Chapter 12. APR Enhanced Lecture Slides

Transcription

1 Chapter 12 APR Enhanced Lecture Slides See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes and animations. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12-1

2 Chapter 12 Spinal Cord and Spinal Nerves 12-2

3 Spinal Cord and Spinal Nerves Spinal Nerves 31 pairs Spinal cord

4 12.1 Spinal Cord Extends from foramen magnum to second lumbar vertebra Segmented Cervical Thoracic Lumbar Sacral Gives rise to 31 pairs of spinal nerves Not uniform in diameter throughout length Cervical enlargement: supplies upper limbs Lumbar enlargement: supplies lower limbs Conus medullaris: tapered inferior end. Cauda equina: origins of spinal nerves extending inferiorly from lumbosacral enlargement and conus medullaris. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumbosacral enlargement Cervical enlargement Level of second lumbar vertebra Brain Level of foramen magnum Roots of spinal nerves Spinal nerves Spinal cord Conus medullaris Cauda equina Filum terminale Posterior view 12-4

5 Spinal Cord Regions Cervical Thoracic Lumbar Sacral Coccygeal

6 Cervical & Lumbosacral Enlargements

7 Medullary Cone & Cauda Equina

8 Spinal Cord Conus medullaris Filum terminale Cauda equina 8

9 Meninges of the Spinal Cord Connective tissue membranes surrounding spinal cord and brain Dura mater: continuous with epineurium of the spinal nerves Arachnoid mater: thin and wispy Pia mater: bound tightly to surface of brain and spinal cord. Forms the filum terminale, which anchors spinal cord to coccyx and the denticulate ligaments that attach the spinal cord to the dura mater Spaces Epidural: anesthesia injected. Contains blood vessels, areolar connective tissue and fat. Subdural: serous fluid Subarachnoid: CSF and blood vessels within web-like strands of arachnoid tissue Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (a) Anterolateral view Duramater Subdural space Denticulate ligament Arachnoid mater Subarachnoid space Pia mater Epineurium of spinal nerve Dorsal root ganglion Spinal nerve Ventral root 12-9

10 Meninges of Spinal Cord

11 Meninges of the Spinal Cord Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior Spinous process of vertebra Transverse process of vertebra Spinal cord Denticulate ligament Dorsal root Dorsal root ganglion Spinal nerve Ventral root Pia mater Body of vertebra Subarachnoid space Periosteum Arachnoid mater Subdural space Dura mater Epidural space filled with adipose tissue Anterior (b) Superior view 12-11

12 Cross Section of Spinal Cord Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central canal White matter Dorsal (posterior) column Ventral (anterior) column Lateral column Spinal nerve Posterior median sulcus Dorsal root Dorsal root ganglion Central canal Ventral root Gray matter Posterior (dorsal) horn Lateral horn Anterior (ventral) horn Rootlets (a) Anterolateral view Ventral root Gray commissure White commissure Anterior median fissure Ascending nerve tracts Descending nerve tracts (c) Anterolateral view 12-12

13 Spinal Cord Gray matter White matter

14 Cross Section of Spinal Cord Anterior median fissure and posterior median sulcus: deep clefts partially separating left and right halves White matter: myelinated axons forming tracts Three columns (funiculi): ventral, dorsal, lateral Each of these divided into tracts (fasciculi; pathways) Gray matter: neuron, cell, cell bodies, dendrites, axons Horns Posterior (dorsal) Anterior (ventral) Lateral (associated with ANS) 12-14

15 Cross Section of Spinal Cord Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Central canal White matter Dorsal (posterior) column Ventral (anterior) column Lateral column Spinal nerve Posterior median sulcus Dorsal root Dorsal root ganglion Central canal Ventral root Gray matter Posterior (dorsal) horn Lateral horn Anterior (ventral) horn White matter Dorsal (posterior) column Ventral (anterior) column Lateral column Dorsal root Rootlets (a) Anterolateral view Ventral root Gray commissure White commissure Anterior median fissure (b) Dorsal root ganglion Ascending nerve tracts Descending nerve tracts (c) Anterolateral view b: Ed Reschke/Peter Arnold, Inc./Getty Images 12-15

