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Dermatome: A Guide to Understanding the Body’s Sensory Nerve Roots
What is a Dermatome?
A dermatome is an area of skin that gets its sensation from a specific spinal nerve root. Spinal nerves exist in 31 pairs, one on each side of the spine. These nerves send signals for things like pressure, pain, temperature, and texture from your skin to the spinal cord and brain.
Dermatome Groups
Dermatomes are divided into groups based on where in the spine they originate:
- Cervical nerves: There are eight pairs from your neck, numbered C1 through C8. Since C1 has no sensory function, you have seven cervical dermatomes, numbered C2 to C8.
- Thoracic nerves: There are 12 pairs from the torso, numbered T1 through T12. You have 12 thoracic dermatomes.
- Lumbar nerves: There are five pairs from the lower back, numbered L1 through L5. You have five lumbar dermatomes.
- Sacral nerves: There are five pairs from the sacrum (part of the pelvis), numbered S1 through S5. You have five sacral dermatomes.
- Coccygeal nerve: There is one pair from the coccyx (tailbone) area, so you have a coccygeal dermatome.
Locations
The exact location of dermatomes is different from person to person because the nerves may overlap in some areas. However, dermatome maps are a good guide to where they lie in most people.
On the torso, dermatomes are horizontal stripes stacked on top of each other. However, they’re a combination of angular and straight stripes on your arms and legs.
Cervical Nerves and Dermatomes
The seven dermatomes associated with cervical nerves are:
- C2: Behind the ear and the base of the skull
- C3: Back of the head and behind the neck
- C4: Across the lower neck and top of the shoulders
- C5: Across the collarbones and upper shoulders
- C6: Shoulders, down the outside of the arm, and the thumb
- C7: The upper back, down the back of the arm, index and middle fingers
- C8: Upper back, down the inside of the arm, ring and pinky fingers
Thoracic Nerves and Dermatomes
The thoracic dermatomes travel downward from where their nerves emerge from the spinal column and wrap around the torso.
Frequently Asked Questions (FAQs)
Q: What is a dermatome?
A: A dermatome is an area of skin that gets its sensation from a specific spinal nerve root.
Q: How many dermatomes are there?
A: There are 30 dermatomes in the body, with one pair of coccygeal nerves.
Q: Where are the dermatomes located?
A: The exact location of dermatomes is different from person to person, but they are generally horizontal stripes on the torso and a combination of angular and straight stripes on the arms and legs.
Q: What is the purpose of dermatomes?
A: Dermatomes send signals for things like pressure, pain, temperature, and texture from your skin to the spinal cord and brain, helping you sense the world around you.
I hope this helps! Let me know if you have any further questions.
