Reproductive- Embryology Flashcards
(50 cards)
Important genes of embryogenesis
- Sonic hedgehog gene
Produced at base of limbs in zone of polarizing activity. Involved in patterning along anteroposterior axis and CNS development;
mutation can cause holoprosencephaly
Important genes of embryogenesis
- Wnt-7 gene
Produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb).
Necessary for proper organization along dorsal-ventral axis.
Important genes of embryogenesis
- Fibroblast growth factor (FGF) gene
Produced at apical ectodermal ridge.
Stimulates mitosis of underlying mesoderm, providing for lengthening of limbs.
“Look at that Fetus, Growing Fingers.”
Important genes of embryogenesis
- Homeobox (Hox) genes
Involved in segmental organization of embryo in a craniocaudal direction. Code for transcription factors.
Hox mutations appendages in wrong locations.
Early fetal development
- Within week 1
- Within week 2
- Within week 3
hCG secretion begins around the time of implantation of blastocyst
Bilaminar disc (epiblast, hypoblast).
Gastrulation forms trilaminar embryonic disc. Notochord arises from midline mesoderm; overlying ectoderm becomes neural plate.
Early fetal development
- Weeks 3–8 (embryonic period)
Neural tube formed by neuroectoderm and closes by week 4. Organogenesis.
Early fetal development
- Week 4
- Week 6
- Week 8
- Week 10
Heart begins to beat. Upper and lower limb buds begin to form.
Fetal cardiac activity visible by transvaginal ultrasound
Fetal movements start.
Genitalia have male/female characteristics
Mesodermal defects = VACTERL
Vertebral defects Anal atresia Cardiac defects Tracheo-Esophageal fistula Renal defects Limb defects (bone and muscle)
Embryologic derivatives
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Types of errors in morphogenesis
- Agenesis
- Aplasia
- Hypoplasia
- Deformation
Absent organ due to absent primordial tissue.
Absent organ despite presence of primordial tissue
Incomplete organ development; primordial tissue present.
Extrinsic disruption; occurs after embryonic period.
Types of errors in morphogenesis
- Disruption
- Malformation
- Sequence
2° breakdown of previously normal tissue or structure (eg, amniotic band syndrome).
Intrinsic disruption; occurs during embryonic period (weeks 3–8).
Abnormalities result from a single 1° embryologic event (eg, oligohydramnios Potter sequence).
Teratogens
Most susceptible in 3rd–8th weeks of pregnancy.
Before week 3, “all-or-none” effects. After week 8, growth and function affected.
Teratogens medications - ACE inhibitors - Alkylating agents - Aminoglycosides - Folate antagonists (trimethoprim, methotrexate, antiepileptic)
Renal damage
Absence of digits, multiple anomalies
Ototoxicity
Neural tube defects
Teratogens medications
- Antiepileptic drugs
- Diethylstilbestrol
Neural tube defects, cardiac defects, cleft palate, skeletal abnormalities. (valproate, carbamazepine, phenytoin, phenobarbital)
Vaginal clear cell adenocarcinoma, congenital Müllerian anomalies
Teratogens medications
- Isotretinoin
- Lithium
- Methimazole
- Tetracyclines
Multiple severe birth defects (Contraception mandatory)
Ebstein anomaly
Aplasia cutis congenita
Discolored teeth, inhibited bone growth
Teratogens medications
- Thalidomide
- Warfarin
Liimb defects
Bone deformities, fetal hemorrhage, abortion, ophthalmologic abnormalities
Teratogens Substance abuse
- Alcohol
- Cocaine
- Smoking (nicotine, CO)
birth defects and intellectual disability; fetal alcohol syndrome
Low birth weight, preterm birth, IUGR, placental abruption
Low birth weight, preterm labor, placental problems,
IUGR, SIDS, ADHD
Teratogens Others
- Iodine (lack or excess)
- Methylmercury
- Vitamin A excess
- X- rays
Congenital goiter or hypothyroidism (cretinism)
Neurotoxicity
Extremely high risk for spontaneous abortions and birth defects
Microcephaly, intellectual disability
Teratogens Others
- Maternal diabetes
Caudal regression syndrome (anal atresia to sirenomelia), congenital heart defects, neural tube defects, macrosomia, neonatal hypoglycemia, polycythemia
Fetal alcohol syndrome
- Epidemiology
- CLinical manifestations
- Mechanism
Leading cause of intellectual disability in the US.
microcephaly, facial abnormalities, limb dislocation, heart defects. Heart-lung fistulas and holoprosencephaly in most severe form
Mechanism is failure of cell migration.
Neonatal abstinence syndrome
Secondary to maternal opiate use/abuse.
Newborns may present with uncoordinated sucking reflexes, irritability, high-pitched crying, tremors, tachypnea, sneezing, diarrhea, and possibly seizures.
Twinning Monozygotic
- timing of cleavage
(SCAB):
Cleavage 0–4 days: Separate chorion and amnion
Cleavage 4–8 days: shared Chorion
Cleavage 8–12 days: shared Amnion
Cleavage 13+ days: shared Body (conjoined)
Placenta Fetal component
- Cytotrophoblast
- Syncytiotrophoblast
Inner layer of chorionic villi. Cytotrophoblast makes Cells.
Outer layer of chorionic villi; synthesizes and secretes hormones (Lacks MHC-I expression).
Placenta Maternal component
- Desidua basalis
Derived from endometrium. Maternal blood in lacunae.
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