The spinal cord is a long, thin bundle, tubular nerve and supporting cells that extend from the medulla oblongata in the brain stem to the lumbar region of the vertebral column. The brain and spinal cord together form the central nervous system (CNS). In humans, the spinal cord begins in the occipital bone where it passes through the foramen magnum, and meets and enters the spinal canal at the beginning of the cervical vertebra. The spinal cord extends between the first and second lumbar vertebrae where it ends. The surrounding vertebral column protects the relatively short spine. Approximately 45 cm (18 inches) in men and about 43 centimeters (17 inches) in women. Also, the spinal cord has a varying width, ranging from 13 mm thick in the cervical and lumbar regions to 6, 4 mm ( 1 / 4 in) thick in the thoracic region.
The spinal cord works primarily in the transmission of nerve signals from the motor cortex to the body, and from afferent fibers from sensory neurons to the sensory cortex. It is also a center for many reflex coordination and contains reflex arcs that can independently control reflexes and central pattern generators.
Video Spinal cord
Structure
The spinal cord is the main route for information connecting the brain and the peripheral nervous system. Much shorter than the spine that protects the human spine, the human spinal cord originates from the brain stem, passes through the foramen magnum, and continues into the medullary cone near the second lumbar vertebra before termination in a fibrous extension known as the terminale phylum.
It is about 45 centimeters (18 inches) in males and about 43 cm (17 in) in women, oval, and enlarged in the cervical and lumbar regions. Cervix enlargement, stretching from the C5 to T1 vertebrae, is where the sensory input comes from and the motor output goes to the arm and rod. Lumbar enlargement, located between L1 and S3, handles sensory input and motor output coming from and going to the foot.
The spinal cord is continuous with the medulla's cavalry, running from the base of the skull to the first lumbar vertebrae. It does not run the full length of the vertebral column in adults. It is made of 31 segments of the branch of one pair of sensory nerve roots and a pair of motor nerve roots. The nerve roots then merge into a bilateral symmetric spinal cord pair. The peripheral nervous system consists of the root of the spine, nerve, and ganglia.
Dorsal roots are afferent fascicles, receiving sensory information from the skin, muscles, and visceral organs to pass to the brain. The roots stop at the dorsal root ganglia, which comprise the cell bodies of the corresponding neurons. The ventral root consists of the efferent fibers arising from motor neurons whose cell bodies are found in the ventral gray horn (or anterior) of the spinal cord.
The spinal cord (and brain) is protected by three layers of tissue or membrane called the meninges, which surround the canal. The dura mater is the outermost layer, and forms a hard protective layer. Between the dura mater and the surrounding bone of the vertebra is a space called the epidural space. The epidural space is filled with adipose tissue, and contains a network of blood vessels. The arachnoid mater, the middle protective layer, is named for its open appearance, like a spider. The space between the arachnoid and the underlying pia mater is called the subarachnoid space. Subarachnoid space contains cerebrospinal fluid (CSF), which may be exemplified by a lumbar puncture, or a "spinal tap" procedure. The smooth pia mater, the deepest protective layer, is closely related to the surface of the spinal cord. The umbilical cord is stabilized in the dura mater by a connecting denticulation ligament, extending from the lateral shear pia mater between the dorsal and ventral roots. The dural sac ends at the vertebral level of the second sacral vertebra.
In the cross section, the peripheral region of the umbilical cord contains a neuronal white matter tract containing axonic and motoric aconics. Internally to this peripheral region is a gray matter, which contains the body of nerve cells arranged in three gray columns that give the region the shape of a butterfly. This central area surrounds the central canal, which is the fourth ventricular extension and contains cerebrospinal fluid.
Elliptical spinal cord in cross section, compressed dorsolateral. Two prominent grooves, or sulci, run along its length. The posterior median squirrel is a dorsal duct, and the anterior median slit is a groove on the ventral side.
Spinal cord segment
The human spinal cord is divided into segments in which spinal cord pairs (mixture, sensory and motor) are formed. Six to eight branches of the motor nerves roots out of the right and left lateral sulcus in a very regular manner. Nerve cells join together to form nerve roots. Similarly, the sensory nerve roots form the right and left lateral sulcus and form the sensory nerve roots. Ventral (motor) and dorsal (sensory) roots combine to form the spinal cord (mixture: motor and sensory), one on each side of the spinal cord. The spinal cord, with the exception of C1 and C2, is formed within the intervertebral foramen (IVF). These roots form a demarcation between the central and peripheral nervous system.
