BIO380H5 Lecture 31: Lecture 31
Document Summary
After the eighth week, the embryonic period is over and the fetal period begins. Some of the functions of the organs are still developing. The respiratory system in the fetus doesn"t have the same function post-birth. The alveoli must be prepared to open once air is introduced into the lung. The fetus swallows the amniotic cavity but never inhales it. Via ultra sound, you can detect some breathing movement by the 10th week, but the fetus is not breathing just contracting its muscles. It is a thin layer of substance that lines the surface of the alveoli. It is important to keep the alveoli open. Babies born before the 26th week of development may not survive due to the underdevelopment of the lungs since the capillaries are not in contact with the alveoli yet, and there is a lack of pulmonary surfactant. The production of surfactant is under the effect of the thyroid hormone and the glucocorticoids.
