The musculoskeletal system
- [Instructor] Alrighty, so we're talking about cartilage, and cartilage is, at the most basic level, a connective tissue that can be found throughout the entire human body. And so cartilage is an extracellular tissue secreted by cells called chondrocytes, which are derived from the same precursor cells as bone, the fibroblast. Now chondrocytes secrete fibrous materials such as collagen, which is a strong fibrous protein, and elastin, which as it's name sort of sounds like, is an elastic protein that provides a rubbery, elastic component to cartilage. And one thing that I just wanted to touch on briefly is something that I personally sort of struggled with for a little while before I realized, ah that's what it is. So cartilage basically is, as I said, a connective tissue, just like bone, just like fat and other connective tissues that you find in the body. Collagen, on the other hand, is one of the building blocks of cartilage. So, I feel like sometimes it was easy for me to confuse these two terms, but realize that cartilage is actually referring to the type of tissue and collagen is referring to the type of protein that is found in cartilage. Now the key thing to remember about collagen and elastin, that make up cartilage, is that it gives cartilage strength and flexibility. And a couple of other key points to remember about cartilage is that it is not innervated, meaning it doesn't have nerve cells, and it is also avascular, meaning it doesn't have any vasculature that runs through it. In other words, it doesn't have arteries and veins and blood vessels that run through. Instead, cartilage receives nutrition and immune protection from the surrounding fluid. So, there are three main types of cartilage found within the body. The first type is called hyaline cartilage. So, you can find hyaline cartilage in the larynx and trachea in the throat portion of the body, and then also in all of the joints where the surfaces of bones are articulating each other. So this is called articular cartilage. And, the main purpose of hyaline cartilage is to reduce friction and absorb shock. The second type of cartilage that you will find in the human body is called elastic cartilage, which can be found in the shape of the outer ear, and also the epiglottis which is the structure that protects your airway whenever you are swallowing food. And so the main purpose of elastic cartilage is to provide shape and support. And then finally we have fibrous cartilage. And you can find fibrous cartilage in the intervertebral discs in the spine and also in an area of the pelvis called the pubic symphysis which is where the two halves of your pelvic bones come together to form a joint there. And the main purpose of fibrous cartilage is to provide rigidity and to absorb the shock that is transmitted between these joints.
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