Final answer:
The development of a calf fetus during gestation involves the growth from a zygote to a fetus, organ and structure development, and rapid growth in the third trimester with critical development in the brain, liver, and ossification process.
Step-by-step explanation:
Fetal Development During Gestation
The development of a calf fetus during gestation is a complex process that starts with a zygote and progresses through the embryonic stage to form a fully developed fetus. During the first trimester, major organs begin to form, the backbone, muscles, and bone tissue start to develop, and the fetus will be able to move its small limbs. By the end of the second trimester, the fetus grows to about 30 cm (12 inches) and becomes active, with the mother typically feeling movements. The placenta now fully takes over nutrition and waste management and hormone production. In the third trimester, rapid growth occurs, and the fetus reaches 3 to 4 kg (6½ -8½ lbs.) and 50 cm (19-20 inches) in length. Organ development continues up to and after birth, with significant growth of the nervous system and liver.
Key Developments:
- The brain continues to expand.
- The ossification process replaces cartilage with bone.
- The liver begins to secrete bile, and bone marrow starts erythrocyte production.
- The development of the amniotic sac and umbilical cord.
- Rapid growth and development of organs in the last trimester.