Dermatomes and myotomes
After working through this study unit you will be able to:
- Learn what dermatomes and myotomes are and how they are formed.
- Describe the distributions and function of dermatomes and myotomes.
- List the relevant landmarks associated with each dermatome as well as the various muscle groups associated with each myotome.
A dermatome refers to an area of skin which is innervated by sensory fibers from the posterior (dorsal) root of a single spinal nerve.
Apart from the spinal nerve C1 and sometimes the coccygeal nerve (spinal nerve Co) that do not have an associated dermatome, the dorsal root of each spinal nerve supplies a segment of skin. Spinal nerves C2-S5, thus, provide sensory innervation to the skin of the entire body, except for the face, which is supplied by the trigeminal nerve (CN V).
A dermatome map is a graphical representation of all the dermatomes on a body surface chart. The two most common dermatome maps that are often depicted in textbooks are the Keegan and Garrett map (1948) and the Foerster map (1933).
This video will help you learn more about the dermatomes of the body using the two most widely used variations of dermatome maps.
Take a closer look at the dermatomes of the human body below.
A myotome describes a group of skeletal muscles which are innervated by somatic motor nerves from the anterior (ventral) nerve root of a single spinal nerve. Myotomes are often described as the motor equivalent of a dermatome.
Take a look at an overview of the myotomes of the human body below.
Take a quiz
Test your knowledge and consolidate it with the following quiz:
Do you want to learn more about spinal nerves and how they form dermatomes? Try out this customizable quiz to improve your understanding. You can tailor it to your preference and save your selection for later!
Take a look at our atlas gallery to further review dermatomes and myotomes of the human body.
Type: Sensory to skin
Source: Posterior (dorsal) root of a single spinal nerve, trigeminal nerve (CN V)
Head, face and neck: Trigeminal nerve (CN V) and spinal nerves C2-C4
Upper limbs: Spinal nerves C5-T2
Thorax and abdomen: Spinal nerves T3-T12
Lower limbs and genitalia: Spinal nerves L1-S5
Type: Motor to skeletal muscles
Source: Anterior (ventral) nerve root of a single spinal nerve
C5: Abduction, external rotation at glenohumeral joint
C5,C6: Flexion at glenohumeral joint, flexion at elbow joint
C6,C7: Extension at glenohumeral joint, flexion and extension at wrist joint
C6,C7,C8: Adduction, internal rotation at glenohumeral joint, extension at elbow joint
C7,C8: Pronation, digital flexion and extension
T1: Adduction and abduction at metacarpophalangeal joints
L1,L2,L3: Internal rotation at hip joint, hip adduction
L2,L3: Hip flexion
L3,L4: Knee extension
L4,L5: Hip extension, foot inversion, foot dorsiflexion
L5,S1: External rotation at hip joint, hip abduction, knee flexion, foot eversion, dorsiflexion at metatarsophalangeal and interphalangeal joints
S1,S2: Foot plantarflexion, plantarflexion at metatarsophalangeal and interphalangeal joints