40 Questions
What percentage of the deoxygenated blood coming from the superior vena cava is diverted to the right ventricle?
50%
Where is the deoxygenated blood shunted towards due to high resistance in the lungs?
Ductus arteriosus
How much oxygen saturation blood leaves the right ventricle after mixing oxygenated and deoxygenated blood?
50%
What is the oxygen saturation of blood after it shunts to the aorta and mixes with blood from the left ventricle?
55%
In fetal circulation, how much of the blood goes through the placenta?
55%
What percentage of blood goes through the lungs in fetal circulation?
12%
Which part of the fetus receives 15% of the blood supply?
Upper limbs
What is the most significant difference between fetal and adult circulation highlighted in the text?
Only 12% of blood goes through lungs in fetal circulation
What percentage of blood flows through the lungs immediately after birth?
100%
Which ventricle pumps approximately 60% in the fetal circulation before birth?
left ventricle
What happens to pulmonary vascular resistance after the expansion of the fetal lungs?
Decreases significantly
What contributes to the increase in aortic pressure at birth?
Loss of placenta
Which of the following pressures decrease due to the expansion of fetal lungs?
Pulmonary arterial pressure
Which chamber of the heart tends to pump more blood immediately after birth?
Left ventricle
What is the primary cause of the decrease in pulmonary vascular resistance post birth?
Expansion of lungs
Which feature of fetal circulation becomes obsolete due to birth-related changes?
placental blood flow
What happens immediately after birth regarding the foramen ovale?
The valve of the foramen ovale fuses to the septum secundum.
What is the consequence of failure in closing the foramen ovale after birth?
Atrial Septal Defect
Why does blood attempt to move backward through the foramen ovale after birth?
Low right atrial pressure and high left atrial pressure
What causes the increased pressure in the left atrium after birth?
More blood reaching the left atrium due to expansion of lungs
What prevents further flow through the foramen ovale after birth?
Fusion of the septum primum to septum secundum
What does failure of ductus arteriosus closure lead to?
Patent ductus arteriosus
Why does blood flow backward through the ductus arteriosus after birth?
Decreased pulmonary arterial pressure
What happens to the ductus arteriosus after birth?
Blood flows backward from aorta into pulmonary artery through it.
Why does the right atrium, ventricle, and pulmonary trunk pressure remain high in certain conditions?
Due to the closure of the foramen ovale and ductus arteriosus
What is the approximate deoxygenated hemoglobin content required for cyanosis to appear?
3g%
Which condition results in central cyanosis appearing throughout the body?
Congestive heart failure
What is peripheral cyanosis primarily limited to?
The extremities
Which of the following can cause 10 L→R shunting defects?
Atrial Septal defect (ASD)
What is the term used to describe abnormalities of the peripheral circulation that can cause peripheral cyanosis?
Polycythemia
What can cause central cyanosis besides congenital cyanotic heart disease?
High altitudes
What contributes to the limited appearance of peripheral cyanosis?
Abnormalities of the peripheral circulation
What is the reason for the constriction of the umbilical vessels after birth?
To prevent fetal blood loss to the placenta
What happens to the umbilical veins after birth?
They constrict to facilitate oxygen and nutrient flow back into fetal circulation
What is Persistent Fetal Circulation also known as?
Pulmonary hypertension of the newborn
What can result in pulmonary vasoconstriction leading to Persistent Fetal Circulation?
Acidosis or hypoxia
What does the umbilical vein convert into after both constrictions?
Ligamentum teres
What happens to the distal part of the umbilical arteries?
Converts into a fibrous ligament
What is likely to result from Persistent Fetal Circulation?
Venous shunting
Why do umbilical arteries initially constrict after birth?
To reduce fetal blood loss to the placenta
Study Notes
Fetal Circulation
- During fetal development, oxygen saturation remains at 65%
- Deoxygenated blood from the superior vena cava is diverted to the right ventricle and pumped through the pulmonary artery
- Due to high resistance in the lungs, blood is shunted through the ductus arteriosus to the aorta, bypassing the lungs
- Oxygenated blood from the inferior vena cava mixes with deoxygenated blood, resulting in 50% oxygen saturation when leaving the right ventricle
- After shunting to the aorta, the oxygen saturation increases to 55%
Blood Flow Distribution in Fetal Circulation
- Only 55% of blood goes through the placenta, with 45% passing through fetal tissues
- 15% of blood goes to the upper limbs, 18% to the lower limbs, and 12% to the lungs
- The left ventricle pumps approximately 60% of the blood, while the right ventricle pumps approximately 40%
Circulation After Birth
- Two major changes occur at birth:
- Loss of placenta, resulting in increased systemic resistance and aortic pressure
- Expansion of lungs, decreasing pulmonary vascular resistance
- These changes lead to the closure of the foramen ovale and ductus arteriosus
Closure of Foramen Ovale and Ductus Arteriosus
- Low right atrial pressure and high left atrial pressure result in blood flow reversal, causing the foramen ovale to close
- The valve of the foramen ovale fuses to the septum secundum, preventing further flow
- Failure of this closure results in Atrial Septal Defect or Patent Foramen Ovale
Cyanosis
- Cyanosis is a bluish discoloration of skin or mucous membranes, appearing when deoxygenated hemoglobin content is 3g% or higher
- There are two types of cyanosis:
- Central cyanosis, affecting the entire body, including mucous membranes and tongue
- Peripheral cyanosis, limited to extremities, also known as acrocyanosis
Complications
- Persistent Fetal Circulation (PFC) or persistent pulmonary hypertension of the newborn
- PFC results in R→L shunting, reverting the newborn back to fetal-type circulation
- Causes of PFC include hypoxia, hypercarbia, acidosis, or cold, leading to pulmonary vasoconstriction and increased pulmonary resistance
Learn about the unique circulation process in a newborn baby's cardiovascular system, including the shunting of blood through the ductus arteriosus and the distribution of oxygenated and deoxygenated blood. Understand how oxygen saturation levels are maintained during this time.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
