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Term Paper on the Spinal Cord
Term Paper Contents:
- Term Paper on Anatomical Structure of the Spinal Cord
- Term Paper on External Features of the Spinal Cord
- Term Paper on Internal Structure of the Spinal Cord
- Term Paper on Blood Supply of the Spinal Cord
- Term Paper on Clinical Segmentation of the Spinal Cord
- Term Paper on Applied Anatomy of the Spinal Cord
Term Paper # 1. Anatomical Structure of Spinal Cord:
Spinal cord is downward continuation of medulla oblongata.
Within the upper 2/3rd of vertebral canal.
Is about 45 cm in adult men and 42 cm in women.
From upper border of atlas vertebra to the lower border of L1 vertebra.
The position of lower end may be variable.
It may extend to lower border of T12 vertebra or downwards to lower border of L2 vertebra.
Spinal cord is covered by meninges, i.e., dura mater, arachnoid mater and pia mater.
The dura mater extends upto second sacral vertebra.
The subarachnoid space of brain is continuous with the subarachnoid space of spinal cord and ends below at the lower border of the second sacral vertebra. It contains C.S.F. and spinal nerves and blood vessels pass through the space.
Term Paper # 2. External Features of the Spinal Cord:
The spinal cord is not having a uniform diameter. It has an upper cervical swelling and lower lumbar swelling. The lower end is tapering and conical, called the conus medullaris. The apex of the conus is continued down as the filum terminale.
The spinal cord gives of 31 pairs of spinal nerves:
i. Cervical nerves – 8
ii. Thoracic nerves – 12
iii. Lumbar nerves – 5
iv. Sacral nerves – 5
v. Coccygeal nerve – 1.
It is situated where nerves of upper limb are attached. It extends between 3rd cervical to the 2nd thoracic segment of the spinal cord.
It is situated where nerves of the lower limb are attached. It lies between L1 to S3 segment of spinal cord (T9 – T12 vertebral level).
The spinal cord is much shorter than the length of the vertebral column. The spinal segments do not lie opposite the corresponding vertebrae. A vertebral spine is always lower than the corresponding spinal segment. It may be stated that in the cervical region there is a difference of one segment in the upper thoracic regions there is a difference of two thoracic segments, and in the lower thoracic region there is a difference of three segments.
Fissures and Sulci:
The anterior median fissure and posterior median sulcus divide the spinal cord into two halves. They extend along the entire length of the cord. The antero lateral sulcus is found along the attachment of the anterior root of the spinal nerve. The postero lateral sulcus gives attachment to dorsal nerve root of spinal cord.
The nerves are attached to the spinal cord by motor ventral and sensory dorsal roots. The dorsal root has a dorsal root ganglion which is sensory in function.
Near the spinal cord, dorsal root divides into medial and lateral divisions and enters the spinal cord. The lateral division carries pain and temperature sensations while medial division carries touch and pressure.
The dorsal and ventral roots unite to form spinal nerve.
The lumbar, sacral and coccygeal nerves arise from conus medullaris – running vertically downwards. It resembles like a tail of a horse. Nerves are situated around the filum terminale and leave the cauda equina at respective foramina to pass through them.
Term Paper # 3. Internal Structure of the Spinal Cord:
A cross section will show:
1. White matter – situated at periphery.
2. Grey matter – situated near the center.
It forms an ‘H’ shaped mass divisible into:
1. Anterior grey column or horn and
2. The posterior grey column or horn.
Lateral horns are situated only in the spinal segments of T2 to L1.
Is directed forwards and laterally. It has a head and base – does not reach the surface of spinal cord. Neurons are motor in function. Axon of these neurons joins and forms the ventral root of spinal cord.
It is directed backwards and laterally extends nearer to the surface and separated from the surface by the dorsi lateral tract.
It has – base, neck, head and apex.
Apex is covered by substantia gelatinosa. Neurons are sensory in function.
Neurons are sympathetic in function situated in the spinal segments of T2 to L1.
