Eli5: What is a spinal disk made of? And do they NEED to be in a spine model?


Example: if you die in a field and all your mustles “disolve?” And all thats left of your body are bones, would the disks also be there?

In: 41

The outer layer of the discs are made of cartilage. Cartilage is a kind of tissue that is flexible, so it can withstand tension. It’s found in many joints, like your knees, to make it so two bones aren’t just grinding in to eachother.

Inside the disk is a gelatin-like substances that make it so the disks can be squished and stretched. When you lean forward, the front of the disks get squished.

The spine needs to be very flexible and stable at the same time, so the discs are definitely needed.

Between the bones there is like a cartilage bubble, inside the bubble is a fluid, this fluid is called Nucleous Pulposus.

This acts like a shock absorber for things to do on the day to day such as bending or even walking. This stuff NEEDS to be there otherwise you would have bone rubbing on bone. People with ruptured discs have a hard time bending or walking cause that cushioning effect isn’t there.

It also surrounds the spinal cord which is vital to control all your body.

As they aren’t made of bone they decay when we die so that’s why we only find bones

It depends on the type of model you’re making. If it’s an osteopathic model, then you can omit them. If it’s an orthopedic or musculoskeletal model, then you should include them.

The discs decompose. Only bone remains. Yes, discs need to be in a spine model. Optional is ligaments that surround the spine. It depends on the purpose of your model.

There are lots of medical illustrations of discs available online. Check out illustrations by Dr. Frank Netter. You’ll see that they lie between the vertebral bodies (the round blocks that comprise the front of the spinal column when stacked up). Depending on how detailed you want to be, the ends of the vertebral bodies that touch the disc are layered in cartilage (called the cartilage endplates). The outer ring of the disc is not cartilage, but multiple layers of collagen fibers oriented in different directions like the ply layers of an automobile tire. In Latin, it is the annulus fibrosus (“fibrous ring”). The middle of the disc is gelatinous, called the nucleus pulposus (fleshy core), and contains living cells that make and maintain the gelatinous material.

One reason the discs are important is that they effect the way the actual bones fit together. This comes up in paleontology a lot. Sometimes people make estimates about the flexibility and position of animal necks and spines that are incorrect because they just set the bones together rather than accounting for cartiledge