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Fossa Ovalis

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The heart is a muscular organ that circulates blood through the circulatory/vascular systems around the body. It assists in the distribution of oxygen to every region of the body. The heart is shaped like a quadrangular pyramid, with the anterior thoracic wall at its apex and the posterior thoracic wall at its base. It is split into two halves by a septum or partition. Four chambers are created by further dividing these sections. It is situated in the middle of the mediastinum and is surrounded by the pericardium, a two-layered sac filled with fluid. Electrical impulses generated by this muscle cause the heart to beat and pump blood throughout the body. The large blood vessels that branch out from the heart supply blood to the upper and lower limbs, thorax, and belly. The cardiovascular system of the body is made up of the heart and the circulatory system.


The heart is made up of four chambers. The upper two chambers of the heart are known as Atria (Right Atrium and Left Atrium). The lower two chambers are known as the Ventricles (Right Ventricle and Left Ventricle). 

  • Right Atrium: The superior vena cava and the inferior vena cava deliver oxygen-poor blood to the right atrium. The right atrium further pumps the blood to the right ventricle. 
  • Right Ventricle: It pumps oxygen-poor blood to the lungs through the pulmonary artery. In the lungs the carboxylated blood change to oxygenated blood. 
  • Left Atrium: After filling the blood with oxygen the pulmonary vein carries the blood to the left atrium. The left atrium pumps oxygenated blood to the left ventricle. 
  • Left Ventricle: It delivers oxygen-rich blood to all the parts of the body. 

What is Fossa Ovalis ?

One of the most important and vital components of the heart is the fossa ovalis. It is located at the heart’s right atrial depression. The depression is leveled with the inter-atrial spectrum. The distance between the right and left atriums in the heart is known as the spectrum. The Foramen Ovale is covered by a thin fibrous film that remains in the Fossa Ovalis after the development of the fetus. The Foramen Ovale forms shortly after birth and remains open throughout fetal development. The depression is typically oval-shaped and plays a significant role in embryonic growth.

Heart Anatomy


Functions of Fossa Ovalis

In the normal heart, the fossa ovalis performs the prevention of blood flow, i.e. blocking the circulation of blood, across the interatrial septum. The interatrial septum contains the fossa ovalis and includes only 20% of the entire septum. A flap of tissue called the septum primum acts as a valve over the fossa ovalis. It is the only area through which the interatrial septum can be traversed without the risk of cardiac perforation. 

After birth, the intake of air into the lungs causes a drop in the pressure in the pulmonary circulatory system. This pressure change pushes the septum primum against the atrial septum, closing the foramen. The septum primum and atrial septum eventually combine together to form a complete seal, forming a depression called the fossa ovalis. Two years later after birth around 75% of people have a completely sealed fossa ovalis. The unsealed ones are known as patent foramen ovale. A small slit-like valvular opening is usually found, at the upper margin of the fossa ovalis, leading upward beneath the limbus, into the left atrium; it is the remains of the fetal aperture the foramen ovale between the two atria

Anatomy of Fossa Ovalis 

The fossa ovalis is a depressed structure, of varying shapes, present in the inferior aspect of the right inter-atrial septum. it is a remnant of an interatrial opening and the foramen ovale, which has a significant role in fetal circulation, the fossa ovalis is the combination of the septum primum and septum secundum. Although the fossa ovalis appears two-dimensional in shape, but it’s actually a three-dimensional structure. It most commonly has an oval shape but may be circular or even elliptical. The shape and size of the fossa ovalis vary from person to person but it correlates with an individual’s weight of heart, age, and body weight. It consists of the septum secundum, septum primum, and the annulus or limbus fossa ovalis which raises around the perimeter of the fossa ovalis. The opening of the inferior vena cava lies just below and rightward to the fossa ovalis. The coronary sinus is located at the interior of the fossa ovalis, and along the same horizontal plane of the fossa ovalis lies the bundle of His. 

The floor of the fossa ovalis is formed from the septum primum which is present on the left atrial side, whereas the septum secundum derived from a bundle of the roof of the atrium, forms the limbus of the fossa ovalis. Physiologic increase in the left heart pressure at the time of birth allows the septum primum to create a tight seal with the septum secundum, forming the fossa ovalis.

Closure of the Foramen Ovale

While the baby develops and begins to use its lungs, pressure builds up in the Foramen Ovale, forcing it to close. As the foramen ovale closes and the margin of the septum secundum in the right atrium transforms into the anulus ovalis, the depression below it becomes the fossa ovalis. Independent respiration and circulation are made possible by the fossa ovalis. Usually, the closure takes place three months after the baby is born. However, there is no set timeline for the closure. The Fossa ovalis may develop from the Foramen ovale within three months or even two years after birth. There are few cases where, the Fossa ovalis never close completely.

