DERMATOME & CUTNEOUS NERVES - PowerPoint Presentation

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DERMATOME & CUTNEOUS NERVES

DR NOOR US SABA

SR, DEPARTMENT OF ANATOMY

JNMCH, AMU, ALIGARH

DEFINITION

DERMATOME

Strip (Area) of skin supplied by a single spinal nerve

CUTANEOUS NERVES

Named branches from nerve plexuses or directly from spinal nerves

Supplying the skin

DERMATOME

Strip (Area) of skin supplied by a single spinal nerve

Adjacent dermatomes overlap

No area of skin is supplied solely by a single spinal nerve

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 cranial nerves 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 Ventral root (

efferent fibers

)

Dorsal root (

afferent fibers

)- arise from spinal ganglion

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 limbSacral 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 efferentsBranches 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

Pair of

ganglionated

chains of nerve fibres

One on either side of vertebral column

From atlas vertebra above to coccyx below

Each trunk bears sympathetic ganglia

DERMATOMES IN UPPER AND LOWER LIMB

Limb buds develop as out-pockets from ventral body wall

Development of upper and lower limbs is similar except-

Buds for forelimb develop around 26

th

day followed by hind limb buds 2 days later

Upper limb rotates 90° laterally whereas lower limb rotates 90° mediallyUpper limb buds lie opposite- C3-T2 & lower limb buds lie opposite- L2-S3

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

Pre axial border- upper nerves

Post axial border- lower nerves

Distal end of limb- intermediate nerves

DERMATOMES OF UPPER LIMB

Two axial lines

Anterior (ventral) axial line

- from angle of Louis across 2nd costal cartilage to the front of limb up to wrist

Posterior (dorsal) axial line

- from C7 across scapula to the back of arm up to elbow