Spinal Nerves Cervical plexus Brachial plexus

Objectives Describe how spinal nerves are formed. Make a list of contributing roots to cervical plexus. Discuss the general arrangement. Describe the location of this plexus. Make a list of the out coming nerves.. Point out the point where the major cutaneous nerves emerge. Describe the brachial plexus Make a list of contributing spinal nerves. Discuss the general arrangement of this plexus. Locate the plexus in the axilla and note important relations to blood vessels. Make a list of the terminal main branches of brachial plexus.

Spinal Nerves The spinal cord is functionally segmented Each segment gives of a pair of spinal nerves (31) 8 cervical, 12 thoracic, 5 lumbar, 5 sacral & one coccygeal Each nerve has a dorsal (sensory) root & a ventral motor root The dorsal has a ganglion containing pseudounipolar neurons

Each spinal nerve arises as rootlets which then combine to form dorsal (posterior) & ventral (anterior) roots. Two roots merge laterally and form the spinal nerve. Dorsal (posterior) root has a ganglion (dorsal root/sensory ganglion) that contains the cell bodies of the sensory neurons Each spinal nerve then divides into a smaller dorsal and a larger ventral ramus

Spinal nerve Typical spinal nerve divides into: 1- Dorsal ramus which supplies structures on the back 2- White ramus communicans to sympathetic trunk and Grey ramus communicans from the sympathetic trunk 3- Collateral branch 4- Ventral ramus 5- Lateral branch 6- Anterior branch

Main Branches of the spinal nerve Dorsal Ramus: innervate deep muscles of the trunk responsible for movements of the vertebral column 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.

Dermatomes Dermatome is: A specific segment of skin supplied by a single spinal nerve. All spinal nerves except for C1 innervate a segment of skin, and so each of these nerves is associated with a dermatome. The skin of the body may be divided into sensory segments that collectively make up a dermatome map.

Dermatomes Cutaneous areas supplied by adjacent spinal nerves overlap. There is therefore little or no sensory loss after interruption of a single spinal nerve or dorsal root

Cervical Plexus Is made of the anterior rami of C1-4 Ansa cervicalis: is a nerve loop made of superior root C1-2 and inferior root C2-3 Ansa cervicalis and anterior ramus of C1 supply infrahyoid muscle Phrenic nerve arises from C3-5

Cervical Plexus Sensory branches of cervical plexus include: Lesser occipital nerve Great auricular nerve Transverse cervical nerve Supraclavicular nerves

Brachial Plexus It is formed by the ventral rami of C5-T1 C5-6 form upper trunk C7 continues as middle trunk C8-T1 form the lower trunk Each trunk divides into anterior and posterior divisions

FORMATION OF BRACHIAL PLEXUS It is formed in the posterior triangle of the neck. Divisions: The plexus is divided into : – Roots – Trunks – Divisions – Cords – Terminal branches

TRUNKS Upper trunk – Union of the roots of C5 & 6 Middle trunk – Continuation of the root of C7 Lower trunk – Union of the roots of C8 & T1

DIVISIONS & CORD Each trunk divides into anterior and posterior division Posterior cord: – From the three posterior divisions Lateral cord: – From the anterior divisions of the upper and middle cords

CORDS & BRANCHES Medial cord – It is the continuation of the anterior division of the lower trunk Branches Branches All three cords will give branches, those will supply their respective regions

BRANCHES (A) From Roots: 1. C5: Nerve to rhomboids (dorsal scapular nerve). 2. C5,6 &7: Long thoracic nerve (B) From Trunk (upper trunk): 1.Nerve to subclavius 2.Suprascapular nerve (supplies supraspinatus & infraspinatus)

Lateral Cord (2LM).Lateral pectoral n.Lateral root to median n.Musculocutaneous n Posterior Cord (ULTRA).Upper subscapular n.Lower subscapular n.Thoracodorsal n.Radial n.Axillary n Medial cord (4MU).Medial pectoral n..Medial root to median n..Medial cutaneous n of arm..Medial cutaneous n of forearm..Ulnar n. C5 C6 C7 C8 T1 (C)BRANCHES From Cords

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