Chapter 3

Question 0

Monozygotic vs Dizygotic

Answer 0

Mono: identical
Di: faternal

Question 1

Stages of prenatal development

Answer 1

Unequal in length: geminal, embryotic, and fetal periods

Question 2

Germinal period

Answer 2

the period of prenatal development that takes place in the first two weeks after conception. It includes the creation of the zygote continued cell division, and the attachment of the zygote to the uterine wall

Question 3

Ectopic pregnancies

Answer 3

the presence of a developing embryo or fetus outside the normal location in the uterus, most commonly in a fallopian tube

Question 4

The embryonic period

Answer 4

The period of prenatal development that occurs two to eight weeks after conception (most important period)
During the embryonic period, the rate of cell differentiation intensifies, support systems for the cells form, and organs appear.
This stage is the most critical time in prenatal development because it is the time the environmental change is most likely to occur.
Endoderm-the inner layer of cells, which develops into digestive and respiratory systems
Mesoderm-the middle of cells, which becomes the circulatory system, bones, muscles, excretory system, and reproductive system
Ectoderm-the outermost layer of cells, which becomes the nervous system and brain, sensory receptors and skin parts

Question 5

Embryo’s life support system

Answer 5

Amnion: the life support system that is a thin bag or envelope that contains a clear fluid in which the developing embryo floats.
Umbilical cord: contains two arteries and one vein, and connects the baby to the placenta
Placenta: a disk-shaped group of tissues in which small blood vessels from the mother and the offspring intertwine but do not join

Question 6

Brain development

Answer 6

At birth 100 billion neurons
Neural tube: first 18-24 days after conception, develops out of the ectoderm
Dendrites: received signals
Axon: send out signals
(Two birth defects from failure of the neural tube to close: anencephaly and spina bifida)
Neurogenesis: at about the fifth month a new generation of neurons
Neural migration: involves cells moving outward from their point of origin to their appropriate locations and creating the different levels, structures, and regions of the brain

Question 7

Teratogen

Answer 7

any agent that can potentially cause a physical birth defect. They include drugs, incompatible blood types, environmental pollutants, infectious diseases, nutritional deficiencies, maternal stress, advanced maternal and paternal age, and environmental pollutants