The Axial Skeleton: the

Spine

• The human skeleton consists of 206 bones. Many of which move or hinge at joints. In conjunction with over 600 muscles these bones enable the human body to achieve a variety of movements.

• The functions of the skeletal system include: -• To provide a lever system against which muscles can pull.• To provide a large surface area for the attachment of muscles.• To protect delicate organs such as the brain.• To give shape to the body.• To give support to the body.• To manufacture red blood cells and to store fat calcium and

phosphate.

• The bones of the body are grouped into two major divisions.

• The axial skeleton consists of the bones, which lie around the longitudinal axis of the body. These include the SKULL, VERTEBRAL COLUMN, STERNUM & RIBS.

• The appendicular skeleton consists of the bones of the LIMBS, PECTORAL (shoulder) GIRDLE, & PELVIC (hips) GIRDLE.

Bone is considered a connective tissue.Its internal structure somewhat resemblesthat of coral in that it is not solid, but filledwith holes. Nonetheless, itprovides sufficient structureto keep us upright and stable.

• Joints are where two or more bones articulate (move).

• Joints are classified according to how much movement they allow.

1. Fibrous – these are fixed or immovable joints such as the cranium, sacrum and the coccyx.

2. Cartilaginous – these are slightly movable joints such as the vertebrae.

3. Synovial – these are freely movable joints such as the shoulder and hip.

FEATURE STRUCTURE FUNCTION

Hyaline/articular cartilage Smooth& spongy covers ends of bones

•Prevents friction between articulating bones

Two layered joint capsule Outer layer – tough & fibrous

Inner – synovial membrane covers all internal surfaces

•To strengthen joint

•To secrete synovial fluid

Synovial fluid Slippery fluid like egg white which fills joint capsule

•Reduce friction

•Nourish cartilage

•To get rid of waste from joint

All synovial joints have the following in common:

In asana the synovial joints are the most important to understand.

There are 6 types of synovial joint.

1. Ball & socket – hip and shoulder.

2. Hinge – knee, elbow and ankle.

3. Pivot – radio-ulna, atlas/axis.

4. Saddle – thumb.

5. Condyloid – wrist.

6. Gliding – between vertebrae in spine.

Atlas/axis: a pivot joint

In this joint the atlas and axis bones articulate to allow rotation as in shaking or nodding your head.

The rest of the spine is comprised of gliding joints and has five areas with reciprocating curves in order to bear weight, provide support and create stability for the body.

Spinal vertebrae are specialized according to location and function.

Cervical Vertebrae

Sacrum and coccyx

Each vertebra, except for those at the sacrum, is separated from the one above and below by discs, which are comprised of a gelatinous substancethat helps the vertebrae glide smoothly as theymove to create axial range of motion.

***A healthy spine moves in 6 directions: forward andbackward, side to side and twisting side to side.The anatomical name for these movements are

Flexion----- forward bending; angle between front of trunk and legs is decreased

Extension--- back bending; angle between front of body and trunk is increased

Lateral flexion---side bending; angle between side of trunk and legs is diminished

Rotation--twisting; vertebrae spin around invisible line down center of spine

The spine is the support for the nervous system, andbecause the spinal cord runs through the vertebralbodies and the nerve fibers for our internal organs aswell as for our muscles and connective tissue divergefrom the spinal column, yoga’s primary activity can beseen as keeping the spine supple and free of compromise.

Disc injury and deterioration is one of the primarycauses of both pinched nerves and back pain.

Maintaining space between the vertebrae and discsassists in optimum functioning of both the spineand nervous system. .

Discs and vertebrae are held together byligaments.

LIGAMENTS (from manual):1. most ligaments are not designed to stretch2. if overstretched will return to normal length3. if chronically overstretched, will become flaccid,

creating instability in the joint4. if stretched beyond 6% of normal, will tear5. give joints their stability

Yoga Principles for the Skeletal System

1. warm joints before stretching and/or strengthening2. balance opposing muscle groups in terms of strength

flexibility3. maintain relaxed attitude to avoid releasing cortisol

stress hormones4. be fully conscious of points of contact between parts

of skeletal system and floor, other body parts and in space

5. draw bones into joint capsules when practicing6. use muscles to create space in the joints

The nervous system is divided into the central nervous system (CNS) = brain and spinal cord and the peripheral nervous system (PNS) = what is outside brain and spinal cord.

