Yoga Anatomy: Skeletal System

by Delight Yoga

The skeletal system includes all the bones and the joints in our body. This system serves four main functions:

Support:
It provides a support and gives firmness to the body.

Protection:
It protects the various delicate organs like i.e. brain or lungs.

Movement:
It provides surface for the attachment of muscles and itself acts as a lever. Thus along with the muscular system, it helps in the movement of various parts of the body or of the body as a whole.

Blood Formation:
Within the soft tissue inside the bone known as bone-marrow, blood-cells are produced. In adults, it is found in few bones, but in newborns and in children it occurs in a large number of bones.


Bones


The live bone is a hard structure but at the same time, it also has elasticity. The hardness is basically because of the deposition of calcium salt in its matrix and this process of deposition is known as calcification. The live bone remains in flux, continuously formed and broken down. Calcium is continuously released in the blood, whenever the blood level of calcium decreases.

Therefore the level of calcium and its ratio to other elements like phosphorus in the blood is an important factor in the formation and maintenance of the bone.

The factors which are responsible for the degeneration of the bones are:
1. The disturbed proportion of calcium and phosphorus in the blood
2. Disturbance in the level of hormones: like estrogen, calcitonin and parathyroid hormones.
3. Lack of exercise.

Degeneration of the bone, causing reduction in the density of the bone, is known as osteoporosis (osteo = of the bone, poro = void). Decreased activity leading to a reduction of normal stress and strain placed on the bones is a major factor in the development of osteoporosis.

Weight-bearing and muscle pull over the bony surface help in the maintenance of the normal density of bones.An exercise that alters the amount of weight on each foot attempts to balance on one foot, raising the heels off the floor etc. helps in the maintenance of the bones’ health condition

 

JOINTS AND LIGAMENTS
 

When two bones come together to form the joint, they form the most vital part of the skeletal system. In infants, all the joints are moveable. As the child grows some of the joints fuse together, to give additional rigidity to various parts (i.e. the skull). The opposing surfaces of the moveable joints are usually covered by a smooth but firm cartilaginous tissue which reduces the stress of friction to a minimum and at the same time allows weight-bearing without discomfort. These joints are held in position firmly by the Ligaments attached to the bones all around the joint surface. Sometimes there are also ligaments inside the joints to give further firmness.

All these joints are ruled internally by a Synovial membrane which secretes the oily Synovial Fluid. This fluid acts as a lubricant and allows the surfaces to move easily over one another.

The integrity and the proper functioning of a joint depend on the health of three factors:
- Hyaline cartilage
- Ligaments
- Synovial membrane

Disturbance in any of these is sure to lead to the restriction of the function of that joint, as can be seen in the condition of osteoarthritis, rheumatic-arthritis or in case of recurrent dislocation of the joint (i.e.shoulder, ankle...)


TYPES OF JOINTS
 

Joints come in a spectrum of shapes depending on the mobility or the stability they require. The shape of the joint reflects its function and its function reflects its shape. We can mainly divide joints into three types:

Ball & Socket
For example the hip joints. It confers the greatest mobility in all planes and is useful for activities such as changing direction while walking and running.

Hinge
For example the knee joint. It provides greater stability and is useful for propelling the body forward.

Compressive
For example the intervertebral. Individually they give low mobility but great stability and protection (for the spinal cord). Mobility of the spinal column comes from combining the limited movement of individual intervertebral joints as a whole.

 

JOINT REACTION FORCES
 

Every action has an equal and opposite reaction. Muscular contraction and gravity create opposing forces across the joint surface, known as joint reaction forces. It is important to spread these forces over the greatest possible joint surface area.

Joint congruency refers to the fit of a joint’s articular surfaces. A joint is congruent when its surfaces fit (or join) together perfectly. Movement out of congruency focuses stress on a small surface area.
A large force focused on a small area of articular cartilage can injure it, eventually causing degenerative changes.

For example, the hip joint has a greater range of motion than the knee joint. Poses like Padmasana require a large amount of external rotation of the hip joint to bring the foot over the opposite thigh. Trying to obtain this rotation from the knee joint creates incongruence because the knee joint is a hinge joint with a very limited capacity of rotation. This incongruence can result in the abnormal distribution of joint reaction forces, injuring the intra-articular structure of the knee. Therefore it is essential to first obtain a full range of motion of the ball and socket hip joint.