61: Fetal and Neonatal Circulation Flashcards
Since the lungs are largely non-functional and the liver only partially functional, special vessels help blood bypass these organs.
Fetal circulation has 4 unique shunts:
Fetal shunts: 1. Placenta (instead of ____ & _____) 2. ductus venosus (shunt away from _____) 3. foramen ovale (__ to __), & 4. ductus arteriosus (__ to ____ to bypass lungs).
Fetus pumps blood in _____ & not in series like adult.
Fetal shunts: 1. Placenta (instead of kidneys & GI) 2. ductus venosus (shunt away from liver) 3. foramen ovale (RA to LA), & 4. ductus arteriosus (RV to aorta to bypass lungs).
Fetus pumps blood in parallel & not in series like adult.
Gas exchange occurs in the _____ for fetus & for lungs in adults. Umbilical vein is highly ______ blood. Placenta delivers nutrients & exchanges ___ & ____.
Gas exchange occurs in the placenta for fetus & for lungs in adults. Umbilical vein is highly oxygenated blood. Placenta delivers nutrients & exchanges O2 & CO2.
In fetus, the lungs have ____ resistance to avoid too much blood since lung reacts differently to hypoxia & has hypoxic _______ & lung is not inflated. Some blood is needed for nourishment though.
In fetus, the lungs have high resistance to avoid too much blood since lung reacts differently to hypoxia & has hypoxic vasoconstriction & lung is not inflated. Some blood is needed for nourishment though.
Special anatomical arrangements:
1) Oxygenated blood returning from the placenta via the umbilical ______ passes through the ductus _____, mainly bypassing the liver, then passes into the inferior vena cava.
2) In the human fetus about 40% of the inferior vena cava flow passes through the foramen _____ into the left atrium from the right atrium. The rest of the flow passes into the right atrium. Blood also enters the right atrium from the superior vena cava and is directed through the tricuspid valve into the right ventricle.
3) The blood from the superior vena cava is deoxygenated blood from the forequarters. About 3/4 or more of the blood from the right ventricle is pumped through the ductus ______ into the descending aorta, bypassing the _____. Thus, the right and left ventricles both pump blood to the descending aorta and their output is largely in parallel rather than in series (as in the adult). Therefore the sum of both ventricles is considered to be the combined cardiac output. A small amount of blood from the right ventricle passes through the lungs and then enters the left atrium.
4) Blood in the _____ aorta passes primarily through hypogastric arteries into the two umbilical arteries and into the placenta. A small portion of the blood flows to the hindquarters and mesentery.
1) Oxygenated blood returning from the placenta via the umbilical vein passes through the ductus venosus, mainly bypassing the liver, then passes into the inferior vena cava.
2) In the human fetus about 40% of the inferior vena cava flow passes through the foramen ovale into the left atrium from the right atrium. The rest of the flow passes into the right atrium. Blood also enters the right atrium from the superior vena cava and is directed through the tricuspid valve into the right ventricle.
3) The blood from the superior vena cava is deoxygenated blood from the forequarters. About 3/4 or more of the blood from the right ventricle is pumped through the ductus arteriosus into the descending aorta, bypassing the lung. Thus, the right and left ventricles both pump blood to the descending aorta and their output is largely in parallel rather than in series (as in the adult). Therefore the sum of both ventricles is considered to be the the combined cardiac output. A small amount of blood from the right ventricle passes through the lungs and then enters the left atrium.
Blood in the decending aorta passes primarily through hypogastric arteries into the two umbilical arteries and into the placenta. A small portion of the blood flows to the hindquarters and mesentery.
After first breath there is ______ of ductos venosus, foramen ovale, and ductus arteriosus.
After first breath there is closure of ductos venosus, foramen ovale, and ductus arteriosus.
________ is triggered by mild hypoxia, hypercapnia, tactile stimuli and cold skin. This is the most difficult breath you will ever take—the pressure is very very _____. Each breath becomes easier due to surfactant. Spanking the baby helps it begin breathing, if it is having difficulty.
Breathing becomes easier once the alveoli are open and the type ____ alveolar pneumocytes deliver surfactant to the air-water interface. Respiratory _____ syndrome is caused by deficiency of surfactant often found in premature births.
