Flashcards in Repro - Embryology (Embryogenesis) Deck (23)
Name 4 important genes of embryogenesis.
(1) Sonic hedgehog gene (2) Wnt-7 gene (3) FGF gene (4) Homebox (Hox) genes
Where is sonic hedgehog gene produced?
Produced at base of limbs in zone of polarizing activity
In what 2 processes is sonic hedgehog gene involved?
(1) Involved in patterning along anterior-posterior axis. (2) Involved in CNS development; mutation can cause holoprosencephaly
What condition can a mutation in sonic hedgehog gene caused, and why?
Involved in CNS development; mutation can cause holoprosencephaly
Where is Wnt-7 gene produced?
Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb).
For what is Wnt-7 necessary?
Necessary for proper organization along dorsal-ventral axis.
Where is FGF gene produced?
Produced at apical ectodermal ridge.
What function does FGF gene serve?
Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.
In what process is homeobox (hox) genes involved?
Involved in segmental organization of embryo in a craniocaudal direction.
What effect do hox mutations have?
Hox mutations --> appendages in wrong location.
What events occur at day 0 of early fetal development?
Fertilization by sperm, forming zygote, initiating embryogenesis
What event occurs within week 1 of early fetal development?
hCG secretion begins around the time of implantation of blastocyst
What events occur within week 2 of early fetal development?
Bilaminar disc (epiblast, hypoblast); Think: "2 weeks = 2 layers"
What are the names of the layers in the bilaminar disc?
What events occur within week 3 of early fetal development?
Trilaminar disc (Think: "3 weeks = 3 layers"); Gastrulation. Primitive streak, notochord, mesoderm, and its organization, and neural plate begin to form.
What events occur weeks 3-8 of early fetal development? What is this time frame called?
Neural tube formed by neuroectoderm and closes by week 4. Organogenesis. Extremely susceptible to teratogens; Embryonic period
What events occur at week 4 of early fetal development?
Heart begins to beat. Upper lower limb buds begin to form; Think: "4 weeks = 4 limbs"
What events occur at week 6 of early fetal development?
Fetal cardiac activity visible by transvaginal ultrasound.
What events occur at week 10 of early fetal development?
Genitalia have male/female characteristics.
What time frame is extremely susceptible to teratogens during early fetal development?
Weeks 3-8 (Embryonic period)
What forms neural tube? By what week in fetal development is the neural tube closed?
Neural tube formed by neuroectoderm and closes by week 4.
What is gastrulation? What does it establish?
Process that forms the trilaminar embryonic disc. Establishes the ectoderm, mesoderm, and endoderm germ layers.