Embryology

Question 1

describe the Hedgehog (HH)proteins

Answer 1

• constitute a family of paracrine factors that are often used by the embroys to induce particular cell types and to create boundaries

Question 2

describe the sonic hedgehod protein

Answer 2

• expressed in the notochord
• patached and smoothened proteins

Question 3

describe holoprosencephaly

Answer 3

• mutations in SHH are the most common cause of holoprosencephaly
• primary defect is incomplete cleavage of the developing brain into separate hemispheres and ventricles
• associated with midline facial anomalies

Question 4

describe fibroblast growth factors (FGFs)

Answer 4

• produced at the tip of the limb bud by a specialized epithelial structure, the Apical Ectodermal Ridge or AER
• AER is responsible for patterning the proximal-distal axis of limb development and maintaining proliferation
• FGFs are responsible for angiogenesis, activating homeobox genes which determine limb patterning and activating SHH

Question 5

describe thalidomide

Answer 5

• thalidomide was used as a sedative and antinauseant for morning sickness
• critical period between week 3-4
• inhibits FGFs at the AER which leads to the proximal limb tissue being lost, while the distal limb tissue remains

Question 6

describe bone morphogenic protein (BMP)

Answer 6

• patterning the dorsal-ventral axis of embryo
• limb development
• bone development
• kidney development
• heart development
• control of skin development and hair follicle growth

Question 7

describe the homeobox genes (HOX)

Answer 7

• master control genes
• bind to DNA and form transcriptional factors and regulate gene expression

Question 8

describe teratogens

Answer 8

• environmental agents that negatively affect fetus

Question 9

describe maternal diabetes

Answer 9

• uncontrolled maternal diabetes mellitus alters the expression of developmental genes and is associated with:
  
  • macrosomia (large baby)
  • CNS/heart/skeletal defects

Question 10

describe TORCH infections

Answer 10

• T = toxoplasmosis
• O = other (syphillis)
• R = rubella
• C = cytomegalovirus (CMV)
• H = herpes simplex (HSV)

Zika too

Question 11

describe congenital toxoplasmosis

Answer 11

• caused by parasite
• transmission to mother: eating raw or undercooked meat or contaminated vegetables and fruits
• 40% change of fetal infection, severity related to gestational age at time of infection
• can cause:
  
  • chorioretinitis: inflammation of retina
  • hydrocephalus: fluid in ventricles
  • intracranial calcifications
  • convulsions
• antenatal screening

Question 12

describe congenital syphilis

Answer 12

• teratogenic at any stage of pregnancy
  
  • transmitted via sexual contact
• lead to:
  
  • still births (hydrops fatalis)
  • deafness
  • hydrocephalus
  • intellctual disability
  • craniofacial anomalies
    
    • saddle nose
    • saber shins
    • Hutchinson teeth
• prevention: antenatal screening and treatment with penicillin

Question 13

describe congenital rubella syndrome

Answer 13

• caused by mother contracting rubella (German measles) during preg.
• Defects:
  
  • cataracts
  • low birth weight
  • sensorineural deafness
  • heart defects
  • intellectual disability

Question 14

describe congenital cytomegalovirus (CMV)

Answer 14

• caused by mother contracting CMV during pregnancy
• 90% of children are asymptomatic at birth
• up to 15% develop symptoms later:
  
  • sensorineural hearing loss
  • ventriculomegaly
  • periventricular calcifications
  • microcephaly
  • hydrocephalus
  • microphthalmia
  • intellectual disability

Question 15

describe herpes simplex in preg.

Answer 15

• congenital - transplacental transmission from infected mother, esp. during 1st trimester
• acquired at the time of delivery
• symptoms:
  
  • vesicular skin lesions
  • encephalitis
  • fever
  • conjuctivitis
  • seizures
• preg. women can be treat with antivirals

Question 16

describe congenital varicella syndrome

Answer 16

• rare disorder caused by infections during 1st and 2nd trimester
• symptoms:
  
  • cutaneous vesicles
  • limb shortening/malformation
  • neuroligical anomalies

Question 17

antibiotic use during pregnancy

Answer 17

• easily crosses placenta and deposits at sites of active calcification
• defects:
  
  • inhibits bone growth
  • permanent yellow-brown discoloration of teeth
  • enamel hypoplasia

Question 18

describe retinoic acid in pregnancy

Answer 18

• Acutane: used for treatment of severe acne
  
  • contraception mandatory during usage
• severely teratogenic
• high doses of vitamin A during preg. can produce same effects
• defects:
  
  • spontaneous abortion
  • neuropsychological impairment
  • premature birth
  • neonatal death

Question 19

alcohol in pregnancy

Answer 19

• alcohol easily crosses placenta and remains in amniotic fluid
• Fetal Alcohol Syndrome (FAS)
  
  • risk is directly related to amount and freq. of consumption
  • disrupts DNA and protein synthesis, inhibits cell migration
• defects:
  
  • smooth philtrum,
  • depressed nasal bridge
  • microcephaly
  • intellectual disability

Question 20

cigarette smoking in preg.

Answer 20

• epigenetic changes: DNA methylation
• nicotine: vasoconstrictor, decreased blood flow through uterine arteries, decreased O2 and nutrient supply to fetus
• CO: impaired O2 delivery to fetus
• defects:
  
  • low birth weight
  • intra uterine growth retardation
  • premature delivery
  • SIDS