The peripheral nervous system further divides into2 branches: the somatic nervous system (SNS), which

coordinates bodily movements and receivesexternal stimuli and is largely under volition

the autonomic nervous system (ANS), whichis largely NOT under conscious control. This is further divided into theSympathetic Nervous System, the ParasympatheticNervous System and the Enteric Nervous System

The Sympathetic Nervous System responds to impending danger is responsible for the increase of one's heartbeat, blood pressure and adrenaline in the system, creates "fight or flight" responses, slows down the digestive system

so that more blood is available to carry oxygen to the vital organs such as brain, heart and muscles.

The enteric nervous system manages every aspect of digestion, from the esophagus to the stomach, small intestine and colon.

It has been described as a “second brain” because it can

operate autonomously. It normally communicates with the

central nervous system through the vagus nerve, a part of

the parasympathetic system and via the prevertebral ganglia

of the sympathetic nervous system. But, studies have

shown that if the vagus nerve is severed, the enteric nervous

system continues to function.

The parasympathetic nervous systemis operative when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and genitourinary systems (rest and digest)

We begin our yoga classes by asking studentsto focus on their breathing so that we canstimulate the parasympathetic nervous system.Through activation of this nervous system, we encourage a non-competitive form of physicalconditioning that heightens awareness, releasestension and constriction in the tissues, and createsinner peace. We create an environment in whichour students can “rest and digest” their sensations, their thoughts, their emotions and the events in their lives.

Sthira sukham asanamThe posture is firm and soft.

Patanjali’s Yoga Sutras 2. 46

orAsana must have the dual qualities of alertness

and relaxation.Desikachar, The Heart of Yoga, p. 181

Yoga and the Spine: Leslie Kaminoff Important Points

1. The 4 reciprocating spinal curves set humansapart from other primates (17).2. Human beings have the smallest base of support, tthe highest center of gravity, the heaviest brain, and they are the least mechanically stable of all creatures.3. The spine exhibits extraordinary balance betweenfirmness/rigidity and softness/plasticity. 4. His discussion of intrinsic equilibrium is essentiallybased on the mechanics of force and tension.

5. Intrinsic equilibrium: the axial skeleton will right and support itself when all mechanical forces are removed from it. These forces amountto muscular tension in our efforts to resist gravity.Removal of this tension releases stored energyin the body. Yoga removes this tension and thusreleases energy. 6. As we move about in the gravitational field, we apply tension and contraction to the spine bythe application of muscular effort. The spine is wonderfully able to neutralize these forces by virtue of its construction.

7. The reciprocating curves dissipate load (force/weight)and the discs absorb compression. The discs, being filledwith fluid, are soft and mobile. The vertebral bodiesare firm/structure. 8. The front of the spinal column is designed to supportthe body’s weight, while the back of the column, comprisedof arches, distribute the forces into the ligaments/connectivetissues (20). 9. The discs, when healthy, are self-correcting.10. In twisting and weight bearing, some of the liquid from the discs leak into the porous bone tissue. When the compressive forces are withdrawn, moisture returns.*11. Flexion, extension and lateral flexion produce asymmetrical forces/movement on the nucleus of the discs.

12. Each time the front part of the spine is compressed,a corrective tension occurs in the ligaments at the backof the spine and vice versa(23).13. The primary curves are kyphotic: thoracic and sacral.A way to identify these are to note which curves touch the floor in sivasana. 14. The secondary curves are lordotic: cervical and lumbar.*15. Spinal flexion is defined as an increase in primarycurves and spinal flexion and extension in cat-cow replicate the shape change of breathing(25).

Lordosis/lordotic. . .curved into the front of the body.

Kyphosis/kyphotic. . .curved away from thefront of the body.

NOTE: Kaminoff’s definition of spinal movementdiffers radically from the traditional definition.

Flexion and extension defined as relationships amongprimary and secondary curves. Forward and back bendingdefined as movements of body in space. AND, he recommends a recuction of the thoracic curve asa safe extension instead of the usual backbend.

In reference to lateral flexion and twisting, Kaminoff’s recommendation is to look closely at the spine to see what’s happening.

We can lengthen the sides of the body w/lateral flexion and we can twist from thehips and shoulders instead of from the spine.

Demo

Axial extension is an additional spinal movement, which results in taking all curves out of the spine.

Back Muscles

Erector Spinae