Dermatomes and major cutaneous nerve Cutaneous nerve A cutaneous nerve is a nerve that innervates the skin.-Human anatomy:In human anatomy, cutaneous nerves are responsible for providing sensory innervation to the skin. They are generally thought of as sensory-only nerves, but they may provide motor innervation to structures in the skin, e.g... s.

A dermatome is an area of skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 that is mainly supplied by a single spinal nerve

Spinal nerve

The term spinal nerve generally refers to a mixed spinal nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body...

.
There are eight cervical nerves

Cervical nerves

The cervical nerves are the spinal nerves from the cervical vertebrae.Although there are seven cervical vertebrae , there are eight cervical nerves . All nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra...

 (C1 being an exception with no dermatome),
twelve thoracic nerves

Thoracic nerves

The thoracic nerves are the spinal nerves emerging from the thoracic vertebrae. Branches also exit the spine and go directly to the Sympathetic Chain Ganglia of the Autonomic Nervous System where they are involved in the functions of organs and glands in the head, neck, thorax and abdomen.-Anterior...

,
five lumbar nerves

Lumbar nerves

The lumbar nerves are the five spinal nerves emerging from the lumbar vertebrae. They are divided into posterior and anterior divisions.-Posterior divisions:...

 and five sacral nerves

Sacral nerves

The five sacral nerves emerge from the sacrum. Although the vertebral components of the sacrum are fused into a single bone, the sacral vertebrae are still used to number the sacral nerves....

.
Each of these nerves relays sensation (including pain) from a particular region of skin to the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

.

Along the thorax

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

 and abdomen

Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...

 the dermatomes are like a stack of discs forming a human, each supplied by a different spinal nerve. Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs. Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.

A similar area innervated by peripheral nerves

Peripheral nervous system

The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...

 is called a peripheral nerve field

Peripheral nerve field

Peripheral nerve field refers to an area of skin innervated by a single peripheral nerve. A peripheral nerve field can also be described as cutaneous nerve distribution.An area innervated by a single dorsal root is called a dermatome....

.

Clinical significance

A dermatome is an area of skin supplied by sensory neurons that arise from a spinal nerve ganglion. Symptoms that follow a dermatome (e.g. like pain or a rash) may indicate a pathology that involves the related nerve root. Examples include somatic dysfunction of the spine or viral infection. Referred pain

Referred pain

Referred pain is pain perceived at a location other than the site of the painful stimulus. An example is the case of ischemia brought on by a myocardial infarction , where pain is often felt in the neck, shoulders, and back rather than in the chest, the site of the injury...

 usually involves a specific, "referred" location so is not associated with a dermatome.

Viruses that hibernate in nerve ganglia (e.g. Herpes zoster

Herpes zoster

Herpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...

or Varicella Zoster viridae) often cause either pain, rash or both in a pattern defined by a dermatome. However, the symptoms may not appear across the entire dermatome.

Important dermatomes and anatomical landmarks

• C2
  Cervical spinal nerve 2
  The cervical spinal nerve 2 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 2 ....
  
   - posterior half of the skull cap
• C3
  Cervical spinal nerve 3
  The cervical spinal nerve 3 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 3 ....
  
   - area correlating to a high turtle neck shirt
• C4
  Cervical spinal nerve 4
  The cervical spinal nerve 4 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 4 .Its control of the thoracic diaphragm has inspired a medical mnemonic: "Cut C4, breathe no more."...
  
   - area correlating to a low-collar shirt
• C6
  Cervical spinal nerve 6
  The cervical spinal nerve 6 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 6 ....
  
   - (radial nerve
  Radial nerve
  The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
  
  ) 1st digit (thumb
  Thumb
  The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
  
  )
• C7
  Cervical spinal nerve 7
  The cervical spinal nerve 7 is a spinal nerve of the cervical segment..It originates from the spinal column from above the cervical vertebra 7 ....
  
   - (median nerve
  Median nerve
  The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....
  
  ) 2nd and 3rd digit
• C8
  Cervical spinal nerve 8
  The cervical spinal nerve 8 is a spinal nerve of the cervical segment.It originates from the spinal column from below the cervical vertebra 7 .- Innervation :...
  
   - (ulnar nerve) 4th and 5th digit and medial-posterior aspect of arm
• T4
  Thoracic spinal nerve 4
  The thoracic spinal nerve 4 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 4 ....
  
   - nipple
  Nipple
  In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and...
  
  s.
• T5
  Thoracic spinal nerve 5
  The thoracic spinal nerve 5 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 5 ....
  
   - Inframammary fold
  Inframammary fold
  Inframammary fold , inframammary crease or inframammary line is the feature of human anatomy which is a natural boundary of a breast from below, the place where the breast and the chest meet. The choice of the term depends on the prominence of the feature. It is also sometimes called inframammary...
  
  .
• T6
  Thoracic spinal nerve 6
  The thoracic spinal nerve 6 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 6 ....
  
  /T7
  Thoracic spinal nerve 7
  The thoracic spinal nerve 7 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 7 ....
  
   - xiphoid process
  Xiphoid process
  The xiphoid process, or xiphisternum or metasternum, is a small cartilaginous process of the lower part of the sternum which is usually ossified in the adult human. By age 15 to 29, the xiphoid usually fuses to the body of the sternum with a fibrous joint. Unlike the synovial articulation of major...
  
  .
• T10
  Thoracic spinal nerve 10
  The thoracic spinal nerve 10 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 10 ....
  
   - umbilicus
  Navel
  The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...
  
   (important for early appendicitis pain)
• T12
  Thoracic spinal nerve 12
  The thoracic spinal nerve 12 is a spinal nerve of the thoracic segment..It originates from the spinal column from below the thoracic vertebra 12 ....
  
   - pubic bone
  Pubis (bone)
  In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
  
   area.
• L1
  Lumbar spinal nerve 1
  The lumbar spinal nerve 1 is a spinal nerve of the lumbar segment..It originates from the spinal column from below the lumbar vertebra 1 .The two terminal branches of this nerve is the iliohypogastric and the ilioinguinal nerves-Muscles:...
  
   - inguinal ligament
  Inguinal ligament
  The inguinal ligament is a band running from the pubic tubercle to the anterior superior iliac spine. Its anatomy is very important for operating on hernia patients.-Anatomy:...
  
  
• L4
  Lumbar spinal nerve 4
  The lumbar spinal nerve 4 is a spinal nerve of the lumbar segment..It originates from the spinal column from below the lumbar vertebra 4 .-Muscles:...
  
   - includes the knee caps
• S2
  Sacral spinal nerve 2
  The sacral spinal nerve 2 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 2nd body of the sacrum -Muscles:...
  
  /S3
  Sacral spinal nerve 3
  The sacral spinal nerve 3 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 3rd body of the sacrum -Muscles:...
  
   - genitalia
  Sex organ
  A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
  
  

See also

• Cutaneous innervation
  Cutaneous innervation
  Cutaneous innervation refers to the area of the skin which is supplied by a specific cutaneous nerve.Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve...
  
  
• Peripheral nerve field
  Peripheral nerve field
  Peripheral nerve field refers to an area of skin innervated by a single peripheral nerve. A peripheral nerve field can also be described as cutaneous nerve distribution.An area innervated by a single dorsal root is called a dermatome....
  
  
• Dorsal root

External links

• Diagram "Adult Dermatome", The New York Times