Dermatomes & Segmental Innervation of The Upper & Lower Limbs

Dermatomes & Segmental Innervation of The Upper & Lower Limbs



Segmental Nerve Supply to The Limbs
• Nerve Supply to the limbs comes
from the Spinal Cord
• The Spinal Cord is protected by the
Vertebral Column
• Vertebral Column consists 33 Spinal
Vertebrae
• 24 are Discrete (typical)Spinal
Vertebrae
• 9 are fused to form the Sacrum &
Coccyx
• There are 5 Distinct Groups of
Spinal Vertebrae
1. Cervical (n=7)2. Thoracic (n=12)3. Lumbar (n=5)4. Sacrum (fused-n=5)5. Coccyx (fused n=4)

ypical Features of A Vertebral Segment
• Each Vertebra makes 1
vertebral segment
• It has the following:
? A Body
? A spine
? 2 Transverse Processes
? 2 Superior Vertebral
Notches
? 2 Inferior Vertebral Notches
? AVertebral Foramen


Features of 2 adjoining Vertebral Segments
• Each vertebra has an
inferior & a superior
vertebral notch on each side
• When any 2 consecutive
vertebrae form a common
joint, their corresponding
inferior and superior
vertebral notches form an
intervertebral foramen
• The Spinal cord passes
through Vertebral Foramina
(most levels)
• Segmental nerves leave the
spinal cord via intervertebral
foramina


The Spinal Cord
• The Gross Shape of the spinal cord
changes from rostral to caudal
• Shows two enlargements at the
cervical and lumbar levels and ends in
a taper (conus medullaris)
• The cross sectional appearance of the
cord shows changes from rostral to
caudal
• In X-section: the spinal cord shows
regional specialisations that match the
4 Vertebral Regions
• Distribution of motoneurones varies
along the rostro-caudal axis of cord