A rib is a curved bone that forms part of the rib cage in the human body. Humans typically have 24 ribs, arranged in 12 pairs, which protect vital organs such as the heart and lungs. Ribs also play a crucial role in the respiratory system by allowing the chest to expand and contract during breathing. Ribs are connected to the spine at the back and, in most cases, to the sternum at the front through cartilage. This structure provides flexibility and strength, enabling the rib cage to support the upper body while allowing for movement. Related topics include thoracic vertebrae and intercostal muscles.