First breath is triggered by mild hypoxia, hypercapnia, tactile stimuli and cold skin. This is the most difficult breath you will ever take—the pressure is very very high. Each breath becomes easier due to surfactant. Spanking the baby helps it begin breathing, if it is having difficulty.
Breathing becomes easier once the alveoli are open and the type II alveolar pneumocytes deliver surfactant to the air-water interface. Respiratory distress syndrome is caused by deficiency of surfactant often found in premature births.
Effect of birth on pulmonary vascular resistance, blood flow, and mean arterial pressure In the fetus, pulmonary vascular resistance is ____, pulmonary blood flow is ____, and mean pulmonary arterial pressure is ____. At birth, each of these three situations rapidly reverses. The primary event is the fall in resistance, which occurs because of the following:
(1) the pulmonary blood vessels are no longer being _____
(2) breathing causes increased PO2, which, in turn, causes ______
(3) local ______ cause vasodilation.
The reason that blood pressure falls after birth is that the fall in pulmonary vascular resistance is _____ than the rise in blood flow.
Effect of birth on pulmonary vascular resistance, blood flow, and mean arterial pressure In the fetus, pulmonary vascular resistance is high, pulmonary blood flow is low, and mean pulmonary arterial pressure is high. At birth, each of these three situations rapidly reverses. The primary event is the fall in resistance, which occurs because of the following:
(1) the pulmonary blood vessels are no longer being crushed
(2) breathing causes increased PO2, which, in turn, causes vasodilation
(3) local prostaglandins cause vasodilation.
The reason that pressure falls after birth is that the fall in pulmonary vascular resistance is greater than the rise in blood flow.
The fetal heart begins beating approximately _____ month following fertilization. HR increases over the course of pregnancy from ~65 to ~140 bpm near birth.
The fetal heart begins beating approximately one month following fertilization. HR increases over the course of pregnancy from ~65 to ~140 bpm near birth.
The outer surface of the mature chorionic ______ is covered with a thin layer of syncytiotrophoblast. Under this are cytotrophoblasts, mesenchyme, and fetal blood vessels. Maternal blood is trapped in the ______ space, between the endometrium on the maternal side and the villi on the fetal side.
In the mature placenta, “_____” arteries from the mother empty directly into the intervillous space, which is drained by maternal veins. The villi look like a thick forest of trees arising from the “______ plate,” which is the analog of the soil from which the trees sprout.
The outer surface of the mature chorionic villus is covered with a thin layer of syncytiotrophoblast. Under this are cytotrophoblasts, mesenchyme, and fetal blood vessels. Maternal blood is trapped in the intervillous space, between the endometrium on the maternal side and the villi on the fetal side.
In the mature placenta, “spiral” arteries from the mother empty directly into the intervillous space, which is drained by maternal veins. The villi look like a thick forest of trees arising from the “chorionic plate,” which is the analog of the soil from which the trees sprout.
Umbilical vein hase higher Hb saturation than uterine vein due to fetal _____.
Fetus has _____ cardiac output & a _____ Hb concentration of HbF—so increased Hb concentration, affinity, & Cardiac Output ensure good oxygenation to the body of the fetus
Umbilical vein hase higher Hb saturation than uterine vein due to fetal Hb.
Fetus has higher cardiac output & a higher Hb concentration of HbF—so increased Hb concentration, affinity, & Cardiac Output ensure good oxygenation to the body of the fetus
When placenta closes, pressure increase in LA, LV, & aorta increases—in other words pressure in ____ (left/right) heart increases & ____ (left/right) heart decreases.
Closure of the foramen ovale is caused by reversal of right/left atrial pressure so pressure gradient is from ____ to _____ atrium like in the adult.
When placenta closes, pressure increase in LA, LV, & aorta increases—in other words pressure in left heart increases & right heart decreases.
Closure of the foramen ovale is caused by reversal of right/left atrial pressure so pressure gradient is from left to right atrium like in the adult.
Increased pulmonary circulation causes increased venous return to the left atrium. There is a decrease in right atrial pressure. The reversal of pressure closes foramen ovale’s valve. Permanent seal forms from in a few months or years. It becomes fossa ovalis. Failure of closure: patent foramen ovale.
