The Bare Bones: An Overview of the Skeletal System

“I am a collection of thoughts and memories and likes and dislikes. I am the things that have happened to me and the sum of everything I’ve ever done. I am the clothes I wear on my back. I am every place and every person and every object I have ever come across. I am a bag of bones stuck to a very large rock spinning a thousand miles an hour.”

–Macauley Culkin

Last post we examined the movement of blood and oxygen throughout the body by studying the circulatory system. Next let’s look at the system responsible for creating our blood cells and providing support and protection for our bodies: the skeletal system.

The average adult body has 206 bones providing many important functions. Our skeleton provides the framework from which movement is possible. Ligaments attach bones to other bones and tendons attach muscles to bones, allowing for movement to occur. If we didn’t have a skeletal structure, we wouldn’t be able to support complex life.

Types of Bones

There are four main types of bones in the human body.

  1. Long bones: as the name implies, long bones are some of the largest bones in the body. This length provides for a high degree of leverage and movement. They consist of a central shaft (known as the diaphysis) and knobs at each end (known as the epiphysus). An example of a long bone is the largest bone in the body, the femur, located in the upper leg between the hips and the knee. In yoga, the length of the femur allows us to move our legs in a very large degree of motion. Just think of the large movement occurring in standing splits as one leg is extends backwards while the other stands upright!

  2. Short bones: as the name implies, short bones are much smaller than long bones. They provide a great amount of support and are often box-like and found close to one another. An example of short bones are the bones found within the wrist. In yoga we often place a lot of weight onto our wrists and ankles. These bones help to bear weight and establish our foundational support. Think of downward facing dog and all the weight that is directed down into the tiny bones in your wrists and ankles!

  3. Flat bones: as the name implies, flat bones are less round than other bones. This is because they are designed to protect our vital organs. Our skull, ribs, and sternum are examples of flat bones. Our sternum and ribs protect our lungs and heart while our skull protects our brain. Flat bones have minimal movement because we always want them in place to protect the organs we need to live. Think about coming into a headstand. Without flat bones for protection, the weight of our bodies would smush our brains!

  4. Irregular bones: irregular bones are the remaining bones that do not fit into the categories above. They often have a very specific function, such as the tiny hammer and anvil in our ears. The most common irregular bones are the vertebrae, which we will examine in more detail in a later post.

The Axial and Appendicular Skeletons

The human skeleton is categorized into two sections: the axial skeleton and appendicular skeleton.

The axial skeleton corresponds to the center of the body and holds the body upright and protects our vital organs. It consists of the skull, vertebral column, and rib cage. A total of 80 bones comprise the axial skeleton.

The appendicular skeleton corresponds to our appendages, our arms and legs. It consists of the shoulder girdle, pelvic girdle, arms, legs, hands and feet. A total of 126 bones comprise the appendicular skeleton.

Note that in the locations where the axial skeleton and appendicular skeleton meet we have the highest range of motion. The ball and socket joints of the shoulder and hips allow for our appendages to move in all different directions. We will examine the joints of the body in a later post.

The major bones of the human skeleton.
The major bones of the human skeleton.

Blood Cell Creation

Our bones are responsible for much more than just protection and support. The outside of our bones are hard but the insides are spongy. Within this spongy tissue lies the bone marrow. Here new red and white blood cells are created all the time. How many blood cells are we talking about? Somewhere around one trillion new blood cells are created each and every day!

Red blood cells are created within red marrow and are responsible for the exchange of oxygen and carbon dioxide. The hemoglobin within red blood cells carries oxygen and carbon dioxide throughout the body.

White blood cells are produced through yellow marrow. White blood cells are our bodies cellular warriors, fighting against foreign substances that have invaded our bodies. For more information on the blood and the blood cells click here.

Mineral Storage

Bones are also responsible for storing minerals that our bodies need. The two most abundant minerals are phosphorus and calcium.

Phospohorus provides a wide range of important functions: aiding in the growth and repair of all tissues and cells, helping the kidneys filter waste, relieving muscle pain after physical exertion, and controlling metabolism. (For more info on phosphorus click here.)

Calcium is the most abundant and one of the most important minerals in the body. Some functions of calcium include: maintaining bone hardness and density, regulating muscle contraction and our heartbeats, aiding blood clotting and the movement of blood through vessels, and aiding in the release of enzymes and hormones. (For more info on calcium click here.)

Bone Disorders

The most common bone-based disorder is osteoporosis. Osteoporosis involves decreased levels in bone mass and density. This increases the risk for fractures. For more information on studies involving osteoporosis and yoga, and some variations on yoga postures designed to aid those with osteoporosis, click here.

Yoga and Bone Reformation

Bones are as alive as any other organ within our body. They are constantly being reformed and replaced with new cells. Two types of cells are responsible for this process: osteoblasts and osteoclasts. Osteoblasts rebuild the bones while osteoclasts break the existing bone down. Instead of being locked in an eternal battle, the two types of cells work in union with one another. Every year about 10% of our skeleton is reformed!

As we age, the number of osteoblasts in our bodies decrease while osteoclast levels remain relatively the same. This leads to a decrease in bone density and overall skeletal degeneration.

Here’s where it is yoga to the rescue! Yoga and different forms of exercise place a healthy stress on the bones which encourages bone reformation and osteoblast production. Yin yoga is especially beneficial for our bones. By staying in a pose for an extending period of time and reducing or releasing muscular engagement, the stretch and stress goes past our muscles and into our bones and connective tissues. This healthy stress promotes our bone remodeling.

Many studies have been conducted that show practicing yoga regularly helps reduce bone density loss. An overview of one such study called “Optimization of Physical Activity as a Countermeasure of Bone Loss: A 5-Year Study of Bikram Yoga Practice in Females” (Sangorgio et. al.) can be found here.

Interesting Facts About Bones

Some interesting facts about bones:

  • The femur is the longest and heaviest bone in the human body. It is stronger than concrete.
  • The stirrup bone in your ear is the smallest bone in the body but plays a big role in processing sound vibrations.
  • Babies are born without hard patellas, the bone protecting the knee. The soft cartilage begins to ossify into hard bone around the age of three.
  • Here are the most commonly broken bones. The collarbone (clavicle), arm bones (humerus, radius, and ulna), hips (actually the head of the femur near its insertion into the hip joint), wrist (actually the distal end of the radius), and the ankle (distal end of tibia and fibula, and the talus.)
  • Women typically have a larger pelvis than men to allow for childbirth. We will see this come into play later when we examine body weight distribution in arm balances.
  • Teeth are not considered bones. They are made of calcified tissue called dentin that is actually stronger than bone.

Our bones take care of us, so let’s take care of our bones with some healthy stress through yoga!

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