Fetal Circulation
True or false: no blood flows from the fetal heart to the fetal lung or from the fetal lung to the fetal heart?
False. A small amount of blood still flows between the fetal heart and lungs to keep them functioning and ready for the first breath. If no blood went through, muscles could atrophy and not function well after birth
Why does acyanotic heart disease matter in the long term?
Right side of the heart can hypertrophy, eventually becoming the higher pressure system of the two which can lead to flow reversal through septal defect and shunting from right to left and cyanosis, which can cause severe longstanding septal defects. Irreversible damage to pulmonary vascular capillary beds from high pressure of blood being pumped through it
Which circulation system is low pressure in a fetus?
Systemic circulation
Which circulation system is high pressure in adults?
Systemic circulation, because it has to carry blood all the way down to our toes and up to our head and neck against gravity
What is the most common cause of cyanotic heart disease?
Tetralogy of fallot, which is a congenital heart condition consisting of four abnormalities
What is the umbilical vein?
The blood vessel that connects the maternal and fetal circulation. Carries all the nutrients and the oxygen that the fetus needs into its circulatory system
What is the umbilical cord?
The cord attached to the fetal belly button that contains the umbilical vein and arteries
What is a ventricular septal defect (VSD)?
When there is a hole in the septum, or the wall dividing the left and right ventricles. This allows oxygen-rich blood from the left ventricle to mix with oxygen-poor blood from the right ventricle. Small VSDs usually close spontaneously but large ones usually require surgery at 3-6 months
What is systemic circulation?
Part of the cardiovascular system (left side of the heart) that carries oxygenated blood away from the heart to the body, and receives oxygenated blood from the lungs
What is pulmonary circulation?
Part of the cardiovascular system (right side of the heart) that carries deoxygenated blood away from the heart to the lungs and returns deoxygenated blood to the heart from body tissues
What does blood do as it passes by tissues?
Picks up byproducts like CO2
What is the function of the lungs?
To oxygenate blood coming from the right side of the heart. Facilitates gas exchange where CO2 is removed from blood and replaced with O2
Which circulation system is high pressure in a fetus?
Pulmonary circulation
Which circulation system is low pressure in adults?
Pulmonary circulation, because the lungs are very close to the heart so you don't need much pressure, and lung vessels are very thin and fragile so too much pressure would lead to fluid seeping out and getting in our lungs, impeding gas exchange
What happens when you clamp the umbilical cord?
Removes the placental circulation, which leads to an increase in the pressure of the systemic circulation in the newborn
What part of the heart receives blood from the superior vena cava and inferior vena cava?
Right atrium
What side of the heart does CO2-rich blood enter through?
Right side of the heart
What is the result of the tetralogy of fallot?
Too little blood goes to the lungs, low-oxygen blood circulates to body tissues, and too little oxygen reaches tissues.
What fetal adaptation solves problems of access to oxygen and nutrients and removal of fetal waste?
Umbilical vessel
What is the mitral valve?
Valve connecting the left atrium and left ventricle (also known as bicuspid valve)
What is the aortic semilunar valve?
Valve through which blood flows frentricle to the aorta
What is the pulmonic semilunar valve?
Valve through which blood flows from the right ventricle to the pulmonary arteries
Why does acyanotic heart disease matter in the short term?
Volume overload to the right side of the heart can damage lung capillaries and cause lung congestion leading to chest infections
What is the vaginal squeeze?
When some of the fluid present in fetal lungs during gestation is physically squeezed out as baby passes through birth canal during vaginal delivery
What is patent ductus arteriosus (PDA)?
When the ductus arteriosus doesn't close. This allows oxygen-rich blood from the aorta to mix with oxygen-poor blood from the pulmonary artery, which can put strain on the heart. Usually treated with surgery at 1 year
What is the fossa ovalis?
When the foramen ovale closes after birth it is called the fossa ovalis
What is an atrial septal defect (ASD)?
When the foramen ovale doesn't close or the flap never formed. This shunts blood from left to right because in breathing human, left side is high pressure system so blood would flow back through foramen ovale into right atrium (low pressure). Child may need surgery to correct defect.
What are the two types of congenital heart disease?
1. Acyanotic 2. Cyanotic
What are the three primary causes of acyanotic heart disease?
1. Atrial septal defect 2. Ventricular septal defect 3. Patent ductus arteriosus
What four things happen when oxygen enters the lungs for the very first time?
1. Capillaries in the lungs are pulled open by the physical expansion of the lungs that happens in response to air entering them 2. Reversal of hypoxic pulmonary vasoconstriction 3. Bradykinin is released into the lungs causing vasodilation so blood vessels open up and allow more blood to flow through 4. Ductus arterioles begins to close and becomes a ligament called the ligamentum arteriosum, which forces more blood to go up the pulmonary trunk and into the pulmonary arteries toward the lungs
What are the three stimuli for a newborn's first breath?
1. Epinephrine 2. Temperature decrease (cold outside womb) 3. Tactile response (response to being touched)
What are the two major changes that happen at birth to establish breathing human circulation?
