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Nerve Trunks & Divisions Lecture: Day 22 Kazuhito Mori, M.Sc., Ph.D. Southwestern University Matias Hipolito Aznar Memorial College of Medicine Neuro-Anatomy Class Presentation

Neuro Anatomy Nerve Trunks

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Page 1: Neuro Anatomy Nerve Trunks

Nerve Trunks & DivisionsLecture: Day 22

Kazuhito Mori, M.Sc., Ph.D.Southwestern University

Matias Hipolito Aznar MemorialCollege of Medicine

Neuro-Anatomy Class Presentation

Page 2: Neuro Anatomy Nerve Trunks

Plait du Jour: Main Dish of the Day

1. Identify Anterior Primary Ramus & Posterior Primary Ramus

2. Name Plexus of Nerves associated with Anterior Rami Cervical Plexus Brachial Plexus Lumbar Plexus Sacrococcygeal Plexus

Tranks & Divisions 1: Objectives

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Trunks & Divisions 2: Definition

1. Trunks The Main Body of an Anatomical Part (as a

Nerve or Blood Vessel) that divides into Branches

2. Plexus A Network of Anastomosing or Interlacing

Nerves or Blood Vessels Nerve Plexus = a network of Intersecting

Nerves consisted of sets of Spinal Nerves that serve the same area of the body as 1 Large Grouped Nerve

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Nervous System

CentralNervous System

PeripheralNervous System

Cranial Nerves(12 pairs)

Spinal Nerves(31 pairs)

Cervical, ThoracicLumbar, Sacral

Coccygeal

Trunks & Plexus 3Location

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A)A) exit the exit the Vertebral ColumnVertebral Column thru thru Intervertebral Intervertebral ForaminaForamina

B)B) arise from the arise from the Spinal CordSpinal Cord first as first as RootletsRootlets①① Rootlets have Rootlets have Anterior & Anterior &

Posterior portionPosterior portion②② Anterior Rootlets converge Anterior Rootlets converge

to form to form Anterior (Ventral) Anterior (Ventral) RootRoot

③③ Posterior Rootlets converge Posterior Rootlets converge to form to form Posterior (Dorsal) Posterior (Dorsal) RootRoot

④④ Anterior Root = Anterior Root = Motor, Motor, EfferentEfferent

⑤⑤ Posterior Root = Posterior Root = Sensory, Sensory, AfferentAfferent

⑥⑥ A Mixed Spinal NerveA Mixed Spinal Nerve (Anterior & Posterior Roots)(Anterior & Posterior Roots)

Trunks & Plexus4: Brief Recap / Facts on Spinal NervesSpinal Nerves…

A)

B)

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A Mixed Spinal Nerve Divides into 2 Rami

1. Anterior (=Ventral) Primary Ramus

2. Posterior (=Dorsal) Primary Ramus

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Anterior (Ventral) Ramus & Posterior (Dorsal) Ramus

1. Dorsal Primary Ramus Lateral Division Medial Division

2. Ventral Primary Ramus

Ventral Primary Rami form Nerve Plexuses

a. Muscular Branch

b. Lateral Cutaneous Branch

c. Anterior Cutaneous Branch

d. White Ramus Communicans: General Visceral Afferents General Visceral Efferents (P

reganglionic Sympathetic)

e. Gray Ramus Communicans: (Postganglionic Sympathetic)

a.

b.

c.

d.

e.

End of Rami, Go to Plexus

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Nerve PlexusNerve Plexus Plexus1: OverviewPlexus1: Overview

From From Ventral Primary RamusVentral Primary Ramus to to PlexusPlexus Cervical PlexusCervical Plexus - the Head, Neck - the Head, Neck

& Shoulders & Shoulders Brachial PlexusBrachial Plexus - the Chest, Shoul - the Chest, Shoul

ders, Arms & Hands ders, Arms & Hands Lumbar PlexusLumbar Plexus - the Back, Abdom - the Back, Abdom

en, Groin, Thighs, Knees, & Calveen, Groin, Thighs, Knees, & Calves s

Sacral PlexusSacral Plexus - the Pelvis, Buttock- the Pelvis, Buttocks, Genitals, Thighs, Calves, & Feet s, Genitals, Thighs, Calves, & Feet

Coccygeal PlexusCoccygeal Plexus Lumbar & Sacral plexus are sometLumbar & Sacral plexus are somet

imes referred to as the “imes referred to as the “LumbosacLumbosacral plexusral plexus” since they’re interconne” since they’re interconnectedcted

