2. Explain How The Increased Rate Of Atelectasis

When the baby is born its circulation needs to be changed because now the baby must breathe by own using its lungs. Increased level of pO2 causes spasm of the umbilical arteries and, as follows, decreased venous return to the right atrium. The vascular resistance in the lungs drops and all cardiac output flows through the pulmonary vessels now. Increased return to the heart through the pulmonary veins causes the raised pressure in the left atrium. As result of the changes described above foramen ovale is closed because the pressure in the left atrium becomes higher than in the right atrium. So, the blood cannot move from the right atrium to the left. After birth takes place the spasm of the Botalli ductus, which connects the descending aorta with the pulmonary artery. But during first 8 hours of baby’s life
A few minutes after delivery Arantius’ duct which in fetus shunts the blood from the left umbilical vein to the inferior vena cava, functionally closes and now all blood goes through the liver. There are few important changes in the lung and they are strongly connected to the changes of circulation. Synthesis and releasing of the surfactant is raised which is critical to prevent atelectasis and to help the alveoli to function properly. Baby’s lungs are capable of amniotic fluid which is reabsorbed after birth through epithelial sodium channels. The lung’s capillaries become dilated thereby increasing the surface for gases exchange and the blood starts its flow through the lungs. The rhythmic breaths also commence. In the fetus the liver functions as a source of erythropoietin production, but after birth this function is shifted to the kidney and that is a cause why the erythropoietin level is dropped. Arantius’ duct and umbilical vein are obliterated with formation of ligamentum venosum and ligamentum teres