Baby circulation right after birth | Circulatory system physiology | NCLEX-RN | Khan Academy

Summary

This script discusses the critical changes that occur in a newborn's circulatory system after birth. It highlights the removal of the placenta and the lungs' first use of air, which trigger a cascade of adaptations. Key points include the constriction of Wharton's jelly, closure of the foramen ovale, dilation of pulmonary arterioles, and the eventual constriction of the ductus arteriosus. These changes ensure the baby's circulation transitions from fetal to neonatal, adapting to life outside the womb.

Takeaways

• 👶 The fetus must adapt to life outside the uterus after birth, especially through changes in the placenta and lungs.
• ✂️ The umbilical cord is clamped and cut at birth, which doesn't hurt the baby or mother because the umbilical cord has no nerves.
• ❄️ Wharton's jelly, surrounding the umbilical vessels, contracts in response to the cooler environment, naturally clamping the vessels.
• ⚡ The removal of the placenta causes a shift from low resistance to high resistance in the baby’s circulation, leading to no more blood flow through the umbilical vein or ductus venosus.
• 💨 The lungs begin taking in air, replacing fluid in the alveoli, which reduces pulmonary resistance and allows blood to flow into the lungs for oxygenation.
• ❤️‍🩹 The foramen ovale, a hole between the right and left atrium, closes within minutes after birth as pressure decreases on the right side of the heart.
• 💡 The ductus arteriosus begins constricting within hours of birth due to higher oxygen levels and lower prostaglandin levels after the placenta is removed.
• 🔄 Blood flow is redirected as the umbilical arteries constrict due to higher oxygen levels, reducing flow to the umbilicus.
• ⏳ These circulatory changes happen in stages over minutes, hours, and days after birth, gradually shifting the baby's blood flow to support independent life.
• 🩸 Oxygenated blood begins flowing efficiently from the lungs to the left atrium and ventricle, then out to the body, marking a significant post-birth circulatory adaptation.

Q & A

What are the two major changes that occur in a baby's body right after birth?

The two major changes are the removal of the placenta and the lungs taking in air for the first time.

How does the umbilical cord cutting process affect the baby?

The umbilical cord cutting does not hurt the baby or the mother because the umbilical cord does not have nerves.

What is Wharton's jelly and what role does it play after birth?

Wharton's jelly is a pale yellowish, jelly-like substance in the umbilical cord that starts to contract around the umbilical vessels when exposed to cold temperatures after birth, acting as a natural clamp.

What happens to the blood flow in the umbilical vein after the placenta is removed?

After the placenta is removed, blood flow in the umbilical vein stops and the blood starts clotting off, leading to the cessation of flow through the umbilical vein and ductus venosus.

How does the blood flow to the lungs change after birth?

After birth, as the lungs take in air, the oxygen levels rise, causing the pulmonary arterioles to dilate and resistance in the lungs to fall, allowing more blood to flow in and get oxygenated.

What is the foramen ovale and how does it change after birth?

The foramen ovale is a fetal circulatory adaptation that allows blood to bypass the lungs. After birth, as the right side pressures fall, a flap of tissue closes off the foramen ovale, effectively sealing it.

How does the ductus arteriosus respond to changes in oxygen levels after birth?

The ductus arteriosus constricts after birth in response to increased oxygen levels in the blood and the removal of the placenta, which causes a drop in prostaglandin levels.

What is the role of prostaglandins in the closure of the ductus arteriosus?

Prostaglandins help keep the ductus arteriosus open in utero. After birth, when their levels drop, the ductus arteriosus begins to constrict and eventually closes.

How does the umbilical arteries' blood flow change after the cord is cut?

After the cord is cut, the umbilical arteries start to constrict due to high oxygen levels and low prostaglandins, leading to almost no blood flow towards the umbilicus.

What is the significance of the changes in the right side of the heart after birth?

The decrease in resistance in the lungs leads to lower pressures on the right side of the heart, allowing it to work more efficiently and adapt to the new circulatory demands after birth.

How quickly do these post-birth circulatory changes occur?

These changes occur rapidly, with some, like the closure of the foramen ovale, happening within minutes, while others, like the constriction of the ductus arteriosus and umbilical arteries, take place over hours.