The spinal cord is a long bundle of nerves and cells that
extends from the lower portion of the brain to the lower back. It carries
signals between the brain and the rest of the body.
extends from the lower portion of the brain to the lower back. It carries
signals between the brain and the rest of the body.
This article covers the key anatomy of the spinal cord and
its functions.
its functions.
It also provides some information about spinal cord
injuries.
injuries.
Anatomy
The length of the spinal cord varies from person to person.
According to some estimates, females have a spinal cord of about 43 centimeters
(cm), while males have a spinal cord of about 45 cm.
According to some estimates, females have a spinal cord of about 43 centimeters
(cm), while males have a spinal cord of about 45 cm.
The spinal cord comprises three parts: the cervical (neck),
thoracic (chest), and lumbar (lower back) regions.
thoracic (chest), and lumbar (lower back) regions.
Three layers of tissue protect the spinal cord: the dura
mater, arachnoid mater, and pia mater. Doctors call these layers “meninges.”
The layers are as follows:
mater, arachnoid mater, and pia mater. Doctors call these layers “meninges.”
The layers are as follows:
- Dura mater: This is the outermost layer of the spinal cord’s
meninges. It is a tough, protective coating. - Epidural space: Between the dura and arachnoid space is the
epidural space. This is where doctors may insert local anesthetic to reduce
pain during childbirth and some surgical procedures, such as those to operate
on a lung or abdominal aneurysm. - Arachnoid mater: The arachnoid mater is the middle layer of
spinal cord covering. - Subarachnoid space: This is located between the arachnoid
mater and pia mater. Cerebrospinal fluid (CSF) is located in this space.
Sometimes, a doctor has to sample CSF to test for the presence of infection,
such as meningitis. They can also inject local anesthetic into this space for
some surgical procedures, such as a cesarean delivery or a knee replacement. - Pia mater: The pia mater is the layer that directly covers
the spinal cord.
Covering the spinal cord and its protective layers is the
vertebral column, or the spinal bones. These bones start at the base of the
skull and extend down to the sacrum, a bone that fits into the pelvis.
vertebral column, or the spinal bones. These bones start at the base of the
skull and extend down to the sacrum, a bone that fits into the pelvis.
The cervical, thoracic, and lumbar regions have different
numbers of bones. Most people have seven spinal bones in the cervical column,
12 in the thoracic column, and five in the lumbar column.
numbers of bones. Most people have seven spinal bones in the cervical column,
12 in the thoracic column, and five in the lumbar column.
Cross-section of the spinal cord
If a person were to take a “slice” of the spinal cord
horizontally, they would see a circular area in the middle covered in
protective layers (the meninges). Extending from this circular area are nerve
projections. These extend from the spinal cord to provide sensation to
different areas in the body.
horizontally, they would see a circular area in the middle covered in
protective layers (the meninges). Extending from this circular area are nerve
projections. These extend from the spinal cord to provide sensation to
different areas in the body.
Key areas of a cross-section of the spinal cord include:
- Gray matter: The gray matter is the dark, butterfly shaped
region of the spinal cord made up of nerve cell bodies. - White matter: The white matter surrounds the gray matter in
the spinal cord and contains cells coated in myelin, which makes nerve
transmission occur more quickly. Nerve cells in the gray matter are not as
heavily coated with myelin. - Posterior root: The posterior root is the part of the nerve
that branches off the back of the spinal column. Looking at the spinal cord
cross-section, the top wings of the gray matter “butterfly” reach toward the
spinal bones. The bottom wings are toward the front of the body and its
internal organs. - Anterior root: The anterior root is the part of the nerve
that branches off the front of the spinal column. - Spinal ganglion: The spinal ganglion is a cluster of nerve
bodies that contain sensory neurons. - Spinal nerve: The posterior and anterior roots come together
to create a spinal nerve. There are 31 pairs of spinal nerves. These control
sensation in the body, as well as movement.
The spinal cord does not extend for the entire length of the
spine. It usually stops in the top parts of the lumbar spine.
spine. It usually stops in the top parts of the lumbar spine.
