A dermatome is an area of

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

that is mainly supplied by afferent nerve fibres from the dorsal root of any given

spinal nerve A spinal nerve is a mixed nerve, which carries Motor neuron, motor, Sensory neuron, sensory, and Autonomic nervous system, autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each s ...

. There are 8

cervical nerves A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into ...

(C1 being an exception with no dermatome), 12 thoracic nerves, 5

lumbar nerves The lumbar nerves are the five pairs of spinal nerves emerging from the lumbar vertebrae. They are divided into posterior and anterior divisions. Structure The lumbar nerves are five spinal nerves which arise from either side of the spinal cord ...

and 5 sacral nerves. Each of these nerves relays sensation (including pain) from a particular region of skin to the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

. The term is also used to refer to a part of an embryonic

somite The somites (outdated term: primitive segments) are a set of bilaterally paired blocks of paraxial mesoderm that form in the embryogenesis, embryonic stage of somitogenesis, along the head-to-tail axis in segmentation (biology), segmented animals. ...

. Along the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

and

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

, 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. An area of skin innervated by a single

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

is called a peripheral nerve field. The word ''dermatome'' is formed from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

'skin, hide' and 'cut'.

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. Certain skin problems tend to orient the lesions in the dermatomal direction. In

referred pain Referred pain, also called reflective pain, is pain perceived at a location other than the site of the painful stimulus. An example is the case of angina pectoris brought on by a myocardial infarction (heart attack), where pain is often felt in t ...

, sensory nerve fibers such as that from dermatomes may come together at the same

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

level as the general visceral afferent fibers such as that from the

heart The heart is a muscular Organ (biology), organ found in humans and other animals. This organ pumps blood through the blood vessels. The heart and blood vessels together make the circulatory system. The pumped blood carries oxygen and nutrie ...

. When the general visceral sensory fiber is stimulated, the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

does not clearly discern whether the

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

is coming from the body wall or from the

viscera In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to a ...

, so it perceives the pain as coming from somewhere on the body wall, e.g. left arm/hand pain, jaw pain. So the pain is "referred to" the related dermatomes of the same spinal segment. Viruses that lie dormant in nerve ganglia (e.g.

varicella zoster virus Varicella zoster virus (VZV), also known as human herpesvirus 3 (HHV-3, HHV3), is one of nine known herpes viruses that can infect humans. It causes chickenpox (varicella) commonly affecting children and young adults, and shingles (herpes zos ...

, which causes both

chickenpox Chickenpox, also known as varicella ( ), is a highly contagious disease caused by varicella zoster virus (VZV), a member of the herpesvirus family. The disease results in a characteristic skin rash that forms small, itchy blisters, which ...

and

shingles Shingles, also known as herpes zoster or zona, is a viral disease characterized by a painful skin rash with blisters in a localized area. Typically the rash occurs in a single, wide mark either on the left or right side of the body or face. T ...

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

Important dermatomes and anatomical landmarks

Following is a list of

s and points that are characteristically belonging to the dermatome of each nerve: Grant 1962 665

* C2 – At least one cm lateral to the occipital protuberance at the

base of the skull The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria. Structure Structures found at the base of the skull are for ...

. Alternately, a point at least behind the ear. * C3 – In the supraclavicular fossa, at the midclavicular line. * C4 – Over the acromioclavicular joint. * C5 – On the lateral (radial) side of the

antecubital fossa The cubital fossa, antecubital fossa, chelidon, inside of elbow, or, humorously, wagina, is the area on the anterior side of the upper part between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (antecubit ...

, just proximally to the elbow. * C6 – On the dorsal surface of the

proximal phalanx The phalanges (: phalanx ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. Structu ...

of the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

. * C7 – On the dorsal surface of the

of the

middle finger The middle finger, long finger, second finger, third finger, toll finger or tall man is the third digit of the human hand, typically located between the index finger and the ring finger. It is typically the longest digit. In anatomy, it is al ...

. * C8 – On the dorsal surface of the proximal phalanx of the little finger. * T1 – On the medial (ulnar) side of the

, just distal to the

medial epicondyle of the humerus The medial epicondyle of the humerus is an epicondyle of the humerus bone of the upper arm in humans. It is larger and more prominent than the Lateral epicondyle of the humerus, lateral epicondyle and is directed slightly more posteriorly in the ...

