Introductory Terms in Embryology Flashcards
Perinatal period
22 weeks gestation to 28 days after birth
- second set of 22 weeks
Postnatal period
after birth:
- Neonatal - u to 1 month after birth
- Infancy - first postnatal year
- Childhood, Puberty, Adolescence, Adulthood
Estimated pregnancy length
281 days +/- 13 days
Clinicians: 40 weeks
Gestational Age
- clinical notion
- the age of the conceptus from the presumed fist day of the last menstrual period
- 2 weeks longer than fertilization age
Fertilization age
age of the conceptus from the fertilization day
Estimated day of delivery
- aka expected date of confinement
- aka due date
Naegele’s rule
EDD = LMP - 3 months + 1 year + 1 week
(or less confusingly..)
EDD = LMP + 9 months and a week (MATH!)
Abortion
-expulsion from uterus of conceptus prior to age of viability (~22-23 week gestation) or conceptus weight
Miscarriage
Spontaneous expulsion from uterus of conceptus before mid-pregnancy (about 20 weeks)
- aka spontaneous abortion
- majority are caused by chromosomal abnormalities
Premature birth
Infants born between stage of viability and 37 weeks
- majority caused by maternal complications of the pregnancy
“all or nothing” period
first two weeks
- not susceptible to teratogenesis
- death of embryo and spontaneous abortion common
“critical period”
- embryonic stage (3-8 weeks)
- most vulnerable to teratogenic agents
- major congenital anomalies possible
Primordial Germ Cells (PGCs)
- identified during 4th week in yolk sac
- weeks 4-6 - migrate to future genital ridge (mitosis along the way)
Gonocytes
- new name for PGCs after formation of primitive gonad
- undergo mitotic divisions within gonads
- female = oogonia
- male = spermatogonia
Primitive Gonad
- somatic support cells for gonocytes
- development stimulated by PGCs
- form ovarian follicles in females and Sertoli cells in males