The nerves that serve The nerves that serve the Chestthe Chest ar are the only ones e the only ones that do not originatthat do not originate from a plexuse from a plexus

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Ventral Primary Ramus to PlexusVentral Primary Ramus to Plexus Plexus2: GeneralsPlexus2: Generals

Upper LimbsUpper Limbs Cervical PlexusCervical Plexus - C1, C2, C3, C4, C5 - C1, C2, C3, C4, C5 Brachial PlexusBrachial Plexus - Formed by - Formed by CCervical & ervical & ThThoracic oracic

Nerves & supplying Nerves & supplying ArmArm & & parts ofparts of ShoulderShoulder

Lower LimbsLower Limbs Lumbar PlexusLumbar Plexus --- L1, L2, L3, L4 (Ventral Branches) --- L1, L2, L3, L4 (Ventral Branches) Sacral PlexusSacral Plexus --- --- L4L4, , L5L5, S1, S2, S3; supplying , S1, S2, S3; supplying Pelvic Pelvic

RegionRegion & & Lower LimbsLower Limbs Coccygeal PlexusCoccygeal Plexus - A small Plexus by - A small Plexus by S5S5 & &CocCoccygealcygeal (Lumbosacral Plexus(Lumbosacral Plexus - by Ventral Divisions of the - by Ventral Divisions of the

LLumbar, umbar, SSacral & acral & CocCoccygeal Nerves; supplying cygeal Nerves; supplying Lower Lower LimbsLimbs & & PerineumPerineum & & Coccygeal AreaCoccygeal Area))

PLEXUS• At the root of the Limbs, the Anterior Rami combine to form complicated Nerve Plexuses• The Cervical & Brachial Plexuses are found at the root of Upper Limbs• The Lumbar & Sacral Plexuses are found at the root of the Lower Limbs

End of Generals

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Cervical PlexusCervical Plexus PlexusC1PlexusC1

formed by the formed by the Anterior DivisionsAnterior Divisions of the of the first 4 Cervical Nervesfirst 4 Cervical Nerves; ; C1-3 form C1-3 form LoopsLoops; ; Ansa CervicularisAnsa Cervicularis Covered by the Covered by the Sternocleidomastoid MuscleSternocleidomastoid Muscle The anterior rami are joined by connecting branches that form loops located in front oThe anterior rami are joined by connecting branches that form loops located in front o

f the origin of f the origin of Levator ScapulæLevator Scapulæ & & Scalenus MediusScalenus Medius divided into 2 Branches; divided into 2 Branches;

CutaneousCutaneous Branches Branches Muscular Muscular BranchesBranches

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Cervical PlexusCervical Plexus Plexus C2Plexus C2

Cutaneous BranchesCutaneous Branches

– Lesser Occipital N.Lesser Occipital N. C2 C2– Great Auricular N.Great Auricular N. C2,3 C2,3– Transverse Cervical N.Transverse Cervical N.

C2,3 C2,3– Supraclavicular N. Supraclavicular N. C3,4 C3,4

Cutaneous BranchesCutaneous Branches

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Cervical PlexusCervical Plexus Plexus C3Plexus C3

SegmentalSegmental Prevertebral MusclePrevertebral Muscle Levator ScapulaeLevator Scapulae

Ansa Cervicalis Ansa Cervicalis (C1-3)(C1-3) OmohyoidOmohyoid SternohyoidSternohyoid SternothyroidSternothyroid

C1 via XII (C1 via XII (hypoglossalhypoglossal)) GeniohyoidGeniohyoid ThyrohyoidThyrohyoid

Phrenic NervePhrenic Nerve Diaphragm Diaphragm (Respiration)(Respiration)

Muscular BranchMuscular Branch

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Brachial PlexusBrachial Plexus Plexus B1Plexus B1

formed by the formed by the Anterior DivisionsAnterior Divisions of the Lower 4 Cervical Nerves ( of the Lower 4 Cervical Nerves (C5, 6, C5, 6, 7, 87, 8) & the greater part of the ) & the greater part of the Anterior DivisionAnterior Division of of T1T1

