30 Yoga anatomY
Discs and ligaments
If you look deeper, you can also see
how sthira and sukha are revealed in
the components of an intervertebral
disc: The tough, fibrous layers of the
annulus fibrosis tightly enclose the
soft, spherical nucleus pulposus. In a
healthy disc, the nucleus is completely
contained all around by the annulus
fibrosis and the vertebra (see figure
2.18). The annulus fibrosis is itself
contained front and back by the
anterior and posterior longitudinal
ligaments, with which it is closely
bonded (see figure 2.17 on page 29).
This tightly contained arrange-
ment results in a strong tendency
for the nucleus to always return to
the center of the disc, no matter in
which direction the body’s move-
ments propel it.
From the top of the cervical spine
to the base of the lumbar spine,
individual vertebrae are dramatically
different in shape based on the func-
tional demands of the varying regions
of the spine (figure 2.19). There are,
however, common elements to all
vertebral structures, as illustrated
by the schematic representation in
figure 2.20.
E5267/Kaminoff/fig2.19/417594/alw/pulled-r1Figure 2.18 The nucleus pulposus is tightly bound
by the annulus fibrosis, which contains concentric
rings of oblique fibers that alternate their direction in
a manner similar to that of the internal and external
obliques of the abdominals.E5267/Kaminoff/fig2.20/417595/alw/pulled-r2C1T10T12L1L5C2C3C7T1
Figure 2.19 Form follows function:
the changing shape of the vertebrae.