Dermatomes + Myotomes Flashcards
What are spinal nerve roots?
Roots connect each spinal nerve to a segment of the cord
What do dorsal roots carry?
Afferent/sensory fibres
What do ventral roots carry?
Efferent/motor fibres
Autonomic fibres
How many pairs of spinal nerves are there?
31
Where does the spinal cord start?
Medulla oblongata
Where does the spinal cord end?
Conus Medullaris at L2
What is the cauda equina?
Descending spinal roots from below L2
Where do C1-7 exit in relation to their vertebrae?
Above the vertebrae
Where does C8 exit in relation to vertebrae?
Between C7 and T1
Where do T1-L5? exit in relation to vertebrae?
Below the vertebrae
Where do S1-4 exit in relation to vertebrae?
Exit via 4 pairs of sacral foramina
Where do S5 and Co1 exit in relation to vertebrae?
Exit via sacral hiatus
What is a ramus?
Mixed spinal nerves divide into rami
What is supplied by the posterior/dorsal ramus?
Deep muscles
Skin of dorsal trunk
What is supplied by the anterior/ventral ramus?
Muscles + skin of limbs
Lateral trunk
Ventral trunk
What is supplied by the rami communicantes?
Components of the autonomic system
What is supplied by the meningeal branch of spinal nerves?
Vertebrae
Ligaments
Blood vessels
Meninges
What happens to the dorsal/posterior rami?
Divides into medial and lateral branches
Supplies skin of back in segmental manner
What happens to the ventral/anterior rami?
Segmental for the trunk
Enter the plexuses to supply the limbs
What is a dermatome?
Area of skin supplied by a single spinal nerve
What is a myotome?
Group of muscle supplied by a single spinal nerve
What is the axial line?
Junction of 2 dermatomes supplied from discontinuous spinal levels
What do axial lines mark?
Centre of ventral or dorsal compartments of the limbs
What is the significance of dermatomes and axial lines?
There is functional overlap between dermatomes but they do not cross axial lines
What are axial borders?
Boundaries of dorsal and ventral compartments marked by superficial veins
What marks the pre-axial border in the upper limb?
Cephalic vein
What marks the post-axial border in the upper limb?
Basilic vein
What marks the pre-axial border in the lower limb?
Great saphenous vein
What marks the post-axial border in the lower limb?
Small saphenous vein
What are the myotomes in the upper limb?
C5 C6 C7 C8 T1
What is the action of the C5 myotome?
Shoulder abduction
External rotation
What is the action of the C6 myotome?
Elbow flexion
Wrist extension
Supination
What is the action of the C7 myotome?
Elbow extension
Wrist flexion
Pronation
What is the action of the C8 myotome?
Finger flexion
Finger extension
What is the action of the T1 myotome?
Finger abduction + adduction
What are the myotomes in the lower limb?
L2 L3 L4 L5 S1 S2
What is the action of the L2 myotome?
Hip flexion
What is the action of the L3 myotome?
Knee extension
What is the action of the L4 myotome?
Ankle dorsiflexion
What is the action of the L5 myotome?
Great toe extension
What is the action of the S1 myotome?
Ankle plantar-flexion
What is the action of the S2 myotome?
Great toe flexion
