Teratogens / Early Fetal Development (HOX, etc.) Flashcards
What 6 drugs are Cat. X?
- Methotrexate
- Warfarin (use heparin)
- Statins
- Isoretinoic acid
- DES
- Thalidomide
Which 3 antibiotic classes are potentially teratogenic?
- Fluoroquinolones (tendon weakness, malformation)
- Aminoglycosides (hearing loss)
- Tetracyclines (discovered teeth)
When is 4 chambered heart seen?
4 weeks
When does fetal movement begin?
8 weeks
Eight, gait
When does ext genitalia resemble the sex of fetus?
10 weeks
TEN, PENis
When do limb buds begin to form?
4 weeks
4 weeks, 4 limbs
What side teratogenic effect do the anti-epilectic drugs carbamazepine and valproic acid have?
Neural tube defects–> if can’t stop the med before pregnancy, begin folate supplements months prior to pregnancy
What abnormality can lithum cause to a fetus?
Ebstein malformation–> a type of cardiac defect
What 2 drugs can increase the risk of spontaneous abortion?
- Isoretinoic acid
2. Warfarin (give heparin to anti-coagulate instead)
What two drugs can cause limb hypoplasia in an infant?
- Cyclophosphamide (alkylating agent)
2. Thalidomide
Mutation in what HOX gene can cause synpolydactyly?
HOXD-13 (extra digits and are fused together)
Which gene is responsible for correct Anterior - posterior (cranial/caudal) organization during development?
Sonic hedgehog gene
*produced at base of limbs in Zone of Polarizing Activity
What gene is responsible for appropriate dorsal/ventral organization of body during development?
Wnt-7 gene
*produced at apical ectodermal ridge (thickened ectoderm at distal end of each developing limb)
What gene is responsible for the elongation of limbs?
FGF gene (stimulates mitosis of underlying mesoderm)
*defects in FGF3 receptor = achondroplasia
What is the function of HOX genes in general?
Involved in segmental organization of embryo in a cranial caudal fashion; mutations may result in appendages in the wrong locations
By what week do all three germ layers exist in the embryo?
Week 3; 3 = trilaminar disc
*gastrulation is the process that forms this trilaminar disc; starts with the epiblast invaginating to form the primitive streak
Wat embyronic structure secretes Hcg?
Syncytiotrophoblast (within week 1)
How do gestational and developmental age differ?
Gestational age is usually about two weeks less than developmental age, because it starts after the last missed period; usually about two weeks after the embryo has begun developing.