For adults, this is usually the first or second lumbar
vertebrae. Children’s spinal cords may stop slightly lower, at the second or
third lumbar vertebrae.
vertebrae. Children’s spinal cords may stop slightly lower, at the second or
third lumbar vertebrae.
Functions
The spinal cord plays a vital role in various aspects of the
body’s functioning. Examples of these key functions include:
body’s functioning. Examples of these key functions include:
- Carrying signals from the brain: The spinal cord receives
signals from the brain that control movement and autonomic functions. - Carrying information to the brain: The spinal cord nerves
also transmit messages to the brain from the body, such as sensations of touch,
pressure, and pain. - Reflex responses: The spinal cord may also act independently
of the brain in conducting motor reflexes. One example is the patellar reflex,
which causes a person’s knee to involuntarily jerk when tapped in a certain
spot.
These functions of the spinal cord transmit the nerve
impulses for movement, sensation, pressure, temperature, pain, and more.
impulses for movement, sensation, pressure, temperature, pain, and more.
Possible injuries
The spinal cord is a delicate part of the body. It is
therefore susceptible to injury. Vehicle accidents, gunshot wounds, and damage
while playing sports are all potential causes of spinal cord injury.
therefore susceptible to injury. Vehicle accidents, gunshot wounds, and damage
while playing sports are all potential causes of spinal cord injury.
Due to the part it plays in providing movement and
sensation, sustaining damage to any part of the spinal cord could cause
permanent changes to a person’s functioning.
sensation, sustaining damage to any part of the spinal cord could cause
permanent changes to a person’s functioning.
Healthcare providers may not always know right away how much
function a person will lose after injury.
function a person will lose after injury.
There are two main types of spinal cord injury: complete and
incomplete.
incomplete.
A complete spinal cord injury causes a complete loss of
sensation and motor function below the level of the injury.
sensation and motor function below the level of the injury.
According to the American Academy of Neurological Surgeons
(AANS), almost half of all spinal cord injuries are complete. The spinal cord
does not necessarily need to be physically cut for a complete injury to occur,
but the damage might be so significant that blood cannot flow to the nerve
tissue, causing it to die.
(AANS), almost half of all spinal cord injuries are complete. The spinal cord
does not necessarily need to be physically cut for a complete injury to occur,
but the damage might be so significant that blood cannot flow to the nerve
tissue, causing it to die.
An incomplete spinal cord injury occurs when the person
still has some function at or below the point of the injury. They may still be
able to move one side of the body or have some function or sensation.
still has some function at or below the point of the injury. They may still be
able to move one side of the body or have some function or sensation.
According to the AANS, around 250,000–450,000 people in the
United States are living with a spinal injury.
United States are living with a spinal injury.
Sometimes, surgical procedures and the passing of time can
reduce some of the effects of a spinal cord injury. Doctors will often use
repeated imaging scans and nerve function studies to determine how significant
a person’s spinal cord damage may be.
reduce some of the effects of a spinal cord injury. Doctors will often use
repeated imaging scans and nerve function studies to determine how significant
a person’s spinal cord damage may be.
Summary
The spinal cord is a complex organization of nerve cells
responsible for movement and sensation. It carries signals between the brain
and the rest of the body.
responsible for movement and sensation. It carries signals between the brain
and the rest of the body.
Having knowledge of the location and structure of the
protective spinal cord coverings can help healthcare professionals provide pain
relief for certain procedures.
protective spinal cord coverings can help healthcare professionals provide pain
relief for certain procedures.
Spinal cord injuries can range from sensory loss to incomplete
or complete paralysis. A person should always wear protective equipment when
playing sports or during other activities to reduce their risk of injury.
or complete paralysis. A person should always wear protective equipment when
playing sports or during other activities to reduce their risk of injury.
However, it will not always be possible to prevent such an
injury.
injury.
Medically reviewed by Elaine K. Luo, MD
Written by Rachel Nall, RN, MSN, CRNA
SOURCE: MEDICAL NEWS TODAY
Kayode Emmanuel Ojo is the Co-Founder and Managing Director at SHEFFA Limited. He is presently studying Computer Science at the National Open University, Victoria Island, Lagos.