the gross anatomy of spinal cord
TRANSCRIPT
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The gross anatomy of spinal cord
By Prof. Dr. Ansari
For Dental students
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A 19-year-old college student, was rock climbing when he fell 30 feet to the ground
Paramedics arriving at the scene found him lying in the supine position, unable to move any extremities and complaining of neck pain. He was awake, alert, and oriented to his current location, the date and day of the week, and the details of his fall. His responses to questioning were appropriate. He complained that he could not feel his arms and legs. The paramedics applied a cervical collar, placed him on a back board, immobilized his head, and transported him to the trauma center by helicopter. X-rays taken upon arrival revealed a fractured fifth cervical vertebra.
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The spinal cord is well protected in the vertebral column
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The spinal cord begins as a continuation of the medulla oblongata of the brain at the level of the foramen magnum in the skull.• Along its course, the spinal cord gives rise to 31
pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.• The spinal cord terminates at the level of the first
or second lumbar vertebrae as the conus medullaris.
• Caudal to the conus medullaris are the nerve roots of the more caudal spinal nerves which are collectively called, because of their appearance, the cauda equina (horse's tail).
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The spinal cord is shaped something like a glass soda-bottle It has a cervical enlargement which begins at roughly C4
and extends to roughly T1 and a lumbar enlargement that extends from roughly the T11 vertebra through the L1 vertebral level.
• The cervical enlargement is the site of the cell bodies of the motor neurons that innervate the upper limbs, as well as the site where the sensory nerves from the upper limbs synapse.
• The lumbar enlargement is the site of the cell bodies of the motor neurons that innervate the lower limbs and the site where the sensory nerves from the lower limbs synapse.
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Meninges of spinal cordThe dura mater is strong, formed of elastic and fibrous tissue. It is the outermost covering of the spinal cord and provides the external layer of the dural sac. Superiorly it adheres to the margin of the foramen magnum where it is in continuity with the cranial dura mater; inferiorly it is anchored to the coccyx by the filum terminale.
The arachnoid mater lines the dural sac, separated from it by a potential space, the subdural space. The arachnoid mater is a thin avascular membrane that also ensheathes the spinal cord and the spinal nerve roots. It is connected to the underlying pia mater by delicate strands of connective tissue, the arachnoid trabeculae. Between the arachnoid and the pia mater lies the subarachnoid space, which contains the CSF.
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Meninges• The pia mater is the innermost membrane covering
the spinal cord and adheres closely to it. • The pia mater ensheathes the spinal nerve roots and
covers the spinal blood vessels. • The spinal cord is suspended in the dural sac by pairs
of segmental denticulate ligaments, composed of pia mater.
• There are 21 pairs of these ligaments, each arising from the side of the spinal cord midway between the dorsal and ventral nerve roots.
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The white matter of spinal cord
• Anterior funiculus• Posterior funiculus• Lateral funiculus• There are ascending and descending tracts in the
white matter of spinal cord.• The posterior funiculus has sensory tracts where as
mixed tracts run in anterior and lateral funiculi.
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The grey matter of spinal cord
• It is H-shaped mass of grey matter.• It has sensory, motor and interneuron.• Anterior horns have motor neurons.• Posterior horns have sensory neurons.• The interneuron's are connecting the sensory with
the other neurons.• The motor neurons are the efferent neurons; the
afferent neurons are situated at the dorsal root ganglia and posterior horns.
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Lateral horns are seen in the first thoracic to second lumbar segments
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APPLIED ANATOMY
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•Neck (cervical) injuries usually result in quadriplegia.• People with injuries to the C1 - C4 level often require a ventilator to breathe.• Shoulder and biceps control can remain with C5 injuries, however wrist and hand movements do not. • C6 injuries can give wrist control but no hand function •while at C7 and T1 individuals can straighten their arms but may have dexterity problems with their hands and fingers.• Spinal cord injuries to the thoracic level and below result in paraplegia, where the hands are not affected.• At T1 through to T8 there may be poor trunk control as a result of the lack of abdominal muscle control.• Lower injuries of T9 to T12 allow for good sitting balance from abdominal muscle and trunk control while injuries to the Lumbar and Sacral regions mean a decrease in control of the hip flexors and legs
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Brown-Sequard syndrome (spinal cord hemisection)
• Refers to injuries limited to one side of the cord. People have weakness and loss of touch sense in one leg but loss of pain and temperature sensation in the other side.
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Slip disk
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Stephen Hawking (1946- )British Physicist, suffering from Amyotrophic lateral sclerosis
• The disorder is characterized by rapidly progressive weakness, muscle atrophy and fasciculations, spasticity, dysarthria, dysphagia, and respiratory compromise.
• It is a form of motor neuron disease caused by the degeneration of neurons located in the ventral horn of the spinal cord and the cortical neurons that provide their afferent input.
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Herpes zoster• It is a virus reactivation from
the dorsal root ganglia.
• There will be unilateral vesicular eruption within a dermatome.
• T3 to L3 dermatome lesions are frequent.
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Herpes zoster ophthalmicus (ophthalmic division of trigeminal n., V1).
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Poliomyelitis (Infantile Paralysis)
It is viral infection of lower motor neuron.
• LMN syndrome at the level of lesion.
• Sensations are not affected.
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References
• Clinically Oriented Anatomy-Keith Moore 6th Edn. (pgs. 496-507)
• http://howmed.net/anatomy/gross-anatomy/spinal-cord-gross-anatomy-internal-structure/
• http://vanat.cvm.umn.edu/neurLab2/SpCdGross.html
• http://academic.pgcc.edu/~tpefok/NOTES/Spinal%20Cord.pdf
• http://apbrwww5.apsu.edu/thompsonj/Anatomy%20&%20Physiology/2010/2010%20Exam%20Reviews/Exam%204%20Review/CH%2012%20Gross%20Anatomy%20of%20the%20Spinal%20Cord.htm
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SAMPLE MCQS• A patient complains of unsteadiness.
Examination shows a marked diminution of position sense, vibration sense, and stereognosis of all extremities. He is unable to stand without wavering for more than a few seconds when his eyes are closed. There are no other abnormal findings. The lesion most likely involves the:-
A.Lateral columns of the spinal cord, bilaterally
B. Inferior cerebellar peduncles, bilaterally *C. Dorsal columns of the spinal cord, bilaterally
D. Spinothalamic tracts, bilaterally
E. Corticospinal tracts
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Sample MCQS
Destruction of lateral spinothalamic tract result in:-• A. Ipsilateral loss of pain & temperature • B. Contralateral loss of light touch & pressure*C. Contralateral loss of the pain & temperature• D. Contralateral loss of proprioceptive• E. Balance is lost
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