Anatomy of the spinal cord

Anatomy of the spinal cord

The spinal cord is the part of the central nervous system running inside the spinal column from which spinal nerves branch out.

Biology

Keywords

spinal cord, nervous system, prolapsed disc, spinal nerve, grey matter, white matter, central canal, motoneuron, ganglion, spine, vertebra, cervical vertebrae, thoracic vertebra, lumbar vertebra, brain, cranial nerve, meninx, neuron, reflex, cerebrospinal fluid, arachnoid mater, lumbar puncture, nerve, human, biology

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Scenes

Spinal cord

  • anterior/ventral root - It consists of the motor fibres emerging from the anterior horn of the spinal cord.
  • posterior/dorsal root - It consists of the sensory fibres that enter the posterior horn of the spinal cord.
  • dorsal root ganglion - Contains the cell bodies of sensory neurons. The axons of the sensory neurons - called sensory fibres - enter the grey matter of the spinal cord through the posterior/dorsal root.
  • anterior horn of grey matter - Contains the cell bodies of motoneurons. The axons of motoneurons, called motor fibres, emerge from the spinal cord through the anterior root.
  • posterior horn of grey matter - The sensory fibres enter here through the posterior root.
  • white matter - The spinal cord consists of an external white matter made up of nerve fibres, and a central grey region made up of nerve cell bodies. Nerve fibres make up pathways in the white matter. Ascending pathways contain sensory fibres that originate in the body, while descending pathways contain motor fibres that originate in the brain. The colour of the white matter is due to the myelin sheath that covers nerve fibres.
  • central canal - It is filled with cerebrospinal fluid, it is continuous with the ventricular system of the brain.

Groups of spinal nerves

  • 8 pairs of cervical nerves
  • 12 pairs of thoracic nerves
  • 5 pairs of lumbar nerves
  • 5 pairs of sacral nerves
  • 1 pair of coccygeal nerves
  • spinal cord
  • horse´s tail - The spinal cord ends in the lumbar region of the spinal column. The Cauda equina or horse's tail is a bundle of spinal nerves.

Position of the spinal cord

  • vertebra - They protect the spinal cord. Nerves emerge above the transverse processes of the vertebrae.
  • spinal disc - Their elasticity provides flexibility for the spinal cord.
  • spinal cord - It consists of an external white matter and a grey, butterfly-shaped central region made up of nerve cell bodies.
  • pia mater - The innermost layer of the meninges, the membranes surrounding the brain and spinal cord.
  • spinal nerve - The 31 pairs of these nerves contain both sensory and motor fibres, thus they are mixed nerves. Fibre bundles outside the central nervous system (brain and spinal cord) are called nerves, while fibre bundles in the central nervous system are called paths.
  • arachnoid - It is a thin membrane with a spiderweb-like structure, it is composed of fibrous tissue and contains cerebrospinal fluid. This fluid protects the central nervous system, providing mechanical protection and decreasing the net weight of the brain.
  • dura mater - The outermost, fibrous layer of the meninges, which envelope the brain and the spinal cord.

Prolapsed disc

  • annulus fibrosus - When it is injured, the nucleus pulposus protrudes. As we age, it loses its flexibility and becomes vulnerable, increasing the risk of spinal disc prolapse.
  • nucleus pulposus - Due to the protrusion of the pulpy nucleus, the prolapsed (or herniated) disc may press the spinal nerve or the spinal cord itself. This can cause pain, numbness, paresthesia, the disturbance of reflexes, as well as problems of vegetative functions (such as urinary or fecal incontinence). Spinal disc prolapse can be treated with exercise, by wearing a back brace, or with surgery.
  • spinal nerve

Nervous system

  • brain
  • spinal cord - The main components of the central nervous system are the brain and the spinal cord. 31 pairs of spinal nerves emerge from the spinal cord.
  • cranial nerves
  • spinal nerves - The peripheral nervous system is composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves. Spinal nerves are mixed nerves: they contain both sensory and motor fibres.

