|
Third Week
|
Timing
|
Source |
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 |
