Spinal Cord

SPINAL CORD

The spinal cord is the main pathway for information, connecting the brain and peripheral nervous system. The human spinal cord is protected by the bony spinal column, which is made up of bones called vertebrae. Although the spinal column is somewhat flexible, some of the vertebrae in the lower parts of the spinal column become fused.

Human brain and spinal cord

The spinal cord is located in the vertebral foramen and is made up of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. A pair of spinal nerves leaves each segment of the spinal cord.

Vertebrae

The length of the spinal cord is about 45 cm in men and 43 cm in women. The spinal cord is shorter than the length of the bony spinal column; the spinal cord extends down only to the last of the thoracic vertebrae. Nerves that extend from the spinal cord from the lumbar and sacral levels must run in the vertebral canal for a distance before they leave the vertebral column. This collection of nerves in the vertebral canal is called the cauda equina (which means "horse tail").

Cauda Equina

The pathophysiology of spinal cord injury can be categorized as acute impact or compression. 

Acute impact injury is a concussion of the spinal cord. This type of injury initiates a cascade of events focused in the gray matter, and results in hemorrhagic necrosis. The initiating event is a hypoperfusion of the gray matter. Increases in intracellular calcium and reperfusion injury play key roles in cellular injury, and occur early after injury. The extent of necrosis is contingent on the amount of initial force of trauma, but also involves concomitant compression, perfusion pressures and blood flow, and administration of pharmacological agents. Preventing or quelling this cascade of events must involve mechanisms occurring in the initial stages. 

Acute Spinal Cord Injury

Spinal cord compression occurs when a mass impinges on the spinal cord causing increased parenchymal pressure. The tissue response is gliosis, demyelination, and axonal loss. This occurs in the white matter, whereas gray matter structures are preserved. Rapid or a critical degree of compression will result in collapse of the venous side of the microvasculature, resulting in vasogenic edema. Vasogenic edema exacerbates parenchymal pressure, and may lead to rapid progression of disfunction. Treatment of compression should focus on removal of the offending mass.

Spinal Cord Compression

References:

http://faculty.washington.edu/chudler/spinal.html

http://www.ncbi.nlm.nih.gov/pubmed/1571001


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Encephalon

ENCEPHALON

The encephalon along with the spinal cord are the two main parts of the Central Nervous System. It includes the brainstem and the prosencephalon.

Brainstem: it is the area at the base of the brain that lies between the deep structures of the cerebral hemispheres and the cervical spinal cord.

Prosencephalon: the part of the brain developed from the anterior of the three primary brain vesicles.

Encephalon

The prosencephalon itself embraces the telencephalon (brain) and the diencephalon.

Telencephalon or cerebrum: the anterior subdivision of the embryonic forebrain or the corresponding part of the adult forebrain that includes the cerebral hemispheres and associated structures.

Diencephalon: the posterior subdivision of the forebrain.

Prosencephalon (red coloured) 

The brainstem consists of three parts: the mesencephalon, pons and medulla oblongata.

Mesencephalon or midbrain: the part of the brain developed from the middle of the three primary vesicles of the embryonic neural tube, comprising the tectum and the cerebral peduncles.

Pons: that part of the central nervous system lying between the medulla oblongata and the midbrain, ventral to the cerebellum.

Medulla Oblongata: located in the brainstem, anterior to the cerebellum, it is a cone-shaped neuronal mass in the hindbrain, controlling a number of autonomic functions.

Brainstem



References:

Fundamentos de Biofísica, José P. Young, MS, PhD


http://www.britannica.com/EBchecked/topic/77391/brainstem

http://www.healthline.com/human-body-maps/

http://medical-dictionary.thefreedictionary.com/


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