Week 3 - Fetal Development Flashcards
Dermatome
That area of skin supplied by a single spinal nerve or spinal segment
Myotome
That area of muscle supplied by a single spinal nerve or spinal segment
Describe the major events that occur during embryonic development from zygote to tubular embryo
Zygote (fertilized egg) - mitotic cleavage - Morula (12-32 blastomeres) - Blastocyst (when cavity forms in morula)
Week 1 - Fertilization and Cleavage: blastocyst organization (cells clump at one end = embryo; flattened outer layer = trophoblasts aka pre placenta); blastocyst “hatches” out of zona pellicida - implants in uterine wall
Week 2 - Implantation and Bilaminar Disk formation:
Epiblasts (floor of amneotic cavity - embryo), hypoblasts (roof of yolk sac), trophoblasts (placenta)
Week 3 - Gastrulation: begins with primitive streak; Epiblast migrate and form endoderm, mesoderm, and ectoderm
List various tests used to detect disease-causing genetic variants and explain why different tests are used in different clinical circumstances
Cytogenetics (Karyotyping): Looking for Structural abnormalities e.g. Gain, loss or rearrangement of an entire chromosome or
portion visible under light microscope (10 Mb)
Chromosomal Microarray: Can tell you gain or loss of chromosomal segments/chromosomes (NOT rearrangement); compare patient to reference
Sequence Analysis: Can tell you loss, gain, or change down to a single base pair of DNA
**When do you use each one clinically?** -- NOT SURE ON THIS PART In general testing done when suspect genetic disease to inform treatment e.g.: • Intellectual disability, developmental delay • Multiple malformations • Stillbirth or neonatal death • Recurrent miscarriages • Infertility • Prenatal diagnosis • Suspected genetic disease
Describe common congenital anomalies in humans and risk factors for these congenital anomalies
Down syndrome - risk factors: maternal age
Spina bifida - risk factors: SES status, environmental risk factors, teratogen exposure
Heart defects - 1% risk in population
Cleft palate/lip - family history?
Define Cytogenetic resolution
Insertions or Deletions of genomic material e.g.
Define Cytogenetic resolution
Insertions or Deletions of genomic material e.g.
Define a translocation
Exchange of two chromosomal segments, usually between two non-homologous chromosomes
What are two types of translocations and risks associated
Reciprocal – exchange of the broken segments (balanced - increased risk in offspring; unbalanced - miscarriage, congenital anomalies)
Robertsonian – fusion of two acrocentric chromosomes (chromosomes w/ centromeres closer to the end of chromosomes) near the centromere
Look at pictures for visual help
What is the critical period during embryogenesis for teratogenesis?
3-9 weeks
What is the critical period during embryogenesis for teratogenesis?
3-9 weeks
Describe fetal alcohol spectrum disorder
FASD is a brain injury that can occur when an unborn baby is exposed to alcohol. It’s a lifelong disorder with effects that include physical, mental, behavioural and learning disabilities.
Features of FASD: Cognitive impairment, larger head, short palpebral fissures, flattened philtrum, thin upper lip
Identify examples of some of the most significant teratogens in our population and their effects
Alcohol - FASD - developmental/neurological deficits, not necessarily dependency
Opioid - dependency issues
Smoking - jittery ?
Zika - microcephaly
Rubella - Damages the liver and how it processes Vitamin A leading to increased levels → Leads to cataracts, microphthalmia, seizures, hearing defects, encephalopathy, increased risk for type one diabetes.
Cat feces - toxoplasmosis
Raw fish - toxoplasmosis
Anti epileptics - neural tube defects
Describe the coelom and indicate the cavities it becomes in the adult
The coelom forms the body cavities
will divide into 3 body cavities:
PERICARDIAL - space around heart
PLEURAL - space around lungs
PERITONEAL - space around GI
Outline the process of neural tube formation
The notochord induces overlying ectoderm
to thicken and form a NEURAL PLATE.
The neural plate invaginates in the midline to produce a NEURAL GROOVE AND FOLDS.
The neural folds fuse to form a NEURAL TUBE below the surface ectoderm. The tube then ‘zips’ up in both cranial and caudal directions. **failure to close results in neural tube defects
At this stage, the embryo can
also be called a NEURULA.
What may disrupt the process of neural tube formation
Lack of folic acid, others??
Outline the process of gastrulation, including the formation of the three primary germ layers and indicate the major adult derivatives of these layers
Gastrulation begins with the formation of the PRIMITIVE STREAK (epiblasts form this) at the caudal end of the embryo
Concurrently, epiblasts delaminate (leave the epiblast layer) and displace cells in the hypoblast layer. These cells form ENDODERM.
Similarly, epiblasts delaminate and form a
middle layer or MESODERM.
Epiblasts remaining on top form ECTODERM
Describe the rationale of ultrasounds in pregnancy
Screening for: amniotic fluid volume, neural tube defects, fetal anatomy (brain, spine, heart, kidneys, limbs, face), fetal growth (BPD, HC, AC, FL), placenta location, may include soft markers of aneuploidy,
Most accurate method for dating - Gestational Age (7-14 weeks - crown-rump length)
What are the major adult derivatives of the three primary germ layers?
Endoderm - nervous system (CNS, PNS), epidermis of skin, eye, teeth, etc
Mesoderm - muscles, bones, cartilage, blood cells and vessels, dermis of skin, kidneys, ureters, genital system
Ectoderm - lining of GI tract, liver, pancreas (except islets), lining of respiratory tract, bladder
What basic lab tests do you have done during pregnancy?
Blood type/screen, hemoglobin, infectious serology, TSH, pap smear, dating scan (7-14 weeks), detailed anatomic scan (18-20 weeks), gestational diabetes screen, group B strep swab
What types of screening tools are available for examining abnormal fetal development?
Maternal age
Ultrasound
Serum biochemistry aka
SIPS (SIPS = serum integrated prenatal screen, Screens for: NTDs, T21 (80% detection rate for SIPS), T18, cannot screen for T13)
NIPT (non-invasive prenatal testing, cell free fetal DNA In serum - Trisomy 21; do this if you have a positive SIPS)
What are the major adult derivatives of the three primary germ layers?
Endoderm - nervous system (CNS, PNS), epidermis of skin, eye, teeth, etc
Mesoderm - muscles, bones, cartilage, blood cells and vessels, dermis of skin, kidneys, ureters, genital system
Ectoderm - lining of GI tract, liver, pancreas (except islets), lining of respiratory tract, bladder
What types of diagnostic tests are available for examining abnormal fetal development?
Amneocentisis (amniotic fluid to obtain fetal cells for testing), Chorinic villus sampling (placental villi), Fetal blood sample (from umbilical cord or heart, very rare)
