What separates the atria?

What separates the atria?

• A. Interatrial septum
• B. Interventricular septum
• C. Coronary sinus
• D. Pectinate muscles

Answer: (A)

The atria are separated by the interatrial septum, a wall that divides the right atrium from the left atrium. This structure ensures that the blood in each atrium remains distinct. During fetal development, there is an opening called the foramen ovale in this region that allows blood to bypass the lungs, and after birth it normally closes, leaving a scar called the fossa ovalis. The other options don’t separate the atria: the interventricular septum sits between the ventricles, not the atria; the coronary sinus is a vein that drains into the right atrium; and pectinate muscles are ridges on the atrial walls that aid contraction but do not divide the chambers.

The atria are separated by the interatrial septum, a wall that divides the right atrium from the left atrium. This structure ensures that the blood in each atrium remains distinct. During fetal development, there is an opening called the foramen ovale in this region that allows blood to bypass the lungs, and after birth it normally closes, leaving a scar called the fossa ovalis. The other options don’t separate the atria: the interventricular septum sits between the ventricles, not the atria; the coronary sinus is a vein that drains into the right atrium; and pectinate muscles are ridges on the atrial walls that aid contraction but do not divide the chambers.