Grey Commissure and Central Canal:
It connects the right and left halves of grey matter and is traversed by the central canal, which is superiorly continuous with the fourth ventricle. Inferiorly canal dilates to form the terminal ventricle in the conus medullaris. It is surrounded by substantia gelatinosa centralis and canal is filled with C.S.F. and is lined by a membrane called ependyma.
White Matter of Spinal Cord:
It is divided into funiculi, situated around the grey matter.
They are classified into:
1. Anterior Funiculus:
It is found between anterior median fissure and ventral root of the spinal nerve.
2. Lateral Funiculus:
It is situated between ventral root and posterior lateral sulcus.
3. Posterior Funiculus:
It is situated between the postero lateral sulcus to the posterior median septum.
Tracts of the spinal cord are bundles of white matter found within the funiculi. These are classified into ascending tracts and descending tracts.
The ascending tracts are sensory tracts and descending tracts motor tracts.
(a) Section appears large
(b) Anterior horn is broader than posterior horn.
Term Paper # 4. Blood Supply of the Spinal Cord:
1. Anterior spinal artery (one)
2. Posterior spinal arteries (two)
3. Spinal branches of vertebral arteries, deep cervical artery, posterior intercostal arteries and lumbar arteries.
Anterior Spinal Artery is a branch from 4th part of vertebral artery. It passes downwards and joins with its fellow of opposite side and forms anterior spinal arterial trunk, which descends along the anterior median fissure and is reinforced by the anterior radicular branches of vertebral, deep cervical, ascending cervical, posterior intercostal and lumbar arteries.
1. Anterior funiculus
2. Right and left lateral funiculus
3. Anterior 2/3 of the grey column.
Posterior Spinal Artery is a branch from 4th part of vertebral artery. It divides into two collateral arteries along the medial and lateral sides of the dorsal nerve roots and forms the posterior arterial trunks. Each trunk is reinforced by posterior radicular artery braches of vertebral, deep cervical, ascending cervical, posterior intercostal and lumbar arteries.
1. Posterior 1/3 of grey column
2. Posterior funiculus
3. A small part of the lateral funiculus.
These are six veins found on the surface of spinal cord.
i. One vein along the anterior median fissure.
ii. One vein along the posterior median sulcus.
iii. One pair of veins on each side of the ventral nerve roots.
iv. One pair of veins on each side of the dorsal nerve roots.
These veins are directly communicating with each other and form a network of veins around the spinal cord.
These veins superiorly communicate with the dural venous sinuses of the posterior cranial fossa. Venous plexus is present in subarachnoid space and communicates with the internal vertebral venous plexus and external vertebral venous plexus.
These veins are not provided with valves.
Term Paper # 5. Clinical Segmentation of the Spinal Cord:
A spinal segment is formed by a portion of the spinal cord with a pair of spinal nerves.
As the spinal cord stops at the lower border of L1 vertebra, the vertebral levels do not correspond with the spinal segments.
To understand the level segmentation is done by:
i. Add one to the number of cervical vertebra. For example, C3 spine corresponds with C4 segment.
ii. Add two to the number of upper six thoracic vertebrae. For example, T4 spine corresponds with T6 segment.
iii. Add three to T7 – T10 spines. For example, T7 spine corresponding with T10 segment.
iv. Add six to T12 spine. So that T12 corresponds with S1 segment of the spinal cord.
v. The sacral and coccygeal segments are situated at the level of L1 spine.
Term Paper # 6. Applied Anatomy of the Spinal Cord:
1. Spinal Shock:
Loss of reflexes after the transaction of the spinal cord. All the body segments below the level of transaction become paralysed and anesthetic.
2. Tabes Dorsalis:
Due to syphilitic infection of the spinal cord.
3. Acute Polio Myelitis:
Due to viral infection of cells of anterior horn of spinal cord, especially at cervical and lumbar swellings of the spinal cord.
4. Syringo Myelia:
Dilatation of the central canal of the spinal cord.
5. Fracture or dislocation of vertebra, prolapse of the intervertebral discs, tumours of meninges or secondary deposits may produce spinal cord lesions.