Closure of the ductus venosus forces portal blood to perfuse the _____. In the fetus, large portion of blood in the portal vein enters the ductus venosus bypassing the liver. Within 3hrs after birth, constriction of vascular smooth muscle turns the ductus venosus shunt into the _____ venosum. The mechanism occurs by _____ PO2 = partial pressure oxygen and _______ prostoglandins.
Closure of the ductus venosus forces portal blood to perfuse the liver. In the fetus, large portion of blood in the portal vein enters the ductus venosus bypassing the liver. Within 3hrs after birth, constriction of vascular smooth muscle turns the ductus venosus shunt into the ligamentum venosum. The mechanism occurs by increased PO2 = partial pressure oxygen and reduced prostoglandins.
Within a few hrs, ductus arteriosus _____ because of constriction of the wall. Thrombosis obliterate the lumen in a month. It becomes _____ arteriosum.
Mechanisms: _______ PO2 and _______ circulating prostaglandin cause constriction. Also bradykinin from the lung is involved.
Failure of closure: patent ductus _______. It leads to pulmory hypertension, and possibly congestive heart failure and cardiac arryhthmias.
Closure of the foramen _____ & ductus ______ turns the fetal heart to the adult heart.
Within a few hrs, ductus arteriosus closes because of constriction of the wall. Thrombosis obliterate the lumen in a month. It becomes ligamentum arteriosum.
Mechanisms: Increased PO2 and decreased circulating prostaglandin cause constriction. Also bradykinin from the lung is involved.
Failure of closure: patent ductus arteriosus. It leads to pulmory hypertension, and possibly congestive heart failure and cardiac arryhthmias.
Closure of the foramen ovale & ductus arteriousus turns the fetal heart to the adult heart.
The NEONATAL circulation is characterized by a reversed flow through the ductus arteriosis to the lung. This enhances O2 uptake by the blood as it passes through the lung.
1) Loss of blood flow through the placenta (umbilical cord constricts due to stretch and increased PO2) produces a _______ of the systemic vascular resistance. This results in an increase in the aortic pressure as well as increased pressures in the left ventricle and left atrium.
2) As a result of respiratory activity the pulmonary vascular resistance is greatly ______ (~five-fold):
i) upon lung expansion the pulmonary vessels are no longer _______.
ii) higher blood oxygen levels produce pulmonary arteriolar ______ as does the release of prostaglandins.
3) These lung effects ______ the pulmonary arterial pressure and right ventricular and right atrial pressures.
4) Following lung inflation a large amount of blood is now directed to the left atrium from the lungs. This _____ left atrial pressure.
5) The increase in left atrial and decrease in right atrial pressures close the valve of the foramen ovale and flow from the inferior vena cava is now limited to the right ______.
6) Within one to three hours the muscular wall of ductus _____ contracts and closes this avenue of flow.
7) With increased aortic pressure and ______ pulmonary arterial pressure the blood flow through the ductus arteriosus is ______. This increases blood flow through the lung, increasing oxygen uptake. This anatomy represents the NEONATAL circulation, although the neonatal period is sometimes defined as the first 4 weeks after birth.
8) After a few hours of ______ plasma PO2 and decreased blood ______ levels the muscular wall of the ductus arteriosus constricts markedly, and within two to three days the constriction is strong enough to stop most blood flow. In one out of every 2000 babies the ductus arteriosus does not close. With delivery at high altitudes (low oxygen levels) a patent ductus arteriosus is fairly common.
9) With closure of the ductus ______ the adult circulation is attained.
The NEONATAL circulation is characterized by a reversed flow through the ductus arteriosis to the lung. This enhances O2 uptake by the blood as it passes through the lung.
1) Loss of blood flow through the placenta (umbilical cord constricts due to stretch and increased PO2) produces a doubling of the systemic vascular resistance. This results in an increase in the aortic pressure as well as increased pressures in the left ventricle and left atrium.
2) As a result of respiratory activity the pulmonary vascular resistance is greatly decreased (~five-fold):
i) upon lung expansion the pulmonary vessels are no longer compressed.
ii) higher blood oxygen levels produce pulmonary arteriolar vasodilation as does the release of prostaglandins.
3) These lung effects reduce the pulmonary arterial pressure and right ventricular and right atrial pressures.
