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Heart Anatomy: Chambers, Valves, Blood Vessels and Functions

Posted on by Prof. Dr. İbrahim Cansaran TANIDIR

The anatomy of the heart is a dynamic muscular structure that manages the body’s blood circulation and consists of four main chambers and delicate valves that determine the direction of blood flow. From the perspective of a pediatric cardiologist, this structure represents a flawless architecture that begins to take shape from the fetal period and separates deoxygenated blood on the right side from oxygenated blood on the left side. This arrangement between the right and left atria and ventricles serves as the main motor that meets the body’s oxygen needs at every stage of life. This biological design of the heart is the most fundamental basis of a healthy life and developmental process.

What Kind of Anatomical Structure Does Our Heart Actually Have?

The anatomy of the heart resembles the plan of a very cleverly designed four-room house. This house has two separate sides, right and left, and rooms with different functions above and below. The right side of our heart is responsible for collecting blood that has circulated through the body and used up its oxygen, in other words, “deoxygenated” blood. This deoxygenated blood first comes to the upper right room, namely the right atrium, then passes through a door and flows into the large lower right room, namely the right ventricle. From there, it is pumped to the lungs with great pressure to be cleaned. The left side undertakes a completely different task. Blood that becomes filled with oxygen and completely clean in the lungs reaches the upper left room (left atrium), and from there passes to the lower left room (left ventricle), which has the strongest muscles of the heart. When the left ventricle contracts, it sends this oxygen-filled source of life to the entire body, from the top of our head to the tips of our toes.

There is a very strong wall separating these two different worlds, namely oxygenated and deoxygenated blood. This thick muscular wall, called the “septum” in medical language, ensures that there is no leakage between the right and left chambers. In addition, there are one-way opening doors, namely valves, at the transition points between the chambers. These valves allow blood to flow only forward and never permit it to leak backward. That rhythmic sound we hear with each heartbeat is actually the sound of these valves opening and closing with perfect timing.

How Does the Heart of a Baby in the Womb Work?

While the baby is in the womb, the baby does not breathe yet, and the lungs do not fill and empty with air. During that period, the lungs are like deflated balloons, and the cleaning process of the blood is entirely undertaken by the placenta, namely the baby’s partner. Since the lungs are out of function, there is no need for blood to go to that area. This is exactly where the miracle of nature begins. In this process we call the fetal period, there are some life-saving shortcuts and hidden doors inside the heart.

Thanks to this temporary system, blood is distributed directly to the body without stopping by the lungs. There is a hole between the right and left atria that allows blood to pass directly across. At the same time, there is a thick bridge vessel between the vessel going to the lungs and the main vessel going to the body (aorta). Thanks to these bridges, the clean blood coming from the mother is delivered without losing time to the rapidly developing brain and organs of the baby. These shortcuts are vital for a baby in the womb, and every baby’s heart is built with this special architecture.

What Changes in the Baby’s Heart After Birth?

When the baby opens their eyes to the world and fills their lungs with air with that first cry, a huge transformation takes place in the body within seconds. That first breath suddenly inflates the lungs that had been waiting like deflated balloons. The lung vessels widen, and blood rushes to the lungs to be cleaned at a speed greater than ever before. This sudden and tremendous pressure change initiates the closing process of those temporary holes and bridge vessels that were life-saving in the womb.

The hole between the atria closes over itself instantly like a mechanical door as the pressure on the left side increases. The bridge vessel between the great vessels senses the rapidly rising oxygen level in the blood and begins to contract on its own, then completely shrinks and closes within a few days. Thus, the right and left sides of the heart become completely isolated from each other and turn into two separate independent pumps, just like in an adult human. This incredible transformation is one of the most fascinating moments of human physiology. However, sometimes disruptions occur in this perfect functioning, and failure of these pathways to close leads to congenital heart diseases.

Can Heart Diseases Be Detected While the Baby Is in the Womb?

Thanks to developing technology, it is now possible to examine the heart of a baby in the womb in detail as if it were in the palm of our hand. Expectant mothers may generally feel anxious about this test, but it is a very safe method that works entirely with sound waves and does not harm the baby in any way. Especially between the eighteenth and twenty-second weeks of pregnancy is the golden period when the structural details of the heart can be seen most clearly.

