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CHAPTER 7
rotatores and quadratus lumborum. The position of all these muscles and their relation–
ship to the spine is comparable to struts on the mast of a ship or inserted in framework
to bear weight, pressure and other stresses, in the direction of its length. Their relation–
ship and attachment to the spine is best demonstrated in two excellent preparations,
published in Gray's
Anatomy,
and may serve as a constant reminder to all concerned with
the initial treatment and physical readjustment of paraplegics and tetraplegics (Fig. 2oa
and b).
SPINAL CORD
External structure
The spinal cord, medulla spinalis, is the caudal continuation of the oblongata and
extends distally from the level between occiput and upper border of the atlas to the
lower border of the first or upper border of the second lumbar vertebra. In length it is
about 45 cm in the male and 42 cm in the female and is divided into cervical, thoracic
and lumbar regions. The cord contains two enlargements:
1
the cervical enlargement (intumescentia cervicalis) extending from C3 to T2, the
largest circumference being at the level of C5/6;
2
the lumbar enlargement (intumescentia lumbalis) which extends from Tio to Ti2
tapering down into the conus terminalis from which the filum terminale descends to the
periost of the 2nd segment of the coccyx.
Spinal nerve roots
Thirty-one pairs of spinal roots spring from the spinal cord, divided into anterior and
posterior roots: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and i coccygeal nerve. While
the upper cervical roots run almost horizontally to enter their respective intervertebral
foramina, the roots of the other regions take a more oblique downwards course, and in
the lumbar region they run almost vertically forming the cauda equina around the filum
terminale. Thus Ci and C2 segments lie beneath spinous process Ci, and C3 segment
beneath C2 spinous process. As a result of the longer course the successive spinal roots
take caudalwards to enter their respective intervertebral foramina Thi segment is in
alignment with spinous process C6, Li segment with spinous process Thi2 and Si
segment with Thi2 process. The knowledge of these anatomical facts is essential for
the clinical diagnosis and surgical treatment of pathological processes, in particular
tumours. Each anterior root joins the corresponding posterior root distally from the
spinal ganglion of the latter, forming the spinal nerve. Fig. 21 shows the topographic
relationship of the spinal cord segments, spinal roots to the individual spinous processes
and vertebral bodies.
The anterior roots conduct all efferent fibres for the innervation of the skeletal
muscles and through the pre-ganglionic sympathetic fibres for the autonomic system,
while the posterior roots consist of afferent fibres. With regard to the problem of efferent
fibres running in the posterior roots see section of Vasomotor Control.
