8.4-8.5 Flashcards
A 9-month process transforms a single cell into a complete infant. - During this time, external factors significantly impact the developing baby.
Prenatal Development
- When an egg (ovum) and a sperm unite, they form a zygote.
Fertilization
: The zygote contains 46 chromosomes, which carry genetic information.
Chromosomes
: Through mitotic division, the zygote splits into multiple cells, each retaining the same 46 chromosomes.
Mitosis
Originated from a single fertilized egg (zygote).
Early in the division process, the zygote splits into two separate masses.
Each mass develops into a separate infant.
Identical features and same sex due to possesing the same set of 46 chromosomes.
Monozygotic (Identical) Twins
Accidental timing.
Common in older women and certain ethnic groups.
Results from either releasing more than one egg simultaneously or ovulating again after conception.
If two eggs are fertilized, the woman may giv birth to fraternal twins (two zygotes), triplets, or more.
Increased likelihood in women taking fertility drugs.
Dizygotic (Fraternal) Twins
Multiple pregnancies often lead to premature birth. The more babies a woman carries, the higher the risk of delivering before 37 weeks.
Premature birth:
Babies from multiple pregnancies are at risk of having ___, affecting their overall development.
Low birth weight:
Expectants mothers with multiple pregnancies require more frequent check-ups to monitor signs of early labor or other complications.
Increased doctor visits:
Doctors may recommend ____of some fetuses to improve the chances of survival for the remaining infants.
Selective termination:
The ethical and moral implications of such decisions fall within _____, which explores how advances in biology and medicine should influence policies and practices
Bioethics concerns:
- Sets the stage for a child’s future health and well-being. The entire prenatal period plays an important role in shaping the developing baby.
Prenatal Development
Stages of Prenatal Development
Germinal, Embryonic, Fetal
2-week period
Begins at conception when the sperm fertilizes the egg.
Germinal Period
The fertilized egg, known as a ____, starts dividing and moves down the fallopian tube toward the uterus.
Germinal Period, zygote
The zygote differentiates into two distinctive masses: the outer cells (which become the ___) and the inner cells (forming the ____).
placenta; embryo
The ____, composed of three layers (____), arrives in the uterus and attaches to the uterine wall through a process called ____.
blastocyst, ectoderm, endoderm, and mesoderm, implantation
_____ establishes a connection between the developing organism and the mother’s blood supply via the ____ and ____.
Implantation; placenta; umbilical cord
From approximately the third week until the eighth week of pregnancy.
The neural tube forms, laying the foundation for the nervous system.
The embryo undergoes rapid growth and differentiation.
Critical structures such as the heart, brain, and limbs take shape.
Embryonic Period
As soon as the embryo begins to receive nourishment from the mother through the placenta, it becomes vulnerable to hazards such as diseases, drugs, and toxins. During critical periods, when major organs are forming, these effects become devastating on the development of the infant.
Critical Period
- Birth defect caused by any substance such as drug, chemical, virus, or other factors.
Teratogen
Common tetrogens is alcohol. Consumption of alcohol during pregnancy can lead to pysical, mental, and behavioral problems.
Fetal Alcohol Spectrum Disorders (FASDs) -
Timeline of the critical periods during early development.
2 to 5 weeks - Central Nervous System
2 to 6 weeks - Heart
3 to 8 weeks - Arms and legs
3 to 8 weeks - Eyes
7 to 12 weeks - Teeth and roof of the mouth
From the ninth week until birth
Continued growth and refinement of organs and body systems.
Physical development prepares the fetus for life outside the womb.
The fetus becomes responsive to external stimuli, including sound and touch.
By the end of this period, the fetus is fully formed and ready for delivery.
Fetal Period
By the 38th week, the fetus is considered
full term.
Most babies are born between ___of gestation
38 and 40 weeks
Babies born before 38 weeks are termed ____
These infants may require life support to survive.
Might face long-term issues, especially if their birth weight is less than___
preterm or premature; 5 ½ pounds.
Refers to the point at which an infant can potentially survive outside the womb.
Age of Viability:
It typically falls between ___ of gestation.
Survival odds increase from ___ at 22 weeks to approximately ___ at 26 weeks.
22 and 26 weeks; 10%; 85%
Refers to the unexpected ending of a pregnancy within the first 20 weeks of gestation.
Most miscarriages occur during the first trimester of pregnancy.
Miscarriage; spontaneous abortion
