DERMATOME CUTNEOUS NERVES DR NOOR US SABA SR
DERMATOME & CUTNEOUS NERVES DR NOOR US SABA SR, DEPARTMENT OF ANATOMY JNMCH, AMU, ALIGARH
DEFINITION �DERMATOME Ø Strip (Area) of skin supplied by a single spinal nerve �CUTANEOUS NERVES Ø Named branches from nerve plexuses or directly from spinal nerves Ø Supplying the skin
DERMATOME Ø Strip (Area) of skin supplied by a single spinal nerve Ø Adjacent dermatomes overlap Ø No area of skin is supplied solely by a single spinal nerve Ø Total mass of muscle supplied by a single spinal nerve is a myotome
NERVE �Whitish chords (having nerve fibers of different dia. ) �Bound together in bundles by fibrous tissue �Fibrous tissue forms endoneureum, perineurium and epineureum �Classification Ø cranial nerves Ø spinal nerves
SPINAL NERVES � 31 Pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral & 1 coccygeal) �Spinal nerves are attached to the spinal medulla by two roots Ø Ventral root (efferent fibers) Ø Dorsal root (afferent fibers)- arise from spinal ganglion ü Both roots unite to form short trunk
SPINAL NERVES �Trunk divides into ventral ramus and dorsal ramus (each ramus contains both afferent and efferent fibers)
SPINAL NERVES �Dorsal ramus (supplies muscles and skin over back of the vertebral column- forming a row of nerves on each side of the midline of the back) �Ventral ramus (supplies the strip of muscle and skin in which it lies)
SPINAL NERVES �Ventral and dorsal ramus (supply a strip of skin from the posterior median line to the anterior median line) �Dermatome- area of skin supplied by a single spinal nerve
DERMATOMES IN HUMAN BODY
SPINAL NERVES �Ventral rami of cervical, lumbar, sacral and coccygeal nerves are more or less plaited together to form nerve plexus �Cervical plexus- head and neck �Brachial plexus- upper limb �Lumbar plexus- lower limb �Sacral plexus- lower limb
SPINAL NERVES �Ganglion of the sympathetic trunk gives grey ramus communicans (post ganglionic) to corresponding ventral ramus �Ganglion of the sympathetic trunk receives white ramus communicans (pre ganglionic) from corresponding ventral ramus of all thoracic and two or three lumbar
SPINAL NERVES �Branches of nerves to skin (cutaneous br. ) contain afferent (sensory) and sympathetic efferents �Branches of nerves to muscles contain efferent, afferent and sympathetic efferents �Applied�Nerve injury- loss of sensation from skin and paralysis of muscle along with loss of sweating, loss of blood vessel control and goose-flesh
SYMPATHETIC TRUNK Ø Pair of ganglionated chains of nerve fibres Ø One on either side of vertebral column Ø From atlas vertebra above to coccyx below Ø Each trunk bears sympathetic ganglia
DERMATOMES IN UPPER AND LOWER LIMB �Limb buds develop as outpockets from ventral body wall �Development of upper and lower limbs is similar except 1) Buds forelimb develop around 26 th day followed by hind limb buds 2 days later 2) Upper limb rotates 90° laterally whereas lower limb rotates 90° medially 3) Upper limb buds lie opposite- C 3 -T 2 & lower limb buds lie opposite- L 2 S 3
DERMATOMES IN UPPER AND LOWER LIMB �Although the original dermatomal pattern changes during growth of the limbs, an orderly sequence of distribution can still be recognized in the adult
DERMATOMES IN UPPER AND LOWER LIMB �Initially, each limb bud projects laterally at right angles from the trunk �Presents pre axial and post axial border 1. Pre axial border- upper nerves 2. Post axial borderlower nerves 3. Distal end of limbintermediate nerves
DERMATOMES OF UPPER LIMB �Two axial lines Ø Anterior (ventral) axial line- from angle of Louis across 2 nd costal cartilage to the front of limb up to wrist Ø Posterior (dorsal) axial line- from C 7 across scapula to the back of arm up to elbow
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