Embryology Flashcards
Which period during embryogenesis is where the most congenital defects can occur?
Embryonic period; weeks 2-8
What occurs during the pre-embryonic period?
(first 2 weeks) Zygote becomes multicellular and turns into the morula
What stages occur during the embryonic period?
Cleavage (morula) Gastrulation (3 germ layers) Organogenesis (organ formation)
What are the 8 possible teratogens that can produce development malformations?
Temperature extremes Mechanical forces Recreational drugs Dietary supplements/Prescription drugs Radiation Maternal malnutrition/diseases Environmental toxins Prenatal infections
What are the 4 variations in teratogen responsiveness?
- Timing of exposure (remember critical period = organogenesis) 2. Genetic variation; i.e. mom’s ability to metabolize 3. Method/Concentration of teratogen 4. Synergistic interactions; i.e. health medication (i.e. hypertension)
At what stages during the cell cycle can non-disjunction occur?
A) Meiosis I where they are homologous chromosomes resulting in all abnormal daughter cells B) Meiosis II where they are sister chromatids resulting in one daughter cell that has normal chromosome #
What is cleavage?
Zygote division and blastocyst formation (zygote -> 2-cell stage -> 4-cell stage -> 8-cell stage –> morula)
What does the trophoblast differentiate into during implantation?
Cytotrophoblast (lines blastocyst) and Syncytiotrophoblast (outer; lines/invades uterine wall)
What does the embryoblast differentiate into during implantation?
Epiblast (contains amniotic sac cavity) and Hypoblast (contains yolk sac cavity)
What is the inner and outer cell mass also known as?
Inner = embryoblast Outer = trophoblast
What major events occur during the embryonic period? (5)
- All major body systems develop
- 2D disk to 3D cylinder
- Folding of the embryo
- Craniocaudal folding - CNS
- Lateral folding - amnion/body wall
What are the 3 main functions of the notochord?
- Structure: rigid axis around which the embryo develops.
- Skeletal: foundation upoin which the vertebral column (vertebral bodies) will form.
- Induction: brings about the formation of the neural tube (future nervous system)
What are the locations the placenta can be in? (3 normal)
- Anterior 2. Posterior 3. Fundal
Where is the extraembryonic mesoderm (XE) layer derived from?
Epiblast and yolk sac
What events occur during embryogenesis?
Oogenesis and Spermatogenesis via Meiosis
What is organogenesis?
The differentiation of the 3 germ layers
Amniotic cavity functions (6)
- Allows symmetrical external growth
- Allows fetus to move freely
- Barrier to infection
- Normal fetal lung development
- Prevents adherence of amnion to embryo/fetus
- Helps maintain homeostatsis
Partial and total placenta previa
Implantation over the cervical os (opening)
Placenta accreta and 2 types
Trophoblastic invasion where placental roots grow deeply into uterine muscular wall.
- Placenta increta - invades muscular tissue
- Placenta percerta - invades other organs, i.e. bladder
Placental Calcification
Placental aging (precipitation of Ca2+ hydroxyapatite)
RF = smoking
Can occur if one has a post-date delivery (after 38 weeks)
Lithopedion
Stone baby - too large of a fetus that the body cannot reabsorb
Oligohydramnios
Low amniotic fluid
- Can result in renal agenesis (1/both kidney malformation) and obstructive uropathy
- Pulmonary hypoplasia and limb defects