During this examination, it is checked whether the four chambers of the heart are growing equally, whether there is a hole in the walls, and whether the valves open and close properly. At the same time, the baby’s heart rate is measured very carefully. A heart that beats too fast or too slowly can lead to heart failure in the baby, so early detection is of vital importance. If a problem is detected in the womb, obstetricians, neonatologists, and pediatric cardiologists immediately come together and plan what will be done from the very first moment the baby is born. This preparation creates an excellent protective shield for babies who start life one step behind.

What Are the Risk Factors in Congenital Heart Diseases?

The formation of a baby’s heart is like a delicate construction process in which millions of cells and genetic codes work in perfect harmony. Sometimes this process may be disrupted due to genetic or external factors. Families often tend to blame themselves, but most of the time, a complex interaction of multiple factors lies behind these developmental problems. The mother having a congenital heart disease, certain genetic syndromes, or some environmental conditions encountered during pregnancy may directly affect the formation of the heart. Especially in chromosomal differences such as Down syndrome, failure of the walls separating the heart chambers to develop is a condition we encounter very frequently.

Some main risk factors that may affect heart development during pregnancy are as follows:

  • Genetic predispositions
  • Chromosomal abnormalities
  • Uncontrolled diabetes
  • Various infections (especially viral infections)
  • Certain medications used
  • Consanguineous marriages

What Does Having a Hole in the Heart Mean and Does It Close?

One of the most commonly heard conditions among the public and one that worries families the most is having a “hole in the heart.” In medical terms, Ventricular Septal Defect is the presence of an opening in the thick muscular wall separating the two large lower ventricles of the heart, or Atrial Septal Defect is the presence of an opening in the thin wall separating the two upper atria of the heart. The clean and high-pressure blood on the left side passes through this hole and mixes with the deoxygenated blood on the right side. This causes the heart and lungs to become more tired than necessary, the baby to become breathless, tire quickly while feeding, and fail to gain weight.

However, not every hole carries the same risk. Where the hole is located in the wall is the biggest indicator of whether it will close on its own. Holes located in the thin membranous area just below the valves of the heart generally tend to close spontaneously in the first years of life as the surrounding tissues cover them like a patch. Holes located right in the middle of the muscle tissue may narrow and disappear over time as the heart muscle grows and strengthens. However, holes located in the outflow tract of the heart, just below the great vessels, or located just below the valves unfortunately do not close spontaneously. In fact, the strong vacuum effect created by blood passing through that area may pull the valve above downward and disrupt its structure. Therefore, holes in this region need to be surgically closed before causing permanent damage to the child’s heart.

How Are Heart Holes Between the Atria Closed?

Holes located between the two small upper chambers of the heart, the atria, are called Atrial Septal Defect (ASD). These holes usually progress more silently compared to lower ventricular holes. Clean blood on the left side gently leaks to the right side. The child lives childhood, runs, plays, and may show no symptoms. However, as years, even decades pass, this extra fluid load placed on the right side causes the right side of the heart to enlarge and tire unnecessarily. If no intervention is performed, rhythm disorders and heart failure become inevitable in adulthood.

Fortunately, today medicine has developed excellent methods to close these holes. Without the need to split the chest wall from end to end or stop the heart, a very thin, soft tube (catheter) is advanced through a vein in the groin all the way into the heart. A tiny two-disc device made of a special metal alloy is advanced through this tube and placed right in the middle of the hole. One disc of the device opens in the left atrium and the other disc opens in the right atrium, and the hole is tightly closed by being sandwiched between them. After the procedure, the child carries no surgical scar on the chest, the heart has not been stopped, and the child is generally discharged from the hospital the next day in a way that allows them to continue running and playing from where they left off.

How Are Heart Vessels That Remain Open After Birth Treated?

