Abc

side view of the four curvatures and of the anterior and posterior anterolateral posterior functional units of the spine v,ew of sP,ne v,ew of sPme

Hatha Yoga Studios For Curved Spines

intervertebral disk between L1 and L2

Thoracic Spine From

sacrum spinous process of T1

transverse process of the atlas spinous process of C7

sacrum anterior functional intervertebral disk between L1 and L2

sacral kyphosis spinous process of T1

transverse processes of thoracic vertebrae T7, T9. and T11

cervical lordosis spinous processes: C7 and T1

thoracic kyphosis spinous process of T12

lumbar lordosis transverse process of the atlas spinous process of C7

f igure 4.10. Three views of the spinal column: a lateral view from the right s'de (a), an anterolateral view from right front (b), and a posterior view from behind (c). The middle image (b) is enough front the side that the four spinal curvatures start becoming apparent. The anterior and posterior functional units are shown separated from one another in the figure on the left (a). The •ubular nature of the posterior functional unit, however, is apparent only in views of individual vertebrae from above (fig. 4.5) or from below (Sappey).

222 ANATOMY OF HATHA Y(H,A

The biomedical literature suggests that nutrients are "imbibed," or absorbed, into the intervertebral disks from the vertebral bodies, which themselves are well supplied with blood, but little is known about this process except that healthy intervertebral disks contain 70-80% liquid and that the spine gets shorter during the day and longer during the night Taken together, these two pieces of information suggest that when the intervertebral disks are compressed by gravity and muscular tension during the day, liquid is squeezed out, and that when tension is taken off tht vertebral column at night, the vertebral bodies can spread apart, allowing the intervertebral disks to absorb nutrients. This would help explain wh it has long been thought that one of the most effective treatments for acut back pain is bed rest, and why a thoughtful combination of exercise am relaxation is therapeutic for most chronic hack ailments.

the posterior functional unit

If we were to locate another isolated spine and saw off most of the anteric functional unit from top to bottom, we would be left with the poster« functional unit—a tube made up of the stack of vertebral arches, all tl restraining ligaments between the arches, and just enough of the posteri* borders of the vertebral bodies and intervertebral disks to complete th tube anteriorly (figs. 4.5a and 4.10a). The interior of the posterior function unit is the vertebral canal, which houses the spinal cord and spinal nerves Each vertebral arch forms small synovial joints with its neigh be through the agency of little facets, or flattened joint surfaces, that ai located on adjacent superior and inferior articular processes. Like oth< synovial joints, these movable facet joints are characterized by joi surfaces covered with cartilage on their articular surfaces, synov I membranes and fluid, and joint capsules that envelop the entire comple annulus anterior posterior fibrosus - -►

nucleus pulposus

Figure 4.11. The intervertebral disk, in a cross-section from above (left), and in mid-sagittal section between two vertebral bodies (right). In the figure on the right, the nucleus pulposus is being squeezed anteriorly by a backbend (Sappe\

annulus anterior posterior fibrosus - -►

nucleus pulposus

Figure 4.11. The intervertebral disk, in a cross-section from above (left), and in mid-sagittal section between two vertebral bodies (right). In the figure on the right, the nucleus pulposus is being squeezed anteriorly by a backbend (Sappe\

■I STASHING POSTl'Rt-S 223

Two inferior articular processes, one on each pedicle, form facet joints with matching surfaces on the superior articular processes of the vertebra below. Although the orientations of the articular processes restrict twisting of the spine in the lumbar region (fig. 1.11), their orientations permit it in the cervical and thoracic regions. You hear and feel the facet joints moving when a skilled body worker cracks your back. And many young athletes can twist their spine when they get up in the morning, and hear a sequence of pops, indicating that facet joints are being released one after another.

Just in front of the superior and inferior articular processes, and just to the rear and to each side of the intervertebral disks, are the interv ertebral foramina, the openings in the vertebral column out of which the spinal nerves emerge (fig. 4.7b). In the lumbar region the locations of these foramina and their spinal nerves make them vulnerable to ruptured intervertebral disks, which may impinge against a spinal nerve and cause shooting pains down the thigh.