. * T2 – At the apex of the

axilla The axilla (: axillae or axillas; also known as the armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm a ...

. * T3 –

Intersection In mathematics, the intersection of two or more objects is another object consisting of everything that is contained in all of the objects simultaneously. For example, in Euclidean geometry, when two lines in a plane are not parallel, their ...

of the midclavicular line and the third intercostal space * T4 – Intersection of the midclavicular line and the fourth intercostal space, located at the level of the nipples. * T5 – Intersection of the midclavicular line and the fifth intercostal space, horizontally located midway between the level of the nipples and the level of the xiphoid process. * T6 – Intersection of the midclavicular line and the horizontal level of the xiphoid process. * T7 – Intersection of the midclavicular line and the horizontal level at one quarter the distance between the level of the xiphoid process and the level of the umbilicus. * T8 – Intersection of the midclavicular line and the horizontal level at one half the distance between the level of the xiphoid process and the level of the umbilicus. * T9 – Intersection of the midclavicular line and the horizontal level at three quarters of the distance between the level of the xiphoid process and the level of the umbilicus. * T10 – Intersection of the midclavicular line, at the horizontal level of the umbilicus. * T11 – Intersection of the midclavicular line, at the horizontal level midway between the level of the umbilicus and the

inguinal ligament The inguinal ligament (), also known as Poupart's ligament or groin ligament, is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal through which an indirect inguinal hernia may ...

. * T12 – Intersection of the midclavicular line and the midpoint of the inguinal ligament. * L1 – Midway between the key sensory points for T12 and L2. * L2 – On the anterior medial thigh, at the midpoint of a line connecting the midpoint of the inguinal ligament and the

medial epicondyle of the femur The medial epicondyle of the femur is an epicondyle, a bony protrusion, located on the medial side of the femur at its distal end. Located above the medial condyle, it bears an elevation, the adductor tubercle,Platzer (2004), p 192 which serve ...

. * L3 – At the

. * L4 – Over the

medial malleolus A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promin ...

. * L5 – On the dorsum of the foot at the third

metatarsophalangeal joint The metatarsophalangeal joints (MTP joints) are the joints between the metatarsal bones of the foot and the proximal bones (proximal phalanges) of the toes. They are analogous to the knuckles of the hand, and are consequently known as toe knuckles ...

. * S1 – On the lateral aspect of the

calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the Tarsus (skeleton), tarsus of the foot which constitutes the heel. In some other ...

. * S2 – At the midpoint of the

popliteal fossa The popliteal fossa (also referred to as hough or kneepit in analogy to the cubital fossa) is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia. Like other flexion surfaces ...

. * S3 – Over the

tuberosity of the ischium The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known colloquially as the sit bones or sitz bones, or as a pair the sitting bones, is a large posterior (anatomy), posterior bone, bony protuberance on the superior r ...

or intragluteal fold * S4 and S5 – In the perianal area, less than one cm lateral to the mucocutaneous zone Following is a list of

cranial nerves Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), of which there are conventionally considered twelve pairs. Cranial nerves relay information between the brain and parts of the body, primarily to and f ...

responsible for sensation from the face: * V1 (1st division of the trigeminal nerve) - associated with herpes zoster ophthalmicus * V2 (2nd division of the trigeminal nerve) * V3 (3rd division of the trigeminal nerve)

Additional images

File:Gray812and814.svg, Diagram of segmental distribution of the cutaneous nerves of the right upper extremity File:Gray826and831.svg, Lower limb File:Gray834.svg, Foot File:Dermatomes and cutaneous nerves - anterior.svg, Major dermatomes and

cutaneous nerve A cutaneous nerve is a nerve that provides nerve supply to the skin. Human anatomy In human anatomy, cutaneous nerves are primarily responsible for providing cutaneous innervation, sensory innervation to the skin. In addition to sympathetic and ...

s (anterior view) File:Dermatomes and cutaneous nerves - posterior.svg, Major dermatomes and

s (posterior view)

References

External links

3D Dermatomes Web App
''Instamedic'' *

''The New York Times'' {{DEFAULTSORT:Dermatome (Anatomy) somatosensory system Neurology Skin anatomy

Clinical significance

Important dermatomes and anatomical landmarks

Additional images

See also

References

External links