Circulatory System of Children: From Fetus to Adulthood

1. Fetal Circulation:

• Formation: Fetal circulation begins to form during the 4th week of pregnancy, with the emergence of the embryonic heart.
• Oxygen in umbilical venous blood: Approximately 80%, significantly higher than venous blood in adults.
• Mixed blood: Blood mixing occurs in several locations, creating a unique circulatory system:
  • Hepatic portal vein and umbilical vein: Oxygenated blood from the placenta travels through the umbilical vein, with a portion flowing to the liver and the rest to the heart via the inferior vena cava.
  • Inferior vena cava near the heart and lower extremity veins: Mixed blood from the lower extremities and inferior vena cava enters the right atrium.
  • Two atria: The foramen ovale allows oxygenated blood from the left atrium to flow into the right atrium, mixing with the deoxygenated blood from the inferior vena cava.
  • Pulmonary artery (PA) from the ductus arteriosus (DA) and aorta (AO): The PA carries deoxygenated blood from the right ventricle to the lungs, but most of the blood is shunted to the AO through the DA, allowing deoxygenated blood from the right ventricle to enter the systemic circulation to nourish the body.

2. Circulatory Changes After Birth:

• Closure of the ductus arteriosus: After birth, when the lungs begin to function, the DA closes (usually within 3-4 days) and becomes fibrous (within 3-4 months), causing deoxygenated blood from the right ventricle to flow to the lungs.
• Closure of the foramen ovale: The foramen ovale gradually closes after birth (within 6 to 10 weeks) due to the higher pressure in the left atrium compared to the right atrium.
• Oxygen saturation in the left and right ventricles: After birth, oxygen saturation in the left ventricle increases to nearly 100%, while the right ventricle drops to around 70-80% due to oxygenated blood from the lungs entering the left atrium, then the left ventricle and systemic circulation.

3. Circulatory Characteristics of Children:

• Valve Locations:
  • Aortic valve: 2 leaflets on the right, 3 leaflets on the left.
  • Pulmonary valve: 2 leaflets on the left.
  • Tricuspid valve: Below the left sternal border.
  • Mitral valve: 5th left intercostal space, midclavicular line.
• Pulse:
  • Newborn: 140-160 beats per minute.
  • 6 months: 130-140 beats per minute.
  • 1 year: 120-130 beats per minute.
  • 5 years: 100 beats per minute.
  • 6 years: 80-90 beats per minute.
  • Adult: 72-80 beats per minute.
• Arterial Blood Pressure:
  • Newborn: 75 mmHg.
  • 3-12 months: 75-80 mmHg.
  • Over 2 years:
    • Systolic: 80 + 2n (n = age in years) mmHg.
    • Diastolic: (Systolic/2) + 10 mmHg.
• Cardiac output: 3.1 ± 0.4 l/min/m2.

Note:

• Postnatal circulatory changes are a natural process, but problems such as persistent foramen ovale, unclosed ductus arteriosus, congenital heart disease, etc., may occur and require timely diagnosis and treatment.
• Children’s circulation changes with age and physical condition. Regular health monitoring is crucial to detect any problems early.
• Blood pressure, pulse, and cardiac output values can vary due to factors like medical conditions, activity, weather, etc.
• This article only provides general information about children’s circulation and cannot replace professional advice from a physician.

Further Information:

• Development of the circulatory system: Children’s circulatory systems continue to develop after birth, with increased size of the heart and blood vessel system, and enhanced blood flow.
• Circulatory-related diseases: In addition to congenital heart diseases, children may also experience circulatory problems like cardiovascular disease, heart rhythm disorders, high blood pressure, anemia, etc.
• Circulatory health care: A healthy diet, regular exercise, stress management, and weight control are crucial factors in protecting children’s circulatory health.

Conclusion:

Children’s circulation has unique characteristics compared to adults. Understanding circulatory changes from the fetal stage to adulthood allows for better monitoring of children’s health.

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