Myotomes and Dermatomes
Myotome and Dermatome Sections
Myotome and Dermatome Overview
Spinal nerves have motor fibres and sensory fibres.
The motor fibres innervate certain muscles, while the sensory fibres
innervate certain areas of skin. A skin area innervated by the sensory
fibres of a single nerve root is known as a dermatome.
A group of muscles primarily innervated by the motor fibres of a single
nerve root is known as a myotome. Although slight variations do exist,
dermatome and myotome patterns of distribution are relatively consistent
from person to person.
Spinal Cord Segmental Myotomes
Myotomes - Relationship
between the spinal nerve & muscle
Dermatomes - Relationship between the spinal nerve
Each muscle in the body is supplied by a particular
level or segment of the spinal cord and by its corresponding spinal
nerve. The muscle, and its nerve make up a myotome. This is approximately
the same for every person and are as follows:
C3,4 and 5 supply the diaphragm (the large
muscle between the chest and the belly that we use to breath).
C5 also supplies the shoulder muscles and
the muscle that we use to bend our elbow .
C6 is for bending the wrist back.
C7 is for straightening the elbow.
C8 bends the fingers.
T1 spreads the fingers.
T1 T12 supplies the chest wall &
L2 bends the hip.
L3 straightens the knee.
L4 pulls the foot up.
L5 wiggles the toes.
S1 pulls the foot down.
S3,4 and 5 supply the bladder. bowel and
sex organs and the anal and other pelvic muscles.
Spinal Cord Segmental Dermatomes
Click to enlarge
Dermatome chart - Map
Dermatome is a Greek word which literally
means "skin cutting". A dermatome is an area of the skin
supplied by nerve fibers originating from a single dorsal nerve
root. The dermatomes are named according to the spinal nerve
which supplies them. The dermatomes form into bands around the trunk
but in the limbs their organisation is more complex as a result
of the dermatomes being "pulled out" as the limb buds
form and develop into the limbs during embryological development.
In diagrams or maps the boundaries
of dermatomes are usually sharply defined. However in life there maybe considerable overlap of innervation between adjacent dermatomes.
Thus, if there is a loss of afferent nerve function by one spinal
nerve sensation from the region of skin which it supplies is not
usually completely lost as overlap from adjacent spinal nerves occurs,
however, there maybe be a reduction or change in sensation.
Support : Types
of Paralysis : Vertebral Column : Spinal
Cord : Myotomes & Dermatomes : Autonomic
Dysreflexia : Spasticity &
Spasms : Temperature Regulation
: Respiratory System : Pressure
Sores : Spinal Cord Injury