The costal cailages of these ribs do not reach the sternum
**Core Concept**
The **costal cartilages** are hyaline cartilage bars that connect the **ribs** to the **sternum**, providing flexibility to the **thoracic cage**. The first seven pairs of ribs are directly attached to the sternum via their costal cartilages.
**Why the Correct Answer is Right**
The correct answer relates to the anatomy of the **false ribs** and **floating ribs**. The 8th, 9th, and 10th ribs are considered **false ribs** because their costal cartilages do not directly attach to the sternum. Instead, they are connected to the 7th rib's costal cartilage, which then connects to the sternum. The 11th and 12th ribs are **floating ribs**, meaning they do not have costal cartilages that reach the sternum or any other rib.
**Why Each Wrong Option is Incorrect**
**Option A:** and **Option B:** are incorrect because the first seven pairs of ribs have costal cartilages that directly reach the sternum.
**Option C:** is incorrect because the 8th, 9th, and 10th ribs' costal cartilages do not directly reach the sternum, but this option is not provided to be evaluated.
**Clinical Pearl / High-Yield Fact**
It's crucial to remember the distinction between **true ribs**, **false ribs**, and **floating ribs** based on their attachment to the sternum, as this knowledge can help in understanding and diagnosing various thoracic conditions.
**Correct Answer:** D. 8, 9, 10, 11 and 12 ribs.