16 Cross Section of Spinal Cord Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Commissures: connections between left and right halves Gray with central canal in the center White Roots: spinal nerves arise as rootlets then combine to form roots Dorsal (posterior) root has a ganglion Ventral (anterior) Two roots merge laterally and form the spinal nerve Central canal White matter Dorsal (posterior) column Ventral (anterior) column Lateral column Spinal nerve Rootlets (a) Anterolateral view (c) Anterolateral view Posterior median sulcus Dorsal root Dorsal root ganglion Central canal Ventral root Gray matter Posterior (dorsal) horn Lateral horn Anterior (ventral) horn Ventral root Gray commissure White commissure Ascending nerve tracts Descending nerve tracts Anterior median fissure 12-16

17 Dorsal rootlets Spinal Nerve Ventral rootlets Dorsal root Ventral root Dorsal root gangion Spinal nerve

18 Organization of Neurons in the Spinal Dorsal root ganglion: collections of cell bodies of unipolar sensory neurons forming dorsal roots. Cord and Spinal Nerves Lateral horn Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Posterior horn Dorsal root Dorsal root ganglion Anterior horn Superior view Ventral root Interneuron Sensory neuron Spinal nerve Autonomic neuron Somatic motor neuron Motor neuron cell bodies are in anterior and lateral horns of spinal cord gray matter. Multipolar somatic motor neurons in anterior (motor) horn Autonomic neurons in lateral horn Axons of motor neurons form ventral roots and pass into spinal nerves 12-18

19 12.2 Reflexes Basic functional unit of nervous system and simplest portion capable of receiving a stimulus and producing a response Automatic response to a stimulus that occurs without conscious thought. Homeostatic. Components Action potentials produced in sensory receptors transmitted to Sensory neuron. To-Interneurons. To-Motor neuron. To- Effector organ which responds with a reflex 12-19

20 Reflex Arc Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 Interneuron Dorsal root Dorsal root ganglion 2 Sensory neuron 1 Sensory receptor Spinal cord Skin 4 Motor neuron Spinal nerve A sensory receptor detects a stimulus. Ventral root 5 Effector organ A sensory neuron conducts action potentials through the nerve and dorsal root to the spinal cord. In the spinal cord, the sensory neuron synapses with an interneuron. (An interneuron is not involved in a monosynaptic reflex arc.) The interneuron synapses with a motor neuron. A motor neuron axon conducts action potentials through the ventral root and spinal nerve to an effector organ. Skeletal muscle 12-20

21 Variety of Reflexes Some integrated within spinal cord; some within brain Some involve excitatory neurons yielding a response; some involve inhibitory neurons that prevent an action Higher brain centers can influence, suppress, or exaggerate reflex responses 12-21

22 Stretch Reflex Muscles contract in response to a stretching force applied to them. Unique because no interneuron. Muscle spindle: specialized muscle cells that respond to stretch. Innervated by specific motor neurons: gamma motor neurons (small diameter neurons). Control sensitivity of muscle spindle. Sensory neurons innervate the noncontractile centers of the muscle spindle cells. These sensory neurons synapse with motor neurons of the spinal cord called alpha motor neurons which in turn innervate the muscle in which the muscle spindle is embedded

23 Stretch Reflex Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sudden stretch of a muscle results in: From brain 1 Muscle spindles detect stretch of the muscle. To brain 2 Sensory neurons conduct action potentials to the spinal cord. 3 4 Sensory neurons synapse directly with alpha motor neurons. Alpha motor neurons conduct action potentials to the muscle, causing it to contract and resist being stretched. Note: The muscle that contracts is the muscle that is stretched. Quadriceps femoris muscle (extensor) Sensory neuron Muscle spindle Alpha motor neuron Gamma motor neuron endings Sensory neuron endings Gamma motor neuron Sensory neuron Patellar tendon Hammer tap Patellar ligament Muscle fiber of muscle spindle Hamstring muscles (flexor) Muscle fiber of muscle St r et c h Stretch reflex Muscle spindle 12-23

