Correct Option
The correct option is Atria — Upper chambers
Explanation
The human heart is a muscular organ divided into four distinct chambers. These chambers are anatomically categorized based on their position (superior or inferior) and their function in the circulation of blood.
Option Analysis
- Option (a) is Incorrect: The atria (singular: atrium) are the two upper chambers of the heart, not the lower ones. Their primary function is to receive blood returning to the heart from the body and the lungs.
- Option (b) is Incorrect: The ventricles are the two lower chambers of the heart. They are responsible for pumping blood out of the heart to the lungs and the rest of the body.
- Option (c) is Correct: The atria are anatomically situated as the upper chambers. They are smaller and have thinner walls compared to the ventricles because they only pump blood into the ventricles below them.
- Option (d) is Incorrect: Ventricles are defined as the lower chambers. There is no anatomical classification of "side chambers" in the standard description of the human heart structure.
Key Takeaway
The heart consists of four chambers: the two upper receiving chambers are called atria, and the two lower pumping chambers are called ventricles.