We mentioned that the vital bridge vessel used to bypass the lungs in the womb should complete its task and close after birth. However, in some babies, especially premature babies, this vessel stubbornly remains open. Clean blood under very high pressure in the aorta continuously flows through this bridge into the pulmonary vessel. The lungs experience an unexpected blood flood. The baby has difficulty breathing, the lungs fill with fluid, and the heart struggles to handle this extra load.

The treatment of this problem is quite pleasing, just like in atrial holes. The open bridge vessel is reached by entering through a thin vascular route from the groin. According to the width and shape of the vessel, flexible caterpillar-like coils or small umbrella-like plugs are placed, and blood flow is stopped immediately. The procedure takes only minutes, and the baby’s lungs relax immediately. However, in some special cases where the vessel is very wide or the baby is too small to be suitable for the device, this vessel may need to be tied externally with a small surgical incision made from the side of the chest.

What Are Cyanotic Heart Diseases Accompanied by Bluish Discoloration?

Some congenital heart diseases have a much more complex anatomy. In these conditions, deoxygenated blood cannot go to the lungs to be cleaned, or oxygenated blood coming from the lungs cannot be pumped to the body. As a result, deoxygenated blood with low oxygen spreads through the body. Families notice this through the bluish-purple color change (cyanosis) appearing on the child’s lips, nail beds, and skin. The management of these babies is a much more delicate process.

The best known of these is the disease called Tetralogy of Fallot. As the name suggests, in this disease, four different anatomical defects are present in the heart architecture at the same time. It is not possible for the child to live a healthy life without correcting these defects that seriously strain the functioning of the heart. The main factor determining how much the child will turn blue is the severity of the narrowing in the pulmonary pathway. The solution is surgical widening of that narrow pathway and patching of the hole. In much more severe diseases such as transposition of the great vessels, urgent interventions immediately after birth and major heart surgeries in the following weeks are essential.

The basic components of Tetralogy of Fallot are as follows:

  • A large hole between the ventricles
  • Narrowing in the vessel going to the lungs
  • Displacement of the aorta toward the center of the heart
  • Excessive thickening of the right ventricular muscle

Which Methods Are Used When Diagnosing Heart Diseases in Children?

The first and most important rule of treating a heart problem is to understand the anatomical problem perfectly. If we think of the heart as a closed box, we must have very powerful tools to see inside it. Our gold standard is always echocardiography. This method allows us to create a three-dimensional, moving, and colored map of the heart entirely through sound waves without giving any radiation to the body. We can see the contraction strength of the heart, the movement of the valves, and where the blood flows from and to at what speed within seconds. The fact that the child does not feel pain during the procedure is the greatest advantage. However, in some complex diseases, the vessels around the heart also need to be examined in great detail. In such cases, advanced imaging technologies come into play.

The methods we most commonly use in diagnosis are as follows:

  • Echocardiography devices
  • Computed tomography scans (Cardiac CT)
  • Magnetic resonance imaging (Cardiac MRI)
  • Cardiac catheterization (Angiography)
  • 24-hour rhythm Holter monitoring

How Are Non-Surgical Heart Treatments Performed and Are They Successful?

In previous years, even the smallest structural problem in the heart required the child’s chest wall to be opened and a long, difficult open-heart surgery to be performed. Today, however, the medical world is at a very different point. Thanks to millimetric tubes and devices advanced through the groin vessels, the need for open-heart surgery has decreased dramatically. These procedures performed in angiography laboratories restore children to health without leaving permanent trauma on their bodies.

For example, congenitally narrowed heart valves whose leaflets are fused together are opened within seconds by advancing a deflated balloon through the vessel and inflating it with high pressure right in the middle of the valve. Narrowed vessels are widened with metal cages (stents). Thanks to these methods, the child does not experience pain, does not stay in intensive care for days, and returns home in a very short time. When performed in experienced centers, the success rates of these procedures are incredibly high and their risks are much lower compared to surgery.

Procedures successfully performed with this method are as follows:

  • Opening valve and vessel stenoses with balloon
  • Placement of stents in vessel stenoses
  • Closure of heart holes with umbrella devices
  • Occlusion of vessels that remain open with plugs
  • Pulmonary valve implantation
Güncellenme Tarihi: 13.10.2026

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