Characteristics of the Circulatory System in Children

1. Fetal Circulation:

• Formation: Fetal circulation begins to form at the end of the second month of pregnancy.

• Characteristics:

• Blood flow: Blood from the right ventricle passes through the ductus arteriosus into the aorta, then nourishes the body and the placenta. Blood from the left ventricle nourishes the lungs but in very small quantities.

• Foramen ovale: The foramen ovale is open, allowing blood to flow from the right atrium to the left atrium, reducing the load on the right ventricle.

• Pressure: Right atrial pressure is higher than left atrial pressure, so blood flows through the foramen ovale into the left atrium.

• Cardiac output: Right ventricular output is higher than left ventricular output.

• Fetal cardiac output: Approximately 450 ml/kg/min.

• Aortic pressure:

• During pregnancy: Aortic pressure is low because blood mainly nourishes the placenta.

• After birth: Aortic pressure increases abruptly due to umbilical cord clamping, as blood no longer nourishes the placenta.

• Ductus arteriosus: The ductus arteriosus closes 3-4 months after birth, becoming the ligamentum arteriosum.

• Foramen ovale: The foramen ovale closes 6-10 weeks after birth.

• Umbilical arteries: The umbilical arteries become fibrous after 2-3 months after birth, transforming into the median umbilical ligaments.

• Umbilical vein: The umbilical vein becomes the ligamentum teres hepatis.

Note: Fetal circulation has special structures that help blood nourish the body and placenta efficiently. After birth, the circulatory system changes to adapt to pulmonary respiration.

2. Circulation in Newborns:

• Heart position:

• First few months after birth: The heart lies horizontally, with the apex located outside the nipple line at T1-2 cm (due to the diaphragm being pushed up).

• 1 year old: The heart lies obliquely, with the apex located outside the nipple line at T1 cm.

• 4 years old: The heart lies straight and the apex slightly deviates to T due to lung and chest development, causing the diaphragm to descend.

• Left atrial pressure: Left atrial pressure is higher than right atrial pressure due to:

• Umbilical cord clamping: The placental capillary network that receives the majority of blood from the fetal aorta is lost, increasing pressure in the aorta, left atrium, and left ventricle.

• Ductus arteriosus: The ductus arteriosus closes due to:

• Increased arterial PO2.

• Decreased pulmonary artery pressure.

• Sudden decrease in prostaglandin E levels.

• Foramen ovale: The foramen ovale closes due to increased volume and pressure in the left atrium.

• Ratio of vein diameter to artery diameter: 1/1 in newborns, 2/1 in adults.

• Ratio of pulmonary artery diameter to aortic diameter:

• <10 years old: pulmonary artery > aorta.

• 10-12 years old: pulmonary artery = aorta.

• Puberty: pulmonary artery < aorta.

• Pulse: 140-160 beats/minute.

• Arterial blood pressure:

• Systolic: 75 mmHg.

• Diastolic: 2/3 of systolic + 10 mmHg.

• Cardiac output: 110 -150ml/kg.

Note: The circulatory system of newborns is still developing and has many differences from adults. Monitoring cardiovascular health for newborns is crucial.

3. Circulation in Older Children:

• Pulse:

• 6 months: 130-140 beats/minute.

• 1 year: 120-130 beats/minute.

• 5 years: 100 beats/minute.

• >6 years: 80-90 beats/minute.

• Arterial blood pressure:

• >1 year: Systolic = 80 + 2n (n is the number of years).

• Cardiac output:

• Breastfed infants: 75-100ml/kg.

• Children >7 years: 50-90 ml/kg.

• Cardiac index: 3,1 +/- 0,4 l/min/m2.

• Note: Arterial blood pressure and cardiac output increase with age, but regular monitoring of cardiovascular health is still essential.

Additional Information:

• How much higher is the arterial blood pressure in the legs than in the arms? 10-20 mmHg.

• Systolic blood pressure in children aged 3-12 months? 75-80 mmHg.

Conclusion: The circulatory system of children has unique characteristics that are suitable for the stage of their body development. Monitoring cardiovascular health in children is very important for early detection of heart problems.

Please note: This is a general description of the circulatory system in children. It is important to consult with a medical professional for personalized advice.