The gray column, (as three gray column areas) in the center of the cord, is shaped like a butterfly and consists of interneuron cell body, motor neuron, neuroglian cell and unmyelinated axons. The anterior and posterior gray columns come as projections of gray matter and are also known as spinal cord horns. Together, gray columns and gray commissure form "H. gray"
The white matter lies outside the gray matter and is composed almost entirely of myelinated motor and sensory axons. "Columns" of white matter carry information up or down the spinal cord.
The right spinal cord ends up in an area called the conus medullaris, whereas the pia mater continues as an extension called the terminale phylum, which anchors the spinal cord to the coccyx. The cauda equina ("ponytail") is a collection of inferior nerves to the conical medullaris that continue to travel through the vertebral column to the coccyx. Cauda equina is formed because the spinal cord stops growing long at about age four, although the vertebral column continues to extend into adulthood. It produces the sacral spinal nerves that originate in the upper lumbar region.
Inside the CNS, the nerve cell body is generally organized into functional groups, called nuclei. Axons in CNS are grouped into tracts.
There are 31 segments of the spinal cord nerves in the human spinal cord: 8 cervical segments form 8 pairs of cervical nerve (C1 spinal cord out of spine between foramen magnum and C1 vertebrae; C2 nerve exits between posterior arch of C1 vertebrae and lamina C2; C3-C8 spinal nerve pass IVF above the corresponding cervical vertebra, with the exception of the C8 pair exiting the vertebral C7 and T1)
In the fetus, the vertebral segment corresponds to the spinal cord segment. However, since the vertebral column grows longer than the spinal cord, the spinal segment does not correspond to the vertebral segment in adults, especially in the lower spinal cord. For example, the lumbar and spinal cord marrow are found between the T9 and L2 vertebra levels, and the spinal cord ends around the L1/L2 vertebral level, forming a structure known as the medullary conus.
Although the body of the spinal cord ends around the level of the L1/L2 vertebrae, the spinal cord for each segment exits at the appropriate vertebral level. For the lower spinal cord nerves, this means that they come out of the much lower (more caudal) vertebral columns than their roots. As these nerves travel from their respective roots to the exit point of the vertebral column, the spinal cord nerve segments form a bundle called cauda equina.
There are two areas where the spinal cord is enlarged:
- Cervical enlargement - corresponds roughly to the brachial plexus nerve, which inverts the upper limb. This includes the spine segment from about C4 to T1. The vertebral level of enlargement is more or less the same (C4 to T1).
- Lumbar enlargement - associated with the lumbosacral plexus nerve, which inverts the lower limb. It consists of a spinal segment of L2 to S3 and is found about the vertebral level from T9 to T12.
Development
The spinal cord is made from part of the neural tube during development. There are four stages of the spinal cord that arise from the neural tube: Nerve plate, neural folds, neural tube, and spinal cord. Neural differentiation occurs in the spinal cord of the tube. When the neural tube begins to develop, notochord begins to secrete a factor known as Sonic Hedgehog or SHH. As a result, the floor plate then also begins to secrete SHH, and this will induce basal plates to develop motor neurons. During the maturation of the neural tube, the lateral wall thickens and forms a longitudinal groove called the sulcus boundary. This lengthens the length of the spinal cord into the back and abdomen part as well. Meanwhile, the upper ectoderm of bone morphogenetic protein (BMP). This induces the roof plate to begin secreting BMP, which will induce the plates of the alar to develop sensory neurons. Opposing morphogenic gradients such as BMP and SHH form different domains of dividing the cell along the ventral dorsal shaft. Dorsal root ganglion neurons differentiate from neural crest ancestors. When the dorsal and ventral columns proliferate, the lumen of the neural tube narrows to form a small central canal of the spinal cord. The plates of alar and basalt are separated by sulcus limitans. In addition, the floor plate also removes the netrins. Netrins act as chemoattractants for decussation of sensory pain and temperature sensory neurons across the axial plate across the anterior white commissure, where they then rise toward the thalamus. After closure of caudal neuropores and ventricular formation of the brain containing choroidal plexus tissue, the caudal spinal cord central channel is filled with cerebrospinal fluid.
