Chapter 3 - Prenatal Development Flashcards
3 phases of pregnancy:
1) Germinal period
2) Period of the embryo
3) Period of the fetus
Stages within the germinal period
- implantation
- growth of placenta/umbilical cord
Blastocyst
A hollow, fluid-filled ball formed by cell duplication by the zygote.
Embryonic disc
The inside of the blastocyst, who’s cells will become the new organism - the baby
Trophoblast
Cells on the outside of the blastocyst, which will become the protective covering structures and provide nourishment to the baby
Implantation
occurs between the 7th and 9th days following conception, when the blastocyst burrows deep into the uterine lining. Begins to grow quickly now, with the trophoblast growing fastest. This process takes place over the course of 2 weeks.
Amnion
The trophoblast grows into the amnion, a membrane that keeps the growing organism safe inside its amniotic fluid.
Amniotic fluid
helps keep the temperature of the prenatal world constant and provides a cushion against any jolts caused by the woman’s movement. A yolk sac grows that produces blood cells until the baby’s liver, spleen, and bone marrow are mature enough to do this on their own.
Chorion
Formed by cells of the trophoblast, a protective membrane that surrounds the amnion. Blood vessels emerge from this and burrow into the uterine wall, while the placenta develops.
Placenta
Membrane that brings the mother’s blood and child’s blood together without mixing directly, allowing oxygen and food to reach the child while waste to be carried away.
Umbilical cord
Grows up to a length of 3 feet, and connects the baby to the placenta. contains one large vein that delivers blood and nutrients to the baby, as well as removing waste.
Period of the embryo
Lasts from implantation through the 8th week of pregnancy.
Neural tube
spinal cord, created by the folding over of the ectoderm.
Period of the fetus
From the 9th week through the end of the pregnancy. The period of “growth and finishing”.
Vernix
A white, cheese-like substance that protects the baby’s skin from chapping during the long months spent bathing in amniotic fluid.
Lanugo
White, downy hair that covers the baby’s body in utero, helping the vernix to stick to the skin.
Age of viability
Occurs sometime between 22 and 26 weeks, marking the period of time when the baby can first survive with help outside the womb.
Teratogen
Refers to any environmental agent that causes damage during the prenatal period. influenced by:
- dose (larger doses over longer time are worse)
- heredity (genetic makeup of mom/baby)
- Negative influences (additional teratogens, poor nutrition, etc.)
- Age (teratogen exposure during the sensitive period could be more harmful than exposure later in the pregnancy)
Fetal Alcohol Spectrum Disorder (FASD)
A term that encompasses a range of physical, mental, and behavioral outcomes caused by prenatal alcohol exposure. Children are given one of three diagnosis, which vary in severity:
- Fetal Alcohol Syndrome (FAS)
- Partial Fetal Alcohol Syndrome (p-FAS)
- Alcohol-related Neurodevelopmental Disorder (ARND)
Fetal Alcohol Syndrome (FAS)
Distinguished by:
a) slow physical growth
b) a pattern of three facial abnormalities
- short eyelid openings
- a thin upper lip
- a smooth or flattened philtrum/ indentation running from the bottom of the nose to the center of the upper lip
c) brain injury, evident in a small head and impairment in at least three areas of functioning, i.e., memory, language and communication, attention span and overactivity, motor coordination, planning and reasoning, and/or social skills. Other physical defects may also be present.
Partial Fetal Alcohol Syndrome (p-FAS)
Characterized by
a) two of the three facial abnormalities mentioned with FAS, and
b) brain injury, again evident in at least three areas of impaired functioning. Mothers of children with p-FAS generally drank alcohol in smaller quantities, and children’s defects vary with the timing and length of alcohol exposure.
Alcohol-related Neurodevelopmental Disorder (ARND)
Characterized by at least three areas of mental functioning are impaired, despite the presence of typical physical growth and the absence of facial abnormalities.
Examples of teratogens
- Prescription and nonprescription drugs
- Illegal drugs
- Tobacco
- Alcohol
- Radiation
- Environmental pollution
- Infectious disease (viruses, bacterial/parasitic infections)
Effects on pregnancy, non teratogen-related
- exercise: presence or absence
- nutrition: good or poor
- emotional stress: presence, absence, and poor or healthy management of said stress
- Rh factor incompatibility
- maternal age and previous births
Rh factor incompatibility
When the mother is Rh-negative (lacks the Rh blood protein) and the father is Rh-positive (has the protein), the baby may inherit the father’s Rh-positive blood type. Even if a little of a fetus’s Rh-positive blood crosses the placenta into the Rh-negative mother’s bloodstream, she begins to form antibodies to the foreign Rh protein. If these enter the fetus’s system, they destroy red blood cells, reducing the oxygen supply to organs and tissues; Intellectual disability, miscarriage, heart damage, and infant death occur.
Why does maternal stress affect the baby…?
When we experience fear and anxiety, stimulant hormones release into our bloodstream, such as epinephrine (adrenaline) and cortisol, known as “fight or flight” hormones, causing us to be poised for action. Large amounts of blood are sent to parts of the body involved in the defensive response - the brain, the heart, and muscles of the arms, legs, and trunk. Blood flow to other organs, including the uterus, is reduced. As a result, the baby is deprived of a full supply of oxygen and nutrients.
