The heart and vascular system of a child

The heart and vascular system of a child

The heart and vascular system of a child

The heart and vascular system of a child is significantly different from that of an adult. Immediately after birth is intense morphological changes of cardio – vascular system. After the ligation of the umbilical cord, the placental circulation stops and the functioning of the pulmonary circulation begins.

Arteries in children are relatively wide and more developed than veins. The capillary network is well developed. The most intense vascular growth occurs in the 1st year of life.

Blood pressure in children is lower than in adults due to the lower pumping capacity of the heart, greater compliance of the vascular wall and the greater width of the lumen of the vessels.

A heart. The heart of a newborn has a flattened conical, oval or spherical shape due to insufficient development of the ventricles and the relatively large size of the atria. Only by the age of 10-14 does the heart acquire the same shape as that of an adult.

Its transverse diameter is 2.7 – 3.9 cm, the average length of the heart is 3.0 – 3.5 cm. The anteroposterior dimension is 1.7 – 2.6 cm.

Due to the high position of the diaphragm, the heart of the newborn is horizontal. The heart takes an oblique position by the first year of life.

The weight of a newborn’s heart is 0.8% of the total body weight, it is relatively larger than that of an adult. The right and left ventricles are the same in thickness, their walls are 5 mm. The atrium and great vessels are relatively large. By the end of the first year of heart weight doubled, to 3 years – tripled. In preschool and primary school age, heart growth slows down and increases again during puberty. By the age of 17, the mass of the heart increases 10 times.

The parts of the heart also grow unevenly. The left ventricle significantly increases its volume, by 4 months it is twice the weight of the right one. The thickness of the walls of the ventricles in a newborn is 5.5 mm, then the thickness of the left ventricle increases to 12 mm, right – to 6–7 mm.

The volume of the heart at birth is about 22sm3, the first year it increases by 20sm3, subsequently – annually 6-10sm3. At the same time, the diameter of the valve holes increases.

In children, the heart is located higher than in adults. The volume of the heart in children is greater in relation to the volume of the chest than in adults. In a newborn, the apex of the heart is formed by both ventricles, by 6 months – only the left. The projection of the heart by 1.5 years from the IV intercostal space descends into the V intercostal space.

In childhood, a qualitative restructuring of the heart muscle occurs. In young children, the heart muscle is undifferentiated and consists of thin, poorly divided myofibrils, which contain a large number of oval nuclei. There is no transverse striation. The connective tissue begins to develop. There are very few elastic elements; in early childhood, muscle fibers are close to each other. With the growth of the child, the muscle fibers thicken, and coarse connective tissue appears. The shape of the nuclei becomes rod-shaped, transverse striation of the muscles appears, and by the age of 2-3 years, the histological differentiation of the myocardium is completed. Other parts of the heart are also being improved.

As the child grows, the cardiac conduction system is improved. In early childhood, it is massive, its fibers are indistinctly contoured. In older children, overmodulation of the cardiac conduction system occurs, therefore, heart rhythm disturbances are often found in children.

The work of the heart is carried out due to the superficial and deep plexuses formed by the fibers of the vagus nerve and cervical sympathetic nodes that contact the ganglia of the sinus and atrioventricular nodes in the walls of the right atrium. The branches of the vagus nerve complete their development by 3-4 years. Until this age, cardiac activity is regulated by the sympathetic system. This explains the physiological increase in heart rate in children during the first 3 years of life. Under the influence of the vagus nerve, the heart rate decreases and arrhythmia of the respiratory type appears, the intervals between heartbeats are lengthened. The functions of the myocardium in children, such as automatism, conduction, contractility, are carried out in the same way as in adults.

Vessels. In young children, the vessels are relatively wide. The lumen of the veins is approximately equal to the lumen of the arteries. Veins grow more intensively and by the age of 15-16 they become 2 times wider than the arteries. The aorta up to 10 years `is already a pulmonary artery, gradually their diameters become the same, during puberty the aorta is wider in width than the pulmonary trunk.

The capillaries are well developed. Their permeability is much higher than that of adults. The width and abundance of capillaries predispose to blood stagnation, which is one of the reasons for the more frequent development of certain diseases in children 1 year of life, such as pneumonia and osteomyelitis. The blood flow rate in children is high, it slows down with age, which is due to the lengthening of the vascular bed as the child grows and the decrease in heart rate.

CONCLUSION

Due to the relatively large mass of the heart and the wide lumen of blood vessels, blood circulation in children is in more favorable conditions than in adults. The relatively large amount of blood and the peculiarities of energy metabolism make significant demands on the child’s heart, in this regard, the working capacity of the child’s heart is higher than that of an adult’s.{“mode”:”full”,”isActive”:false}

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