spinal stability and bending

The anterior and posterior functional units are described separately to clarify the concepts, but in fact they are bound together inextricably. The architectural arrangement that links them is propitious: it permits spinal movements and at the same time it insures spinal stability. For example, backward bending will compress t he vertebral arches together posteriorly while spreading the front surfaces of the vertebral bodies apart anteriorly, and forward bending will pull the vertebral arches slightly apart while compressing the intervertebral disks in front. These movements, however, can be taken only so far because the entire complex is stabilized by ligaments (figs. 4.12-13). As just mentioned, the anterior and posterior longitudinal ligaments reinforce the flexible anterior functional unit, and the joint capsules for the facet joints help hold the vertebral arches toget her. In addition, there are yet more ligaments superimposed on the posterior functional unit—interspinals ligaments that run between adjacent spinous processes, a supraspinous ligament that connects the tips of the spinous processes, flat elastic ligaments known as ligamenta flava that connect adjacent laminae, and the cervical nuchal ligament. which is an elastic extension of the supraspinous ligament that reaches the head.

(Technical note: Quadrupeds such as dogs and cats have well-developed nuchal ligaments whose elasticity keeps their heads on axis without constant expenditure °f muscular energy. Because of our upright posture, the significance of the nuchal ligament in humans is greatly reduced in comparison with that of quadrupeds, but 't probably has a least a minor role in helping to keep the head pulled to the rear. It's no substitute for muscular effort, however, as evidenced by drooping heads in

124 WATmur OF HATHA >OC;A

the spine as a whole

We've seen representative vertebrae at each segment of the spine, am we've seen how their linked front portions form the anterior function; unit and how their linked vertebral arches form the posterior function; unit. Then we looked at how the combination of anterior and postern functional units along with their restraining ligaments permits and yi limits bending. Now we need to examine the spine as a whole within th body (fig. 4.4). The depth of the four curvatures can be evaluated from tf side (figs. 4.ioa-b). If they are too flat the spine will not have much sprin: like action when you walk and run, but if the curvatures are t. pronounced, especially in the lumbar region, the spine will be unstable Excess curvatures are more common—an orthopedist would tell you that "lordosis" is an excess anterior curvature in the lumbar region and that "kyphosis" is an excess posterior curvature of the chest. And sometim people have what is called a reverse curvature in the neck, one that convex posteriorly instead of anteriorly.

From either the front or the back, the spine should look straight. If 1 doesn't, it is usually because of an imbalance such as one leg being short pedicles portion of ligamentum flavum removed to reveal joint posterior longitudinal ligament ligamenta flava articulating processes

Flava Ligament

laminae intervertebral disks

Figure 4.12. Views of the ligaments in the lumbar portion of the vertebral can from inside looking out. On the left (a) is an image looking posteriorly toward the vertebral laminae, ligamenta flava, pedicles (cut frontally), and transverse processes. On the right (b) is an image looking anteriorly toward the posterior longitudinal ligament, the posterior surfaces of the vertebral bodies, intervertebr. disks (indicated by dotted lines), and pedides (again in frontal sec tion; Morris).

ligamenta flava pedicles laminae a.

intervertebral disks b.

portion of ligamentum flavum removed to reveal joint supenor and inferior articulating processes posterior longitudinal ligament

Figure 4.12. Views of the ligaments in the lumbar portion of the vertebral can from inside looking out. On the left (a) is an image looking posteriorly toward the vertebral laminae, ligamenta flava, pedicles (cut frontally), and transverse processes. On the right (b) is an image looking anteriorly toward the posterior longitudinal ligament, the posterior surfaces of the vertebral bodies, intervertebr. disks (indicated by dotted lines), and pedides (again in frontal sec tion; Morris).

4 STANDING POSTl'RIS 225

than the other, which causes the pelvis and spine to be angled ofT to the side. This creates a side-to-side curvature known as scoliosis, a condition which always includes a right-left undulation of compensatory curvatures higher up in the spine that ultimately brings the head back in line with the body. These compensatory curvatures develop because our posture adjusts itself to maintain the plumb line of gravity from head to toe with the least possible muscular effort, even if it results in distortions and chronic aches and pains.

the deep back muscles

We can't make a posture with just bones, joints, and ligaments: something has to move them. An engineer designing a plan for putting the body into motion might suggest using three layers of rope-and-pulley systems. The innermost layer would consist of miniature systems of ropes and pulleys connecting the smallest adjacent skeletal segments, the intermediate layer would consist of larger systems connecting bigger segments, and the outermost layer would consist of the largest and longest systems connecting the segments of the skeleton which are the furthest apart. And indeed, we supraspinous ligament intervertebral foramina anterior longitudinal ligament

Intervertebral Foramen

inferior articular process. L3

vertebral bodies,

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