I think it's your heart because its LHL (Lung, Heart, Lung) and then the ribs protect those organs.
Heart
your lungs and your heart
Superficial
A horse's heart is located in the same place as a human's. It is between the lungs and ribs and above the diaphragm.
The ribs located between the 5th and 8th ribs in the human body are the 6th and 7th ribs.
The sternum, also known as the breastbone, is located in the center of the chest. It connects to the ribs and collarbones and plays a crucial role in protecting the heart and lungs.
the flesh and padding muscles in between each
The thoracic cavity is bounded by the ribs. It houses vital organs such as the heart and lungs, providing protection while allowing for expansion and contraction during breathing. The intercostal muscles located between the ribs assist in this process of respiration.
The inter coastal muscles in between the ribs make the ribs expand. the pleural membrane is like a slippery skin that sticks to the ribs and when they expand the lungs expand aswell.
Intercostal musles are present between the ribs.
the lungs are anterior to the ribs
Your lungs are in the thoracic cavity, which includes the chest down to the diaphragm. The lungs are located on both sides of the heart in pleural cavities.Source:http://www.dummies.com/how-to/content/what-is-in-the-thoracic-cavities.html