4) Following lung inflation a large amount of blood is now directed to the left atrium from the lungs. This increases left atrial pressure.
5) The increase in left atrial and decrease in right atrial pressures close the valve of the foramen ovale and flow from the inferior vena cava is now limited to the right atrium.
6) Within one to three hours the muscular wall of ductus venosus contracts and closes this avenue of flow.
7) With increased aortic pressure and decreased pulmonary arterial pressure the blood flow through the ductus arteriosus is reversed. This increases blood flow through the lung, increasing oxygen uptake. This anatomy represents the NEONATAL circulation, although the neonatal period is sometimes defined as the first 4 weeks after birth.
8) After a few hours of increased plasma PO2 and decreased blood prostaglandin levels the muscular wall of the ductus arteriosus constricts markedly, and within two to three days the constriction is strong enough to stop most blood flow. In one out of every 2000 babies the ductus arteriosus does not close. With delivery at high altitudes (low oxygen levels) a patent ductus arteriosus is fairly common.
9) With closure of the ductus arteriosus the adult circulation is attained.
Patent Ductus Arteriosus: ~1 of every 2000 newborns end up with continuously _____ ductus arteriosus (with small opening there are no symptoms but a murmur exists) with larger openings breathing is _____, feeding is _____, HR and sweating are _____ and weight is low: endocarditis risk is ______ as germs in blood tend to adhere to valves, heart and/or ductus where turbulance destroys smooth lining of vessels. Surgical techniques exist to close the ductus.
Coarctation of the aorta: Smooth muscle of the ductus arteriosus that invaded the descending aorta _____ the area following birth. Associated with ____ BP in regions perfused by the aorta above constriction.
Ventricular septal defects: Among the most common of birth defects occurring in .1 to .4 % of all births and making up 20-30% of congenital heart lesions, VSD involves a ____ in wall between the ventricles. A small VSD rarely causes problems and often closes by itself. A large VSC can cause problems, often in the first months of life, due to blood flow from the ____ to the ____ ventricle. This can cause _______ heart failure and must often be treated with surgical closure.
Atrial Septal Defects: Appear in about one of every 1500 births. If hole is large enough there is significant blood movement from the ___ atria to the ____ atria, possibly leading to volume overload of the right heart. If untreated can lead to pulmonary ______, right heart enlargement and heart failure.
Tetralogy of Fallot: A combination of 1) pulmonary ____ (improper development of the pulmonary valve, which represents 8-12% of all congenital heart defects), 2) _____ of the aorta so it overrides the ventricular septum, 3) right ventricular _____ and 4) a ventricular ____ defect. This is the most common cause of the blue baby syndrome.
Patent Ductus Arteriosus: ~1 of every 2000 newborns end up with continuously open ductus arteriosus (with small opening there are no symptoms but a murmur exists) with larger openings breathing is difficult, feeding is poor, HR and sweating are elevated and weight is low: endocarditis risk is life threatening as germs in blood tend to adhere to valves, heart and/or ductus where turbulance destroys smooth lining of vessels. Surgical techniques exist to close the ductus.
Coarctation of the aorta: Smooth muscle of the ductus arteriosus that invaded the descending aorta constricts the area following birth. Associated with high BP in regions perfused by the aorta above constriction.
Ventricular septal defects: Among the most common of birth defects occurring in .1 to .4 % of all births and making up 20-30% of congenital heart lesions, VSD involves a hole in wall between the ventricles. A small VSD rarely causes problems and often closes by itself. A large VSC can cause problems, often in the first months of life, due to blood flow from the left to the right ventricle. This can cause congestive heart failure and must often be treated with surgical closure.
Atrial Septal Defects: Appear in about one of every 1500 births. If hole is large enough there is significant blood movement from the left atria to the right atria, possibly leading to volume overload of the right heart. If untreated can lead to pulmonary hypertension, right heart enlargement and heart failure.
Tetralogy of Fallot: A combination of 1) pulmonary stenosis (improper development of the pulmonary valve, which represents 8-12% of all congenital heart defects), 2) dextroposition of the aorta so it overrides the ventricular septum, 3) right ventricular hypertrophy and 4) a ventricular septal defect. This is the most common cause of the blue baby syndrome.
