The Abdominal and Pelvic Brain
Byron Robinson, M. D.
THE TRUNK OF THE SYMPATHETIC NERVE
(NERVUS TRUNCUS SYMPATHICUS).
"Otie glorious hour of conquering strife is worth an age of quiet
We do well what we do automatically.
The trunk of the vaso-motor (sympathetic) nerve has
experienced a variety of names:
SYNONYMS: The lateral cords of the sympathetic;
the principal cords of the sympathetic; the lateral ganglionic chain of
the sympathetic; the nodular cords of the sympathetic.
GERMAN: Grenzstrang, Hauptstrang, Knotenstrang.
The nerve strands connecting the ganglia of the
sympathetic trunk are termed commissural cords. The trunk of the
sympathetic nerve presents the form of an elongated elipse enclosing the
vertebral column, united at the proximal and distal ends by unpaired ganglia.
The trunk consists of a vertical, symmetrical, bilateral ganglionated cord
with indefinite union at the proximal end (ganglion of Ribes) and distal
ends (Ganglion Coccygeum). The number of ganglia and roots correspond
in general to the number of spinal nerves. Exceptions occur in which
the ganglia coalesce, as in the reduction of the seven cervical to the
usual number of three. The total number of trunk ganglia (3, cervical),
(11, dorsal), (4, lumbar) and (4, sacral) vary from 20 to 25. The
form of the trunk ganglia varies and may be elongated, olive, spindle,
triangle, pyramidal, irregular shaped. The ganglia in general are
located ventral to the transverse processes and on the lateral surfaces
of the vertebrae. However, the relation of the ganglia in each segment
to the vertebra varies. The trunk ganglia vary in dimension from
3/4 of an inch long (inferior cervical ganglion) to less than the size
of a grain of wheat. The terminations, both proximally and distally,
of the elongated elliptical ganglionated trunk are obscurely united by
ganglia or commissura, cords.
A ganglion is composed of a larger or smaller number
of multipolar nerve cells enclosed in a capsule of connective tissue.
The bilateral symmetrical vertical ganglionated trunk
of the sympathetic is connected to the spinal cord by means of the rami
communicantes, which are two bands of nerves extending from the spinal
nerves to the ganglia of the trunk of the sympathetic.
These central communicating branches are known as gray (sympathetic) and
white (visceral) rami communicantes. The ganglionated trunk of the
sympathetic nerve emits important visceral branches from its different
segments (cervical, dorsal, lumbar and sacral) to the viscera of the thoracic,
abdominal and pelvic cavities. The following table will present a
bird's-eye view of the segments of the trunk of the sympathetic nerve with
their important branches.
SUPERIOR MEDIAN GANGLION (RIBES) (GANGLION SUPERIOR MEDIUS).
I. Trunk of the cervical sympathetic. (Truncus Sympathicus
Cervicales). Two to three.
1. Superior cervical ganglion (ganglion cervicale
2. Middle cervical ganglion (ganglion cervicale
3. Inferior cervical ganglion (ganglion cervicale
II. Trunk of the dorsal sympathetic. (Truncus Sympathicus Dorsalis).
Ten to twelve.
Emits splanchnic nerves.
III. Trunk of the lumbar sympathetic. (Truncus Sympathicus
Four to five.
Emits lumbar branches to plexus aorticus.
IV. Trunk of the pelvic sympathetic. (Truncus Sympathicus Pelvinus).
Four to five.
Emits visceral nerves.
INFERIOR MEDIAL GANGLION (GANGLION COCCYGEUM).
I. Branches of the Cervical Trunk of the Sympathetic.
The cervical sympathetic trunk is a projection proximalward
(toward the cranium) along the great cervical vessels.
The branches of the three cervical ganglia and commissural
cord are distributed to structures of the head, neck and thorax and consist
(a) Motor fibres to involuntary muscles (pupil dilators).
(b) Vaso-motor fibres to head, neck and proximal
(c) Pilo-motor fibres along cervical spinal nerves.
(d) Cardiomotor fibres.
(e) Secretory fibres.
The trunk cervical ganglia are located on the prevertebral
muscle dorsal to the carotid artery. It extends from the first rib
to the base of the skull.
The cervical sympathetic trunk is characterized
by the absence of the white rami communicantes. The cervical ganglia,
usually coalesced, from seven to three in number, are important on account
of the emitting of the pharyngeal plexus and cardiac nerves.
A. Superior Cervical Ganglion (Ganglion Cervicale
SYNONYMS: Supreme cervical ganglion (ganglion cervicale
supremum); the great cervical ganglion (ganglion cervicale magnum); the
fusiform cervical ganglion (ganglion cervicale fusiforme); the olive-shaped
cervical ganglion (ganglion cervicale olive).
The superior cervical ganglion, 3/4 of an inch in
length is the largest of the sympathetic trunk ganglia. It is located
at the base of the skull between the internal jugular vein and internal
carotid artery. It is irregular in form, however, chiefly spindle-shaped.
The commissural cord connects it to the middle cervical ganglion.
