The Spinal Nerves 脊神经

1. The Spinal Nerves脊神经 山东大学医学院 解剖教研室 李振华

2. General description • 31 pairs spinal nerves: • Cervical nerves—8 pairs (C1-C8) • Thoracic nerves—12 pairs (T1-T12) • Lumbar nerves—5 pairs (L1-L5) • Sacral nerves—5 pairs (S1-S5) • Coccygeal nerves—1 pair (Co1)

3. General Description • Formation: each spinal nerve is formed by union of anterior and posterior roots at intervertebral foramen • The anterior root－contains motor fibers for skeletal muscles. Those from T1 to L2 contain sympathetic fibers; S2 to S4 also contain parasympathetic fibers. • The posterior root－contains sensory fibers whose cell bodies are in the spinal ganglion.

4. Functional Components of Spinal Nerves • Somatic efferent nerve fibers (SE): fibers that transmit motor impulses from spinal cord to skeletal muscles. • Visceral efferent nerve fibers (VE): fibers that transmit motor impulses from spinal cord to smooth muscles, cardiac muscle and glands. • Somatic afferent nerve fibers (SA): fibers that transmit exteroceptive and proprioceptive impulses from body to spinal cord • Visceral afferent nerve fibers (VA): fibers that transmit interoceptive impulses from the viscera to spinal cord

5. Branches of spinal nerves • Anterior branch • Posterior branch • Communicating branch • Meningeal branch

6. Cervical plexus 颈丛 • Formation: formed by anterior rami of C1-C4 spinal nerves • Position: lies in front of the origin of levator scapulae and scalenus medius and deep to the superior part of the sternocleidomastoid C1 C2 C3 C4

7. Branches of Cervical Plexus • Cutaneous branches: • Lesser occipital 枕小神经 • Great auricular 耳大神经 • Transverse nerve of neck 颈横神经 • Supraclavicular nerves 锁骨上神经 • Emerge around middle of posterior border of sternocleidomastoid, to supply skin of neck and scalp between auricle and external occipital protuberance

8. Branches of Cervical Plexus Phrenic nerve膈神经 • Arises from anterior rami of C3-C5 (motor and sensory) • Runs vertically downward across the front of the scalenus anterior • Enters the thorax by passing betweem the subclavian a. and v.

9. Branches of Cervical Plexus Phrenic nerve膈神经 • Accompanied by pericardiophrenic vessels and passes anterior to lung roots between mediastinal pleura and pericardium to supply motor and sensory innervation to diaphragm • Sensory fibers supply to pleurae, pericardium and peritoneum of diaphragm; usually right phrenic nerve may be distributed on live, gallbladder and biliary system.

10. Brachial Plexus 臂丛 • Formation: Formed by anterior rami of C5-C8 and T1 spinal nerves • Position: Passes through the scalene fissure to posterosuperior of subclavian artery, then enters the axilla to form three cords

11. Main branche of brachial plexus • Lateral cord外侧束 • musculocutaneous n. 肌皮神经 • lateral root of median n. 正中神经外侧根 • Medial cord内侧束 • medial root of median n. 正中神经内侧根 • ulnar n. 尺神经 • Posterior cord后束 • radial n. 桡神经 • axillary n. 腋神经

12. Main Branche of Brachial Plexus Musculocutaneous nerve 肌皮神经 • Origin: arises from the lateral cord of the brachial plexus. • Distribution: • Biceps brachii • Brachalis BBC nerve • Coracobrachialis • Skin on anterior aspect of forearm

13. Main Branche of Brachial Plexus Mediannerve正中神经 • Origin: arises from the medial and lateral cord of the brachial plexus. • Muscular branches: • Flexor of forearm except brachioradialis flexor carpi ulnaris and ulnar half of flexor digitorum profundus • Thenar except adductor pollicis, first two lumbricals • Cutaneous branches： • Skin of thenar, central part of palm, • Palmar aspect of radial three and one-half fingers, including middle and distal fingers on dorsum • Injury: Apehand 猿手

14. Main Branche of Brachial Plexus Ulnar nerve尺神经 • Origin: arises from the medial cord of the brachial plexus. • Muscular branches: Flexor carpi ulnaris, ulnar half of flexor digitorum profundus, hypothenar muscles, interossei, 3rd and 4th lumbricals and adductor pollicis; • Cutaneous branches： Skin of hypothenar, palmar surface of ulnar one and one-half fingers, ulnar half of dorsum of hand, posterior aspect of ulnar two and one-half fingers • Injury: clawhand 爪形手

15. Radial nerve 桡神经 • Origin: arisefrom the posterior cord of the brachial plexus • Course: Winds around the back of the arm in the spinal groove of the back of the humerus between the heads of the triceps. It pierces the lateral fascial septum above the elbow and divides into superficial and deep branches.

