cartilage
The Spanish word 'cartílago' translates to 'cartilage' in English. Cartilage is a type of flexible but strong connective tissue found in various parts of the body, such as joints, throat and nose. 'Cartílago' is a noun in Spanish, as it names a body part, similar to how 'cartilage' is a noun in English.
The shark is famous for its skeleton made entirely of cartilage.
This in Spanish we use the makeup of animals to talk about their body structure. In this case, stating that a shark's skeleton is comprised entirely of cartilage.
The surgeon repaired the cartilage in my knee.
When talking about surgeries, we often use the body part and the substance or structure that was treated in Spanish. Here, we are speaking about a surgeon repairing knee cartilage.
The cartilage of the ear is less hard than bone.
In Spanish, we use the structure of various body parts to describe their hardness or softness. In this case, we're contrasting the less hard ear cartilage with bone.