Spinal Nerves Cervical plexus Brachial plexus
Feb 08, 2016
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 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
C8T1
(C)BRANCHES From Cords
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