Appendix 1
The Chronological Development of The Unborn Child


Third Week



The central nervous system appears.
Beginning of 3rd week Sadler, p 411
Embyonic blood vessels begin developing. 3rd week after fertilization Moore, p 76

Blood vessels appear.

3rd week after fetilization Williams, p161
Somites, which will develop into the 33 pairs
of vertebrae in the spinal column, are growing.
3rd week after conception Rugh, p 35
The vascular system appears.
Middle of the 3rd week Sadler, p 208
Blood cells are developing. End of 3rd week after fertilization Moore, p 76
Blood cells and blood vessels are differentiated. End of the 3rd week of development Sadler, p 77
Embryoscopy can directly visualize the embryo/
fetus during the first trimester, paving the way to improved early prenatal diagnosis and treatment. Utilizing high-resolution fiberoptic endoscopy, testing can be done as early as 3 weeks after conception. The face can be visualized as early as 4 weeks. Numerous diagnoses have already been done but these just scratch the surface of the technology's potential.
3rd -4th weeks after conception Reece, pages 775, 777, & 778
Although the embryo begins developing
immediately after conception, the most visible
advances occur during the third to eighth weeks.
3rd - 8th weeks after fertilization Moore, p 2
The most important features of the body's future
form are determined at this time because of the
many organs that are formed during this period.
3rd - 8th weeks Sadler, p 108
Most major organs and organ systems are formed
during the embryonic period. The mother may not
be aware of her pregnancy during this critical
period, especially in the third and fourth weeks
when the embryo is quite vulnerable.
During 3rd - 8th weeks Sadler, p 106 & p 107
The organs and systems of the body are formed. From late in the 3rd week through the
8th week
Larsen, p 319
Blood and blood vessels begin to develop. Days 13-15 after fertilization England, p 110
The embryo begins to form blood cells. Day 17 after conception Rugh, p17
The first blood vessels form Day 18 of development Larsen, p 123
The embryo begins to form a heart Day 18 after conception Rugh, p 17
The nervous system begins to form. Day 18 after conception

Rugh, p 33



The brain's divisions--the forebrain, the midbrain, and the hindbrain--are demarcated. Day 19 Larsen, p 275

The central nervous system begins to form.

Day 19 after fertilization Sadler, front pages
The foundation of the brain, spinal cord and entire nervous system is established. The eyes also begin to be formed. Day 20 after conception Rugh, p 33
The thyroid gland starts to develop. Day 20 after fertilization Moore, p 5
Liver cells begin to draw together. Day 21 after conception Rugh, p 42


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