Previous findings by Viktor Hamburger and Rita Levi-Montalcini in female embryos have been confirmed by more recent studies that have shown that the removal of nerve cells by programmed cell death (PCD) is necessary for proper assembly of the nervous system.
Overall, spontaneous embryonal activity has been shown to play a role in neurons and muscle development but may not be involved in the initial formation of connections between spinal neurons.
Blood supply
The spinal cord is supplied with blood by three arteries that run along its length beginning in the brain, and many arteries are approaching it via the side of the spine. The three longitudinal arteries are the anterior spinal artery, and the right and left posterior spinal arteries. This journey is in the subarachnoid space and sends a branch to the spinal cord. They form anastamose (connection) through the anterior and posterior segmental medial artery, which enters the spinal cord at various points along its length. The actual caudal blood flow through these arteries, derived from the posterior cerebral circulation, is not sufficient to maintain the spinal cord outside the cervical segment.
The major contribution to arterial blood supply from the spinal cord beneath the cervical region is from radially posterior and anterior radial artery radials, which travels to the spinal cord along with dorsal and ventral root roots, but with one exception not directly connected to any of the three arteries longitudinal. These intercostal and lumbar artery radicals arise from the aorta, providing major anastomoses and complementing the bloodstream to the spinal cord. In humans the largest anterior radicular artery is known as the Adamkiewicz artery, or anterior radicular artery (ARM), which usually occurs between L1 and L2, but can occur anywhere from T9 to L5. Disorders of blood flow through this critical radicular artery, especially during surgical procedures involving the sudden interruption of blood flow through the aorta eg during repair of the aortic aneurysm, may cause spinal cord infarction and paraplegia.
Maps Spinal cord
Function
Somatosensory Organization
The somatosensory organization is divided into medial dorsal lemniscus channels (sensory touch/proprioception/vibration pathways) and anterolateral systems, or ALS (pain/temperature sensory pathways). Both sensory pathways use three different neurons to obtain information from peripheral sensory receptors to the cerebral cortex. These neurons designated primary, secondary and tertiary sensory neurons. In both pathways, the body of the primary sensory neuron is found in the dorsal root ganglia, and the central axon project into the spinal cord.
In the medial-medial column leminiscus channel, the primary axon of neurons enters the spinal cord and then enters the dorsal column. If the primary axon enters below the T6 spine level, the axon runs in the gracilis fascia, the medial part of the column. If the axon enters the level above T6, it moves in cuneatus fasciculus, which is lateral to the fasciculus gracilis. Either way, the main axon rises to the lower medulla, where it leaves the fasciculus and its synapse with the secondary neuron in one of the dorsal columna nuclei: either the gracilis nucleus or the core cuneatus, depending on the pathway it needs. At this point, the secondary axon leaves its nucleus and passes anterior and medial. The collection of secondary axons that do this is known as an internal arcuate fiber. The internal arcuate fibers decussate and continue to rise as the contralateral medial lemniscus. The secondary axons of the medial lemniscus eventually end up in the posterolateral ventral nucleus (VPLN) of the thalamus, where they synapse with tertiary neurons. From there, tertiary neurons rise through the posterior branches of the internal capsule and end up in the primary sensory cortex.
Proprioception on the lower extremities differs from the upper and upper extremities. There are four neuron pathways for lower extremity proprioception. This line originally follows the dorsal spino-serebelar path. It is regulated as follows: proprioceptive receptors of lower extremities -> peripheral processes -> dorsal ganglion roots -> central process -> Clarke columns -> Ã, neuron sequence 2 -> oblogata medal (Caudate nucleus) Ã, -> Ã, neuron sequences to -3 -> VPLN thalamus Ã,â € "> Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Ã, Korona radiataà ¢ â'¬ >?
The anterolateral system works somewhat differently. The axons of the primary neurons enters the spinal cord and then rise one to two levels before the synapse in the gelatinous substantia. The tracts that go up before synapses are known as Lissauer channels. After the synapse, the secondary axons decussate and rise in the anterior lateral portion of the spinal cord as the spinothalamic tract. This channel goes up to VPLN, where the synapse is in tertiary neurons. The tertiary neuronal axon then travels to the primary sensory cortex through the posterior limb of the internal capsule.
