Are you senior of a visible learner? reverse out our online video lectures and start your anatomy course now for free! Location and Structure of The Spinal Cord As part of The central anxious system, The spinal cord (medulla spinalis) is held in place by ligaments and is well protected in The spinal canal of The vertebral column. It begins at The foramen magnum, at The base of The skull (medulla oblongata). Along The spine are two spindle-shaped increase (intumescentia cervicalis and intumescentia lumbalis) that deal with motor input and output innervation to and from The limbs. The mean result of The spinal cord is conical-shaped and tapered and is thus understood as The conus medullaris. Surrounding The spinal cord and projecting downwards is a slim connecting filament where The spinal cord ends (filum terminale). Connective fiber entraps and protects The whole spinal cord, creating epidural space that is filled with fatty adipose tissue, a network of venous plexuses, and blood vessels. In this way, The outermost layer protects The sensitive spinal cord from damage. FurThermore, The spinal cord has two skinny grooves which burn along its whole length. The first groove fissura mediana ventralis way along The anterior ventral side, and The second groove sulcus medianus dorsalis runs on The back dorsal side. In a manner of speaking, both symmetrically “split” The spinal cord into a left and a right half. The spinal cord is classified lengthwise into thirty-one to thirty-three segments. In each section of both sides of The spinal cord, dorsal sensory nerve roots register and ventrolateral roots exit, combining to form spinal nerves on The right and The left sides. These spinal nerves emerge from openings in The intervertebral foramen between 2 spinal vertebrae. believed that, in newborn babies, The spinal canal and The spinal cord still have The common length, The spinal guts exit The vertebral column at The same level as Their intervertebral foramina. As The adolescent mind develops, The vertebral column sprouts faster than The spinal cord, which means that The spinal nerves must travel much longer to exit The vertebral column. This leads to The development of The so-called horse’s tail (cauda equina), which is a dense collection of downward-extending spinal nerves. In adults, above The story of The first lumbar segment, spinal nerves only burn in a downward, or caudal, fashion. The length of The cord is estimated to be about 45 cm in males and 43 cm in females. Spinal cord section The spinal cord itself is not visibly segmented; The part into segments is only for topographical and functional classification. Every segment is a cross-section of The spinal cord with its corresponding pair of incoming sensory and outgoing motor spinal nerves. part are suggested to in relation to The vertebrae : eight cervical part forming The cervical nerves (since The first cervical spinal nerve exits above The first cervical vertebra), twelve thoracic segments making up The thoracic nerves, five lumbar segments collectively referred to as The lumbar nerves, five sacral segments forming The sacral nerves, and one to 3 coccygeal segments. Spinal guts The border between The central and peripheral anxious systems is determined at The transition between each spinal segment in The frontal and rear side roots. From There, The spinal tuber conform part of The peripheral anxious system. Thirty-one spinal nerves arise from The spinal column through The intervertebral foramen opening between close vertebrae. Each spinal nerve pair corresponds to a spinal cord segment (see table below). amount of cervicales eight pairs C1 – C8 The first spinal nerve pair rises between The occipital bone and The atlas. amount of thoracales twelve match T1 – T12 The first thoracic nerve pair rises between T1 and T2. Number of lumbales five pairs L1 – L5 The first lumbar pair emerges between L1 and L2. Number of sacrales five pairs S1 – S5 The first sacral nerve pair emerges between S1 and S2. Number of coccygei one – three pairs, partly rudimentary The first nerve pair emerges between The first and second coccygeal vertebrae. Spinal cord cross-section A cross-section of The spinal cord reveals gray, butterfly-shaped matter surrounded by neuronal white matter. The spinal cord has a several demeanor affecting on The height of The cross-section. It is largest around The cervical and lumbar regions, since a high number of neuron conduits dealing with motor information to The limbs are located There. Spinal cord grey fact (substantia grisea) Spinal cord hoary fact consists of neuronal cell bodies (somata) and glial cells resembling a butterfly when seen from a cross-section. This butterfly shape has a symmetric construction where both halves of The gray matter are connected by The commissura grisea, The central region of which surrounds The canalis centralis and contains cerebrospinal fluid. Both fraction of The spinal cord hold a so-called dorsal horn (cornu dorsale), a ventral horn (cornu ventrale), and, between segments C8 and L1, an more lateral horn (cornu laterale). In its 3-dimensional longitudinal perspective, 3 columns develop: The columna dorsalis, columna ventralis, and columna lateralis. During The primitive stage, The dorsal horn expands from The alar plate. It cans The sensory neurons of The afference system. The ventral horn derives from The basal plate and contains motor nerve cells (motor neurones), The nerve fibers of which affect The axial muscles. Postganglionic neurons of The sympaThetic are located in The lateral horn. The structure of grey matterTwo different systems are used to describe The function of cells within The gray matter. 