A Quick Look At The Different Function Of Osteocytes

The human body is a complex and intricate machine, with eleven systems that function both on their own and in congruence with one another. And with 206 bones in the body, understanding the formation and functions of the skeletal system can seem overwhelming at first glance. But by breaking down and classifying the distinct parts of the skeletal system and its bones, much like scientists have enumerated the eleven systems of the body, what was once a daunting task becomes easy to comprehend. Bones of the skeletal system are made of three types of cells: osteocytes, osteoblasts, and osteoclasts.

Each of these three cells has their own purpose. However, the osteocyte makes up 90-95% of all the cells in bones. The average adult has around 42 billion osteocytes.  And, like many parts of the body, scientists are not entirely certain of the function of osteocytes.

What Are Osteocytes?

kinds of osteocytes

As osteoblasts travel along the bone matrix, they get stuck and become incorporated into the tissue, forming an osteocyte. As more of these cells are formed, they attach to one another and remain in contact with tissue on the surface of the bone through channels called canalicul. Canalicul function much like veins and use their canals to deliver nutrients and remove waste. Through their formation, osteoblasts work to strengthen and repair bones.

These cells are also the longest-living type of cell in bones and can survive decades. In fact, they have an average half-life of 25 years, making them close to the longest living cell in the body. As people grow older, they are produced at a slower rate and in smaller quantity, while the existing osteocytes begin to die. This is why conditions such as osteoporosis tend to affect older populations.

Comparing Osteoblasts, Osteoclasts, and Osteocytes

comparing osteoblasts, osteoclasts, and osteocytes

While all three work together to give you strong bones, each of these cells has a unique form and function.

Osteoblasts

osteoblasts

Osteoblasts are connective tissue cells and can be found on the exterior of the bone. These bone-forming cells can be stimulated to create osteocytes. Osteoblasts excrete a cellular matrix, and as they do, they get trapped. These cells then turn into osteocytes. An estimated 10-20 percent of osteoblasts end up being differentiated into osteocytes.

Osteoclasts

the osteoclasts

The direct opposite of osteoblasts, osteoclasts are bone-resorbing cells. The root “clast” means “to break down.” And, that’s exactly what osteoclasts do – they break down bone.  Unlike other bone cells, osteoclasts have multiple nuclei; this happens as osteoclast cells fuse with one another. Osteoclasts are formed from stem cells in the bone marrow that also form phagocytic cells which are cells that break down other cells.

Osteocytes

osteocytes

These are the cells that make up the vast majority of all bones. Unlike osteoclasts and osteoblasts that remain on the surface of the bone, these cells are found inside the bone. They manufacture type I collagen and other substances that make up the bone matrix of the skeletal system. Because they are formed by osteoblasts, they are not capable of cellular division through mitosis.

The Function of the Osteocyte

the function of the osteocyte

These cells work to strengthen your bones through bony remodeling. Most bony remodeling from osteocytes functions as either a result of mechanical or endocrinological stress. Through your normal daily life, they are being stimulated to strengthen your bones. Having cells that do not function properly or effectively can lead to serious medical conditions as microscopic damage to the bone will worsen.

Mechanical Stress

mechanical stress

One way this is done is through muscle activity. Throughout just regular motions, the activity of your muscles causes very small deformations on your bones, similar to the wear and tear done simply by driving your car. But, unlike cars, humans are self-healing machines. And as these small deformations happen throughout daily life, osteocytes use the opportunity to strengthen your bones. Some researchers have even posited that a lack of muscle activity can then result in the weakening of bones.

While simply existing causes enough damage to your bones to call these cells into action, some people take it further. Individuals who are invested in martial arts and similar practices will often do things such as punch cement walls. While this doesn’t break the bones of the hand if done correctly, it does create microfissures in the bone tissue. These microfissures are then repaired by the osteocytes’ production of collagen, and the bone is strengthened. By practicing this regularly, one can significantly strengthen their bones and make them less likely to fracture.

Endocrinological Role

endocrines system

The function of the osteocyte reaches much farther than the skeletal system. Researchers believe these cells act as moderators between body systems. They are responsible for pulling calcium from the bones if the body’s mineral levels are too low. By functioning similarly to an endocrine cell, these cells are able to provide soluble factors to tissues both inside and outside of the skeletal system.

For relatively inert cells, osteocytes are able to accomplish a surprising amount. In addition to being able to create molecular modification, they can relay signals over long distances of the body, similar to the connectivity of the nervous system. They do this by utilizing canaliculi, channels used for communication. Osteocytes contain glutamate transformers, which in congruence with the canaliculi, allow them to relay and receive messages throughout the body. These glutamate transformers aid in promoting nerve growth after a bone fissure.

Furthermore, these impressive bone cells contain proteins, such as sclerostin, that have shown to be a primary part of mineral metabolism. Through this and the nervous system-like connections that osteocytes create, they are able to influence biomineralization and metabolism for both the skeletal system and the body as a whole.

Researchers have found that stimulation of an osteocyte opens hemichannels to release multiple types of biochemical signaling molecules, one of which is ATP, or adenosine tri-phosphate. ATP is created during a process called the Krebs cycle. ATP is how the body stores and uses energy. It is essentially the gasoline that keeps the body going. This makes osteocytes an integral part of the metabolic function.

The Osteocyte in Control

osteocyte controls

As the primary cell in the bone, researchers believe that these bone cells actually control the activities of osteoblasts and osteoclasts. They are able to do this using a basic multicellular unit (BMU), which is a temporary structure where bone remodeling occurs. Osteocytes release a signal through their own cellular matrix and into that of osteoblasts to recruit the osteoblasts for bone remodeling.

Death of the Osteocyte

death of the osteocytes

As previously mentioned, as one age, these cells tend to die and not be replaced. However, bone conditions, such as osteoporosis and osteopenia can be the result of genetic or environmental conditions and can cause the death of these cells in a young person far before their time. At birth, babies usually have less than 1 percent of dead osteocytes, while that number increases drastically to 75 percent after the age of 80.

These cells can also die as a result of senesis, necrosis, and apoptosis. Senesis is the aging the cell, necrosis is degeneration, and apoptosis is programmed cell death. Apoptosis can be stimulated due to situations such as hypoxia, which is the lack of oxygen in the tissue. Cellular hypoxia can occur from something as simple as bed rest; the lack of movement decreases the flow of the body’s resources and parts of the body can suffer after not receiving necessary nourishment.

Conclusion

conclusion

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From developing a nervous system-like web of communication to stimulating their own production to balancing minerals throughout the body, osteocytes are able to accomplish an impressive amount from where they hide inside the bone matrix. These mononucleic cells are able to control and influence not only their own skeletal system, but each of the eleven systems of the human body.

The intricate machine that is the human body takes the collaborative efforts of an unfathomable number of cells and cell types. And when one type of cells begin to stop working well, it changes not just the entire system, but the entire body. Having healthy and properly functioning osteocytes is a vital part of having a healthy body in general. Functioning is a collective effort, and each part of the body has an essential role.


It is always interesting to look back and see huge scientific discoveries that we now realize are entirely flawed. Researchers are always coming to learn and understand more about the human body. Each time a discovery is made, it is easy to look back on generations before and wonder how they ever had such wrong ideas about how our bodies work.

As we are constantly learning more about how our bodies function, it can be extremely difficult to keep up with the latest research and findings. But by breaking down the body systems and investing research into each of them, the task becomes manageable. Understanding both the physiology and the function of the bones is a daunting task, especially when you’re facing a degenerative bone disorder. Don’t do it on your own – contact us today.