The main branches of the superior cervical ganglion
Central communicating branches
1. Gray rami communicantes
2. Communicantes with cranial
Peripheral branches of the distribution.
3. Emits branches to pharynx.
4. Emits superior cervical
5. Branches, to vessels
B. Middle Cervical Ganglion (Ganglion Cervicale
SYNONYMS: The thyroid ganglia (Ganglion Thyroideum).
The middle cervical ganglion sends branches:
1. (Central Communicating Branches) gray rami
communicantes (no white).
2. The subclavian loop (Ansa Vieusseni, French
anatomist, 1641-1716) enclosing the
subclavian artery and joining the middle and inferior cervical ganglia.
3. Peripheral branches of distribution, the
middle cervical cardiac nerve.
4. Branches to the thyroid body.
C. Inferior Cervical Ganglion (Ganglion Cervicale
SYNONYMS: The first thoracic ganglion (Ganglion
Thoracicum primum); the vertebral ganglion (Ganglion Vertebrale); the stellate
ganglion (Ganglion Stellatum).
The inferior cervical ganglion is irregular in dimension,
form, location and branches. The inferior cervical nerve emits:
1. (Central Communicating Branches) gray rami
communicantes (no white).
2. Subclavian loop.
3. Communications with larynx.
4. (Peripheral branches of distribution).
The inferior cervical cardiac nerve.
5. Branches to vessels
(a) Vertebral plexus.
(b) Subclavian plexus.
The bilateral trunks of the cervical sympathetic
are not directly united by transverse nerve strands.
II. Branches of the thoracic or dorsal trunk of the Sympathetic.
The dorsal or thoracic ganglia composing the dorsal
or thoracic trunk of the sympathetic generally consists of eleven ganglia
of varied form and dimension connected by commissural cords of marked dimension.
The important feature of the thoracic sympathetic trunk is that the distal
five or six ganglia give origin to the three splanchnic or visceral nerves
which richly supply the abdominal viscera. The branches forming the
ganglionated thoracic cord may be divided into two kinds (a) central branches
connecting with other nerves; (b) peripheral branches distributed in a
plexiform manner to the thoracic and abdominal viscera. The significant
feature of the thoracic trunk of the sympathetic is the presence of the
white rami communicantes (visceral nerves). The central communicating
branches are (both) the white and gray rami communicantes. The peripheral
branches of distribution of the thoracic trunk arise both from the ganglia
and the commissural cord. The important distributing branches in
the practice of medicine for the abdominal viscera are the three splanchnic
nerves; the distal ends of the splanchnic nerves practically form the abdominal
brain - the visceral ruler of the peritoneal organs. The splanchnic
nerves are the abdominal visceral nerves. The following table presents
a bird's eye view of the branches of the thoracic sympathetic trunk:
Branches of the thoracic sympathetic trunk.
1. (Central communicating branches) white
2. Gray rami communicantes.
3. (Peripheral branches of distriubtion).
(Pulmonary from II, III, and IV ganglia) to form the pulmonary plexus.
4. Aortic (from proximal 5 ganglia) to suply
5. The three splanchnic nerves (from the distal
7 thoracic ganglia and commissural cords) to supply the abdominal viscera.
A. The Great Splanchnic Nerve (Nervus Splanchnicus
Arises from the thoracic trunk between the fifth
and ninth ganglia. By the coalescence of several irregular strands
a nerve of marked dimension is formed which passes distalward in the dorsal
mediastinum and perforating the crus of the diaphragm terminates as the
principal mass of the abdominal brain (semilunar ganglion). The great
splanchnic ganglion (ganglion splanchnicum maxium) is found on the trunk
of the great splanchnic nerve within the thoracic cavity.
B. The Small Splanchnic Nerve (Nervus Splanchnicus
The small splanchnic nerve arises from the trunk
of the thoracic sympathetic in the region of the ninth and tenth ganglia.
It courses adjacent to the bodies of the distal thoracic vertebrae, perforates
the crus of the diaphragm adjacent to or with the great splanchnic and
terminates irregularly in the abdominal brain, (and occasionally in the
so-called aortic-renal ganglion).
C. The Least Splanchnic Nerve (Nervus Splanchnicus
Minimus - inferior or tertius).
The least splanchnic nerve arises from the last
thoracic ganglion in the sympathetic trunk (or from the small splanchnic).
It perforates the diaphragm and terminates in the plexus renalis.
The bilateral thoracic trunks of the sympathetic are not directly united
by the transverse nerve strands similar to the lumbar and sacral trunks.
III. Branches of the Lumbar Sympathetic Trunk.
The lumbar trunk of the sympathetic consists usually
of four ganglia joined by commissural cords. It is continuous proximally
with the thoracic and distally with the sacral trunk of the sympathetic.
The lumbar trunk is located on the bodies of the lumbar vertebrae internal
to the origin of the psoas muscle and ventral to the lumbar vessels.
