Embryology 2 - Fertilization to Implantation Flashcards
Our body froms from cells found in the ___.
Blastocyst
What are the Main Events during Preimplantation (3)?
- Mitosis to increase cell number
- Blastocyst morphogenesis
- Blastocyst hatching
Blastocyst consists what two cell types?
- Trophectoderm (TE)
- epitheliumof blastocyst
- Inner Cell Mass
- pluripotent
What does Totipotent mean?
Capable of producing all cell types (i.e. embryonic and extraembryonic)
What does Pluripotent mean?
Capable of producing cell types only of the body
What does Differentiated mean?
Mature cell type in adult body
What is Molar Pregnancy?
- Blastocyst is made up of only trophectoderm and is missing the ICM
- TE forms chorionic villi continuously, resulting in hyatidiform mole or molar tissue, which becomes cystic
What are some symptoms of Molar Pregnancy (6)?
- No fetus detected by ultrasound
- Abnormally high hCG level in blood test
- Enlarged uterus
- Vaginal bleeding
- Hypertension
- Edema
What are the Pluripotency Genes in ICM?
- Oct4 (Pou5f1)
- Nanog
- Sox2
What is Aneuploidy?
Abnormal number of chromosomes
Percentage of pregnancies that end in miscarriage before the 20th week?
50
Aneuploidy is caused by ___.
Meiotic nondisjunction
What is Meiotic Nondisjunction?
the unequal allocation of chromosomes in egg or sperm
What is the main risk factor for meiotic nondisjunction?
- Advanced Maternal Age
- oocytes arrest in prophase (before 1st meiotic division) in the fetus
- stage of arrest might not be ideal to protect oocyte from environmental insult
- meiosis resumes at puberty, just before ovulation and completes at fertilization
- oocytes arrested for 40 years might be prone to damage that interferes with meiosis
What syndrome is caused by Trisomy 21 and what are some of its symptoms?
Down Syndrome
- Mental retardation
- Flat faces
- Slanting Eyes
- Small ears
- Growth retardation
- Heart defects
- 1:2,000 women <25 years old
- 1:100 in women >40 years old
What is the syndrome caused by Trisomy 18 and what are some of its symptoms?
Edwards Syndrome
- Mental retardation
- Skeletal defects
- Small jaw
- Low set ears
- Heart defects
- Kidney defects
What is the syndrome caused by Trisomy 13 and what are some of its symptoms?
Patau Syndrome
- Mental retardation
- Holoprosencephaly
- Eye defects
- Cleft lip & palate
- Heart defects
- Extra digits
What is Turner Syndrome and what are some of its symptoms?
XO or X monosomy
- Female appearance
- No ovaries,
- Short stature
- Webbed neck
- Braod chest
- Skeletal deformities
What is Klinefelter Syndrome and what are some of its symptoms?
XXY
- Tall and slim
- Enlarged breasts
- Broad pelvis
- Less body hair
- Infertile
- Testicular atrophy
- Learning difficulties
What are some Female Factors Contributing to Infertility (3)?
- Most common are problems with ovulation, advanced age, or blocked tubes
What are some Male Factors Contributing to Infertility (3)?
- Most common are low sperm count, low sperm motility, abnormal morphology
What is Preimplantation Genetic Diagnosis (PGD)?
- Used to select the embryos with normal chromosome or genetic make-up for transfer to the uterus
What are the Pituitary Hormones (Names and Function)?
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
Follicle maturation and ovulation
Hormone production by follicles
What are the Ovarian Hormones (Names and Function)?
- Estrogen
- Progesterone
Regulate endometrial cycle
When fertilization does not occur, what happens?
- Egg is released but sperm is absent
- Endometrial lining degenerates
What are the Hormones Involved in Maintenance of Endometrial Lining in Pregnancy?
What is the Alteration of Hormones by Abortion Pill RU-486?
- Causes endometrial degeneration by binding to progesterone receptor and preventing progesterone action
What is the Alteration of Hormones by Birth Control Pills?
Contain progesterone and estrogen, which inhibit ovulation by preventing FSH and LH release
What is the Alteration of Hormones by the “Morning After Pill”?
Contains higher dose of birth control pill, delays ovulation and prevents sperm from reaching egg (which takes 5-6 days)
At implantation, trophectoderm differentiates what two types of cells?
- Cytotrophoblast
- Syncytiotrophoblast
What are Syncytiotrophoblasts and what do they do?
Invasive cells that migrate into endometrium and pull blastocyst in
- produce hCG
- engulf maternal blood vessels to establish uteroplacental circulation
What is Placenta previa?
premature placenta detachment and hemorrhaging
What is the normal implantation site?
Anterior or Posterior wall of the uterus
What are some Possible Causes of Ectopic Pregnancy (3)?
- Scarring from pelvic inflammatory disease
- Endometriosis
- Prior surgery
What are some Symptoms of Ectopic Pregnancy (4)?
- overdue menstruation
- vaginal bleeding
- lower abdominal pain one side
- low hCG level in blood test
What does the Chorionic Villus do?
site of maternal-fetal exchange
When does the Primary stem villus develop?
- Develops day 11-13
When does the secondary stem villus develop?
- Develops day 16
- Trophoblast layers grow and enclose lacunae (space filled with maternal blood)
When and how does the tertiary stem villus develop?
- Develops day 21
- Villus forms barrier between maternal and fetal blood flow
- Fetal blood vessesl form from mesoderm core of villus
What is the Function of the Placenta?
Does job of the lung (gas exchange) and kidney (waste removal)
What are some Substances that Pass from Fetus to Mother through Chorionic Villi (7)?
- CO2
- Water, electrolytes
- Urea, uric acid
- Creatine
- Bilirubin
- Hormones
- Red blood cell antigens
What are some Substances that can pass from mother to fetus through Chorionic Villi (9)?
- O2
- Water, electrolytes
- Nutrients (carbohydrates, amino acids, lipids)
- Hormones
- Antibodies
- Vitamins
- Iron, trace elements
- Drugs
- Toxic substances (alcohol, some viruses)
What is Erythroblastosis fetalis?
- Condition caused by maternal antibodies passing to the fetus via the placenta
What happens after separation of Embryo from Uterine Wall?
Chorioamnionic membrane will form around the developing body
What is the Function of the Amnionic Sac?
Provides space for fetus to grow in
What is the Function of Amniotic Fluid?
Suspends fetus in sac and also acts as shock absorbant
What is the Definition of Ultrasonography and how is it used in pregnancy?
- High frequency waves applied to abdominopelivc area and reflected from tissues to create images
- Used to monitor growth parameters of embryo/fetus and to manage high risk pregnancies
What is Maternal Serum Screening?
- Blood test to analyze serum for biochemical markers
- Low AFP level: chromosome aneuploidy
- High AFP level: body abnormality
What is Cell-free fetal DNA (cffDNA) analysis?
DNA fragments from trophoblasts analyzed for blood type, specific genetic disorders, and aneuploidy
What is Amniocentesis and when can it be performed?
Amniotic fluid contains biochemical markers and fetal cells for genetic or chromosome analysis
Done when fetus reaches 14 weeks
What is Chorionic Villus Sampling and when can it be performed?
Villus sample contains lots of cells used for immediate genetic analysis
Can be done earlir than amniocentesis (at 7 weeks)