1st system: Rexed laminae hoary fact is arranged into ten different layers according to The size and thickness of The nerve cells: Dorsal horn: Laminae I–V/VI Ventral horn : Lamina VII and VIII, which contains lamina IX (built from The nuclei of motoneurons). grizzled commissure: Lamina X 2nd system: differentiating grey fact into layers and nuclei (The sorting of nerve cells according to Their functional association) using Their Latin notations. Some laminae hold specific nuclei: Lamina I: zona marginalis Lamina II: substantia gelatinosa Rolandi Lamina III, IV: nucleus propriusLamina VII: substantia intermedia lateralis (aona intermedia)The motor neurones in The ventral horn are ordered according to The groups of nuclei outlined in The table below. Medial nucleus community of The ventral horn Lateral nucleus groups of The dorsal horn Central nucleus groups of The ventral horn cervical cord Dorsomedialis Dorsolateralis Phrenicus Ventromedialis Ventrolateralis Accessorius Retrodorsolateralis In this way, The ventral horn is described as having a somatosensory organization. The cervical medulla, for example, has The relating somatosensory organization: Nucleus community Medial nucleus groups of The ventral horn Lateral nucleus groups of The ventral horn Ventrolateralis Dorsolateralis Retrodorsolateralis Function Neck and back musculature Shoulder Lower arm Little finger Intercostal muscles Upper arm Hand Abdominal musculature Somatosensory organization does not culminate with The level of The spinal cord; raTher, cells for The shoulder girdle are found on The furThest cranial and descend caudally from The upper arm to The lower arm and hand. Cells for The extensor musculature are arranged in The ventral area of The ventral horn, while The cells for flexor muscles are located in The dorsal area. The spinal cord proprioceptive mechanism (propriospinal system) The spinal cord propriospinal duct is an inner system for The transmission of information. It is filled up of a contribution of ascending and descending nerve cells that originate in The spinal cord itself. These heart fibers eiTher widen The length of many spinal segments, run inside a single segment connecting different levels of The spinal cord, or cross over each oTher. The propriospinal system lays The foundations for The monosynaptic and polysynaptic reflexes. Propriospinal system cell typesAssociation cells —connect flat-lying nerve cells on different spinal segments via The fasciculi proprii ipsilateral. Commissural cells —connect contralateral lying cells of The same segment through The commissura alba. Relay cells (interneurons) —connect ipsilateral lying cells of The same segment (e.g., Renshaw cells , which are inhibitory interneurons). Renshaw cubicle inhibition is a retrograde frequent inhibition created by a negative feedback mechanism. Renshaw cubicle are wakt by alpha motor neurons when They receive excitatory collateral from The alpha neuron’s axon, resulting in The inhibition of Their personal actions. This mechanism prevents unwanted muscular oscillatory movements from occurring. A step to The clinic: tetanus infection Infection with The bacterium Clostridium tetani causes a build-up of toxins in The spinal cord that damage The inhibitory neurons of The muscle nerve cells, arising in hyperactive incoming alpha motor neurons. This leads to severe tonic-clonic muscle contractions. Spinal cord white fact (substantia alba) Spinal cord white matter is created of ascending and descending nerve fibers; These yarn (funiculi), bundles (fasciculi), and tracts (tractus) reach country of grizzled matter togeTher with glial cells and, as a whole, form The supporting tissue of The nervous system. White fact keep be divided into The following strands: Funiculus posterior caught between The posterolateral and posterior median sulcus, above all ascending fibers) Funiculus lateralis (found between The exit of The anterior nerve roots and The posterolateral sulcus) Funiculus anterior (found between The anterior median fissure and The lateral anterior nerve roots) The last two strands also make up part of The ventral funiculus. White mind exalting tracts Ventral funiculus area Dorsal funiculus tracts Spinocerebellar projection tracts Tractus spinothalamicus lateralis Fasciculus gracilis Tractus spinocerebellaris posterior Tractus spinothalamicus anterior Fasciculus cuneatus Tractus spinocerebellaris anterior Tractus spinotectalis White matter dismounting tracts Pyramidal area = Tractus corticospinalis Extrapyramidal tracks Vegetative tracts Tractus corticospinalis lateralis Tractus vestibulospinalis Tractus parependymalis both sides of The central canal Tractus corticospinalis anterior Tractus reticulospinalis ventralis et lateralis from The arch The vegetative tracts rarely build closed bundles Tractus reticulospinalis lateralis out of The Medulla oblongata Tractus tegmentospinalisFasciculi proprii latch directly onto The gray matter of The spinal cord proprioceptive apparatus. The Reflex Arc A reflex is an uncontrollable answer to a stimulus. Afferent heart fibers send Their excitation directly to The motor neuron cells of The incipient horn which, through Their efferent nerves, control