Chapter 3 Flashcards
Implantation
Occures between 7-9 days. The blastocyst burrows deep into the uterine lining.
Amnion
Membrane that encloses the developing organism in amniotic fluid, which helps keep the temperature of the prenatal world constant and provides a cushion against any jolts caused by the woman’s movement.
Chorion
Surrounds the amnion. From the chorion, tiny fingerlike villi, or blood vessels, emerge.
Placenta
Permits food and oxygen to reach the developing organism and waste products to be carried away by bringing the embryo’s and mother’s blood close together.
Umbilical Cord
First appears as a primitive body stalk and, during the course of pregnancy, grows to a length of 1-3 feet. The umbilical cord contains one large vein that delivers blood loaded with nutrients and two arteries that remove waste products.
Embryo
The period that lasts from implantation through the eighth week of pregnancy. During these brief weeks, the most rapid prenatal changes take place as the groundwork is laid for all body structures and internal organs.
Neural Tube
The ectoderm folds over to form the neural tube, or primitive spinal cord.
First Trimester
Three prenatal periods:
- ) Germinal
- ) Embryo
- ) Fetus
Germinal Period
1-2 weeks
One-celled zygote multiplies and forms a blastocyst.
The blastocyst burrows into the uterine. Structures that feed and protect the developing organism begin to form - amnion, chorion, yolk sac, placenta, and umbilical.
Embryo Period
3-4 & 5-8 weeks.
A primitive brain and spinal cord appear. Hear, muscles, ribs, backbone, and digestive tract begin to develop.
Many external body structures (face, arms, legs, toes, fingers) and internal organs form, and production and migration of neurons in the brain begin. The sense of touch starts to develop, and the embryo can move.
Fetus Period
9-12 weeks.
Longest prenatal period. “Growth and Finishing” phase.
Rapid increase is size begins. Nervous system, organs, and muscles become organized and connected, touch sensitivity extends to most of the body, and new behavioral capacities (kicking, thumb sucking, mouth opening, and rehearsal of breathing) appear. External genitals are well-formed, and the fetus’s sex is evident.
Second Trimester
13-24 weeks.
The fetus continues to enlarge rapidly. In the middle of this period, the mother can feel fetal movements. Vernix and lanugo keep the fetus’s skin from chapping in the amniotic fluid. Most of the brain’s neurons are in place by 24 weeks. Eyes are sensitive to light, and the fetus reacts to sound.
Third Trimester
25-38 weeks.
The fetus has a good chance of survival if born during this time. Size increases. Lungs mature. Rapid brain development, in neural connectivity and organization, enables sensory and behavioral capacities to expand. In the middle of this period, a layer of fat is added under the skin. Antibodies are transmitted from mother to fetus to protect against disease. Most fetuses rotate into an upside-down position in preparation for birth.
Vernix
A white cheeselike substance on the skin that protects from chapping from amniotic fluid.
Lanuago
White, downy hair helping the vernix stick to the skin.
Age of Viability
The point of which the baby can first survive. Occurs sometime between 22-26 weeks.