The journey from conception to birth spans approximately 38 weeks. A single fertilized egg transforms into a fully formed infant through three distinct trimesters, each marked by precise developmental milestones.
In the first two weeks, the fertilized egg implants in the uterine wall and cells begin dividing rapidly. The heart starts beating by week 4. Limb buds appear by week 6. At week 8, all major organ systems have begun forming and the embryo measures about 1.6 cm. By week 12, the fetus is roughly 6 cm long and weighs about 14 grams. Fingers and toes are fully formed and facial features become visible.
Growth accelerates during the second trimester. By week 16, the fetus makes sucking and swallowing motions. At week 20, many pregnant individuals feel fetal movement for the first time. The fetus measures about 25 cm and weighs approximately 300 grams at this point. By week 24, weight reaches about 600 grams and length reaches 30 cm. Lung tissue develops during this period, but the lungs are not yet ready for independent breathing.
The third trimester centers on rapid weight gain and organ maturation. By week 28, survival outside the womb is possible with intensive medical support. At week 32, the fetus weighs about 1.7 kg. By week 36, most organ systems are fully mature. A full-term birth at weeks 38 to 40 typically produces a baby weighing between 3 and 4 kg.
Alcohol is a teratogen, a substance that causes birth defects. It crosses the placental barrier and exposes the fetus to the same blood alcohol level as the mother. Alcohol exposure during any trimester can cause Fetal Alcohol Spectrum Disorders (FASDs). The most severe form is Fetal Alcohol Syndrome (FAS), which causes lasting physical and cognitive impairments including facial abnormalities, growth deficiencies, and learning disabilities. No amount of alcohol is considered safe during pregnancy. The worksheet also addresses tobacco and certain medications as additional teratogens with measurable effects on fetal growth and birth weight.
| Question | Answer |
|---|---|
| Form Name | Development Of A Human Fetus Form |
| Form Length | 12 pages |
| Fillable? | No |
| Fillable fields | 0 |
| Avg. time to fill out | 3 min |
| Other names | development of a human fetus lab answer key, development of a human fetus lab answer key pdf, lab development of a human fetus answer key, human fetal growth lab answers |