The human skeletal system is primarily composed of two types of skeletal tissue, bones and cartilage. Bones provide the framework for the human body and help protect internal organs from trauma. They also aid in red blood cell production, store minerals, and support movement. Cartilage keeps the bones connected, helps them move, and prevents friction damage at the ends of joined bones. It provides flexible support and shaping in external structures like the nose and ears as well as internal structures, such as the windpipe.
Human bones come in a variety of shapes and sizes, but there are only two types of bone composition. Compact bone is the hardest and often most recognizable skeletal tissue. This type of bone tissue covers and protects the delicate interior structures of most bones. At the center of many bones, there is network of blood vessels and red blood cell-producing bone marrow. These exist within canals of the second type of bone tissue, called spongy bone.
The human body contains three types of cartilage: fibrocartialge, elastic cartilage, and hyaline cartilage. Fibrocartilage is a specialized skeletal tissue that absorbs shocks in areas of the body that are regularly compressed, like the knee and vertebral discs. It is the densest and strongest type of cartilage.
Elastic cartilage is generally considered the most flexible cartilage. Within the human body, this type of skeletal tissue is found primarily in the outside structure of the ear. It also composes a small, trapdoor-like structure, called the epiglottis, at the entrance of the larynx. The primary function of elastic cartilage is to maintain its shape while adding support to its covering.
For a brief period in human development, hyaline cartilage is the only skeletal tissue in the human body. It forms the temporary skeleton of human embryos and lays the framework for bone development. Hyaline cartilage remains important in bone development in the form of costal cartilage in the ribcage and articular cartilage on the tips of bones that form joints. Both of these forms of hyaline cartilage aid in smooth movement and uncomplicated growth of bones.
Hyaline cartilage is also a supportive skeletal tissue. The human windpipe, called the trachea, and the structures that extend the form the windpipe into the lungs, referred to as bronchi, are composed of this type of cartilage. The larynx, or voice box, and the outside structures of human noses are also made primarily of hyaline cartilage.