Eustachian Valve occurs in

The correct option is B

Right auricle of heart

The correct option is B.

Explanation of the correct option:

1. The Eustachian valve is the fetal remnant of inferior vena cava.
2. The Eustachian valve is present at the junction of the right auricle and inferior vena cava of the heart.
3. It aids in the diversion of oxygenated blood from the IVC to the foramen ovale, allowing it to bypass the pulmonary circulation.
4. It is considered that the fetus has a functioning valve that allows oxygenated blood from the IVC to flow directly into the foramen ovale, avoiding pulmonary circulation.

Explanation of the incorrect option:

Option A:

There are no valves present in the middle ear. The middle ear contains three ossicles (tiny bones) that are flexible in nature.

Option C:

The aortic valve is present at the junction of the aorta and left ventricle which prevents the backflow of blood into the ventricles.

Option D:

The eustachian tube connects the middle ear and pharynx.

Final Answer: Eustachian valve occurs in the Right auricle of the heart.