24 Golgi Tendon Reflex Prevents contracting muscles from applying excessive tension to tendons Golgi tendon organ. Encapsulated nerve endings that have at their ends numerous terminal branches with small swellings associated with bundles of collagen fibers in tendon. Located in tendon near muscle Prevent damage to tendons that could be caused by excessive tension Produces sudden relaxation of the muscles Example: weight lifter suddenly drops heavy weight. Sudden movements of clean and jerk put so much tension on tendons like Achilles, they could break. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Intense stretch of a skeletal muscle results in: 1 Golgi tendon organs detect tension applied to a tendon. 2 Sensory neurons conduct action potentials to the spinal cord. 3 4 Sensory neurons synapse with inhibitory interneurons that synapse with alpha motor neurons. Inhibition of the alpha motor neurons causes muscle relaxation, relieving the tension applied to the tendon. Note: The muscle that relaxes is attached to the tendon to which tension is applied. Muscle contraction increases tension applied to tendons. In response, action potentials are conducted to the spinal cord. Sensory neuron Tendon Golgi tendon organ Muscle Golgi tendon organ Sensory neuron Alpha motor neuron Hamstring muscles (fexor) Golgi tendon refex To brain Inhibitory interneuron 12-24

25 Withdrawal Reflex Function is to remove a body limb or other part from a painful stimulus. Reciprocal innervation: causes relaxation of extensor muscle when flexor muscle contracts. Also involved in stretch reflex. Crossed extensor reflex: when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb

26 Withdrawal Reflex Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stimulation of pain receptors results in: To brain 1 Pain receptors detect a painful stimulus. Sensory neuron Sensory neurons conduct action potentials to the spinal cord. Sensory neurons synapse with excitatory Interneurons that synapse with alpha motor neurons. Excitation of the alpha motor neurons results in contraction of the flexor muscles and withdrawal of the limb from the painful stimulus. Quadriceps femoris muscle (extensor) Hamstring muscles (fexor) 4 3 Alpha motor neuron Excitatory interneuron Sensory neuron 1 Stimulus Pain receptor Withdrawal reflex 12-26

27 Withdrawal Reflex with Reciprocal Innervation Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Reciprocal innervation 1 2 During the withdrawal reflex, sensory neurons conduct action potentials from pain receptors to the spinal cord. Sensory neurons synapse with excitatory interneurons that are part of the withdrawal reflex. Quadriceps femoris muscle (extensor) Reciprocal innervation Inhibitory interneuron Collateral branch from sensory neuron 3 Collateral branches of the sensory neurons also synapse with inhibitory interneurons that are part of reciprocal innervation. Hamstring muscles (flexor) Sensory neuron To brain 4 The inhibitory interneurons synapse with alpha motor neurons supplying the extensor muscles, causing them to relax and not oppose the flexor muscles of the withdrawal reflex, which are contracting. Withdrawal reflex Alpha motor neuron 2 Excitatory interneuron 12-27

28 Withdrawal Reflex with Crossed Extensor Reflex Crossed extensor reflex Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. During the withdrawal reflex, sensory neurons from pain receptors conduct action potentials to the spinal cord. Sensory neurons synapse with excitatory interneurons that are part of the withdrawal reflex. The excitatory interneurons that are part of the withdrawal reflex stimulate alpha motor neurons that innervate flexor muscles, causing withdrawal of the limb from the painful stimulus. 4 5 Collateral branches of the sensory neurons also synapse with excitatory interneurons that cross to the opposite side of the spinal cord as part of the crossed extensor reflex. The excitatory interneurons that cross the spinal cord stimulate alpha motor neurons supplying extensor muscles in the opposite limb, causing them to contract and support body weight during the withdrawal reflex. 1 Sensory neuron To brain Quadriceps femoris muscle (extensor) Alpha motor neuron Hamstring muscles (flexor) Alpha motor neuron Excitatory interneuron Withdrawal reflex Crossed extensor reflex 12-28

