develop

37
Q

how is gastroschisis repaired?

A

Intestines are put into a plastic bag and sealed, fluids and anti-inflammatories are given to settle the inflammation. Intestines should fall back into the abdomen where the silo (bag) can be removed and everything can be sewn back together

38
Q

where and when does fertilisation occur?

A

ampulla region of the uterine tube within 24 hours of fertilisation

39
Q

when does the morula form?

A

3 days after fertilisation

40
Q

when does the blastocyst implant?

A

hatches from zona pellucida and implants at day 6

41
Q

what happens during week 2 of fertilisation?

A
  • Trophoblasts differentiate into two layers: synctioblast, cytotrophoblast.
  • Embryoblasts differentiate into 2 layers: epiblasts dorsally and hypoblast ventrally.
  • Two cavities: amniotic cavity dorsal to epiblast. Yolk sac cavity ventral to hypoblast
42
Q

what is the hydatidiform mole?

A

no fetus - only the placenta forms

43
Q

what genes does the placenta come from?

A

paternal genes

44
Q

how does the hydatidiform mole look?

A

Generally large, composed of grape-like clusters of swollen chorionic villi. Uterus fills with the placenta.

45
Q

how is a hydatidiform mole treated?

A

Requires hysterectomy for removal – like a tumour. Grows into the endometrium

46
Q

when does a hydatidiform mole form?

A
  • Single spermatozoon fertilizes oocyte that lacks a nucleus, mitosis w/o cleavage.
  • 2 spermatozoa may fertilize oocyte that lacks a nucleus (46XX, 46XY).
  • 90% 46XX indicating that mono-spermic fertilisation is dominant.
47
Q

what is a partial hydatiform mole?

A

some evidence of embryonic development can be found

48
Q

what is the karyotype for partial hydatiform mole?

A

triploid (69XXX, 69XXY, 69XYY)

49
Q

what causes partial hydatiform mole?

A

Often because of fertilisation of an oocyte containing female pronucleus by 2 spermatozoa or an abnormal diploid sperm

50
Q

what happens during week 3 of fertilisation?

A

• Two layers are transformed into three layers as epiblasts travel to the midline, travel and push the hypoblasts outwards;

establishes body’s axis

51
Q

what are the 3 layers formed in week 3 and what do they form?

A

o ectoderm – nervous system and skin
o mesoderm – muscle, connective tissue and bone
o endoderm – gut

52
Q

what causes sirenomelia?

A

Epiblast cells stop invaginating too soon, insufficient mesoderm produced –> not enough cells in mesoderm to separate the legs.

53
Q

why do few people with seronmelia survive?

A

Often associated with kidney and gastrointestinal defects, so few survive to have the legs separated

human development (20 decks)

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