Spinal Nerves

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SPINAL NERVES

They are those that make connection with the spinal cord and are responsible for the innervation of the trunk, upper limbs and parts of the head. There are 31 pairs in all, 33 if we count the two pairs of vestigial coccygeal nerves, which correspond to the 31 existing spinal segments.

Are:

  • 8 pairs of Cervical Nerves
  • 12 pairs of Thoracic Nerves
  • 5 pairs of Lumbar Nerves
  • 5 pairs of Sacral Nerves
  • 1 pairs of Coccygeal Nerves
Relationship of nerve roots to vertebrae
 
Relationship of nerve roots to vertebrae
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Each spinal nerve is formed by the union of the dorsal (sensory) and ventral (motor) roots, which attach, respectively, to the posterior lateral and anterior lateral grooves of the medulla through root filaments.

The Ventral Root It emerges from the ventral surface of the spinal cord as several radicles or filaments that usually combine to form two bundles near the intervertebral foramen.

The Dorsal Root is larger than the ventral root in size and number of radicles; they attach along the posterior lateral groove of the spinal cord and join to form two bundles that penetrate the spinal ganglion.

The ventral and dorsal roots join immediately beyond the spinal ganglion to form the spinal nerve, which then emerges through the interspinous foramen.

The spinal ganglion is a set of nerve cells in the dorsal root of the spinal nerve. It has oval shape and size proportional to the dorsal root in which it is located. It is near the intervertebral foramen.

SPINHAL NERVE FORMATION & #8211; VENTRAL AND DORSAL ROOTS
 SPINHAL NERVE FORMATION - VENTRAL AND DORSAL ROOTS
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

The spinal nerve separates into two primary divisions, dorsal and ventral, immediately after the junction of the two roots.

Dorsal Branches of Spinal Nerves

The dorsal branches of the spinal nerves, usually smaller than the ventral and posteriorly directed, divide (except for the first cervical, fourth and fifth sacral and coccygeal) into the medial and lateral branches to innervate the muscles and skin of the posterior regions of the spinal nerves. neck and trunk.

Dorsal Branches of Cervical Spine Nerves

The first cervical dorsal branch called the suboccipital nerve emerges superior to the posterior arch of the atlas and inferior to the vertebral artery. It penetrates the suboccipital trigone by innervating the major and minor posterior rectus muscles of the head, superior and inferior obliques and the semi-spinal head.

The second cervical dorsal branch and all other cervical dorsal branches emerge between the posterior arch of the atlas and the axis of the axis below the innervated inferior oblique muscle, receiving a connection from the dorsal branch of the first cervical, and dividing into one. large medial branch and a small lateral branch. The medial branch is called the occipital major nerve, which together with the occipital minor nerve, innervate the scalp skin to the vertex of the skull. It innervates the semi-spinal muscle of the head. The lateral branch innervates the splenium, very long, and semi-spinal muscles of the head.

The third cervical dorsal branch is divided into medial and lateral branches. Its medial branch runs between the spinal muscles of the head and semi-spinal neck, piercing the splenium and trapezius muscles to terminate in the skin. Deep into the trapezius muscle, it gives rise to a branch, the third occipital nerve, which pierces the trapezius muscle to terminate in the skin of the lower occipital region, medial to the larger occipital nerve. The lateral branch often joins that of the second cervical dorsal branch.

The dorsal branches of the five lower cervical nerves are divided into medial and lateral branches. The medial branches of the fourth and fifth run between the semi-spinal neck and semi-spinal muscles of the head, reach the spinous processes of the vertebrae and pierce the splenium and trapezius muscles to terminate in the skin. The medial branch of the fifth may not reach the skin. The medial branches of the three lower cervical nerves are small and terminate in the semispinatus neck, semispinatus, multifidus, and interspinatus muscles. The lateral branches innervate the iliocostal muscles of the neck, very long neck and very long head.

DORAL RAMES OF CERVICAL SPINAL NERVES
DORAL RAMES OF CERVICAL SPINAL NERVES
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
DORAL RAMES OF CERVICAL SPINAL NERVES
DORAL RAMES OF CERVICAL SPINAL NERVES
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Dorsal Branches of Thoracic Spinal Nerves
They are divided into medial and lateral branches. Each medial branch runs between the articulation and the medial margins of the superior cost-transverse ligament and the intertransversal muscle, while each lateral branch runs between the ligament and the intertransversal muscle before bending posteriorly over the medial side of the levator muscle. rib.

THORACIC SPINAL NERVE DORAL RAMES
THORACIC SPINAL NERVE DORAL RAMES
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.
THORACIC SPINAL NERVE DORAL RAMES
THORACIC SPINAL NERVE DORAL RAMES
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Dorsal Branches of Lumbar Spinal Nerves
The dorsal branches of the lumbar nerves pass back medially to the intertransversal muscles, dividing into the medial and lateral branches. The medial branches run close to the articular processes of the vertebrae to terminate in the multifidus muscle; they are related to the bone between the accessory and nipple processes and can groove it. In addition, the upper three give rise to the cutaneous nerves that pierce the latissimus dorsi aponeurosis on the lateral margin of the erector spinae and laterally cross the iliac muscle to reachlift the skin of the gluteal region.

Dorsal ramus of a lumbar spinal nerve
 Dorsal ramus of a lumbar spinal nerve
Source: NETTER, Frank H .. Atlas of Human Anatomy. 2 ed. Porto Alegre: Artmed, 2000.

Dorsal Branches of Sacral Spinal Nerves
The upper three are covered at the exit by the multifidus muscle, dividing into the medial and lateral branches. The medial branches are small and end in the multifidus muscle. The lateral branches join and with the lateral branches of the last lumbar and dorsal branches of the fourth sacral nerve, form dorsal loops to the sacrum; from these loops branches run dorsally to the sacrotuberal ligament to form a second series of loops under the gluteus maximus muscle; Of these, two or three gluteus branches pierce the gluteus maximus muscle to innervate the skin of the gluteus region.

Ventral Branches of Spinal Nerves
The ventral branches of the spinal nerves innervate the limbs and anterolateral surfaces of the trunk. The cervical, lumbar, and sacral unite near their origins to form plexuses.

Spinal Plexus

Cervical Plexus

Brachial Plexus

Thoracic Nerves

Lumbar Plexus

Sacral Plexus

Coccygeal Plexus