What Is Spongy Bone?

A diagram of the anatomy of a bone, showing the spongy bone.
In adults, most red bone marrow can be found in spongy bone.
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  • Written By: Niki Foster
  • Edited By: Andrew Jones
  • Last Modified Date: 30 November 2014
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Spongy bone, also called cancellous or trabecular bone, is one of the two types of calcium tissue that make up bones in the human body. Spongy bone is lighter, softer, and weaker than compact or cortical bone, the other type of calcium tissue, but it has a greater surface area and is much more vascular, or supplied with blood vessels. Spongy bone is found on the inside of some bones, and it is surrounded by the stronger, more protective compact bone. Cancellous bone tissue is found at the end of long bones, at joints, and in the vertebrae, the bones of the spinal column. Cancellous bone makes up a larger portion of the bone than the external compact bone tissue.

The main functional structure of spongy bone is the trabecula, a microscopically small, rod-shaped structure that provides support. Trabeculae are found in many different parts of the body, but they are most often made of collagen. Spongy bone is the only tissue to feature trabeculae made of bone. The large surface area and high vascularity of cancellous bone make it ideal for metabolic activity, such as ion and nutrient exchange.

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Spongy bone often contains red bone marrow, the site of production of blood cells. The bone marrow fills up the open spaces between the trabeculae. While the spongy bone tissue itself does not contain blood vessels, the surrounding marrow is full of capillaries, and helps transfer nutrients and other metabolic products from the blood to the bone tissue.

At birth, all of the bone marrow in the human body is red. As a person ages, the bone marrow at the center of long bones is slowly converted to yellow bone marrow, made mostly of fat cells, which does not synthesize blood cells. The bone marrow of a typical adult is half red and half yellow. However, yellow bone marrow can be converted back to red bone marrow if necessary, in the case of severe blood loss.

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anon951823
Post 10

What is the other calcium in bone besides bone?

anon318542
Post 7

Love it how my instructor does not know what she's talking about "spongy bone is hard exterior of bone."

anon292448
Post 6

@Planch: Actually, the long bone, yes at the ends the epiphysis, do contain spongy bone and compact bone and red marrow. The inner part of the bone is the diaphysis, then the actual inside, the medullary cavity is not actually hollow. It is filled with red marrow, but as you age, it recedes. So in due time it will be somewhat hollow, but it will never be completely hollow because there will always be some red marrow in the medullary cavity.

I just don't want anyone walking around thinking all their bones are hollow when they are not. I actually had a human anatomy and physiology lecture about this today.

Planch
Post 3

Here's a trivia question for you: What contains the spongy bone in adults?

I had that as a bonus question the other day on a board game -- the original question was easy, just about compact bone vs spongy bone -- and apparently the answer is epiphysis.

Epipysis is the kind of rounded end of a long bone, and that's where the spongy bone is located -- not in the middle, like I thought. Apparenlty the middle of many bones is actually hollow!

pharmchick78
Post 2

Have you ever seen a spongy bone slide under a microscope? It looks so interesting, really exactly like a sponge.

When I was studying bone health in university, and it's really scary to see some of the unhealthy spongy bone samples.

For example, the difference between a healthy spongy bone and a bone in someone who has undergone bone cancer, or even osteoporosis, is fascinating.

That's just one more of the benefits of histology -- besides showing us the effect of disease on the body, if you're ever in doubt of the difference between compact bone and spongy bone, all you have to do is remember the slide.

EarlyForest
Post 1

Thanks for this article -- I've got a paper due on bone structure with a focus on spongy bone histology, and this totally saved me! Thanks!

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