Spinal Cord, Function, Anatomy and Structure
The spinal cord is a long, tube-like band of tissue. It connects your brain to your lower back. Your spinal cord carries nerve signals from your brain to your body and vice versa. Read the article to know more.
Dr. Nivedita2 Aug, 2024
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Spinal Cord: Pathway that Connects the Central Nervous System to the Peripheral Nervous System
The spinal cord is a tube-like structure located inside the vertebral column. It’s a hollow tube with a central canal that is continuous with the 4th ventricle, containing cerebrospinal fluid. It is covered by all three meninges. Together, the brain and spinal cord make up the central nervous system. The spinal cord is a continuation of the brainstem and anatomically begins at the occipital bone, passing out of the foramen magnum( big hole in your skull) and then entering the spinal canal at the beginning of the cervical vertebrae. It extends to the first and second lumbar vertebrae, where it tapers to become the cauda equina (a bunch of spinal nerves exiting the spinal cord together at the end).Structure
As the main pathway of connection between the brain and the peripheral nervous system, it is much shorter than its protecting spinal column. It passes through the foramen magnum and continues through to the conus medullaris(terminal portion of spinal cord) near the second lumbar vertebra before terminating in a fibrous extension of meninges known as the filum terminale. It is about 45 centimeters long in males and about 43 centimeters in females. It is ovoid-shaped and enlarged in the cervical and lumbar regions. The cervical enlargement, stretching from the C5 to T1 vertebrae, is where sensory input comes from and motor output goes to the arms and trunk. The lumbar enlargement, located between L1 and S3, handles sensory input and motor output coming from and going to the legs.Internal Structure
In the cross-section, the peripheral region of the cord contains neuronal white matter tracts with sensory and motor axons. Inside this peripheral region is the gray matter, which contains the cell bodies of the nerves arranged in three gray columns that give the region its butterfly shape. This central region surrounds the central canal, which is an extension of the 4th ventricle and contains cerebrospinal fluid (CSF). The gray column in the center of the cord is shaped like a butterfly and consists of cell bodies of interneurons, motor neurons, neuroglia, and unmyelinated axons. The anterior and posterior gray columns present as projections of the gray matter and are also known as the horns of the spinal cord. The white matter is located outside of the gray matter and consists almost entirely of myelinated motor and sensory axons. Columns of white matter carry information either up or down the spinal cord.Spinal Nerves
The human spinal cord is divided into segments from which pairs of spinal nerves arise. Spinal nerves are mixed in nature. Sensory nerve rootlets form off right and left dorsolateral sulci and form sensory nerve roots. The ventral (motor) and dorsal (sensory) roots combine to form spinal nerves (mixed; motor and sensory). There are 31 spinal cord nerve segments in a human spinal cord: 8 cervical segments forming 8 pairs of cervical nerves, 12 thoracic segments forming 12 pairs of thoracic nerves, 5 lumbar segments with 5 pairs of lumbar nerves, 5 sacral segments with 5 pairs of sacral nerves, and 1 coccygeal segment.Function
The spinal cord helps in the transmission of motor signals from the brain to the body and sensory signals from the body to the brain. It is a center for the coordination of reflexes and contains reflex arcs that can independently control reflexes. Additionally, the spinal cord plays a crucial role in motor control and sensory processing, acting as a conduit for neural signals and facilitating communication between the brain and peripheral body parts.Spinal Cord FAQs
What is multiple sclerosis (MS) and how does it affect the spinal cord?
Multiple sclerosis (MS) is an autoimmune disease where the immune system attacks the protective covering of nerves, including those in the spinal cord. This leads to inflammation and scarring (sclerosis) that disrupts the transmission of nerve signals. Symptoms can include muscle weakness, coordination problems, and fatigue, which can vary widely among individuals.
What is spinal stenosis?
Spinal stenosis is the narrowing of spaces within the spine, which can put pressure on the spinal cord and nerves. Symptoms may include back pain, numbness, muscle weakness, and impaired bladder or bowel control, depending on the severity and location of the stenosis.
What is a spinal cord tumor?
A spinal cord tumor is an abnormal growth of cells within or around the spinal cord. Symptoms vary depending on the tumor’s size and location but can include pain, neurological deficits, and loss of function in affected areas.
What is transverse myelitis and its effects on the spinal cord?
Transverse myelitis is an inflammation of both sides of one segment of the spinal cord, disrupting the transmission of nerve signals. This condition can cause pain, muscle weakness, paralysis, sensory problems, and bladder and bowel dysfunction.
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