C4 usually gives a branch to C5 & T1 frequently receives 1 from the T2 C4 usually gives a branch to C5 & T1 frequently receives 1 from the T2 ((C4-C5C4-C5 / / T1-T2T1-T2))

extends from the Lower Part of the side of the neck to the extends from the Lower Part of the side of the neck to the AxillaAxilla. Their n. Their nerves are erves are Nearly Equal in SizeNearly Equal in Size BUTBUT their Mode of Communication their Mode of Communication VARYVARY

The most constant arrangement are The most constant arrangement are C5C5 & & C6C6; forming ; forming Upper TrunkUpper Trunk imm immediately after the ediately after the Intervertebral ForaminaIntervertebral Foramina

C8 & T1C8 & T1 unite to form unite to form Lower TrunkLower Trunk C7C7 runs out alone runs out alone as the as the Middle TrunkMiddle Trunk

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Brachial PlexusBrachial Plexus Plexus B2Plexus B2

3 Trunks3 Trunks——UpperUpper, , MidMiddledle & & Lower Lower are formeare formed as they pass under thd as they pass under the Clavicle, each trunk se Clavicle, each trunk splits into plits into AnteriorAnterior && PoPosterior sterior DivisionsDivisions

The The Anterior DivisionAnterior Divisionss of the of the UpperUpper & & MiddlMiddle Trunkse Trunks form “ form “Lateral Lateral CordCord“ on the Lateral Si“ on the Lateral Side of the 2nd part of thde of the 2nd part of the Axillary Arterye Axillary Artery

The The Anterior DivisionAnterior Division of the of the Lower TrunkLower Trunk pa passes down on the sses down on the MediMedial Sideal Side of the of the Axillary Axillary ArteryArtery as “ as “Medial CorMedial Cordd““

The The Posterior DivisionsPosterior Divisions of All 3 Trunks form the of All 3 Trunks form the Posterior CordPosterior Cord behind behind the 2nd portion of the the 2nd portion of the AAxillary Arteryxillary Artery

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Brachial PlexusBrachial Plexus PlexusB3PlexusB3

Anatomical RelationsAnatomical Relations In the neck, the plexus lies in the In the neck, the plexus lies in the Posterior Posterior

TriangleTriangle covered by the skin, covered by the skin, PlatysmaPlatysma & & DDeep Fasciaeep Fascia

crossed by the crossed by the Supraclavicular NervesSupraclavicular Nerves, the , the Inferior Belly of the Inferior Belly of the OmohyoidOmohyoid

crossed by the crossed by the External Jugular VeinExternal Jugular Vein & the & the Transverse Cervical ArteryTransverse Cervical Artery

emerges between the Scaleni Anterior & Memerges between the Scaleni Anterior & Medius; its Upper Part lies edius; its Upper Part lies aboveabove the 3rd part the 3rd part of the Subclavian Artery, while Lower Trunk of the Subclavian Artery, while Lower Trunk (C8 & T1) is (C8 & T1) is behindbehind the artery the artery

3rd Part of Subclavian Artery3rd Part of Subclavian Artery Above ---Above --- Scaleni Anterior & MediScaleni Anterior & Medi

usus Behind --- Behind --- Lower Trunk (C8 & T1)Lower Trunk (C8 & T1)

passes passes behindbehind the Clavicle, the Subclavius the Clavicle, the Subclavius & the Transverse Scapular Vessels& the Transverse Scapular Vessels

lies lies onon the 1st digitation of the Serratus Ant the 1st digitation of the Serratus Anterior & the Subscapulariserior & the Subscapularis

In the axilla it is placed In the axilla it is placed laterallateral to the 1st por to the 1st portion of the Axillary Artery, tion of the Axillary Artery, surroundssurrounds the 2nd the 2nd part of the Arterypart of the Artery

gives off its terminal branches to the Upper gives off its terminal branches to the Upper Limb at the Lower part of the AxillaLimb at the Lower part of the Axilla

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Lumbo-Sacral Plexus

Formed by Formed by Ventral Ventral DivisionsDivisions of of LLumbar Nervesumbar Nerves SSacral Nervesacral Nerves CocCoccygeal Nervescygeal Nerves

SuppliesSupplies Lower LimbsLower Limbs Perineum AreaPerineum Area Coccygeal AreaCoccygeal Area

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Lumbar Plexus formed by the loops of communication betwe

en the Anterior Divisions of L1, L2, L3 & the greater part of L4

L1 often receives a branch from T12 situated in the Posterior Part of the Psoas Major in front of the Transverse Processes of the Lumbar Vertebræ

