3
CHAPTER
SKELETAL SYSTEM
E
very system of the body is involved in every movement we make. Without the active
participation of the nervous, circulatory, endocrine, respiratory, digestive, immune, con-
nective tissue, fl uid, skeletal, ligamentous, and muscular systems (to mention just a few),
we wouldn’t be able to create the movements of the breath or lift our arms overhead and
fold forward into uttanasana, much less launch the body through space into a handstand.
dynamiC BalanCe oF Body SyStemS
Any part of the body that we turn our attention to is part of more than one system: While
bones are generally considered part of the skeletal system, they also play important roles
in other systems, such as the circulatory, nervous, immune, and endocrine systems. The
bones are part of the circulatory and immune systems because red and white blood cells
are created in the bone marrow. They are part of the nervous system because of the role
calcium has in the working of neurons, and they are part of the endocrine system because
of the hormones secreted by bone cells that play a role in our metabolism. None of these
systems can work alone. Without the circulatory system, other systems such as the respira-
tory, endocrine, and digestive systems would not be able to distribute oxygen, hormones,
and nutrients to the cells of the body. Without the nervous system, it would be impossible
to coordinate the muscles of the limbs or to modulate the dilation of the blood vessels to
supply the bones, brain, heart, or muscles with enough blood. All of the systems of the
body are overlapping and interdependent (fi gure 3.1, page 46).
If we focus on just one or two systems in studying anatomy and yoga, we run the risk
of terribly oversimplifying the incredible effects that the practice of asana has on every
system in the body. On the other hand, we can dive deeply into a single point of focus and
fi nd incredible complexity that enriches our experience of the whole. For the purposes of
this book, the focus is on the role of the skeletal and muscular systems in generating the
movements that create asana, knowing that starting at any beginning point can bring us
into a relationship with all the other systems and tissues in the body.
muSCuloSkeletal SyStem
Bones, ligaments, muscles, and tendons all weave together into a dynamic whole. The skel-
etal portion of the musculoskeletal system is made up of the bones, ligaments, and other
tissues that make up the joints: synovial fl uid, hyaline cartilage, and fi brocartilaginous discs
and wedges. The muscular portion is made up of the muscles and tendons that cross the
joint space and attach to the bones, as well as the nerve endings that organize the exquisite
sequencing and timing of our muscle actions. All of these tissues are either composed of
or wrapped in layers of connective tissue.
The skeletal system and the muscular system are often treated as separate systems.
When we consider how movement is generated, it makes more sense to think of them as
one musculoskeletal (or skeletomuscular) system. The muscles and bones work intimately
together to negotiate our relationships to gravity and space, to provide our upright posture,
and to help us move through the world, feed ourselves, use tools, and create change.
Without the structure and support of the skeletal system, the muscles would be a puddle
of contractile tissue with nothing to move. On the other hand, without the movement