However, there is no importance to it, and is called Patent Foramen Ovale (PFO). If it is not close, then it does not impact the heart and has no symptoms at all. Most people do not even realize the existence of the PFO within them. Many Medical researchers have found that 34% of people have the problem of PFO. A small hole is formed where the Fossa ovalis should have been formed. PFO can be identified by a medical diagnosis like Echocardiogram.

Importance of Fossa Ovalis 

The foramen ovale before birth allows the oxygenated blood that enters the right atrium through the inferior vena cava, to enter the left atrium, and to clog the flow back the opposite way, through the way of valve. Due to this function of foramen ovale the heart doesn’t work hard to pump blood where it is not needed. 

The location of the fossa ovalis is required for a number of significant surgical procedures. Patent foramen ovale and atrial septal defect repair, Right heart catheterization, Percutaneous balloon valvuloplasty, Radiofrequency catheter ablation, Pulmonary vein isolation, Left atrial appendage closure, Catheter-based mitral valve repair, Hemodynamic assessment of the mitral valve, Paravalvular leak closure are few surgical procedures that require the position of fossa ovalis. 

Disorders of Fossa Ovalis

  1. Patent Foramen Ovale (PFO): Patent Foramen Ovale occurs when there is a failure of closure of the foramen ovale created by the septa. The size of a patent foramen ovale largely depends on its clinical severity. It is characterized clinically by the presence of migraines, decompression sickness, and paradoxical emboli and strokes. This type of defect generally works like a flap valve, opening during particular conditions of increased pressure in the chest, such as during strain while having a bowel movement, cough, or sneeze.
  2. Atrial septal defect (ASD): Atrial septal defects are the result of the failure to form either the interatrial septa (septum primum, septum secundum) or sinus venosus. It may occur in isolation or as part of a syndrome. Several genes have been implicated in the development of atrial septal defects. Atrial septal defects may undergo spontaneous closure depending on their initial size at the time of diagnosis, found to be the best predictor of the progression of such defects. Atrial septal defects that are not diagnosed until adulthood can damage the heart and lungs, shortening life.
  3. Rheumatic heart disease: It is a condition where the heart valves have been damaged permanently by rheumatic fever. The shape and structure of the fossa ovalis are changed in the course of rheumatic heart disease. This disease results in extensive scarring of valves and other components of the heart. Shortness of breath and chest discomfort, fever, Nodules (lumps under the skin), and swollen, tender red, and extremely painful joints are a few symptoms of Rheumatic heart disease. 
  4. Cardiac arrhythmias: It is an irregular heartbeat. This problem in the heart rhythm occurs when the electrical signals that coordinate the heart’s beats don’t work properly. The defective signaling causes the heart to beat too fast (tachycardia) or too slow (bradycardia) or irregularly. Fluttering in the chest, racing heartbeat, slow heartbeat, chest pain, and shortness of breath are a few symptoms of cardiac arrhythmias. The treatment of heart arrhythmias may include medications, catheter procedures, implanted devices, or surgery to control or eliminate fast, slow or irregular heartbeats. 

FAQs on Fossa Ovalis

Question 1: Where is the Heart located? 


The heart is located in the front of the chest. It is present slightly behind and to the left of the sternum (breastbone). The ribcage protects the heart. 

Question 2: What is the function of the Fossa ovalis?


During the development of the fetus, The blood passes from the right atrium to the left atrium through the foramen ovale, bypassing the non-functional fetal lungs as the fetus takes oxygen from the placenta. 

Question 3: What causes a Patent Foramen Ovale?


When the Fossa ovalis is not sealed completely, then such a condition is called Patent Foramen Ovale. It is normal until birth. The flap that closes the foramen ovale takes around 6 months to 1 year of time after the birth to do so.

Question 4: Who develops Patent Foramen Ovale? 


Every individual has them at birth, but later the depression usually closes. Patent Foramen Ovale is common and is found in every 1 out of 4 adults. It is more likely to be in newborns who have a congenital heart defect. 

Question 5: What causes the foramen ovale to close after birth?


After birth, oxygen-rich blood is already present in the left atrium. Due to this, it doesn’t need blood from the right atrium. That is why the foramen ovale normally closes soon after birth. 

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Last Updated : 03 Nov, 2022
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