This Plexus DIFFERS from the Brachial Plexus in NOT forming an intricate interlacement, BUT the several nerves of distribution arise from 1 or more of Spinal Nerves

L1 receiving a twig from T12 splits into Upper & Lower Branches

Upper & Larger Branch Iliohypogastric Nerves Ilioinguinal Nerves

Lower & Smaller Branch Genitofemoral Nerve with L2

<L2, L3, L4> Ventral Divisions --- Obturator Nerve Dorsal Divisions

Smaller Branch (L2 & L3) Lateral Femoral Cutaneous Nerve

Larger Branch (L2 & L3) Femoral Nerve with L4 Dorsal Div.

If The Accessory Obturator exists, it is formed by 2 Small branches given by L3 & L4

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Sacral PlexusSacral Plexus formed byformed by

Lumbosacral TrunkLumbosacral Trunk L4L4 (partially) (partially) L5L5 (Anterior Division) (Anterior Division)

S1S1 (Anterior Division) (Anterior Division) S2S2 (Anterior Division) partially (Anterior Division) partially S3S3 (Anterior Division) (Anterior Division)

appears at the Medial Margin of the appears at the Medial Margin of the Psoas MajPsoas Majoror & runs downward over the & runs downward over the Pelvic BrimPelvic Brim to join to join S1S1

S3S3 (Anterior Division) (Anterior Division) Upper Branches ---Upper Branches --- Sacral PlexSacral Plex

usus Lower Branches ---Lower Branches --- Pudendal PlPudendal Pl

exusexus The nerves of this Plexus converge toward the The nerves of this Plexus converge toward the

Lower part of the Lower part of the Greater Sciatic ForamenGreater Sciatic Foramen & for & form a flattened band from the Anterior & Posteriom a flattened band from the Anterior & Posterior surfaces where several branches arise. The br surfaces where several branches arise. The band itself continues as the and itself continues as the Sciatic NerveSciatic Nerve

Sciatic NerveSciatic Nerve on the Back of Thigh splits;on the Back of Thigh splits; Tibial NervesTibial Nerves Common Peroneal NervesCommon Peroneal Nerves

These 2 nerves sometimes arise separately froThese 2 nerves sometimes arise separately from the Plexus; their independence can always bm the Plexus; their independence can always be shown in Dissectione shown in Dissection

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Coccygeal PlexusCoccygeal Plexus

• Coccygeal Plexus– S5 receiving S4 (Communic

ating Filament)– Coccygeal Nerve

• Anococcygeal Nerves originate from the plexus; consist of a few fine filaments piercing the Sacrotuberous Ligament to supply the skin on the Coccyx region

Page 20: Neuro Anatomy Nerve Trunks

Clinical Consideration: Plexus Disorders

Plexuses, interwoven nerve fibres from different spinal nerves could be damaged by Injury, Tumors, Blood Collections or Autoimmune Reactions

Pain, Weakness & Loss of Sensation occur in Upper or Lower Limb

EMG & Evoked Responses help to locate the damage

MRI locates the damage & identifies the cause

Treating the disorder causing the problem could improve nerve functions

Is Your Brachial Plexus OK, Maria?

Page 21: Neuro Anatomy Nerve Trunks

You should now be able to …

1. Differentiate Anterior & Posterior Primary Rami

2. Name Plexus of Nerves associated with Anterior Ramus as well as their Anatomical Formation

Cervical Plexus Brachial Plexus Lumbar Plexus Sacrococcygeal Plexus

Salamat !

Closing Slide: Before You Go Home

Page 22: Neuro Anatomy Nerve Trunks

References Cited

Clinical Neuroanatomy 6th ed., Richard S. Snell, MD, PhD Clinical Anatomy (By Regions) 8th ed., Richard S. Snell, MD, PhD Clinical Anatomy (By Systems), Richard S. Snell, MD, PhD Atlas of Human Anatomy 4th ed., Frank H. Netter, MD Clinically Oriented Anatomy 5th ed., K.L. Moore, PhD, FIAC, FRSM Gray’s Anatomy of the Human Body, Philadelphia: Lea & Febiger Fundamental Neuroscience 3rd ed., Duane E. Haines, PhD Webster’s New Explorer Medical Dictionary, Federal Street Press National Institute of Neurological Disorders & Stroke (NINDS), Bethesda, M

A, U.S.A.