The musculature. This feedback steals place on The level of The spinal cord and is known as a simplistic reflex. The underlying neural circuit is referred to as The reflex arc. In this way, a reflex check occur quickly without The adjournment of routing signals through The brain since afferent sensory neurons synapse directly in The spinal cord instead. As such, The afferent siren come The spinal cord eiTher by passing directly to a individual motor neuron, creating a single chemical response (monosynaptic reflex) or via The connection of one or more interneurons that connect sensory-afferent signals with motor-efferent signals (polysynaptic reflex). Monosynaptic reflex Monosynaptic reflexes have only one synapse between The receptor and effector, i.e., between outgoing motor response and incoming sensory. The patellar reflex is an case of a monosynaptic reflex. A smack to The patellar ligament belief The quadriceps muscle to extend. Receptors provide a signal that travels back to The spinal cord and stretches The muscle spindle in The quadriceps femoris muscle. The sensory afferents send The signals to The dorsal horn, which synapse only once in The anterior horn at segments L2–L4; The efferent fibers Then send an impulse to The lumbar plexus, which is isolated in The femoral nerve, and Then send it back to The muscle to cause its contraction. The concern of testing this reflex lies in testing, not its strength, but raTher what its consistency is over time. Polysynaptic reflex Polysynaptic reflexes have complex synapses between receptor and effector. Electrical impulses are transferred from a sensory neuron to a motor neuron via at least one interneuron. An example: Polysynaptic evacuation reflex The abandonment reflex is a preventive reflex. Nociceptors trigger a sensory impulse in The nerves producing an excitation that travels to many levels of The spinal cord. The sensory neuron Then synapses with interneurons that reach to motor neurons. Some of These send motor impulses to The flexors to allow withdrawal. basis include: Cremasteric reflex physical reflex ignore reflex Spinal filament Blood Supply Supply of blood via arteries The three main aorta that supply The spinal cord arrive from The vertebral arteries: Anterior spinal artery: The vessel is found in The anterior median fissure, has a caudal flow and ends at The sulcus of The sulco-commissural artery . Posterior spinal arteries: These two supply arteries run adjacent to The entrance of The dorsal root and branch out within The spinal cord. Additionally, The intercostales posteriores vessel in The thorax region and The lumbar arteries in The lumbar region (both outlets of The aorta) update rami spinales to supply The thoracic spine and The lumbar spine. The large rami spinalis in The intumescentia lumbalis area is called The arteria radicularis magna (Adamkiewicz). The spinal cord is encirclt by a vasocorona (vascular ring) where The aorta spinalis ventralis Anastomosen branches off from The spinales dorsales arteries. These branches from The vasocorona penetrate and supply The white matter. Spinal cord vein drainage artery drainage works via The incipient spinal vein and both posterior spinal veins. The efferent veins drain into The epidural venous plexus. The Spinal Meninges The connective tissue of The spinal meninges encompasses membranes that envelop The whole spinal cord in order to protect and nourish it. Above The foramen magnum, They continue as brain meninges. Dura mom meninges (dura mater spinalis) Dura mater is highly responsive to pain and is The utmost layer of The protective membrane. It shape a so-called Thecal sac made from an outer and intrinsic dural fold. The utmost sheet of The spinal canal is The insincere or periosteal layer. Between The furrow is where The epidural and peridural space is located; it cans The venous plexus (plexus venosus vertebralis internus) and oily tissues. The dural sac works as soft padding for The spinal cord and is used as protection during spinal movements. Epidural anesThesia (PDA) The government of a regional analgesic into The epidural space (PDA) is often used for pain relief during labor, or, in The form of an epidural caTheter, for The treatment of chronic pain. smooth meninges = Arachnoid moTher (arachnoid mater) and pia mater spinalis The arachnoid mom lies between The two oTher meninges, The dura mater and The pia mater, which are disintegrated by subarachnoid space in which cerebrospinal variable flows and ends with The conus medullaris. Dura mater and arachnoid mater fill The spinal canal caudally. stick Sites for mellifluous Extraction Cerebrospinal variable is a transparent fluid that is largely composed of The interstitial fluid of oTher tissues. It cans tiny protein and some lymphocytes. An infection of The central nervous system changes The appearance of The cerebrospinal fluid so that it is possible to diagnose certain conditions by examining it. Lumbar stick A lumbar puncture is an extraction of cerebrospinal liquid from The subarachnoid space; this liquid is employed for diagnostic purposes. The stab point is originated around The cauda equina between The lumbar vertebrae LIII and LIV, and LIV and LV, as There is lower risk of damage to The spinal cord in These spaces. The front and back roots of cauda equina soften The penetration of The needle. Cisternal punctureThe puncture point for this fluid-extraction procedure is in The midline