Spinal Nerves + Cutaneous Innervation

spinal nerve is formed from an anterior (efferent fibers) + posterior (afferent) spinal root

—> the 2 roots fuse and leave the vertebral canal through the intervertebral foramen

—> outside the vertebral canal the spinal nerve divides into posterior branch + anterior branch + communicating branch

the posterior root of the spinal nerve contains the spinal ganglion

—> spinal ganglion contains the cell bodies of the afferent nerves entering the spinal cord

motor fibers

• deep muscles (epaxial muscles) of the back

sensory fibers

• skin areas of the back + buttock

• Suboccipital nerve (C1)

• Greater occipital nerve (C2)

• third occipital nerve (C3)

• superior clunial nerves ( L1 - L3)

• middle clunial nerves (S1-S3)

motor fibers

• muscles of anterior + lateral walls of the trunk

• muscles of the limbs

sensory fibers

• to corresponding skin areas

• cervical plexus

• brachial plexus

• thoracic nerves (segmental organisation)

• lumbar plexus

• sacral plexus

• coccygeal plexus

• it connects with the sympathetic chain ganglion

• it usually forms 2 indipendent branches —> white + gray

White branch

• visceromotor fibers pass via white branch to sympathetic chain ganglion —> there they are relayed to neurons

Gray Branch

• axons of the neurons partly reenter the spinal nerve as postganglionic fibers via the gray branch

31 pairs

• Cervical Nerves (8) —> innervate skin + muzscles of upper limbs, head, neck (C1-C8)

• Thoracic nerves (12) —> innervate intercostal muscles, skin + muscles of back + thorax (T1-T12)

• Lumbar Nerves (5) —> innervate muscles + skin of abdomen, thighs, skin of genital organs (L1-L5)

• Sacral Nerves (5) —> innervate skin + muscles of lower extremities (S1-S5)

• Coccygeal Nerves (1) —> rudimentary in humans

is an area of skin innervated by a posterior root of a single spinal nerve

—> area radicularis sensoria

• adjacent dermatomes may overlap but never cross the midline of the body

• dematomes retain segmental organisation on the thorax, abdomen + are arrenged longitudinally along the long axes of the limbs

group of muscles innervated by an anterior root of a single spinal nerve

—> area radicularis motorica

refers to the structure innervated by a single peripheral nerve

Peripheral skin nerve field (area nervina sensoria)

• area of skin innervated by a single peripheral nerve

Peripheral muscle nerve field (area nervina motorica)

• group of muscles innervated by a single peripheral nerve

by branches of the trigeminal nerve —> each division passes out of the cranial cavity to innervate part of the face

—> all face covered except from the part of the ear

• Opthalmic nerve —> supraorbital nerve

• Maxillary nerve —> infraorbital nerve

• Mandibular nerve —> mental nerve

Upper part:

• opthalmic nerve

Middle-posterior part —> posterior branches of spinal nerves

• greater occipital nerve

• third occipital nerve

Latero-Posterior parts:

• lesser occipital nerve (cervical plexus)

Anterior Part:

• transverse cervical nerve (cervical plexus)

Posterior Part:

• posterior branches of spinal nerves

Lateral Parts

• great auricular nerve (cervical plecus)

Supraclavicular nerves (cervical plexus)

all from brachial plexus

Axillary Nerve —> superior lateral cutaneous nerve of arm

Radial Nerve —> inferior lateral cutaneous nerve of arm

Medial Cutaneous Nerve of Arm —> innervation of the medial aspect of arm

Intercostal Nerves (thoracic nerves) —> innervate a little axillary part of the arm

Medial Cutaneous Nerve of Forearm —> medial part

Musculocutaneous Nerve —> lateral part

Radial Nerve —> posterior part

Articular Branch of Ulnar Nerve —> sensory innervation of elbow joint

ULNAR NERVE

• dorsal branch —> 4th + 5th fingers and ulnar side of 3rd finger

• superficial branch —> 5th finger + ulnar side 4th finger

RADIAL NERVE

• superficial branch —> 1st + 2nd finger and radial sode of 3rd finger (only proximal + middle phalanges)

MEDIAN NERVE

• Palmar branch —> skin of thenar eminence

• common palmar digital nerves —> 1st, 2nd, 3rd fingers + radial side of the 4th digit and distal phalanges on both palmar + dorsal sides

• Ilioinguinal Nerve (lumbar plexus)

• Genitofemoral nerve (lumbar plexus)

• lateral cutaneous nerve of thigh (lumbar plexus)

• femoral nerve (sacral plexus)

• Obturator nerve (lumbar plexus)

• posterior cutaneous nerve of thigh (sacral plexus)

  
  

• root of penis/mons pubis

• anterior 1/3 of the scrotum/labia majora

• superomedial part of thigh

medial side of thigh

anterolateral side of thigh

Anterior cutaneous branches —> anterior side of thigh

Saphenous nerve

• infrapatellar branch -> skin inferior to patella

• medial cutaneous nerve of leg —> medial part of lower leg

medial thigh

• Inferior clunial nerve —> distal part of gluteal region

• Perineal branches —> perineal skin

Sciatic Nerve (SP)

• common fibular nerve

• tibial nerve

Lateral Sural Cutaneous nerve —> lateral calf

Superficial Fibular nerve

• medial dorsal cutaneous nerve —> medial side of 1st-3td toe and lateral side of 2nd toe

• intermedial dorsal cutaneous nerve —> lateral 3rd. whole 4th and medial 5th toe

Deep fibular nerve

• lateral dorsal digital nerve of toe —> lateral side 1st toe

• medial dorsal digital nerve of toe —> medial side 2nd toe

Medial sural cutaneous nerve

• Sural nerve —> calf + lateral side of heel

Medial plantar nerve

• proper plantar digital nerve of toe —> medial side of 1st toe

• common plantar digital nerves —> lateral side of 1st toe, both sides 2nd-3rd toe, medial side 4th toe

Lateral plantar nerve:

• superficial branch: lateral side of 4th toe + whole 5th toe

• Supraclavicular nerves (CP)

• Thoracis nerves (intercostal nerbes)

• Iliohypogastric nerve (LP)

• Posterior branches of the spinal nerves

Medial supraclavicular nerves —> skin over manubrium

Intermediate …. —> infraclavicular region

Lateral … —> acrominal region

• lateral cutaneous branches —> lateral part of the mammary + inframammary regions of abdomen

• aterior cutaneous branches —> medial parts ….

lateral cutaneous branch —> lateral abdomen

anterior cutaneous branch —> around superficial inguinal ring

Medial cutaneous branches

Lateral cutaneous branches

• superior + middle clunial nerve