Section 2 — Pregnancy Hormones, Placentation & Early Circulation

hCG

Human chorionic gonadotropin

What 2 secretes human chorionic gonadotropin (hCG) and what does it do

Secreted by trophoblasts cells (of the blastocysts), later chorion (very little - hCG levels declines a lot)

It prompts corpus luteum to continue secretion of estrogen and progesterone

When does human chorionic gonadotropic rise until / when does it start to decline

it rises until end of 2nd month → declines when placenta begins to secrete progesterone and estrogen

Why does human chorionic gonadotropin (hCG) begin to decline at month 2

because the placenta takes over secreting estrogen and progesterone so we don’t need the corpus luteum to do that anymore

which hormone is detected in pregnancy tests

hCG - human chorionic gonadotropin

Placentation

formation of placenta from embyronic tissue and maternal tissue

What is the embyronic tissue used during placentation

chorion (formed from inner cell mass of blastocyst)

What is the maternal tissue used during placentation

decidua basalis

Mother and baby blood supply

They are close but don’t intermix → placenta forms barrier in between → allows for exchange between the two

how does circulation develop

yolk sac → produces first blood cells

By end of third week → system of paired vessels → can hear heartbeat of baby

what are the two Unique vascular modifications and what do they do

umbilical arteries → carry deoxygenated blood → fetus to placenta

umbilical veins → carry oxygenated blood → placenta to fetus

Teratogens

Harmful substances that can cross placental barriers and enter fetal blood → congenital abnormalities (appeart from birth) or death

alcohol, nicotine, medication (sedatives)

Thalidomide

Sedative medication for morning sicknes → teratogenW

What happens if two sperms penetrate one egg

zygote would be nonfunctional