Lecture Human anatomy and physiology - Chapter 13: The peripheral nervous system and reflex activity (part c)

The peripheral nervous system and reflex activity (part c) provides knowledge of spinal nerves. The goal is for you to learn: Describe the formation of a spinal nerve and the general distribution of its rami; define plexus, name the major plexuses and describe the distribution and function of the peripheral nerves arising from each plexus.

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PowerPoint® Lecture Slides

prepared by Janice Meeking, Mount Royal College

C H A P T E R

13

The Peripheral Nervous

System and Reflex Activity: Part C

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Spinal Nerves

their point of issue from the spinal cord

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Cervical nerves

C 1 – C 8

Thoracic nerves

T 1 – T 12

Lumbar nerves

L 1 – L 5

Sacral nerves

S 1 – S 5 Coccygeal nerve Co 1

Cervical plexus

Intercostal nerves

Cervical enlargement

Lumbar enlargement

Cauda equina

Brachial plexus

Lumbar plexus

Sacral plexus

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Spinal Nerves: Roots

via two roots

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Spinal Nerves: Roots

• Contain sensory (afferent) fibers from sensory neurons in the dorsal root ganglia

• Conduct impulses from peripheral receptors

nerves, which then emerge from the vertebral column via the intervertebral foramina

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Dorsal root

ganglion

Gray matter White matter Ventral root Dorsal root

Dorsal and ventral rootlets

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.

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Spinal Nerves: Rami

• Dorsal ramus

• Larger ventral ramus

join to the ventral rami in the thoracic region

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Spinal Nerves: Rami

nerve networks called plexuses (cervical,

brachial, lumbar, and sacral)

several branches

supply muscles of the ribs, anterolateral

thorax, and abdominal wall

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Dorsal ramus Ventral ramus

Intercostal nerve

Spinal nerve Rami communicantes

Dorsal root ganglion Dorsal root Ventral root

Sympathetic trunk ganglion

Sternum

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

Branches of intercostalnerve

• Lateral cutaneous

• Anterior cutaneous

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Cervical Plexus

back of head, and shoulders

• Major motor and sensory nerve of the

diaphragm (receives fibers from C3–C5)

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Hypoglossal nerve (XII)

Lesser occipital nerve

Greater auricular nerve

Ansa cervicalis

Phrenic nerve Supraclavicular nerves

Accessory nerve (XI)

Transverse cervical nerve

Ventralrami:

Ventral rami

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• 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

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Upper Middle Trunks

Lower

Roots (ventral rami):

Upper subscapular Lower subscapular Thoracodorsal Medial cutaneous nerves of the arm and forearm

Long thoracic Medial pectoral Lateral pectoral

Nerve to subclavius Suprascapular

Dorsal scapular

Posterior divisions

Anterior divisions

Lateral Posterior

Cords

Medial Axillary Musculo- cutaneous Radial Median Ulnar

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Upper Middle Lower

Lateral Medial Posterior

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Brachial Plexus: Nerves

• Axillary—innervates the deltoid, teres minor, and skin and joint capsule of the shoulder

• Musculocutaneous—innervates the biceps brachii

and brachialis and skin of lateral forearm

• Median—innervates the skin, most flexors and

pronators in the forearm, and some intrinsic muscles

of the hand

• Ulnar—supplies the flexor carpi ulnaris, part of the

flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand

• Radial—innervates essentially all extensor muscles, supinators, and posterior skin of limb

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Median nerve

Musculocutaneous nerveRadial nerve

Humerus

Ulna

Ulnar nerveMedian nerve

Radius

Radial nerve (superficial branch) Superficial branch of ulnar nerve

Dorsal branch of ulnar nerve

Digital branch of ulnar nerve Muscular branch

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Lumbar Plexus

psoas muscle

skin of anterior thigh and medial surface of leg

foramen to innervate adductor muscles

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(a) Ventral rami and major branches

of the lumbar plexus

Anterior femoral cutaneous

Saphenous Obturator

Iliohypogastric Ilioinguinal Femoral

Ventral rami Ventral

rami:

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

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• 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

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Superior gluteal Lumbosacral trunk

Inferior gluteal

Common fibular Tibial Posterior femoral cutaneous Pudendal Sciatic

Ventral rami and major branches

of the sacral plexus

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Superior gluteal Inferior gluteal

Common fibular

Deep fibular Superficial fibular Plantar branches

Tibial Sural (cut)

Posterior femoral cutaneous

Pudendal Sciatic

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

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Innervation of Skin

the cutaneous branches of a single spinal

nerve

dermatomes

single spinal nerve will not cause complete

numbness

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C2 C3 C4 C5 T1 T2

T2 T3 T4 T5

C6 C8

C6

T6 T7 T8 T9 T10 T11 T12 L1 S2 S3 L1 L2

L3

L4

L5

L2 L3

L4

L5

S1

C5 C6

C8

T2

C5 C6

S1

Anterior view

C2 C3 C4 C5 C6 C7 C8

T1 T2 T3 T4 T5 T6 T8 T9 T10

T11 T12 L1

S1

(b) Posterior view

L5 S2 S1

S1

S3

S2 S2 S1

S4 S5

L5 L5

L4

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Innervation of Joints

produces movement at a joint also innervates the joint and the skin over the joint

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