The lumbar ganglia are not always bilaterally symmetrical in dimension,
location, distance from each other and form. The ganglia are larger
than those of the dorsal or sacral trunk. The commissural cords of
the lumbar sympathetic trunk are longer, stronger and more irregular in
number than the dorsal or sacral. The branches from the lumbar gangliated
trunk consist of two sets, viz.:
A. Central Communicating Branches.
1. The first two or three lumbar spinal nerves
possess visceral branches which form white rami communicantes joining the
proximal lumbar ganglia or commissural cord.
These white rami communicantes comprise vaso-motor
fibres for the tractus genitalis and motor fibres for the uterus and bladder.
2. Gray Rami Communicantes which pass to the
ventral primary divisions of the lumbar nerves. The rami communicantes
(white and gray) are irregular in length, dimension and location.
B. Peripheral Branches of Distribution from
the lumbar ganglia and commissural cord arises and pass to the plexus aorticus
and aorta. The lumbar sympathetic trunk sends branches to the plexus
ureteris. The branches are irregular in length, dimension, number
and location. The bilateral sympathetic trunk is directly united
by several transverse nerve strands, chiefly extending from ganglion on
one side to that on the other.
IV. Branches of the Sacral Sympathetic Trunk.
The sacral trunk of the sympathetic is a continuation
of the lumbar trunk. It terminates in a plexiform coalescence over
the coccyx with the trunk of the opposite side. The distal termination
of the sacral sympathetic trunks are known as the ganglion impar or coccygeal
ganglion. There are usually four ganglia which united by a commissural
cord decrease in dimension from sacral promontory to coccyx. The
ganglia are generally not bilaterally symmetrical in location, dimension
or equidistant from each other. The usual location is on the ventral
surfcae of the sacrum on the internal border of the sacral foramina.
The ganglia scralia vary in number, dimension, location and form.
The bilateral sacral sympathetic trunks are united directly by numerous
transverse nerve cords which are arranged in a plexiform manner (which
I have termed plexus intertrunci sacralis). The middle sacral trunk
of the sympathetics, like that of the cervical and distal lumbar receives
no white rami communicantes from the spinal nerves.
The visceral branches (Pelvic Splanchnic) of the
II, III and IV sacral nerves join the pelvic plexus (pelvic brain) without
being directly connected with the sacral sympathetic trunk. These
nerves, however, are to be considered homologous with the white rami communicantes
of the thoracic and lumbar (abdominal splanchnics).
The II, III and IV sacral nerves transmit to the
tractus genitalis (uterus) tractus intestinalis (rectum) and tractus urinarius
(bladder) motor and inhibitory nerves, and also vaso-dilator fibres for
the tractus genitalis.
The branches of the sacral sympathetic trunk are
of two kinds, viz.:
A. Central Communicating Branches.
I. Gray rami communicantes arise from the
ganglia and join the ventral primary division of the sacral and coccygeal
nerves. There are no white rami communicantes.
B. Peripheral Branches of Distribution are:
1. Visceral branches of limited dimension
which arise mainly from the proximal ganglia of the trunk and commissural
cord and pass medianward to join the interiliac plexus and pelvic brain
as well as the three kinds of pelvic viscera and adjacent vessels.
2. Parietal branches limited in dimension
which ramify on the ventral surface of the sacrum, especially in relation
with the sacral artery, forming what I have termed the plexus intertrunci
The four segments of the trunk of the sympathetic
nerve, cervical, dorsal, lumbar and sacral, differ according to location
The white rami communicantes (visceral nerves abdominal
splanchnics) stream from the dorsal and proximal lumbar ganglia.
The visceral nerves of the pelvic sympathetic trunk
(pelvic splanchnics) do not pass through the sacral ganglia but through
the II, III and IV sacral nerves.
The distributing branches of the pelvic sympathetic
trunk are the least important of any segmental trunk. The bilateral
cervical and dorsal sympathetic trunks are practically not directly united
by transverse nerve cords, the bilateral lumbar and pelvic trunks are united
by numerous transverse nerve cords (and plexuses).
The bilateral cervical sympathetic trunks are united
by two localized prevertebral plexuses, the pharyngeal and cardiac.
The bilateral dorsal sympathetic trunks are united
by a single prevertebral colossal pelvus-abdominal brain.
Ganglionic coalescence occurs chiefly in the cervical
trunk. The ganglia are the most irregular in the pelvic trunk, the
largest in the cervical and lumbar trunks.
The commissural cords are multiple supernumerary
in the lumbar and sacral trunks only.
The cervical sympathetic trunk and pelvic brain
are the only segments so far subject to surgical intervention (extirpation).
|Fig. 6. The trunk of the vasomotor
nerve here presented was dissected under alcohol with care as regards connexions
and relations. The ellipse formed by the two lateral trunks is evident.
The ellipse extends from the cranium to the coccyx. The two nerve
trunks are especially united at the cranium (cervical part) at the coeliac
axis (abdominal part) and the distal end (pelvic part). Between the
two lateral trunks of the nervus vasomotoritis lies the plexus aorticus,
thoracicus, cerebrum abdominale, plexus aorticus abdominalis, interiliac
nerve disc, plexus interiliacus, cerebrum pelvicum.