located below The external occipital protuberance where The needle enters into The cisterna magna. Cerebrospinal variable is admitted from The cisterna cerebellomedullary. A cisternal stab is sometimes proceeded out on miniature children because, in a child ’s body, The spinal cord is plenty elder caudal, so a lumbar stick is often not appropriate. However, due to The risk of injury by The needle entering The medulla, this is a very rare procedure. Spinal knot Injuries Meningocele and myelomeningocele (spina bifida aperta) = “ split spine ” Spina bifida is a birth defect wherein The closing of The backbone and membranes around The spinal cord is not completed before birth. During immature development, The clasp of The neural tube and spine is incomplete, killing The meninges to be forced into The gaps between The vertebrae (meningocele). In some cases, The unknown section of The spinal column lets The spinal cord to protrude through an opening (myelomeningocele). The most conventional locality for this spinal defect is The mean back; however, rare cases involving The middle back as well as The neck have been seen in recent years. Only in so-called spina bifida occulta does The spinal cord fabric remain intact. The outer portion of some of The vertebrae is not completely closed, but splits in The vertebrae are so little that The spinal cord does not protrude. The skin at The site may have a bit of hair growing from it, or a dimple or birthmark. The medicine of spina bifida encompasses neurosurgical closure and resultant Therapies to maintain The closure’s integrity. WheTher The function is profitable presume on The level of The defect. As with all spinal cord defects and injuries, The higher The defect on The spine, The less favorable The prognosis. The belief of this condition are supposed to be both genetic and environmental. Lack of adequate folate during pregnancy also plays a major role. Problems associated with this defect include challenges in bladder control, poor walking abilities, and learning disabilities. Spinal cord harm comprehensive spinal cord injury: The perfect dysfunction of an individual spinal segment imperfect spinal cord injury: The unilateral losses of function of The spinal cord at a certain spinal level The symptom complex includes paralysis, sensory disturbances, and disruption of vegetative functions. Depending on where The injury occurs, paraplegia (total paralysis of The legs) or quadriplegia (total paralysis of both arms and legs) may also occur. Spinal cord harm usually The result of distressing accidents. However, inflammation (e.g. poliomyelitis and multiple sclerosis), tumors, and disc herniation can also cause a spinal cord injury. Note: Every spinal cord injury should be treated as a neurological emergency. Spinal disc herniation (prolapse nuclei pulposi) = lumbar disc herniation (BSP) Disk herniation is produced eiTher by trauma or The degeneration of The intervertebral disc, The contents of which (nucleus pulposus) get pressed against The spinal cord, resulting in The rupture of The membrane. A consideration is filled between: Prolapsed disk (a comprehensive prolapse of The nucleus pulposus through wounded annulus fibrosis) obtruded disc (an imperfect projection or herniation, whereby The nucleus pulposus bulges into The spinal canal, although The fibrous ring of The disc still remains intact or is only slightly torn) Spinal cord virus (myelitis) Myelitis is a remarkable disorder with mostly immunological and allergic causes. The inflammation check be spread out over The whole spinal cord or occur in a slender region (disseminated myelitis). Inflammation may damage The myelin and axon causing sensory loss or paralysis. There are a number of different types of myelitis. Parainfectious myelitisSpinal cord inflammation can be caused by infectious diseases such as measles, mumps, and rubella. Poliomyelitis puerile paralysis) Poliomyelitis is an contagious disease killed by The poliovirus, which provides a viral illness in The hoary matter, leading to muscle paralysis, muscle weakness, or death. The Standing Committee on Vaccination (STIKO) at The Robert Koch Institute, Therefore, recommends vaccination for polio after The second month of a baby’s life. Tetanus The toxin of tetanus pathogen, understood as C. tetani, damages The inhibitory synapses of The CNS. The uninhibited motoneurons lead to convulsions and structural muscle spasms and The relating symptoms: risus sardonicus, opisthotonus, and tonic and clonic seizures. A tetanus infection has a lofty mortality rate and, if gone untreated, inevitably leads to death. STIKO recommends a primary vaccination after an infant’s second month of life. Transverse Myelitis Transverse myelitis suggests to an inflammation of The spinal cord. The inflammation damages nerve fibers so extensively that They lose Their myelin coating, leading to decreased electrical conductivity in The nervous system (caused by, for example, endocarditis or septicemia). Meningococcal MyelitisMeningitis can spread directly to The spinal cord due to its topographical proximity. complex Sclerosis Commonly suggested to encephalomyelitis, in this condition The nerve sheaths in The brain and The spine is damaged. This can result in a variety of physical as well as mental disorders. same explanation of myelitis The carrying pathogens are responsible for this disorder:
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