16. Radial nerve 桡神经 • Distribution: • Extensor muscles of arm and forearm, brachioradialis; • skin on back of arm, forearm, and radial side of dorsum of hand and radial two and one-half fingers • Injury: wristdrop垂腕

17. Main Branche of Brachial Plexus Axillary腋神经 • Origin: arises from the posterior cord of the brachial plexus. • Distribution: Deltoid and teres minor muscle; skin over deltoid and upper posterior aspect of arm • Injury: result in deltoid andteres minor paralysis (loss of shoulser abdution and weel external rotation) with loss of sensation over the deltoid

18. Common brachial plexus injuries

19. Upper plexus injury Stretching the angle between the head and shoulder

20. Lower brachial plexus injury • Stretching the angle between the arm and trunk

21. Anterior branches of thoracic nerves • Intercostal nerves (anterior rami of T1- T11) • Subcostal nerve (anterior ramus of T12) • Distribution: distributed to intercostales and anterolateral abdominal muscles, skin of thoracic and abdominal wall, parietal pleura and peritoneum

22. Segmental Innervation of Skin • Adjacent dermatomes overlap considerably, so that to produce a region of complete anesthesia at least three contiguous spinal nerves have to be sectioned.

23. Segmental Innervation of Skin Dermatome: the area of skin supplied by a single nerve, and, therefore, a single segment of the spinal cord. On the trunk the dermatomes extend round the body from the posterior to the anterior median plane. • T2 Sternal angle • T4 Nipple • T6 Xiphoid process • T8 Costal arch • T10 Umbilicus • T12 Midpoint between umbilicus and symphysis pubis

24. Lumbar plexus腰丛 • Formation: formed by anterior rami of L1-L3, a part of anterior rami of T12and L4 L1 L2 L3 L4

25. Main branche of lumbar plexus • Position: lies within substance of psoas major • Branches • Iliohypogastric 髂腹下神经 • Ilioinguinal 髂腹股沟神经 • Lateral femoral cutaneous 股外侧皮神经 • Femoral 股神经 • Obturator 闭孔神经 • Genitofemoral 生殖股神经

26. Branches of Lumbar Plexus • Femoral nerve passes deep to inguinal ligament; supplies anterior thigh muscles (quadriceps, sartorius and pectineus), hip and knee joint, and skin on anteromedial side of thigh, saphenous nerve is distributed to skin of medial side of leg and foot • Obturator nerve Enters thigh through obturator foramen; supplies medial group of muscles of thigh, obturator externus, and skin of medial side of thigh

27. Sacral Plexus 骶丛 L4 • Formation: formed by anterior rami of L4 and L5 spinal nerves (the lumbrosacral trunk) and anterior rami of sacral and coccygeal nerves Position: lies in pelvic cavity, anterior to sacrum and piriformis L5 S1 S2 S3 S4 S5 Co

28. Main branches of sacral plexus • Superior gluteal n.臀上神经 • Inferior gluteal n.臀下神经 • Pudendal n. 阴部神经 • Posterior femoral cutaneou n. 股后皮神经 • Sciatic n. 坐骨神经

29. Branches of Sacral Plexus • Sciatic nerve坐骨神经 Leaves pelvis through infrapiriform foramen to enter gluteal region, runs inferiorly laterally deep to gluteus maximus, passing midway between the greater trochanter of femur and ischial tuberosity to back of thigh, lying deep to long head of biceps femoris, normally divided into tibial and common peroneal nerves just above popliteal fossa; innervates semitendinosus, semimembranosus and biceps femoris and has articular branches to hip and knee joints

30. Branches of Sacral Plexus • Tibial nerve 胫神经 Decends through popliteal fossa and lies on popliteus; then runs inferiorly with posterior tibial vessels and terminates beneath flexor retinaculum by dividing into medial and lateral plantar nerves; supplies posterior muscles of leg and knee joint

31. Branches of Sacral Plexus • Common peroneal nerve腓总神经 Arises at apex of popliteal fossa and follows medial border of biceps femoris and its tendon; passes over posterior aspect of head of fibula and then winds around neck of fibula, deep to peroneus longus, where it divides into deep and superficial peroneal nerves

32. Branches of Sacral Plexus • Deep peroneal nerve腓深神经 • Arises between peroneus longus and neck of fibula; descends on interosseous membrane and enters dorsum of foot • Supplies anterior muscles of leg, and skin of first interdigital cleft • Superficial peroneal nerve腓浅神经 • Arises between peroneus longus and neck of fibula and descends in lateral compartment of leg • Supplies peroneus longus and brevis and skin on anterior surface of leg and dorsum of foot

33. Superficial peroneal n. Deep peronealn.