29 Interactions with Spinal Cord Reflexes Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ascending axon Ascending tract Interneuron To brain Site of divergence From brain Descending axon Descending tract Sensory neuron Site of convergence Motor neuron Effector organ Sensory receptor Skin Skeletal muscle Sensory information goes to brain; e.g., pain. Descending tracts from brain carry info to reflexes. Neurotransmitters produce either EPSPs or IPSPs modifying the reflex

30 12.3 Spinal Nerves Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Consist of Axon bundles Schwann cells Connective tissue Endoneurium: surrounds individual neurons Perineurium: surrounds axon groups to form fascicles Epineurium: surrounds the entire nerve Epineurium Perineurium Endoneurium Schwann cell Fascicle Axon Adipose tissue Artery and vein Loose connective tissue 12-30

31 31 Pair of Spinal Nerves

32 Posterior (Dorsal) & Anterior (Ventral) Roots

33 Posterior (Dorsal) Root Ganglia

34 Posterior (Dorsal) and Anterior (Ventral) Rootlets

35 Spinal nerves Posterior root ganglia Posterior rami Anterior rami

36 Organization of Spinal Nerves Thirty-one pairs of spinal nerves First pair exit vertebral column between skull and atlas Last four pair exit via the sacral foramina Others exit through intervertebral foramina Eight pair cervical, twelve pair thoracic, five pair lumbar, five pair sacral, one pair coccygeal Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cervical nerves Thoracic nerves Lumbar nerves Sacral nerves Coccygeal nerves C T L Posterior view Duramater Cervical plexus (C1 C4) Brachial plexus (C5 T1) Cauda equina S1 S2 S3 S4 S5 Co Lumbar plexus (L1 L4) Sacral plexus (L4 S4) Coccygeal plexus (S5 Co) Lumbosacral plexus (L1 S4) 12-36

37 Dermatomal Map Spinal nerves indicated by capital letter and number Dermatomal map: skin area supplied with sensory innervation by spinal nerves Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Functions Cervical nerves Thoracic nerves C T Head movement Diaphragm movement Neck and shoulder movement Upper limb movement Rib movement inbreathing, vertebral column movement, and tone in postural back muscles C5 C6 T1 C4 T1 C7 C8 L1 L2 S3 T2 T3 T4 T5 T6 T7 T8 T9 S4 C2 C3 T10 T 1 1 T12 S3 C4 C5 T1 C6 C7 T1 C8 L2 T2 C6 T1 L2 C6 C8 C7 C2 S3 C3 C4 T3 T4 T5 T6 T7 T8 T9 T10 T 1 1 T12 L1 S4 T1 T2 S2 S5 Co L2 C5 C6 C7 C L1 Hip movement L3 L3 S2 L3 S2 Lumbar nerves 2 3 L4 L4 L4 L4 L5 4 5 Lower limb movement S1 L5 S1 L5 S1 L5 S1 L5 S1 Sacral nerves Coccygeal nerves (a) Posterior view

38 Branches of Spinal Nerves Dorsal Ramus: innervate deep muscles of the trunk responsible for movements of the vertebral column and the C.T. and skin near the midline of the back. Ventral Ramus: what they innervate depends upon which part of the spinal cord is considered. Thoracic region: form intercostal nerves that innervate the intercostal muscles and the skin over the thorax Remaining spinal nerve ventral rami (roots of the plexus): form five plexuses (intermingling of nerves). Ventral rami of C1-C4= cervical plexus Ventral rami of C5-T1= brachial plexus Ventral rami of L1-L4= lumbar plexus Ventral rami of L4-S4= sacral plexus Ventral rami of S4 and S5= coccygeal plexus Communicating Rami: communicate with sympathetic chain of ganglia

39 Branches of Spinal Nerves Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal root (spinal) ganglion Spinal nerve Dorsal root of spinal nerve Ventral root of spinal nerve Rootlets Communicating rami Ganglion of sympathetic chain Dorsal ramus of spinal nerve Ventral ramus of spinal nerve (intercostal nerve) Roots of Splanchnic nerve (a) Anterolateral view Dorsal rootlets Intervertebral foramen (b) Posterior view Dorsal root ganglion Spinal nerve Transverse process of vertebra (cut) b: McGraw-Hill Higher Education, Inc./Rebecca Gray, photographer/don Kincaid, dissections 12-39