1. First breath 2. Clamping of the umbilical cord
What are the two temporary structural changes in the fetal heart and blood vessels to allow circulation to bypass the lungs?
1. Foramen ovale 2. Ductus arteriosis
What are the signs of congenital heart disease after birth?
1. Heart murmur detected with stethoscope 2. Cyanosis (bluish tent)
What categories are looked at on the apgar score?
1. Heart rate 2. Respirations 3. Reflex irritability 4. Muscle tone 5. Color (How Ready Is This Child)
What three challenges do fetuses face?
1. How do you get oxygen if you can't breathe inside your sac of fluid? 2. How do you get nutrients if you don't have direct access to food? 3. What do you do with your waste products?
What does it mean for the human heart to consist of two pumps?
1. Pump on right side of heart receives deoxygenated blood returning from the body and pumps it out to the lungs for oxygenation 2. Pump on left side of heart receives oxygenated blood from the lungs and pumps it out to the body tissues and vital organs
What is the path of blood in a fetus with the foramen ovale?
1. Right atrium 2. Foramen ovale 3. Left atrium 4. Bicuspid valve 5. Left ventricle 6. Aorta 7. Body
What is the path of blood in a fetus with the ductus arterosis?
1. Right atrium 2. Tricuspid valve 3. Right ventricle 4. Pulmonary trunk 5. Ductus arteriosis 6. Aorta 7. Body
What is the path of blood in breathing humans?
1. Right atrium 2. Tricuspid valve 3. Right ventricle 4. Pulmonary trunk 5. Pulmonary arteries 6. Lungs 7. Pulmonary vein 8. Left atrium 9. Bicuspid valve 10. Left ventricle 11. Aorta 12. Body
How does fetal blood get to the left side of the heart since the lungs are not yet functioning?
1. Some blood passes straight from the right atrium to the left atrium through the foramen ovale 2. Some blood goes through the tricuspid valve into the right ventricle and up the pulmonary trunk and then passes through the ductus arteriosus so it can jump straight to the aorta and bypass the lungs
What are risk factors for having a fetus with congenital heart disease?
1. Suspected Down's syndrome 2. Earlier child with heart malformation 3. Mother had congenital heart disease 4. Maternal infection (rubella) 5. Fetal exposure to medications, drugs, or alcohol 6. Certain auto-antibodies in maternal bloodstream
What are the four fetal cardiac adaptations?
1. Umbilical vessels 2. Ductus venosis 3. Foramen ovale 4. Ductus arteriosis
What are the two fetal adaptations that facilitate exchange of oxygen from maternal blood supply via the placenta?
1. Umbilical vessels 2. Ductus venosus
What are the four abnormalities involved in tetralogy of fallot?
1. Ventricular septal defect 2. Overriding aorta 3. Pulmonary valve stenosis 4. Right ventricular hypertrophy
When are most congenital cardiac anomalies discovered?
18 - 20 weeks into pregnancy when fetal heart
How long after birth does it take for the baby's first breath?
6 seconds
What is the incidence of congenital heart disease?
9 out of every 1,000 live births
What is an overriding aorta?
A congenital heart defect where the aorta is displaced such that it straddles the ventricular septal defect and seems to arise from both ventricles. This allows some oxygen-poor blood from the right ventricle to enter the aorta and go out to the body instead of the lungs
What is pulmonary valve stenosis?
A narrowing or thickening of the valve connecting the right ventricle to the pulmonary artery. This means the heart has to work extra hard to pump blood to the lungs, and not enough blood reaches the lungs
What is the apgar score?
A score to see how healthy a newborn is. Maximum score is 10 where child receives 0-2 points for each category
What is the placenta?
A vascular organ that attaches to the inside of the uterus and connects the mother's circulation to fetal circulation
What is the function of the ductus venosis?
Allows blood coming in through the umbilical vein to bypass the fetal liver (hepatic circulation) and go straight to the inferior vena cava to enter the right atrium
What is the function of the ductus arteriosis?
Allows blood to jump from the pulmonary trunk into the aorta
What is the function of the foramen ovale?
Allows blood to pass directly from the right atrium to the left atrium. Works because in the fetal heart the right side is the high pressure system so blood will flow into the left side of the heart on a gradient
When are fetal lungs ready to be filled with air?
At 28-32 weeks when type 2 alveolar cells have produced enough surfactant to overcome surface tension in the alveoli
Why don't you see cyanosis in acyanotic heart disease?
Blood from left side of heart is oxygenated so when it is shunted to the right side it doesn't make the baby blue
What is peripheral cyanosis?
Bluish tinge in hands and feet of newborn. Very common and can occur when children are unwell for any reason or are cold
Why is the ductus venosis a useful adaptation?
By allowing oxygenated maternal blood to bypass the liver, it can go straight to the inferior cava and access the fetal brain more quickly
What should you do if you notice amniotic fluid is low for a fetus?
Check fetal kidneys, because fetal urine is an important contributor to amniotic fluid
What is the function of the fetal inferior vena cava?
