Lumbar nerves
Encyclopedia
The lumbar nerves are the five spinal nerves emerging from the lumbar vertebrae
. They are divided into posterior and anterior divisions.
The lateral branches supply the Sacrospinalis.
The upper three give off cutaneous nerves which pierce the aponeurosis of the Latissimus dorsi at the lateral border of the Sacrospinalis and descend across the posterior part of the iliac crest
to the skin of the buttock, some of their twigs running as far as the level of the greater trochanter
.
They are joined, near their origins, by gray rami communicantes from the lumbar ganglia
of the sympathetic trunk
.
These rami consist of long, slender branches which accompany the lumbar arteries
around the sides of the vertebral bodies, beneath the Psoas major.
Their arrangement is somewhat irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami
from two ganglia.
The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans
.
The nerves pass obliquely outward behind the Psoas major, or between its fasciculi
, distributing filaments to it and the Quadratus lumborum.
The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus.
The smaller part of the fourth joins with the fifth to form the lumbosacral trunk
, which assists in the formation of the sacral plexus
.
The fourth nerve is named the nervus furcalis, from the fact that it is subdivided between the two plexuses.
Lumbar vertebrae
The lumbar vertebrae are the largest segments of the movable part of the vertebral column, and are characterized by the absence of the foramen transversarium within the transverse process, and by the absence of facets on the sides of the body...
. They are divided into posterior and anterior divisions.
Posterior divisions
The medial branches of the posterior divisions of the lumbar nerves run close to the articular processes of the vertebræ and end in the Multifidus.The lateral branches supply the Sacrospinalis.
The upper three give off cutaneous nerves which pierce the aponeurosis of the Latissimus dorsi at the lateral border of the Sacrospinalis and descend across the posterior part of the iliac crest
Iliac crest
-External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *...
to the skin of the buttock, some of their twigs running as far as the level of the greater trochanter
Greater trochanter
The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system.It is directed a little lateralward and backward, and, in the adult, is about 1 cm lower than the head...
.
Anterior divisions
The anterior divisions of the lumbar nerves (rami anteriores) increase in size from above downward.They are joined, near their origins, by gray rami communicantes from the lumbar ganglia
Lumbar ganglia
The lumbar ganglia are paravertebral ganglia. The lumbar portion of the sympathetic trunk typically has 4 lumbar ganglia. The lumbar splanchnic nerves arise from the ganglia here, and contribute sympathetic efferent fibers to the nearby plexuses....
of the sympathetic trunk
Sympathetic trunk
The sympathetic trunks are a paired bundle of nerve fibers that run from the base of the skull to the coccyx.-Structure:...
.
These rami consist of long, slender branches which accompany the lumbar arteries
Lumbar arteries
The lumbar arteries are in parallel with the intercostals.They are usually four in number on either side, and arise from the back of the aorta, opposite the bodies of the upper four lumbar vertebræ....
around the sides of the vertebral bodies, beneath the Psoas major.
Their arrangement is somewhat irregular: one ganglion may give rami to two lumbar nerves, or one lumbar nerve may receive rami
Rami
Rami or RAMI can refer to:*Rami, the plural of ramus, literally a branch, as of a plant, nerve, or blood vessel*Specifically, rami are upward portions on both sides of the mandible...
from two ganglia.
The first and second, and sometimes the third and fourth lumbar nerves are each connected with the lumbar part of the sympathetic trunk by a white ramus communicans
White ramus communicans
The thoracic, and the first and second lumbar nerves each contribute a branch, white ramus communicans to the adjoining sympathetic ganglion.They contain myelinated preganglionic sympathetic fibers ....
.
The nerves pass obliquely outward behind the Psoas major, or between its fasciculi
Muscle fascicle
In anatomy, a fascicle is a bundle of skeletal muscle fibers surrounded by perimysium, a type of connective tissue.Specialized muscle fibers in the heart that transmit electrical impulses from the Atrioventricular Node to the Purkinje Fibers are fascicles, also referred to as bundle branches...
, distributing filaments to it and the Quadratus lumborum.
The first three and the greater part of the fourth are connected together in this situation by anastomotic loops, and form the lumbar plexus.
The smaller part of the fourth joins with the fifth to form the lumbosacral trunk
Lumbosacral trunk
The lumbosacral trunk is nervous tissue that connects the lumbar plexus with the sacral plexus.-Structure:The lumbosacral trunk comprises the whole of the anterior division of the fifth and a part of that of the fourth lumbar nerve; it appears at the medial margin of the psoas major and runs...
, which assists in the formation of the sacral plexus
Sacral plexus
-External links:*...
.
The fourth nerve is named the nervus furcalis, from the fact that it is subdivided between the two plexuses.