Chapter 3 Flashcards
The Germinal Period
period of prenatal development that takes place in the first 2 weeks after conception
-creation of the fertilized egg followed by cell division and attachment of the zygote to the uterine wall
Blastocyst
inner mass of cells that will eventually develop into the embryo
Trophoblast
outer layer of cells that will later provide nutrition and support
Implantation
the attachment of the zygote to the uterine wall
- takes place 11 to 15 days after conception
The embryonic period
the period of prenatal development that occurs from 2 to 8 weeks after conception
-the rate of cell differentiation intensifies, support systems for cells form and organs appear
Endoderm
inner layer of cells in an embryo
-will develop into the digestive and respiratory systems
Mesoderm
the middle layer of cells in an embryo
-will become the circulatory system, bones, muscles, excretory system and reproductive system
Ectoderm
the outermost layer of cells in an embryo
-will become the nervous system and brain, sensory receptors and skin parts
Amnion
a bag like structure containing a clear fluid in which the developing embryo floats
Organogenesis
the process of organ formation during the first two months of prenatal development
When does the neural tube become the spinal cord
3 weeks after conception
When do the eyes begin to appear in a developing embryo
21 days
When do the cells of the heart begin to differentiate
24 days
What occurs during the 4th week of developmet
-urogenital system becomes apparent
-arm and leg buds emerge
-heart takes shape and blood vessels appear
What occurs form the 5th to 8th week of development
-arms and legs differentiate further
-face starts to form
-intestinal tract develops
The fetal period
lasting about 7 months
-growth and development continue during this time
3 months after conception
-fetus becomes active: moving arms and legs, opening and closing mouth, moving head
-Facial features and limbs are distinguishable
4 months after conception
-growth spurt occurs in the body’s lower parts
-mother can feel arm and leg movements
5th month after conception
-Skin has formed - toenails and fingernails
-fetus shows preference for position in womb
6th month
-eyes and eyelids completely formed
-fine layer of hair covers head
-grasping reflex present
-irregular breathing movements occur
-becomes viable
Last 2 months of pregnancy
-fatty tissues develop
-various organ systems are functioning fully
-fetus grows longer and gains substantial weight
anencephaly
-highest regions of the brain fail to develop
-head end of the neural tube fails to close
Neurogenesis
the generation of new neurons
-takes place in 5th prenatal week and continues throughout the remainder of the prenatal period
Neuronal migration
-celling moving outward from their point of origin to their appropriate locations and creating different levels, sturctures and regions of the brain
-occurs 6 to 24 weeks
