congenital defects and embryology

Question 1

what does congenital mean?

Answer 1

present at birth

Question 2

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

Answer 2

20%

75% of these are minor abnormalities

Question 3

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

Answer 3

half

Question 4

in how many births is the cause unknown?

Answer 4

70%

Question 5

name some of the causes of birth defects?

Answer 5

• genetic/chromosomal
• drugs
• environmental

Question 6

what drugs can cause birth defects?

Answer 6

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

Question 7

what environmental factors can cause congenital defects?

Answer 7

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

Question 8

what does a lack of folic acid lead to?

Answer 8

birth defects

Question 9

how can birth defects be prevented using folic acid?

Answer 9

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

Question 10

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

Answer 10

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

Question 11

when is the embryonic period?

Answer 11

between 3 and 5 weeks

Question 12

when is the fetal period?

Answer 12

between 8 weeks and birth

Question 13

what are major congenital defects defined as?

Answer 13

requiring medical/surgical treatment

Question 14

what are minor congenital defects defined as?

Answer 14

anomaly that doesnt require intervention

Question 15

name some major congenital defects

Answer 15

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

Question 16

what is anencephaly?

Answer 16

born without a skull

Question 17

what is omphalocele?

Answer 17

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

Question 18

what is phocomelia?

Answer 18

shortened limbs

Question 19

what is spina bifida?

Answer 19

failure of closure of spinal cord and vertebral column

Question 20

what is talipes equinovarus?

Answer 20

club foot

Question 21

what is hypospadias?

Answer 21

urethra detached from penis

Question 22

what is congenital diaphragmatic hernia?

Answer 22

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

Question 23

how can congenital diaphragmatic hernia be treated?

Answer 23

simple sutures

Question 24

what is gastroschisis?

Answer 24

body wall has not closed so abdominal contents leak outside

Question 25

name minor congenital defects

Answer 25

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

Question 26

what is syndactyly?

Answer 26

when fingers are fused together

Question 27

what is polydactyly?

Answer 27

having an extra finger

Question 28

what is ankyloglossia?

Answer 28

tongue tied

Question 29

what is cryptorchidism?

Answer 29

undescended testes

Question 30

how is cryptorchidism corrected?

Answer 30

usually spontaneously corrected within 3 months

Question 31

what complications can arise if cryptorchidism isnt treated?

Answer 31

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

Question 32

what is holoprosencephaly?

Answer 32

loss of midline structures

Question 33

how can severity of holoprosencephaly differ?

Answer 33

o Severity can vary from mild to severe

Question 34

what are the causes of holoprosencephaly?

Answer 34

genetic or environmental

Question 35

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

Answer 35

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

Question 36

how can a cleft lip/palate be repaired?

Answer 36

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

Question 37

how is gastroschisis repaired?

Answer 37

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

Question 38

where and when does fertilisation occur?

Answer 38

ampulla region of the uterine tube within 24 hours of fertilisation

Question 39

when does the morula form?

Answer 39

3 days after fertilisation

Question 40

when does the blastocyst implant?

Answer 40

hatches from zona pellucida and implants at day 6

Question 41

what happens during week 2 of fertilisation?

Answer 41

* 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

Question 42

what is the hydatidiform mole?

Answer 42

no fetus - only the placenta forms

Question 43

what genes does the placenta come from?

Answer 43

paternal genes

Question 44

how does the hydatidiform mole look?

Answer 44

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

Question 45

how is a hydatidiform mole treated?

Answer 45

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

Question 46

when does a hydatidiform mole form?

Answer 46

* 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.

Question 47

what is a partial hydatiform mole?

Answer 47

some evidence of embryonic development can be found

Question 48

what is the karyotype for partial hydatiform mole?

Answer 48

triploid (69XXX, 69XXY, 69XYY)

Question 49

what causes partial hydatiform mole?

Answer 49

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

Question 50

what happens during week 3 of fertilisation?

Answer 50

• Two layers are transformed into three layers as epiblasts travel to the midline, travel and push the hypoblasts outwards; establishes body's axis

Question 51

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

Answer 51

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

Question 52

what causes sirenomelia?

Answer 52

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

Question 53

why do few people with seronmelia survive?

Answer 53

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