A baby is born with a congenital cardiac defect that allows right atrial blood to bypass the lungs and enter the left atrium . Which of the following structural defects must be surgically repaired to save this baby's life ?

Options

A. Ductus venosus
B. Foramen ovale
C. Ductus arteriosus
D. Ductus vena cavas

Answer

To solve the question regarding the congenital cardiac defect in a baby, we can follow these steps:

### Step 1: Understand the Problem
The question states that a baby has a congenital cardiac defect that allows blood from the right atrium to bypass the lungs and enter the left atrium. This indicates that there is a structural defect in the heart that is causing this abnormal blood flow.

### Step 2: Identify the Relevant Structures
In the heart, the right atrium receives deoxygenated blood from the body, and it normally sends this blood to the lungs for oxygenation. The left atrium receives oxygenated blood from the lungs. If blood from the right atrium is entering the left atrium directly, it suggests a defect in the septum that separates these two chambers.

### Step 3: Analyze the Options
The options provided are:
1. Ductus venosus
2. Foramen ovale
3. Ductus arteriosus
4. Ductus venacavus

We need to identify which of these structures is responsible for the mixing of blood between the right and left atria.

### Step 4: Focus on Foramen Ovale
The foramen ovale is a small hole in the septum between the right and left atria. In a normal fetal heart, this opening allows blood to bypass the non-functioning lungs. After birth, this opening usually closes. If it remains open (a condition known as patent foramen ovale), it can allow deoxygenated blood from the right atrium to mix with oxygenated blood in the left atrium.

### Step 5: Conclusion
To save the baby's life, the structural defect that must be surgically repaired is the foramen ovale. This repair will prevent the mixing of deoxygenated and oxygenated blood, ensuring proper circulation and oxygenation.

### Final Answer
The structural defect that must be surgically repaired is the **foramen ovale**.

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