Prenatal Development and Birth Flashcards
(39 cards)
Prenatal development is divided into three main periods, which are…
1) Germinal period
2) Embryonic period
3) Fetal period
The germinal period lasts from __-__ weeks.
0-2 weeks
The embryonic period lasts from __-__ weeks.
3-8 weeks
The fetal period lasts from __ weeks to _____.
9 weeks - birth
About a week after conception, the cell mass, now called a _________, forms two distinct parts – a shell that will become the ________ and a nucleus that will become the _______.
blastocyst
placenta
embryo
___________: the process, beginning about 10 days after conception, in which the developing organism burrows into the placenta that lines the uterus, where it can be nourished and protected as it continues to develop.
Implantation
_______ = the organ that surrounds the developing embryo and fetus, sustaining life via the umbilical cord.
Placenta
Germinal Period
An estimated __% of all zygotes do not grow or implant properly and thus do not survive the germinal period. Many of these organisms are abnormal; few women realize they were pregnant.
60%
Embryonic Period
About __% of all embryos are aborted spontaneously, most often because of chromosomal abnormalities. This is usually called an early miscarriage.
20%
Fetal Period
About __% of all fetuses are aborted spontaneously before viability at 22 weeks or are ‘stillborn,’ defined as born dead after 22 weeks. This is much more common in poor nations.
5%
__________: the outer cells (placenta) attach into the uterus (failing about __% of the time).
Implantation
60%
The start of the third week after conception initiates the embryonic period, during which the formless mass of cells becomes a distinct being – not yet recognizably human but worthy of a new name, _______.
embryo
During the embryonic period…
- Major _____ and _____ develop.
- ______ tube –> central nervous system
- _____ structure (indifferent gonad)
organs & limbs
Neural tube
Unisex structure
The organism is called a _____ from the beginning of the 9th week after conception until birth.
fetus
If the __rd chromosomes are XY, the SRY gene on the Y triggers the development of male sexual organs.
23rd
The X chromosome is bigger and has more genes, but the Y chromosome has a crucial gene, called ___, that directs the embryo to make male hormones and organs.
SRY
During the fetal period…
- ___ organs develop
- _____ development is significant
- Age of variability occurs around __ weeks
Sex organs develop
Brain development
22 weeks
____ __ ______: the age (about 22 weeks after conception) at which a fetus might survive outside the mother’s uterus if specialized medical care is available.
Age of viability
First trimester…
- ________, _______, _____ periods.
- ______ and main ______ develop.
Second trimester…
- increasing maturation (especially of the ____).
- increased _____ differentiation (finger nails, hair, etc.).
- reaching ________ (at 22 weeks).
Third trimester…
- maturation of the neurological, respiratory and cardiovascular systems.
- _____ ______ develops.
- maternal relationship; connections to the outer world.
germinal, embryonic, fetal period
gender, main organs develop
brain
organ
viability
brain cortex
About 38 weeks (266 days) after conception, the fetal brain signals the release of hormones, specifically _______, which prepares the fetus for delivery and starts labor, as well as increases the mother’s urge to nurture the baby.
oxytocin
Stages of Labor…
1) : The _____ dilates to allow passage of the baby’s head.
2) : The baby’s head moves through the ________ of the vagina (the baby’s head “crowns”) and emerges. completely.
2) : Expulsion of the ________.
1) cervix dilates
2) opening
3) expulsion of the placenta
______ _____: A quick assessment of a newborn’s health. The baby’s color, heart rate, reflexes, muscle tone, and respiratory effort are given a score of 0, 1, or 2 twice – at one minute and five minutes after birth – and each time the total of all five scores is compared with the maximum score of 10 (rarely attained).
Apgar scale (appearance, pulse, grimace, activity, and respiration)
Most newborns weigh approximately ___ pounds and score at least __ out of 10 on the Apgar scale.
7.5 pounds
7 out of 10 - Apgar scale
Every week, scientists discover an unexpected ________, which is anything – drugs, viruses, pollutants, malnutrition, stress, and more – that increases the risk of prenatal abnormalities.
teratogen