40 Posterior ramus Rami Anterior ramus Gray ramus Sympathetic ganglion White ramus

41 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cervical Plexus Roots (ventral rami): C1, C2, C3, C4 Branches Other nerves (not part of cervical plexus) Hypoglossal nerve (XII) Accessory nerve (XI) Lesser occipital nerve Greater auricular nerve Nerve to sternocleidomastoid muscle Superior root of ansa cervicalis Branch to infrahyoid muscles Transverse cervical nerve Ansa cervicalis Nerve to trapezius muscle Branches to infrahyoid muscles Inferior root of ansa cervicalis C1 C4 C1 C2 C3 C4 C5 C1-C4 Innervates superficial neck structures, skin of neck, posterior portion of head Ansa cervicalis: loop between C1 and C3 Phrenic nerve From C3-C5 (cervical and brachial plexuses) Innervate diaphragm Supraclavicular nerves Phrenic nerve Anterior view

42 Cervical Plexus Phrenic Nerve

43 Phrenic Nerve

44 Brachial Plexus Roots (ventral rami): C5, C6, C7, C8, T1 Trunks: upper, middle, lower Anterior divisions Posterior divisions Cords: posterior, lateral, medial Major branches: Axillary nerve Radial nerve Musculocutaneous nerve Median nerve Ulnar nerve Dorsal scapular nerve Sub clavian nerve Suprascapular nerve Posterior cord Axillary nerve Lateral cord Radial nerve Musculocutaneous nerve Medial and lateral pectoral nerves Median nerve Thoracodorsal nerve Upper and lower subscapular nerves Ulnar nerve Anterior view Medial cord Medial brachial cutaneous nerve Medial antebrachial cutaneous nerve T1 C6 C5 C7 C5 T1 Upper trunk Middle trunk Long thoracic nerve C8 Lower trunk C4 from cervical plus C5-T1 Five ventral rami form three trunks that separate into six divisions then form cords that give rise to: Branches/nerves Axillary Radial Musculocutaneous Ulnar Median Smaller nerves such as pectoral, long thoracic, thoracodorsal, subscapular, suprascapular 12-44

45 Brachial Plexus

46 Axillary n. Brachial Plexus Median n. Musculocutaneous n. Superior, Middle, and Inferior Trunks of Brachial Plexus Radial n. Ulnar n.

47 Axillary Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Axillary Nerve Posterior cord of brachial plexus, C5 C6 Movements/Muscles Innervated Laterally rotates arm Teres minor Abducts arm Deltoid Cutaneous (Sensory) Innervation Inferior lateral shoulder Posterior cord Lateral cord Medial cord Axillary nerve Teres minor Deltoid Posterior views

48 Axillary Nerve 12-48

49 Radial Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Radial Nerve Posterior cord of brachial plexus, C5 T1 Movements/Muscles Innervated Extends elbow Triceps brachii Anconeus Flexes elbow Brachialis (part; sensory only) Brachioradialis Extends and abducts wrist Extensor carpi radialis longus Extensor carpi radialis brevis Supinates forearm and hand Supinator Extends fingers Extensor digitorum Extensor digiti minimi Extensor indicis Extends and adducts wrist Extensor carpi ulnaris Abducts thumb Abductor pollicis longus Extends thumb Extensor pollicis longus Extensor pollicis brevis Cutaneous (Sensory) Innervation Posterior surface of arm and forearm, lateral two-thirds of dorsum of hand Posterior cord Lateral cord Medial cord Long head of triceps brachii Medial head of triceps brachii Anconeus Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris Extensor indicis Radial nerve Lateral head of triceps brachii Brachioradialis Extensor carpi radialis longus Extensor carpi radialisbrevis Supinator Adductor pollicis longus Extensor pollicis brevis and longus Posterior view Posterior view Anterior view

