Structure of a Nerve
• Bundle of axons • Nerve fibers in
PNS have myelin sheath • Layers of connective tissue
– Epineurium 外膜 – Perineurium 束膜 – Endoneurium 内膜
– Thoracic region – forms intercostal nerve
• Meningeal branch – reenters vertebral canal, innervates meninges, vertebrae, & spinal ligaments
• Communicating rami
• Innervates upper limb & Pectoral girdle & shoulder muscles， skin
锁骨上分支 胸长神经、肩胛背神经、肩胛上神经 锁骨下分支 肩胛下神经、胸内侧神经、胸外侧神经、胸背神经 腋神经
T1
肌皮神经 正中神经 尺神经 桡神经 臂内侧皮神经 前臂内侧皮神经
Distal Branches
Spinal Nerve Plexuses
Spinal Nerve Plexuses
• Ventral rami of spinal nerves fuse and form networks with ventral rami of other spinal nerves.
– Crossing of fibers
• A peripheral nerve may contain axons from several spinal segments.
• T2 – T12 do not form plexuses
Spinal Nerve Plexuses
• Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plal nerve
– to triceps brachii, extensors of arm, forearm,wrist, hand, fingers
• Wrist drop
• Median nerve
– to flexors of wrist, hand, fingers
• Ganglion – cluster of cell bodies outside CNS
脊神经成分
1. 躯体运动纤维 骨骼肌 2. 内脏运动纤维 支配平
滑肌、心肌和腺体。 3. 躯体感觉纤维 分布于
皮肤、骨骼肌、肌腱和 关节，将痛、温、触、 压感觉和本体感觉传入 中枢。 4. 内脏感觉纤维 分布于 内脏、心血管和腺体， 将感觉冲动传入中枢。
Cervical plexus
• C1 – C4 (+ C5)
– cutaneous nerves, mostly sensory from skin of neck & back of head
– Phrenic nerve to diaphragm
• Motor stimulation for breathing!
• Peripheral nerves: sensory and motor divisions
• Sensory (afferent) – carry impulse to the CNS
• Motor (efferent) – carry impulses from CNS
• Mixed – sensory and motor fibers carry impulses to and from CNS; most common type of nerve
– can be compressed
• Carpal Tunnel Syndrome
• Ulnar nerve
– (“funny bone”) – to flexors in hand
• “Claw hand”
Brachial plexus
• Axillary Nerve
to teres minor and deltoid M
Spinal Nerves
Spinal nerves
• 31 pairs arise from spinal cord
• Five groups correspond to regions of spinal cord and vertebrae – Cervical 8 pr. – Thoracic 12 pr. – Lumbar 5 pr. – Sacral 5 pr. – Coccygeal 1 pr.
Structure of a Nerve
Distal Branches
• Dorsal ramus – innervates skin of the back, muscles & joints of its corresponding level
• Ventral ramus – innervates ventral & lateral skin & muscles of the trunk; also gives rise to nerves of limbs
• Musculocutaneous nerve
the coracobrachialis, biceps brachii, and the brachialis
Brachial plexus
• Long thoracic N
serratus anterior
• Thoracodorsal N
Latissimus dorsi
膈神经（C 3 –5 ）
运动纤维支配膈肌。 感觉纤维分布于胸膜、 心包和膈下面腹膜。
经前斜角肌前面下行，经锁骨下动脉、静脉之 间入胸腔，经肺根前方，心包两侧下行至膈。
Brachial plexus
• C5 – T1
• Complex fusion, splitting, fusion, & division into nerves