Some "pain fibers" in the ALS deviate from their path to VPLN. In one of these aberrations, the axon travels to the reticular formation of the midbrain. Reticular formation then projects into a number of places including the hippocampus (to create memories of pain), centromedian core (causing diffuse, non-specific pain) and various parts of the cortex. Additionally, some ALS assons project to periaqueductal ash in the pons, and the axons that form the periaqueductal gray then project to the nucleus raphes magnus, which project back to where the pain signal originated and inhibit it. It helps control the sensation of pain to some extent.
Motor organization
The corticospinal tract serves as a motor lane for upper motor neuronal signals originating from the cerebral cortex and from primitive brain stem nuclei.
The upper cortical motor neurons originate from the Brodmann 1, 2, 3, 4, and 6 areas and then descend on the posterior branches of the internal capsule, through the cerebral crus, down through the pons, and into the medullary pyramid, where about 90% of the axons cross over to the contralateral side in the decussation of the pyramid. They then descend as a lateral corticospinal tract. This axon is synced with a lower motor neuron in the ventral horn of all levels of the spinal cord. The remaining 10% of axons descend on the ipsilateral side as ventral corticospinal ducts. This axon also synergizes with the lower motor neurons in the ventral horn. Most of them will cross to the contralateral side of the umbilical cord (via an anterior white commissure) just before the synapse.
The midbrain of the brain includes four motor tracts that send the upper motor neuron axons to the spinal cord to lower motor neurons. These are the rubrospinal tract, the vestibulospinal tract, the tektospinal tract and the reticulum-endinal tract. The rubrospinal tube falls with the lateral corticospinal tract, and the remaining three descend with the anterior corticospinal tract.
The lower motor neuron function can be divided into two distinct groups: the lateral corticospinal tract and anterior anterior cortical ducts. The lateral tube contains the upper motor neuron axons that synapse in the lateral dorsal (DL) motor of the lower neurons. The DL neuron is involved in the control of the distal extremities. Therefore, the DL neuron is found specifically only in cervical and lumbosacral enlargement in the spinal cord. There is no decussation in the lateral corticospinal tract after decussation in the medullary pyramids.
The anterior corticospinal duct drops ipsilaterally in the anterior column, where axons appear and either synapse in the ventromedial motor neuron (VM) low in the ipsilateral ventral horn or descussate on the anterior white commissure where they synapse on the motor neuron below the VM contralaterally. Tectospinal, vestibulospinal and reticulospinal ipsilateral fall in the anterior column but not synapses in anterior white commissures. Instead, they only synapse in lower ipsilateral lower motor neurons. The lower motor neuron VM controls the large postural muscles of the axial skeleton. The lower motor neurons, unlike DL, are located in the ventral horn along the path along the spinal cord.
Spinocerebellar tract
Proprioceptive information in the body runs into the spinal cord via three pathways. Below L2, proprioceptive information radiates to the spinal cord in the ventral spinocerebellar tract. Also known as the anterior spinocerebellar channel, the sensory receptors take information and travel to the spinal cord. The cell body of this primary neuron is located in the dorsal root ganglia. In the spinal cord, the synapse axons and the secondary neuronal axons decussates and then runs into the superior cerebral stem where they decussate again. From here, information is brought to the deep nucleus of the cerebellum including the fastigial and interposed nuclei.
From levels L2 to T1, proprioceptive information enters the spinal cord and rises ipsilaterally, where synapses are within the Clarke nucleus. Secondary neuronal axons continue to rise ipsilaterally and then into the cerebellum through the inferior cerebral butt. This channel is known as the dorsal spinocerebellar channel.
From above T1, proprioceptive primary axis enters the spinal cord and rises ipsilateral until it reaches the cuneate accessory core, where they are synaptic. Secondary acne goes to cerebellar through the cerebellar pedestal inferior elsewhere, this axis synaps on the cerebellum nuclei. This channel is known as a cuneocerebellar channel.
The motor information runs from the brain to the spinal cord through the spinal cord droplet. The descending tract involves two neurons: the upper motor neuron (UMN) and the lower motor neuron (LMN). The nerve signals move down the top motor neurons up to the synapses with the lower motor neurons in the spinal cord. Then, the lower motor neuron performs a nerve signal to the root of the spine where the efferent nerve fibers carry the motor signal toward the target muscle. The descendent tract consists of white matter. There are several descending tracts serving different functions. The corticospinal tracts (lateral and anterior) are responsible for coordinated limb movements.
Clinical interests
Congenital disorders are diastematomyelia in which part of the spinal cord is divided normally at the upper lumbar vertebral level. Sometimes a split can occur along the spinal cord.