50 Radial Nerve 12-50

51 Musculocutaneous Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Musculocutaneous Nerve Origin Lateral cord of brachial plexus, C5 C7 Movements/Muscles Innervated Flexes shoulder Biceps brachii Coracobrachialis Flexes elbow and supinates forearm and hand Biceps brachii Flexes elbow Brachialis (also small amount of innervation from radial nerve) Cutaneous (Sensory) Innervation Lateral surface of forearm Musculocutaneous nerve Biceps brachii Brachialis Posterior cord Lateral cord Medial cord Coracobrachialis Anterior views Posterior view 12-51

52 Musculocutaneous Nerve 12-52

53 Ulnar Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Ulnar Nerve Medial cord of brachial plexus, C8 T1 Movements/Muscles Innervated Flexes and adducts wrist Flexor carpi ulnaris Flexes fingers Part of the flexor digitorum profundus controlling the distal phalanges of little and ring fingers Adducts thumb Adductor pollicis Controls hypothenar muscles Flexor digiti minimi brevis Abductor digiti minimi Opponens digiti minimi Flexes metacarpophalangeal joints and extends interphalangeal joints Two medial (ulnar) lumbricales Abducts and adducts fingers Interossei Cutaneous (Sensory) Innervation Medial third of hand, little finger, and medial half of ring finger Adductor pollicis Posterior view Anterior view Flex or digitorum profundus Ulnar nerve Flexor carpi ulnaris Posterior cord Lateral cord Medial cord All dorsal and palmar interossei Hypothenar muscles The two medial (ulnar) lumbricales Anterior view

54 Ulnar Nerve 12-54

55 Median Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Median Nerve Medial and lateral cords of brachial plexus, C5 T1 Movements/Muscles Innervated Pronates forearm and hand Pronator teres Pronator quadratus Flexes and abducts wrist Flexor carpiradialis Flexes wrist Palmaris longus Flexes fingers Part of flexor digitorum profundus controlling the distal phalanx of the middle and index fingers Flexor digitorum superficialis Controls thumb muscle Flexor pollicis longus Controls thenar muscles Abductor pollicis brevis Opponens pollicis Flexor pollicis brevis Flexes metacarpophalangeal joints and extends interphalangeal joints Two lateral (radial) lumbricales Cutaneous (Sensory) Innervation Lateral two-thirds of palm of hand, thumb, index and middle fingers, and the lateral half of ring finger and dorsal tips of the same fingers Flexor digitorum profundus Flexor pollicis longus Pronator quadratus Thenar muscles The two lateral (radial) lumbricales Posterior view Anterior view Carpal tunnel deep to flexor retinaculum Palmaris longus Pronator teres Median nerve Flexor carpi radialis Posterior cord Lateral cord Medial cord Flexor digitorum superficialis Anterior view

56 Brachial Plexus - Median Nerve

57 Other Nerves of the Brachial Plexus Small nerves that innervate muscles acting on scapula and arm Pectoral Long thoracic Thoracodorsal Subscapular Suprascapular Innervate the skin of the medial arm and forearm 12-57

58 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lumbar and Sacral Plexuses L1 Lumbar plexus: ventral rami of L1-L4 Sacral plexus: ventral rami of L4-S4 Usually considered together because of their close relationship Four major nerves exit and enter lower limb Obturator Femoral Tibial Common fibular (peroneal) Superior gluteal Tibial Iliohypogastric Ilioinguinal Lateral femoral cutaneous Genitofemoral Femoral Obturator Lumbosacral trunk Inferior gluteal Sciatic Common fibular (peroneal) Posterior femoral cutaneous L4 S4 Roots ( ventral rami) Posterior divisions Anterior divisions Nerves L1 L2 L3 L4 L5 S1 S2 S3 S4 S5 Pudendal Anterior view

59 Lumbar Plexus Femoral n. Obturator n. Lumbosacral trunk

60 Sacral Plexus Sciatic n. Tibial n. Common Fibular n. Superficial Fibular n. Deep Fibular n. Tibial n. Fibular n. 60

61 Obturator Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Obturator Nerve Lumbosacral plexus, L2 L4 Movements/Muscles Innervated Rotates thigh laterally Obturator externus Adducts thigh Adductor magnus (adductor part) Adductor longus Adductor brevis Gracilis Adducts thigh and flexes knee Cutaneous (Sensory) Innervation Superior medial side of thigh Obturator externus Adductor magnus L2 L3 L4 Obturator nerve Adductor brevis Adductor longus Gracilis Medial view Anterior view 12-61

