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Spinal cord

In vertebrates, the spinal cord is the part of the central nervous system Central nervous system

The central nervous system represents the largest part of the nervous system [i], including the brain a ... 

 that is enclosed in and protected by the vertebral column.

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In vertebrates, the spinal cord is the part of the central nervous system Central nervous system

The central nervous system represents the largest part of the nervous system [i], including the brain a ... 

 that is enclosed in and protected by the vertebral column.

Structure


In humans, the spinal cord extends through the spinal canal, starting at the brain Brain

In animal [i]s, the brain, or encephalon , is the control center of the central nervous system [i]. ... 

 and extending downward. In the adult, it ends at the vertebral level of L1 or L2. This terminal part of the spinal cord is known as the conus medullaris. Like the brain, the spinal cord is covered by three meninges: the outer dura mater, the arachnoid membrane, and the innermost pia mater, with cerebrospinal fluid found in the subarachnoid space. The cord within the pia mater is stabilized within the dura mater by the connecting denticulate ligaments which come off the pia mater laterally between the dorsal and ventral roots.

Spinal cord segments


The spinal cord can be divided up into 31 different sections known as spinal cord segments. In a given spinal cord segment, two sets of nerve rootlets emerge from the cord on each side. The anterior Anatomical terms of location

In human and zoological anatomy [i], several terms are used to describe the location of organ [i]s and o ... 

 rootlets form the ventral Anatomical terms of location

In human and zoological anatomy [i], several terms are used to describe the location of organ [i]s and o ... 

 roots, while the posterior Anatomical terms of location

In human and zoological anatomy [i], several terms are used to describe the location of organ [i]s and o ... 

 rootlets form the dorsal roots. The ventral and dorsal roots will later join to form paired spinal nerve Spinal nerve

The term spinal nerve generally refers to the mixed spinal nerve [i], which is formed from the dorsal an ... 

s, one on each side of the spinal cord. The segment is then named after these nerves.

There are 31 spinal cord segments:
  • 8 cervical segments
  • 12 thoracic segments
  • 5 lumbar segments
  • 5 sacral segments
  • 1 coccygeal segment


It is important to note that a spinal cord segment is not always found at the same level as its corresponding vertebra Vertebra

Vertebrae are the individual irregular bones [i] that make up the vertebral column [i] — a flexuou ... 

, especially in the lower spinal cord segments. In a fetus, the vertebral levels originally correspond with the spinal cord segments. The vertebral column, however, grows longer than the spinal cord. In the adult, the cord ends around the L1/L2 vertebral level, with all of the spinal cord segments located superiorly to this. For example, the segments for the lumbar and sacral regions are found between the vertebral levels of T9 and L2. The S4 spinal nerve roots arise from the cord around the upper lumbar/lower thoracic vertebral region, and descend downward in the vertebral canal. After they pass the end of the spinal cord, they are considered to be part of the cauda equina. The roots for S4 finally leave the vertebral canal in the sacrum.

There are two regions where the spinal cord enlarges.
  • Cervical enlargement - corresponds roughly to the brachial plexus Brachial plexus

    The brachial plexus is an arrangement of nerve fibres running from the spine, through the neck, the axilla [i] ... 

     nerves, which innervate the upper limb Upper limb

    In human anatomy [i], the upper limb refers to what in common English is known as the arm, that is, ... 

    . It includes spinal cord segments from about C4 to T1. The vertebral levels of the enlargement are roughly the same .
  • Lumbosacral enlargement - corresponds to the lumbosacral plexus nerves, which innervate the lower limb Human leg

    In common usage, a human [i] leg [i] is the lower limb [i] of the body [i], extending from the hip [i] ... 

    . It comprises the spinal cord segments from L2 to S3, and is found about the vertebral levels of T9 to T12.

Injury


Spinal cord injuries are caused by damage to the spinal cord, such as falling on the neck or back, or having the spinal cord moved or disrupted in another way. The vertebral bones or intervertebral disks can shatter, causing the spinal cord to be punctured by a sharp fragment of bone. Usually victims of spinal cord injuries will suffer loss of feeling in certain parts of their body. In good cases a victim might only suffer loss of hand or foot function. More severe injury may result in paraplegia, tetraplegia, or full body paralysis below the site of injury to the spinal cord.

The two most common areas of the spinal cord most injured are the cervical spine and the lumbar spine .

Embryology

In the human fetus Fetus

A fetus is a developing mammal [i] after the embryonic [i] stage and before birth [i] ... 

, the spinal cord extends all the way down to the sacral vertebrae. As a person matures, the rest of the body grows faster than the spinal cord, so that adulthood, the spinal cord reaches only to the level of the first or second lumbar vertebrae. Below this level, there is no spinal cord, only spinal nerve Spinal nerve

The term spinal nerve generally refers to the mixed spinal nerve [i], which is formed from the dorsal an ... 

s that form the cauda equina.

See also

  • cauda equina
  • conus medullaris
  • meninges
  • spinal nerves Spinal nerve

    The term spinal nerve generally refers to the mixed spinal nerve [i], which is formed from the dorsal an ... 

  • lumbar puncture Lumbar puncture

    In medicine [i], a lumbar puncture is a diagnostic [i] procedure that is done to collect a sample of cerebrospinal fluid [i] ... 



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