Cartilage, a type of connective tissue, is made of cells called chondrocytes and the material these cells secrete. According to Professor Bruce Babiarz, Rutgers University, the relatively stiff structure of cartilage plays a very important role in the development of a fetus, as the form of the skeleton is first laid down as cartilage before it is replaced with bone. There are three main types of cartilage and each has distinct features: hyaline, elastic, and fibrocartilage.
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Compared to other types of cartilage, hyaline cartilage has fewer fibers in its matrix, and under a microscope this type of cartilage looks very smooth, according to Austin Community College. In addition, Professor Babiarz notes that, because of the lack of fibers, hyaline cartilage is sometimes called "pure cartilage."
The SUNY Downstate Medical Center discusses how hyaline cartilage lines the nasal septum, the structure that separates the right and left nostrils; it forms the rings of the trachea, commonly known as the wind pipe; it connects the ribs to the sternum, allowing them limited movement; and it lines the ends of growing bone.
Elastic cartilage has a structure that is relatively similar to hyaline cartilage. The main difference between these two types of cartilage is that elastic cartilage contains a large amount of a protein called elastin. These elastin fibers, as the name suggests, readily stretch, and enable elastic cartilage to be very flexible.
SUNY Downstate Medical Center notes that elastic cartilage is found in the ear and the epiglottis, which is the flap that closes over the top of the trachea when you swallow, preventing food from going down the trachea and entering the lungs.
Professor Barbiaz describes fibrocartilage as a transitional tissue located between dense regular connective tissue and bone. Fibrocartilage contains many collagenous fibers, which are stiffer and less flexible than the elastic fibers of elastic cartilage. SUNY Downstate Medical Center notes that these fibers are very thick and interlaced with each other.
According to SUNY Downstate Medical Center, fibrocartilage is present between the discs of the vertebrae in the spine; it forms menisci, or the crescent-shaped structures that cushion certain joints including the knee; it forms the pubic symphysis, which is the joint formed by the meeting of the right and the left pubic bones; and it is often present where ligaments and tendons are attached to bones.