Copyright © 2010 Pearson Education, Inc. Figure 13.6

CervicalnervesC1 – C8

ThoracicnervesT1 – T12

LumbarnervesL1 – L5

Sacral nervesS1 – S5

Coccygeal nerve Co1

Cervical plexus

Intercostalnerves

Cervicalenlargement

Lumbarenlargement

Cauda equina

Brachial plexus

Lumbar plexus

Sacral plexus

Copyright © 2010 Pearson Education, Inc. Figure 13.7 (a)

Dorsal rootganglion

Gray matterWhite matterVentral rootDorsal root

Dorsal andventral rootlets of spinal nerve

Dorsal ramusof spinal nerveVentral ramusof spinal nerve

Sympathetic trunkganglion

Spinal nerveRami communicantes

Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as rootlets and join laterally to form the spinal nerve.

Copyright © 2010 Pearson Education, Inc. Figure 13.7 (b)

Dorsal ramus

Ventral ramus

Intercostal nerve

Spinal nerve

Rami communicantesDorsal rootganglion Dorsal rootVentral root

Sympathetic trunkganglion

Sternum

(b) Cross section of thorax showing the main roots and branches of a spinal nerve.

Branches of intercostalnerve

• Lateral cutaneous• Anterior cutaneous

Copyright © 2010 Pearson Education, Inc.

Cervical Plexus

• Formed by ventral rami of C1–C4

• Innervates skin and muscles of the neck, ear, back of head, and shoulders

• Phrenic nerve• Major motor and sensory nerve of the

diaphragm (receives fibers from C3–C5)

Copyright © 2010 Pearson Education, Inc. Figure 13.8

Hypoglossalnerve (XII)

C1

C2

C3

C4

C5

Segmentalbranches

Lesser occipitalnerveGreater auricularnerve

Ansa cervicalis

Phrenic nerveSupraclavicularnerves

Accessory nerve (XI)

Transversecervical nerve

Ventralrami:

Ventral rami

Copyright © 2010 Pearson Education, Inc. Table 13.3

Copyright © 2010 Pearson Education, Inc.

Brachial Plexus

• Formed by ventral rami of C5–C8 and T1 (and often C4 and T2)

• It gives rise to the nerves that innervate the upper limb

• Major branches of this plexus:

• Roots—five ventral rami (C5–T1)

• Trunks—upper, middle, and lower

• Divisions—anterior and posterior

• Cords—lateral, medial, and posterior

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (a)

Upper

Middle Trunks

Lower

Roots (ventral rami):

Upper subscapularLower subscapularThoracodorsalMedial cutaneousnerves of the armand forearm

Long thoracicMedial pectoralLateral pectoral

Nerve tosubclaviusSuprascapular

Dorsal scapular

Posteriordivisions

Anteriordivisions

Lateral

PosteriorCords

Medial

AxillaryMusculo-cutaneousRadialMedianUlnar

Posteriordivisions

Trunks Roots

C4

C5

C6

C7

C8

T1

(a) Roots (rami C5 – T1), trunks, divisions, and cords

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (d)

Anteriordivisions

(d) Flowchart summarizing relationships within the brachial plexus

Major terminalbranches(peripheral nerves)

Cords Divisions Trunks Roots(ventralrami)

MusculocutaneousMedianUlnarRadialAxillary

AnteriorPosteriorAnteriorPosterior

PosteriorAnterior

Upper

Middle

Lower

LateralMedial

Posterior

Posteriordivisions

Trunks Roots

C5

C6

C7

C8

T1

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (c)

Median nerve

Musculocutaneous nerveRadial nerveHumerus

Ulna

Ulnar nerveMedian nerve

Radius

Radial nerve (superficial branch)

Superficial branch of ulnar nerveDorsal branch of ulnar nerve

Digital branch of ulnar nerveMuscular branchDigital branch

(c) The major nerves of the upper limb

Axillarynerve

Anteriordivisions

Posteriordivisions

Trunks Roots

Copyright © 2010 Pearson Education, Inc. Table 13.4

Copyright © 2010 Pearson Education, Inc.

Lumbar Plexus

• Arises from L1–L4

• Innervates the thigh, abdominal wall, and psoas muscle

• Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg

• Obturator nerve—passes through obturator foramen to innervate adductor muscles

Copyright © 2010 Pearson Education, Inc. Figure 13.10

(a) Ventral rami and major branches of the lumbar plexus

Iliohypogastric

L1

L2

L3

L4

L5

IlioinguinalGenitofemoral

Lateral femoralcutaneousObturatorFemoralLumbosacraltrunk

Lateral femoralcutaneous

Anterior femoralcutaneousSaphenous

Obturator

IliohypogastricIlioinguinalFemoral

Ventral rami Ventralrami:

(b) Distribution of the major nerves from the lumbar plexus to the lower limb

Copyright © 2010 Pearson Education, Inc. Table 13.5

Copyright © 2010 Pearson Education, Inc.

Sacral Plexus

• Arises from L4–S4

• Serves the buttock, lower limb, pelvic structures, and perineum

• Sciatic nerve• Longest and thickest nerve of the body

• Innervates the hamstring muscles, adductor magnus, and most muscles in the leg and foot

• Composed of two nerves: tibial and common fibular

Copyright © 2010 Pearson Education, Inc. Figure 13.11 (a)

SuperiorglutealLumbosacraltrunkInferiorgluteal

CommonfibularTibialPosteriorfemoralcutaneousPudendalSciatic

Ventral rami and major branches of the sacral plexus

L4

L5

S1

S2

S3

S4

S5Co1

Ventral rami Ventral rami:

Copyright © 2010 Pearson Education, Inc. Figure 13.11 (b)

Superior glutealInferior gluteal

Common fibular

Deep fibularSuperficial fibularPlantar branches

TibialSural (cut)

Posterior femoralcutaneous

PudendalSciatic

(b) Distribution of the major nerves from the sacral plexus to the lower limb

Copyright © 2010 Pearson Education, Inc. Table 13.6

Copyright © 2010 Pearson Education, Inc.

Innervation of Skin

• Dermatome: area of skin innervated by cutaneous branches of a single spinal nerve

• All spinal nerves except C1 participate in dermatomes

• Dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness

Copyright © 2010 Pearson Education, Inc. Figure 13.12

C2C3

C4

C5T1

T2

T2T3T4T5

C6

C8C7 C7

C6

T6T7T8T9T10T11T12L1S2S3

L1

L2

L3

L4

L5

L2

L3

L4

L5

S1

C5

C6

C8

T2

C5

C6

S1

Anterior view

C2

C3C4C5C6C7C8

C8 C8

C7 C7

T1T2T3T4T5T6T7T8T9

T10

T11T12

L1L2 L3

S1(b) Posterior view

L5S2S1

S1

S3

S2 S1S2

S4S5

L5L5

L4L5L5

L4

C6 C6

C5

L4

L3

L2

L1

L4

Copyright © 2010 Pearson Education, Inc.

Innervation of Joints

• Hilton’s law: Any nerve serving a muscle that produces movement at a joint also innervates the joint and the skin over the joint