Did you know that it is our bones, not our brains that convey feelings of fatigue? The bones in our body are regarded as one of the most phenomenal tissues found in the body. Without them, we wouldn’t have any definite shape and our way of movement would be to creep on the ground like slugs. At the first stages of life, the human skeleton is made up mostly of fibrous membranes and cartilages. As we grow, these cartilages are replaced by strong bones and those that do remain as cartilages are usually found in areas where greater flexibility is needed.
Basic Structure, Types and Locations
Water is the primary composition of cartilage tissue. A group of cartilage tissue is collectively known as a skeletal cartilage. Because it is made up mostly of water, cartilages are extremely resilient which means it can spring back to its original shape. Take note that cartilages don’t have any nerve endings or any blood vessels. The perichondrium surrounds the cartilage and functions to resist outward expansion of the cartilage when it is being compressed. The perichondrium is also the location where blood vessels terminate; giving the cartilage cells the necessary nutrients through a process known as diffusion.
Imagine a frosted glass and picture it being inside your body; that would be your hyaline cartilages. Hyaline cartilages, which provides support coupled with resilience and flexibility, are the most abundant type of skeletal cartilages. Some examples of hyaline cartilages found in the body are the ones that cover the end parts of most movable joints, the cartilages that connect the ribs to the sternum and the nasal cartilages.
Elastic cartilages are cousins of hyaline cartilages since they basically have the same looks but elastic cartilages contain more elastic fibres. Because of the abundance of elastic fibres, elastic cartilages are able to stand up to repeated bending without presenting any damage. Only two known skeletal locations where elastic cartilages exist and they are the epiglottis and the external ear.
Between elastic cartilages and hyaline cartilages, fibrocartilages places in between the two. They possess great tensile strength and a characteristic unique to fibrocartilages, highly compressible. Fibrocartilages are found in sites that are subjected to both stretch and heavy pressure like the menisci of the knee and the discs in between the vertebrae.
Growth of Cartilage
What makes a bone stable is the presence of hard matrix which makes growth possible in an outward motion. Cartilages on the other hand have a flexible matrix. The flexible matrix can accommodate mitosis, making it ideal as foundation of embryonic skeleton to provide new skeletal growth.
Cartilages can grow in two ways, namely appositional growth and interstitial growth. In appositional growth of cartilages, the cells that surround the perichondrium secrete new matrix forming substances on the cartilage tissue. The opposite happens during interstitial growth. The new matrix is formed from within the cartilage.
Do take note that calcified cartilages are not bones. There is always a distinct difference between bones and cartilage.