Developmental disorders

Question 1

define teratogenesis

Answer 1

development of a congenital abnormality

Question 2

define sensitive/critical period

Answer 2

a period of development during which an organ or system is susceptible to genetic or environmental factors that can alter the development program

Question 3

categories of developmental disorders

Answer 3

• structural malformations
• defects in brain development, can cause behavioural defects
• ducts in fetal growth, birth weight and tissue maturation
• effects leading to premature birth, still birth or neonatal death

Question 4

examples of genetic causes

Answer 4

cyclopia from mutation in Shh
problems with somite segmentation (delta-notch, wnt, fgf)
aortic arch remodelling (tbx1) and cardia outflow tract remodelling

Question 5

effect of hypoxia and genetic causes

Answer 5

not all congenital heart defects linked to genes, hypoxia can have a significant effect
caused by smoking, living at high altitude, maternal diabetes, high BMI etc.

Question 6

key environmental factors

Answer 6

ionising radiation
pollution
drugs
maternal infection
metabolic disorders
smoking, trauma, pressure effects

Question 7

define teratogen

Answer 7

agent or factor that causes malformation of an embryo

for each factor there will be a critical period

Question 8

ionising radiation effect

Answer 8

mutations and chromosome breakage affecting cell division, increases likelihood of leukaemia
increased in places with atomic bomb and Chernobyl
critical period 8-14 weeks

Question 9

thalidomide effect (drug)

Answer 9

critical period 21-40 days
causes miscarriage, still birth, craniofacial and limb defects
thought to inhibit angiogenesis in embryonic limb buds

Question 10

retinoic acid effect

Answer 10

synthetic form of vitamin A
can cause spontaneous abortion, defect of face/ears/cardiovascular system
critical period up to 120 days

Question 11

alcohol effect

Answer 11

fetal alcohol syndrome

microcephaly, intellectual disabilities, low bridge of nose, hypertelorism

Question 12

rubella effect (infection)

Answer 12

most common cause of virus induced congenital malformations

deafness, cataracts, heart defects, damage to CNS, still birth

Question 13

syphilis effect (infection)

Answer 13

can cross placental barrier from 5th month

stillbirth or neonatal death

Question 14

Zika virus

Answer 14

infection is usually mild or asymptomatic
targets neuronal cells
causes microcephaly, craniofacial disproportion, spasticity anf seizures, brainstem dysfunction

Question 15

diabetes effect

Answer 15

advanced diabetes with vascular involvement associated with 10x increase in neural tube defects, palate and facial defects and lower limb defects

Question 16

trauma and pressure effects

Answer 16

oligohydramnios = insufficient amniotic fluid, can lead to pressure defects like club foot
amniotic band syndrome = twists of amniotic membrane can cause partial limb amputation by loss of blood supply