Reproduction and development Part 8 Flashcards
When does the embryo obtain nutrients directly from the endometrium
during its first 2-4 weeks
outer layer of the blastocyst is called the
trophoblast
Trophoblast mingles with the endometrium and eventually forms the
placenta
Exchange between maternal and embryonic circulatory systems
- supplies nutrients and immune protection
-exchanges respiratory gases - disposes of metabolic wastes of the embryo
The first trimester is the main period of
organogenesis.
- during this stage the embryo is very susceptible to damage
At 8 weeks, all the major structures of the adult are present in rudimentary form, and the embryo is called
fetus
When does the heart begin to beat? When can it be detected?
Begins at 4 weeks
detected at 8 weeks
What happens during the second trimester
The fetus growsto about 30cm in length and is very active
How early can a mother feel fetal movements
as early as one month into the second trimester
What happens during the third trimester
the fetus grows to about 3-4 kb in weight and 50 cm in length
What can decrease fetal activity
It may decrease as the fetus fills the available space
Childbirth begins with labor
a series of strong rythmic contraction that push the fetus and placenta out of the body
when labor begins
local regulators, prostaglandins, and hormones induce and regulate further contractions of the uterus
In response to suckling by the infant, and changes in estradiol levels
the hypothalamus signals the anterior pituitary to secrete prolactin
Prolactin stimulates the mammary glands to
produce milk
