Development, Heredity and Aging

Hormone changes during Pregnancy

1. First Trimester- Human chorionic gonadotropin (hCG) increases until it reaches a maximum concentration near the end of the first 3 months of pregnancy and then decreases to a low level thereafter.
2. Second Trimester- Progesterone continues to increase until it levels off near the end of pregnancy. Early in pregnancy, progesterone is produced by the corpus luteum in the ovary; by the second trimester, production shifts to the placenta.
3. Third Trimester- Estrogen increases slowly throughout pregnancy but increases more rapidly as the end of pregnancy approaches.  Early in pregnancy, estrogen is produced only in the ovary; by the second trimester, production shifts to the placenta.

Formation of Neural Tube

Development of the Face

Development of the Face:

1. 28 days after fertilization. The  face develops from five processes: frontonasal, two maxillary, and two mandibular
2. 33 days after fertilization. Nasal placodes, areas of thickening, appear in the frontonasal process.
3. 40 days after fertilization. Maxillary processes extend toward midline. The nasal placodes also move toward the midline and fuse with the maxillary processes to form the jaw and lip.
4. 48 days after fertilization. Continued growth brings structures more toward the midline.
5. 14 weeks after fertilization. Contributions of each process to the adult face.

Parturition