Biology 156: Fetal Development Online Lab Unit 4

Fetal Development

There are many important developments from the time fertilization occurs to the time a baby is born. I am going to pick 10 events that I think are significant in this process.

Fertilization- This is when the sperm penetrates the egg and is the creation of a zygote. The whole process takes around 24 hours and occurs 1 day post ovulation.
Implantation-Trophoblast cells continue to engulf and destroy cells of the uterine lining stimulating new capillaries to grow and beginning the growth of the placenta. This is very important because this is where the fetus will live for the rest of the pregnancy. Implantation starts around day 5 and continues up to day 12
Embryonic period ends- By this time eyes, ears, and limbs are well formed. The embryo no longer has a tail, and intestines are starting to move into the body cavity. This event is important because now the first trimester is over. Major physiological changes have taken place and brain waves can be identified. This period ends at 56-60 days
Brain Structure in Place- Now things are really beginning to come together, vocal cords allow the fetus to make sounds, and sockets for teeth are forming along with hair follicles. Intestines have reached the abdominal cavity and start to practice contraction while the liver forms bile, and pancreas produces insulin. Genetalia are starting to form and the fetus is capable of reflexes. This is important because the different body systems are starting to function and practice for the real world. These events happen at 10 weeks after fertilization.
Baby Movement- The heartbeat can be heard clearly with external instruments. Sex organs are clearly distinguishable and the fetus is becoming more flexible with movements of head , mouth, lips, arms, wrist, hands, legs, and toes. This stage is important because it is becoming easier to monitor the progress of the baby and also all of the body systems are starting to work together. This happens at 12 weeks
Hearing Possible- bones of the ear harden and the fetus can hear sounds like mom breathing, heartbeat, and digestion. This is important because in this way the fetus is starting to interact with the outside. This happens at 22 weeks
Lungs Can Breathe Air- Lungs produce surfactant and are capable of breathing air. This is extremely important because it means the fetus is getting closer and closer to being able to survive on its own. This happens at 26 weeks
Brain Surface Convolutions Begin- Rythmic breathing and temperature is controlled entirly by the brain. Also red blood cell production has been taken over by red bone marrow. The baby is becoming more and more developed and its cellular functions are starting to work properly on their own. This happens at 28 weeks
Immune System develops- The fetus starts to develop its own immune system, and has sleeping cycles. Fetus can now scratch itself. This is important to have a functioning immune system for when the baby is born. This development starts at 32 weeks
Full term- All systems are complete and functioning. Baby now has 300 bones that will later fuse and turn into 206. There are 70 different reflex behaviors the nervous system can display that are unlearned and necessary for survival. The abdomin is plump with the liver producing red blood cells. The skull is composed of fontanels to ease with birth and the baby should have rotated with head down towards the cervix. The baby is ready to be born. 40 weeks