Developmental origins of disease symposium

Question 1

what occurs during fertilisation - day 1?

Answer 1

fusion & 2nd meiotic division.

zygote is diploid with 46 chromosomes

Question 2

what occurs during days 2-3?

Answer 2

cleavage.
blastomeres (embro cells).
morula forms

Question 3

what occurs during days 4-5?

Answer 3

morula develops cavity, forming blastocyst.
outer layer of blastocyst thins out & becomes trophoblast which helps to form placenta.
rest of cells are pushed up to form inner cell mass, creating embryonic pole.
blastocyst has reached uterine lumen & ready for implantation.

Question 4

what occurs during days 6-7?

Answer 4

embryo forms bilaminar disc.
inner cell mass differentiates into epiblast & hypoblast.
hypoblast forms extraembryonic membranes.
epiblast forms embryos.
amniotic cavity develops within epiblast mass.

Question 5

what occurs during primary yolk sac day 6-8?

Answer 5

extraembryonic membrane creates yolk sac which contains nutrients that supply embryo before the placenta functions.

Question 6

what occurs during week 3+?

Answer 6

embryo/bilaminar disc forms 3 distinct layers - gastrulation.
epiblast is known as ectoderm.
hypoblast is replaced by cells from epiblast & becomes endoderm.
epiblast gives rise to mesoderm.
hypoblast degenerates. epiblast gives rise to all 3 germ layers.

Question 7

what occurs during week 4+?

Answer 7

flat disc folds into 2 directions: longitudinal (cephalocaudal) brings head & tail closer together; lateral (transverse), bringing amniotic cavity down, creating future gut tube inside peritoneal cavity.

Question 8

what do dermomyotomes form?

Answer 8

connective tissue & skeletal muscle

Question 9

what do sclerotomes form?

Answer 9

bone & cartilage - vertebral arch

Question 10

what does the intermediate mesoderm give rise to?

Answer 10

urogenital system. kidneys, gonads, urogenital ducts & associated glands

Question 11

what do mesodermal cells become?

Answer 11

membranes of the body - pericardium, pleura, peritoneum.

Question 12

what are the signs of UTI and which investigations are carried out?

Answer 12

pyuria, difficulty in obtaining MSU, high index of suspicion.
dipstick for nitrates, urine culture, suprapubic aspiration.

Question 13

give an example of a malformed single defect, its features & treatment

Answer 13

pyloric stenosis.
males 4:1. non bilious projectile vomiting.
hypochloraemic. metabolic alkalosis.
pyloromyotomy

Question 14

give an example of a deformed single defect and its treatment

Answer 14

dysplastic hip.
g=female 9:1. breech. asymmetric skin folds.
Barlow test to dislocate. ortolani test to relocate.
early: conservative treatment. late: surgical correction

Question 15

give examples of disruption single defects.

Answer 15

intestinal atresia
oesophageal atresia
duodenal atresia 
jejunal/ileal atresia
polyhydramnios 
intestinal obstruction

Question 16

what is a sequence single defect and give some examples?

Answer 16

single defect but multiple abnormalities.

breech deformation sequence, amniotic band disruption sequence.

Question 17

give examples of chromosomal abnormalities that arise from multiple defects?

Answer 17

abnormalities in chromosome number and structure.
sex chromosome abnormalities. 
mosaicism. 
fragile sites. 
imprinting.

Question 18

what are some of the features of Down syndrome?

Answer 18

clinodactyly
simian crease
congenital heart defects
duodenal atresia
hypotonia 
delayed development 
good social skills

Question 19

give examples of single gene mutations (multiple defects).

Answer 19

Marfans, haemophilia, mitochondrial disease