Pregnancy Flashcards
When and where is the usual site of fertilization?
usually occurs in upper ⅓ of oviduct, typically within 24 hours after ovulation (sperm cells can actually survive up to five days in female reproductive tract)
What is a zygote?
fertilized ovum
What do zygotes undergo?
rapid mitotic divisions
- after 3 days, morula (solid ball of cells) is formed
- morula reaches uterus on day 4
- over the next two days, morula develops into blastocyst (hollow ball with inner cavity known as blastocoel) that is ready to be implanted in uterine wall
What is a trophoblast?
outer layer of blastocyst cells responsible for providing nutrients to developing embryo
What is the inner cell mass?
cluster of cells at one end of blastocyst that will form the embryo itself
What does the trophoblast secrete?
- enzymes involved in implantation
- hormone hCG that maintains CL
Why does trophoblast secrete enzymes?
enzymes digest proteins on uterine lining – which carves hole in endometrium for implantation
Why does trophoblast secrete human chorionic gonadotropin (hCG)?
absolutely essential for success of pregnancy as it maintains functional CL in ovary until placenta takes over steroid hormone production at end of first trimester
What do pregnancy tests detect?
presence of hCG in urine
What does high concentration of progesterone produced by CL do?
prevents myometrial (uterine muscle) contractions that would expel the newly implanted blastocyst
What does high concentration of estrogen produced by CL do?
maintains functional uterine lining, which is critically important for successful implantation
How is trophoblast involved with placenta?
trophoblast constitutes fetal part in developing placenta
What does placenta allow?
exchange of nutrients and metabolic wastes between maternal and fetal blood
What is the placenta formed by?
interlocking maternal and fetal structures
What are the fetal structures involved in forming placenta?
- placental villi
- finger-like projections that protrude into pools of maternal blood within intervillus spaces that are supplied by maternal arterioles
How does fetal blood continuously flow between placental villi and fetal circulation?
by means of umbilical artery and vein found within umbilical cord
What occurs as maternal blood percolates through intervillus spaces?
it exchanges oxygen, nutrients and fetal metabolic wastes with fetal blood in villi, and then exits through uterine vein
What are hormones secreted by the placenta important for?
maintenance of pregnancy
What are the hormones secreted by placenta? (5)
- hCG
- E
- P
- human placental lactogen (hPL)
- relaxin
What does hCG do?
maintains CL of pregnancy until end of first trimester
What does estrogen (E) do?
stimulates growth of myometrium, strengthening it for parturition
What does progesterone (P) do?
suppresses uterine contractions
What does human placental lactogen (hPL) do?
affects maternal metabolism to make more glucose and fatty acids available for fetus
Which hormones are involved in maturation of mammary glands?
E, P, and hPL
What does relaxin do?
softens cervix and loosens pubic symphysis between pelvic bones in preparation for parturition
Hormones of Pregnancy: Brief Review
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Maternal-Placental-Fetal Unit
REVIEW LECTURE VIDEO
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