Collects all of the blood from the lower extremities and returns it to the right atrium
What is the most frequently diagnosed congenital problem?
Congenital heart disease
On what day of gestation does the fetus have all the parts of the heart that it needs to breathe?
Day 49
What are the benefits of prenatal screening?
Gives parents time to make important decisions about terminating pregnancy or surgically correcting or treating malformations. Allows parents to plan for child's management
Why does the ductus arterioles stay open during gestation?
High levels of prostaglandins. At birth, the levels of this compound drop so the DA begins to close
What is the difference between cyanotic and cyanotic congenital heart disease?
In acyanotic heart disease, oxygenated blood is shunted from the left side of the heart to the right side. In cyanotic heart disease, deoxygenated blood is shunted from the right side of the heart to the left side of the heart
What happens to fluid originally present in fetal lungs that isn't squeezed out during vaginal squeeze?
It is absorbed into the lymphatic and pulmonary circulation
What does it mean if blood is blue?
It is high in carbon dioxide (low in oxygen)
What does it mean if blood is red?
It is high in oxygen
What is the left side of the heart responsible for?
It pumps oxygenated blood out to the body and receives oxygenated blood from the lungs. Works with oxygenated blood
What is the right side of the heart responsible for?
It receives the deoxygenated blood coming back to the heart from the body and pumps blood to the lungs for oxygenation. Works with deoxygenated blood
Where does oxygenated blood from the mother enter the fetal circulatory system?
Joins at the vessels that supply blood to the liver
What side of the heart does oxygenated blood enter through?
Left side of the heart
What is the function of the fetal aorta?
Located in the left ventricle, the aorta carries blood out to the body tissues to feed the fetal gut and transport blood to the fetal liver
What happens if your lung has limited access to oxygen because you are choking on something blocking your airway?
Lung will constrict its blood vessels in the non-functioning lung so the heart can send more blood to the functioning parts of the lung
What might be the explanation for a baby experiencing a marked deterioration in his condition 1-2 days after birth and receiving prostaglandins as therapy?
May have a congenital heart defect so it relies on the ductus arteriosus. When the DA starts to close a few days after birth, baby may need prostaglandins to keep it
What happens to the foramen ovale after the first breath?
More blood flow to the lungs results in more flood flow returning from the lungs which pushes the foramen ovale closed until it eventually fuses
What is central cyanosis?
More severe version of bluish color change, including blue in lips and face
What are you likely to see in parents with children in the NICU?
Mothers tend to have more acute symptoms of PTSD, and fathers have higher rates of PTSD later on
What is hypoxic pulmonary vasoconstriction?
Narrowing of blood vessels in lungs in response to low oxygen levels
What is the path through which air enters the lungs?
Nose - Pharynx - Larynx - Trachea - Bronchi - Bronchioles - Alveoli
When you are face to face with another person, where is the left side of the heart?
On your right side. It is the side closest to the person's left arm, which is the right side when you are looking at them
What is the ligamentum venosum?
One week after baby is born, ductus venosus closes and becomes ligamentum venosum
Why is fetal circulation considered mixed oxygen circulation?
Oxygenated blood enters fetal circulation via the placenta, and some of it can go essentially straight to the right atrium. Blood coming from the upper extremities however is very deoxygenated and also enters the right atrium through the superior vena cava. The deoxygenated and highly oxygenated blood mix in the right atrium to form mixed oxygen blood
What is the grand central station of the circulatory system?
The heart
What is the most important muscle in the human body?
The heart
Why is maternal blood entering hepatic circulation a problem?
The liver acts as a blood reservoir and has many sinusoids that fill with blood while liver cells are working, so blood gets stuck there for a long time and fetal brain needs oxygenated blood quickly
What is essentially functioning as the fetal lung in utero?
The placenta (provides oxygen from mother)
What are the umbilical arteries?
The two blood vessels that carry deoxygenated blood and waste products out toward the mother
Why is it interesting that the umbilical vein and the pulmonary vein are called "veins"?
They are carrying oxygenated blood. Usually veins are carrying deoxygenated blood back to the heart to go to the lungs and arteries are carrying oxygenated blood away from the heart to the body tissue, but the umbilical vein and the pulmonary vein are carrying oxygenated blood to the fetal heart
What do lungs look like in a fetus?
They are not yet expanded and oxygen levels are very low so there is widespread constriction of blood vessels
Why are babies born via caesarian section more likely to be congested and sneeze more after birth?
They don't have fluid squeezed out during vaginal squeeze so it takes longer for remaining fluid to be absorbed
Why do we have two separate circulation systems?
They operate under different pressures
What is right ventricular hypertrophy?
Thickening of the muscular wall of the right ventricle, which can block the flow of blood through the pulmonary valve. This occurs because right ventricle has to work extra hard to pump blood through narrowed valve
What is the main function of the circulatory system?
To deliver oxygen and nutrients to l organs and other body tissues and to remove and carry away from them their waste products (CO2 and metabolism byproducts)
