The spinal cord is a critical part of the human body, playing a vital role in coordinating the communication between the brain and other parts of the body. It is responsible for sending and receiving messages to and from the brain through various nerves, which makes it is an essential structure for our overall well-being. The spinal cord plays a crucial role in our movements, sensation, and reflexes. In this article, we will provide you with an overview of what the spinal cord looks like and the critical features that make up this complex structure.
What is the Spinal Cord?
The spinal cord is a tubular structure made of delicate nerve tissues that extend from the brain’s base down to the lower back. The spinal cord lies in the spinal canal, which is formed by the vertebrae column. This structure is approximately 18 inches (45 cm) long and about 1/2 inch (1.3 cm) wide. The spinal cord is made up of 31 segments, each consisting of a pair of spinal nerves that enter and exit at each level of the spinal cord.
The Structure of Spinal Cord
The spinal cord consists of an outer layer of white matter and an inner layer of gray matter. The white matter consists of axons, which are responsible for transmitting signals to and from the brain, while the gray matter contains the cell bodies of neurons and neuroglia.
The white matter in the spinal cord is arranged in three columns, which are found on either side of the cord. Each of these columns contains a bundle of nerve fibers that are grouped into tracts, which carry information to and from the brain. The dorsal column carries information about touch, vibration, and proprioception, while the lateral column carries information about pain and temperature. The ventral column carries information about movement, muscle tone, and reflexes.
The gray matter in the spinal cord is H-shaped, and it contains cell bodies of neurons and neuroglial cells. The gray matter is arranged into ten zones that are divided into laminae, where each lamina carries out a specific function. The dorsal laminae are responsible for processing sensory information, while the ventral lamina is responsible for processing motor information.
Coverings of Spinal Cord
The spinal cord isn’t just a series of nerves that extends from the brain but also consists of various coverings, each with its particular function. Below are the three primary coverings of the spinal cord:
The outermost layer of the protective covering of the spinal cord is the Dura Mater. It is made up of tough connective tissue that attaches to the skull through the foramen magnum and runs down to the sacrum’s tip. The Dura Mater acts as a shield, protecting the spinal cord from physical trauma, and it is a hard, fibrous membrane that also contains intervertebral discs.
The middle layer of the protective covering of the spinal cord is the Arachnoid Mater. This layer is a delicate membrane made up of thinly stretched connective tissue that lies between the Dura Mater and the pia mater. The name arachnoid comes from the arachnoid villi, which are finger-like projections that protrude from the membrane on the superior section of the brain in the subarachnoid space. These projections aid in draining CSF (Cerebrospinal Fluid).
The innermost layer of the protective covering of the spinal cord is the Pia Mater. This layer is a thin, transparent membrane that directly covers the surface of the spinal cord, connecting into the lateral and median fissures. It contains numerous small blood vessels that allow for the supply of oxygen and nutrients to the spinal cord.
The Spinal Nerves
The spinal cord is responsible for carrying signals to and from different parts of the body, and it does this through a system of nerves. The spinal cord has 31 pairs of spinal nerves that emerge from the nerve roots at each segment. The spinal nerves serve as a link between the brain and the rest of the body. They carry the incoming sensory messages from the sensory organs and carry the outgoing motor messages from the brain and spinal cord to the muscles and glands.
Cervical, Thoracic, Lumbar, and Sacral Segments
The spinal cord is divided into four regions based on different segments: cervical, thoracic, lumbar, and sacral segments. The cervical segment is made up of 7 vertebrae, and the spinal cord passes through the neck region. The thoracic segment runs through the chest and is made up of 12 thoracic vertebrae. The lumbar section consists of five bones, the lumbar vertebrae, which are located in the lower back region. The sacral segment runs from the lumbar region to the tailbone and is made up of five fused vertebrae.
The Cervical Region
The cervical region is located in the neck region, and it controls the upper parts of the body like the neck, shoulders, and arms. The cervical region is responsible for the reflexes of the hand, wrist, and elbow.
The Thoracic Region
The thoracic region is located in the chest area, and it controls the trunk’s movement, including the chest and back. The thoracic region is responsible for reflexes that occur in the abdominal muscles.
The Lumbar Region
The lumbar region is situated in the lower back, and it controls the lower body’s movement, including the hips, legs, and feet. The lumbar region is responsible for reflexes that occur in the legs and feet.
The Sacral Region
The sacral region is the section at the bottom of the spine, and it controls the bladder and genital areas’ movement. The sacral region is responsible for reflexes that occur in the bladder and genital area.
The spinal cord and Spine
The spinal cord is connected to the spine through a series of nerves, which allow for the transmission of signals. The spine serves as the central axis of our skeletal system and provides support for our bodies. The spine is composed of bony structures called vertebrae that form a protective bony covering around the spinal cord. The intervertebral discs are composed of cartilage that lies between the vertebrae, which acts as shock absorbers, allowing for easy movement of the spinal cord.
The spinal cord is a complex and vital structure that plays a critical role in our body’s overall functioning. It is responsible for transmitting signals from the brain to the other parts of the body and vice versa. The spinal cord’s structure is composed of different regions and coverings that work synergistically to protect and provide support to the cord.
List of Common Questions about Spinal Cord
- What is the spinal cord?
- What is the structure of the spinal cord?
- What are the coverings of the spinal cord?
- What are the spinal nerves?
- How many segments does the spinal cord have?
 “Spinal Cord Injury: Hope Through Research,” National Institute of Neurological Disorders and Stroke, 3 Sep. 2019. [Online]. [Accessed 16 Jan. 2021]. Available: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Spinal-Cord-Injury-Hope-Through-Research
 N. Wallace R, “Spinal cord: Structure, Function and Injury,” A Johns Hopkins Press Health Book, Maryland, 2015.