肋骨像一个笼子 (因此也称rib cage)。主要包括四部分：bones（骨头）、cartilage（软骨）、sternum（胸骨）与vertebra（脊柱），如下图：

Cartilage is attached to the front portion of your ribs and allows your chest to expand as you move and breathe. But your ribs and associated cartilage have limited flexibility

肋骨主要有12对，分为两部分：true ribs (1-7 pairs,  which are attached directly to the sternum by cartilage known as costal cartilage) and false ribs (8-12 pairs)。其中，11与12根肋骨又称floating ribs。如下图：

There is another way to divide the 8-12 pairs of ribs into two groups: false ribs (8-10 pairs) and floating ribs (11,12 paris). Anyway, the 8-10 pairs are attached to to the last pair of the true ribs. 

The ribcage supports the upper body, protects internal organs, including the heart and lungs, and assists with breathing. Rib injuries include bruises, torn cartilage and bone fractures. Chest trauma may also cause life-threatening injuries such as a punctured lung or a ruptured aorta. 

(Two great picts are from https://www.healthline.com/human-body-maps/costal-cartilage#1  There are other wonderful picts in this website)

From： http://clickmypicture.com/ribs-sternum/

https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/rib-injuries

https://www.livestrong.com/article/248642-what-are-the-symptoms-of-torn-cartilage-in-the-ribs/