62 Obturator Nerve 12-62

63 Femoral Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Femoral Nerve Origin Lumbosacral plexus, L2 L4 Movements/Muscles Innervated Flexes hip Psoas major Iliacus Pectineus Flexes hip and flexes knee Sartorius Extends knee Vastus lateralis Vastus intermedius Vastus medialis Extends knee and flexes hip Rectus femoris Cutaneous (Sensory) Innervation Anterior and lateral branches supply the anterior and lateral thigh; saphenous branch supplies the medial leg and foot Psoas major Iliacus Sartorius Vastus lateralis Rectus femoris Vastus intermedius L2 L3 L4 Femoral nerve Pectineus Vastus medialis Anterior view Medial view Anterior view

64 Femoral Nerve 12-64

65 Tibial and Common Fibular Nerves The two nerves together referred to as the sciatic (ischiadic) nerve 12-65

66 Sciatic Nerve 12-66

67 Tibial Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Tibial Nerve Origin Lumbosacral plexus, L4 S3 Movements/Muscles Innervated Extends hip and flexes knee Biceps femoris (long head) Semitendinosus Semimembranosus Extends hip and adducts thigh Adductor magnus (hamstring part) Plantar flexes foot Plantaris Gastrocnemius Soleus Tibialis posterior Flexes knee Popliteus Flexes toes Flexor digitorum longus Flexor hallucis longus Cutaneous (Sensory) Innervation None L4 L5 S1 S2 S3 Biceps femoris long head Semimembranosus Semitendinosus Tibial nerve Adductor magnus Gastrocnemius Medial and Lateral Plantar Nerves Origin Tibial nerve Movements/Muscles Innervated Flex and adduct toes Plantar muscles of foot Cutaneous (Sensory) Innervation Sole of foot Popliteus Flexor digitorum longus Tibialis posterior Soleus Flexor hallucis longus Sural Nerve (Not Shown) Origin Tibial nerve Movements/Muscles Innervated None Cutaneous (Sensory) Innervation Lateral and posterior one-third of leg and lateral side of foot Anterior view Posterior view Medial plantar nerve to plantar muscles Lateral plantar nerve to plantar muscles Posterior view

68 Tibial Nerve 12-68

69 Common Fibular (Peroneal) Nerve Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin Common Fibular (Peroneal) Nerve Lumbosacral plexus, L4 S2 Movements/Muscles Innervated Extends hip and flexes knee Biceps femoris (short head) Cutaneous (Sensory) Innervation Lateral surface of knee L4 L5 S1 S2 Common fibular (peroneal) nerve Deep Fibular (Peroneal) Nerve Biceps femoris short head Origin Common fibular (peroneal) nerve Movements/Muscles Innervated Dorsiflexes foot Tibialis anterior Fibularis tertius Extends toes Extensor digitorum longus Extensor hallucis longus Extensor digitorum brevis Cutaneous (Sensory) Innervation Great and second toe Fibularis longus Fibularis brevis Tibialis anterior Extensor digitorum longus Extensor hallucis longus Origin Superficial Fibular (Peroneal) Nerve Common fibular (peroneal) nerve Movements/Muscles Innervated Plantar flexes and everts foot Fibularis longus Fibularis brevis Cutaneous (Sensory) Innervation Dorsal anterior third of leg and dorsum of foot Anterior view Lateral view Superficial fibular (peroneal) nerve Fibularis tertius Extensor digitorum brevis Anterior view Deep fibular (peroneal) nerve 12-69

70 Common Fibular Nerve 12-70

71 Other Lumbosacral Plexus Nerves Nerves that innervate the skin of the suprapubic area, external genitalia, superior medial thigh, posterior thigh Gluteal nerves Pudendal nerve Iliohypogastric nerve Ilioingual nerve Genitofemoral nerve Cutaneous femoral 12-71

72 Coccygeal Plexus S5; coccygeal nerve Muscles of pelvic floor Sensory information from skin over coccyx 12-72