Animation

  • brain
  • spinal cord - The main components of the central nervous system are the brain and the spinal cord. 31 pairs of spinal nerves emerge from the spinal cord.
  • cranial nerves
  • spinal nerves - The peripheral nervous system is composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves. Spinal nerves are mixed nerves: they contain both sensory and motor fibres.
  • 8 pairs of cervical nerves
  • 12 pairs of thoracic nerves
  • 5 pairs of lumbar nerves
  • 5 pairs of sacral nerves
  • 1 pair of coccygeal nerves
  • spinal cord
  • horse´s tail - The spinal cord ends in the lumbar region of the spinal column. The Cauda equina or horse's tail is a bundle of spinal nerves.
  • vertebra - They protect the spinal cord. Nerves emerge above the transverse processes of the vertebrae.
  • spinal disc - Their elasticity provides flexibility for the spinal cord.
  • spinal cord - It consists of an external white matter and a grey, butterfly-shaped central region made up of nerve cell bodies.
  • pia mater - The innermost layer of the meninges, the membranes surrounding the brain and spinal cord.
  • spinal nerve - The 31 pairs of these nerves contain both sensory and motor fibres, thus they are mixed nerves. Fibre bundles outside the central nervous system (brain and spinal cord) are called nerves, while fibre bundles in the central nervous system are called paths.
  • arachnoid - It is a thin membrane with a spiderweb-like structure, it is composed of fibrous tissue and contains cerebrospinal fluid. This fluid protects the central nervous system, providing mechanical protection and decreasing the net weight of the brain.
  • dura mater - The outermost, fibrous layer of the meninges, which envelope the brain and the spinal cord.
  • anterior/ventral root - It consists of the motor fibres emerging from the anterior horn of the spinal cord.
  • posterior/dorsal root - It consists of the sensory fibres that enter the posterior horn of the spinal cord.
  • dorsal root ganglion - Contains the cell bodies of sensory neurons. The axons of the sensory neurons - called sensory fibres - enter the grey matter of the spinal cord through the posterior/dorsal root.
  • anterior horn of grey matter - Contains the cell bodies of motoneurons. The axons of motoneurons, called motor fibres, emerge from the spinal cord through the anterior root.
  • posterior horn of grey matter - The sensory fibres enter here through the posterior root.
  • white matter - The spinal cord consists of an external white matter made up of nerve fibres, and a central grey region made up of nerve cell bodies. Nerve fibres make up pathways in the white matter. Ascending pathways contain sensory fibres that originate in the body, while descending pathways contain motor fibres that originate in the brain. The colour of the white matter is due to the myelin sheath that covers nerve fibres.
  • central canal - It is filled with cerebrospinal fluid, it is continuous with the ventricular system of the brain.
  • annulus fibrosus - When it is injured, the nucleus pulposus protrudes. As we age, it loses its flexibility and becomes vulnerable, increasing the risk of spinal disc prolapse.
  • nucleus pulposus - Due to the protrusion of the pulpy nucleus, the prolapsed (or herniated) disc may press the spinal nerve or the spinal cord itself. This can cause pain, numbness, paresthesia, the disturbance of reflexes, as well as problems of vegetative functions (such as urinary or fecal incontinence). Spinal disc prolapse can be treated with exercise, by wearing a back brace, or with surgery.
  • spinal nerve

Narration

Our nervous system is divided into the central nervous system and the peripheral nervous system. The main components of the central nervous system are the brain and the spinal cord. The peripheral nervous system is composed of 12 pairs of cranial nerves and 31 pairs of spinal nerves.

In the cervical region 8 pairs of nerves emerge from the spinal cord. There are 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves and 1 pair of coccygeal nerves. The spinal cord ends in the lumbar region of the spinal column. The cauda equina or horse's tail is a bundle of spinal nerves. Spinal nerves are responsible for carrying information between the central nervous system and other parts of the body. The spinal cord is the centre of many reflexes, such as the patellar reflex, and contains nerve fibres ascending to and descending from the brain.

The spinal cord is protected by the vertebrae. Nerves emerge above the transverse processes of the vertebrae. The elasticity of the intervertebral discs provides flexibility for the spinal cord.
The spinal cord - and the brain - are also protected by three layers of membranes, called meninges: the external dura mater, the arachnoid mater and the internal pia mater. The arachnoid mater is a thin membrane with a spiderweb-like structure, it is composed of fibrous tissue and contains cerebrospinal fluid. This fluid protects the central nervous system, providing a mechanical protection and decreasing the net weight of the brain.

The spinal cord consists of an external white substance and a grey, butterfly-shaped central region made up of nerve cell bodies. Nerve fibres make up pathways in the white matter. Ascending pathways contain sensory fibres that originate in the body, while descending pathways contain motor fibres that originate in the brain.
The colour of the white matter is due to the myelin sheath that covers nerve fibres. The anterior horn of the grey matter contains the cell bodies of motoneurons. The axons of motoneurons, called motor fibres, emerge from the spinal cord through the anterior root. The sensory fibres enter the posterior horn of the grey matter through the posterior root. The central canal is filled with cerebrospinal fluid, it is continuous with the ventricular system of the brain.

Intervertebral discs consist of two main parts: the annulus fibrosus or fibrous ring and the nucleus pulposus or pulpy nucleus. As we age, the fibrous ring loses its flexibility and becomes vulnerable, increasing the risk of spinal disc herniation. A herniated disc may apply pressure to the spinal nerve or the spinal cord itself, which can cause pain, numbness, paresthesia, reflex disorders and paralysis, as well as problems with vegetative functions (such as urinary or fecal incontinence). Spinal disc herniation can be treated with exercise, by wearing a back brace, or with surgery.

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