Brachial plexus Cervical part 1 2 Branches from roots 1 3 Branches from trunks 1 A Axillary part 14 Branches from cords 1 4
Upper limb myotomes 1 5
Upper limb dermatomes 16
Types of brachial plexus injury 16
Axillary nerve 1 9 Radial nerve 19-21 Ulnar nerve 21-24 Median nerve 24-27 Lower limb myotomes 27 Lower limb dermatomes 7/ Lumbosacral plexus 28 Femoral nerve 29 Common peroneal nerve 29 Tibial nerve 30-31 Sciatic nerve 3 1
Lateral cutaneous nerve of thigh 32 Neurological control of the bladder 32
the brachial plexus: cervical part_
The roots of the brachial plexus are formed by the anterior primary rami of C5-T1 inclusive, with occasional contributions from C4 and T2. The roots lie between the scalene muscles in the neck. (Do not confuse the roots of the plexus with the roots of the segmental spinal nerves, which are intrathecal). C5 and C6 form the upper trunk, C7 forms the middle trunk, and C8 and T1 form the lower trunk. (Preganglionic sympathetic nerve fibres to the upper limb arise from T2-T6, ascend in the sympathetic trunk, synapse in cervicothoracic ganglia, and pass to the upper limb mainly through the lower trunk of the plexus. An important localizing point to note is that preganglionic fibres en route to the eye via the stellate ganglion arise from T1.) The trunks are found in the posterior triangle of the neck. The subclavian artery lies in front of the lower trunk.
Each trunk forms an anterior and a posterior division. The divisions lie behind the clavicle. The three posterior divisions form the posterior cord, the anterior divisions of the upper and middle trunks form the lateral cord, and the anterior division of the lower trunk continues as the medial cord. The divisions and commencement of the cords lie in the posterior triangle of the neck.
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