Injuries
Spinal cord injuries can be caused by trauma to the spine (stretching, bruising, applying pressure, breaking, laceration, etc.). Vertebral or intervertebral discs may rupture, causing the spinal cord to be punctured by sharp bone fragments. Usually, the victim of a spinal injury will experience a loss of feeling in certain parts of their body. In milder cases, the victim may only suffer from loss of hand or foot function. More severe injuries can cause paraplegia, tetraplegia (also known as quadriplegia), or full-body paralysis under the spinal cord injury site.
Damage to the upper motor neuron axons in the spinal cord results in a characteristic pattern of ipsilateral deficits. These include hyperreflexia, hypertonia and muscle weakness. Lower motor neuronal damage results in a characteristic pattern of its own deficit. Instead of all sides of the deficit, there are patterns related to the myotome that are affected by the damage. In addition, lower motor neurons are characterized by muscle weakness, hypotonia, hiporefleksia, and muscle atrophy.
Spinal shock and neurogenic shock can occur from spinal cord injury. Spinal shock is usually temporary, lasting only 24-48 hours, and in the absence of temporary sensory and motor function. Neurogenic shock lasts for weeks and can lead to loss of muscle tone due to inactivity of the muscles under the injured site.
The two areas of the most commonly injured spinal cord are the cervical spine (C1-C7) and the lumbar spine (L1-L5). (C1, C7, L1, L5 notations refer to the location of certain vertebrae either in the cervical, thoracic, or lumbar regions of the spine.) Spinal cord injury may also be non-traumatic and caused by disease (transverse myelitis, polio, spina bifida, ataxia Friedreich, spinal cord tumor, spinal stenosis etc.)
In the US, 10,000-12,000 people become paralyzed each year due to various injuries to the spinal cord.
Treatment
Spinal or suspected spinal cord injury requires immediate immobilization including the head. A scan will be required to assess the injury. Steroids, methylprednisolone, can help like physical therapy and possibly antioxidants. Treatment should focus on limiting post-injury cell death, promoting cell regeneration, and replacing lost cells. Regeneration is facilitated by maintaining electrical transmission within the nerve element.
Lumbar puncture
The spinal cord ends at the L1-L2 vertebral level, while the subarachnoid space - a compartment containing the cerebrospinal fluid extends to the lower limit of S2. Lumbar puncture in adults is usually performed between L3-L5 (cauda equina level) to avoid damage to the spinal cord. In the fetus, the spinal cord extends along the spine and backwards as the body grows.
Tumor
Tumor tulang belakang dapat terjadi di sumsum tulang belakang dan ini bisa di dalam (intradural) atau di luar (ekstradural) dura mater.
Gambar tambahan
Lihat juga
- Neutral spine
- Brown-SÃÆ' © quard syndrome
- Paraplegia spastik herediter
(HSP, atau paraplegia spastik familial - FSP, sindrom StrÃÆ'¼mpell-Lorrain) - Poliomielitis, sindrom Pasca polio
- Operasi ekstremitas atas di tetraplegia
- Zona Redlich-Obersteiner
- Degenerasi kombinasi sumsum tulang belakang gabungan
- Tethered sindrom medula spinalis
Referensi
Tautan eksternal
- Histologi Kabel Tulang Belakang - Banyak gambar bagus dari Universitas Cincinnati
- Spinal Cord Medical Notes - Catatan medis online pada sumsum tulang belakang
- "The Nervous System: Sensory dan Tracts Motor dari Spinal Cord" (PDF) . Napa Valley College/Southeast Community College Lincoln, Nebraska . Diperoleh 20 Mei 2013 .
- eMedicine: Spinal Cord, Topographical and Functional Anatomy
- WebMD. 17 Mei 2005. Spina Bifida - Ikhtisar Topik Informasi tentang spina bifida pada janin dan sepanjang masa dewasa. Kesehatan anak WebMD. Diakses 19 Maret 2007.
- Potensi untuk perbaikan cedera tulang belakang Diperoleh 6 Februari 2008.
- 4000 set gambar digital, menunjukkan pola ekspresi spasial untuk berbagai gen pada tali tulang belakang tikus dewasa dan juvenile dari Institut Allen untuk Ilmu Otak
- photomicrographs tulang belakang
Source of the article : Wikipedia
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