Spinal Cord Diagram with Detailed Illustration

The spinal cord is the most important part of the human body and is a constituent of our Central Nervous System. It is the main centre of control and coordination of all the reflex actions of our body.

• The spinal cord diagram helps us understand that the spinal cord extends from the medulla oblongata in the brainstem.
• It runs through the vertebral column of the backbone to its lumbar region.
• The cord terminates at the intervertebral disc between the vertebral bodies L1 and L2.
• The spinal cord, in association with the brain and the nervous tissues, controls all the sensory coordination of the body.
• It is responsible for transmitting nerve signals from the brain to the body and vice versa.
• The cord is also covered by meninges and enclosed by the neural arches.

Key Terms: Spinal Cord Diagram, Spinal Cord, Brain, Central Nervous System, Tissues, Human Body, Nerves, Brainstem, Grey Matter, White Matter, Vertebral Column, Peripheral Nervous System, Meninges

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Spinal Cord Anatomy

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The spinal cord diagram illustrates that the cord generally has a length of 40 cm and a width of 2 cm in adults. It consists of 31 segments each, each of which originates a pair of spinal nerves. 

• The spinal cord is divided into five different segments, among which are 31 pairs of spinal nerves. 
• These nerve fibres transmit sensory information from different parts of the body to the Central Nervous System.
• This is done with the help of the afferent fibres. 
• The growth of the spinal cord ceases around the age of 4, whereas the vertebral column continues to grow till the ages of 14-18. 

Due to this developmental disparity between the spinal cord and the vertebral column during body growth, the spinal cord manages to occupy only the upper two-thirds of the vertebral column.

• The segments of the spinal cord are :

Cervical Segment

The cervical segment includes eight pairs of spinal nerves.

Thoracic Segment

The thoracic segment includes 12 pairs of spinal nerves.

Lumbar Segment

The lumbar segment includes five pairs of spinal nerves.

Sacral Segment

The sacral segment includes five pairs of spinal nerves.

Coccygeal Segment

The coccygeal segment includes one pair of spinal nerves.

Anatomy Of The Spinal Cord 

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Structure of Spinal Cord

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The spinal cord is enclosed in a hollow canal inside the vertebral column. This canal originates from the skull itself. The spinal nerves arise from the different areas of the vertebral column.

• The different regions of the spinal cord include the neck, chest, abdomen, and pelvis.

When we carefully look into the cross-section of the spinal cord, we find two types of matter or regions. They are then divided into Grey Matter and white matter. 

Grey Matter

The Central Canal is present at the centre of the grey matter, with the CFS (Cerebrospinal Fluid) filled around it. It is mainly the Central part of the spinal cord, which gives the appearance of the shape of a butterfly. 

• The grey matter consists of the neuronal cell bodies.
• It shows four horns (projections), which are situated anteriorly, laterally, and posteriorly. 
• Most of the Central Nervous System cells are present in this region.

White Matter

The grey matter is surrounded on its boundary by white matter. It includes a collection of axons that induces communication between various layers of the Central Nervous System. 

• The white matter houses the pathways or links that help the brain control and coordinate with the various functions of the body. 
• Tracts are present in the white matter. 

Both types of tracts, namely the ascending tracts and the descending tracts, coordinate with each other to carry sensory outputs from the brain to different neurons all over the body.

• They are a group of axons that transmit specific sensory data.

Meninges

The spinal cord along with the spinal nerves are covered by the Meninges. It consist of three layers, namely:

• Dura Matter: It is the outermost part of the meninges, which includes two layers, namely the periosteal and the meningeal. 
• Arachnoid Matter: It is the middle layer which lies between the epidural and subarachnoid space.
• Pia Mater: It is the innermost which is responsible for covering of the spinal cord.

Epidural Space

There is the epidural space between the periosteal and meningeal layers of the dura mater. 

Subarachnoid Space

Also, in between the arachnoid and the pia mater lies the subarachnoid space, which is filled with the CSF (CEREBROSPINAL FLUID). 

Posterior Root

The posterior root is responsible for branching off the back of the spinal column. In a cross-section of the spinal cord, the top wings of the grey matter "butterfly" reach toward the spinal bones. 

• The bottom wings are oriented toward the body's internal organs.

Spinal Nerve

The spinal nerve consists of the union of the posterior and anterior roots. It is made up of 31 pairs of nerves. The nerve is responsible for the regulation of both sensation and movement in the body. 

Anterior Root

The anterior root is defined as the portion of the nerve that arises from the front of the spinal column.

The Spinal Cord

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Functions of Spinal Cord

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Some of the important functions of the spinal cord are given below : 

• The spinal cord acts as a bridge between the brain and the peripheral nervous system. 
• It plays an important role in providing structural support and in the maintenance of the body posture.
• The cord transmits sensory outputs from the brain to various parts of the body.
• It induces flexible movements.
• The spinal cord acts as the main coordinating centre of all the reflex actions of our body.
• The white matter of the spinal cord consists of myelin, which performs the function of electrical insulation.
• It accepts sensory inputs from the receptors.
• The cord provides them to the brain to process the received data.

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Spinal Cord Injuries

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Any injury to the spinal cord permanently impacts the spinal cord and the normal sensory functioning of the whole body. In simple words, the effect on the cord is irreversible. 

• It affects the strength, reflexing, and body posture along with the voluntary control of the limbs of the body. 

Along with the spinal nerves and the vertebral column, any spinal cord injuries have an impact on the normal functioning of the other muscles and the vital organs of the body. 

• Injury to the spinal cord can result in two types of paralysis, which are as follows:

Tetraplegic Paralysis

In tetraplegic paralysis, the patient loses the ability to use all four limbs and torso.

Paraplegic Paralysis

In paraplegic paralysis, the patient loses the ability to use only the legs. The arms are not affected by this paralysis. 

Some of the harmful impacts on the human body resulting from injury of the spinal cord are given below : 

• Inability to use the limbs voluntarily.
• Loss of sensation.
• Reflexes become late or exaggerated.
• Unwanted changes in sexual functions.
• Deep shooting pain because of injured or damaged nerve fibres.
• Shortness in breathing, cough, and intense muscle spasms.

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Things to Remember

• The spinal cord maintains an exceptional memory which remembers our postures and becomes used to them
• There are about 120 muscles present in the cord.
• Giraffes and humans possess equal amounts of vertebrae around their spinal cord. 
• Our spinal cord is exceptionally flexible, as it can even bend back enough to cover two-thirds of a whole circle.
• It was the first bone to grow in our body. 
• The cord starts to develop just only after two months of conception.

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