Trabeculae of Bone: Definition & Function

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  • 0:00 What Are Trabeculae?
  • 1:25 Types of Cells in Trabeculae
  • 3:10 Change and Growth
  • 4:55 Lesson Summary
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Lesson Transcript
Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Trabeculae of bone provide structural support to the spongy bone found at the ends of long bones. In this lesson, we will learn about the structure of trabeculae and how they can grow and change in response to mechanical stress.

What Are Trabeculae?

Imagine that you could shrink yourself and go into your hip and then inside the bone tissue at the end of your femur (the largest bone in your leg). What would you see there? At the ends of long bones like the femur, the bone is actually not solid but is full of holes that are connected to each other by thin rods and plates of bone tissue known as trabeculae.

This type of porous bone is known as cancellous bone, and it's found at the ends of long bones like the femur and also in the pelvic bones, ribs, skull, and the vertebrae in the spinal column. Cancellous bone also contains a lot of red bone marrow that fills up the spaces between trabeculae. This bone marrow is really important because it is where all the blood cells in your body are made.

Although cancellous bone has a lot of holes in it, it is still very strong. Every time you walk or run or jump, you put large mechanical stresses on the bones in your hips, spine, and pelvis, and they don't break. This strength is provided by the trabeculae.

Although it might look like trabeculae are randomly arranged, this isn't true! They're carefully constructed by your body to support the areas that experience the most stress, just like braces are used to hold up a building. As you move, you create stress on the trabeculae and they can grow and change shape and direction in order to give you the support you need to have an active life.

What Types of Cells Are in Trabeculae?

If you could shrink yourself even more and go inside a trabecula, you would find three types of cells that work together to keep your bones strong and healthy: the osteoblasts, osteocytes, and osteoclasts.

Cells called osteoblasts are responsible for making bone tissue. They are secreted in rings called lamellae that expand outward as the trabeculae get larger. As new tissue grows around the osteoblast, a hard ceramic material called calcium phosphate begins to surround the cell. When it becomes completely surrounded by hard bone tissue, each osteoblast will stop making new bone tissue and turn into an osteocyte.

Osteocytes are responsible for sensing when the bone is damaged or being subjected to stress. They live inside the bone tissue in small spaces and are connected to each other through tiny cracks in the bone tissue called canaliculi. Osteocytes don't make new bone tissue anymore, but they tell the other cells what do to and make sure that your trabeculae are growing and changing so that they can meet the demands that you place on them as you go about your daily activities.

The third important cell in bone tissue is the osteoclast. Osteoclast means 'bone-eating cell,' and these cells are responsible for destroying old or damaged bone so that it can be repaired and replaced by osteoblasts.

In healthy bones, the process of remodeling bone tissue by destroying old bone and replacing it with new bone is ongoing and very carefully regulated. The trabeculae need to provide the necessary support without becoming too thick, since that could reduce the space available for bone marrow and make the bone unnecessarily heavy. It's even more important that they don't become too thin, which could cause the bone to fracture easily.

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