The skeletal system is made up of bones, cartilage, ligaments, and tendons, but only bones are considered organs.

Here's why:

* Organs are composed of different tissues working together to perform a specific function.

* Bones are made of different types of tissues: bone tissue itself (both compact and spongy), cartilage, connective tissue, blood vessels, and nerves. These tissues work together to provide support, protection, and movement.

Cartilage, ligaments, and tendons are not organs. They are tissues that contribute to the skeletal system's function but are not organs themselves.

Here's a breakdown:

* Cartilage: A type of connective tissue that provides cushioning and flexibility.

* Ligaments: Connective tissue that connects bones to each other.

* Tendons: Connective tissue that connects muscles to bones.

So, while the skeletal system includes cartilage, ligaments, and tendons, the only true organs within it are the bones themselves.