21. Spinal Cord Extends from the foramen magnum of the skull to the first or second lumbar vertebra(L1& L2)31 pairs of spinal nerves arise from the spinal cordCauda equina is a collection of spinal nerves at the inferior endThe cord does not extend the entire length of the vertebral column – so a group of nerves leaves the inferior spinal cord and extends downward. It resembles a horses tail and is called the cauda equina
42. Another spinal cord picture Dorsal ramusof spinal nerveVentral ramus of spinal nerve
5The Spinal Nerves-immediately after being formed the spinal nerves split into dorsal and ventral rami.Figure 7.25b
63. Gross Anatomy of Spinal Cord Thicker at the neck and end of the cord (cervical and lumbar enlargements)Reason: large group of nerves leave the cord to serve the arms and legs .
7Spinal Cord Anatomy Meninges cover the spinal cord Spinal nerves leave at the level of each vertebraeDorsal rootAssociated with the dorsal root ganglia—collections of cell bodies outside the central nervous systemVentral rootContains axons
8Spinal Cord Anatomy Internal gray matter is mostly cell bodies Dorsal (posterior) hornsAnterior (ventral) hornsGray matter surrounds the central canalCentral canal is filled with cerebrospinal fluidExterior white mater—conduction tractsDorsal, lateral, ventral columns
9Spinal Cord Anatomy Up close view of cervical enlargement Figure 7.20 (1 of 2)
10Spinal Cord Anatomy Up close view of lumbar enlargement Figure 7.20 (2 of 2)
124. Spinal Nerves31 nerves connecting the spinal cord and various body regions.8 paired cervical nerves12 paired thoracic nerves5 paired lumbar nerves5 paired sacral nerves1 pair of coccygeal nerves
13Spinal NervesThere is a pair of spinal nerves at the level of each vertebrae for a total of 31 pairsFormed by the combination of the ventral and dorsal roots of the spinal cordNamed for the region from which they ariseFigure 7.25a
145.Anatomy of Spinal Nerves Spinal nerves divide soon after leaving the spinal cordDorsal rami—serve the skin and muscles of the posterior trunkVentral rami—form a complex of networks (plexus) for the anterior
155.& 7. Plexuses Sacral Plexus Plexus- ventral rami C1-T1 and T12-S4 branch extensively and join one another lateral to the vertebral column forming complicated nerve plexuses that serve motor and sensory needs***Except for T2 to T12,Ventral Rami from C1- T1 form Cervical & Brachial plexusesVentral rami from L1-S4 form Lumbar and Sacral plexuses6. Serve motor and sensory needs of the limbsVentral rami from T2-T12 do not form plexuses..they serve the muscles of intercostal spaces and the skin and muscles of the anterior and lateral trunkSacral Plexus
16This diagram shows the nerves leaving from the vertebral canal Note: There are 7 cervical vertebrae but 8 pairs of cervical nerves.C1 – C7 emerge above the vertebrae for which they are named.C8 emerges between C7 and T1.The remaining spinal nerve pairs emerge below the same numbered vertebra.
17PNS: The Spinal NervesLook how the dorsal and ventral roots merge to form the spinal nerve then split again to form the ventral and dorsal ramiFigure 7.25b
206. Spinal NervesEach connects to the spinal cord by 2 roots – dorsal and ventral.Ventral roots are motor while dorsal roots are sensory.
21Dorsal root – sensory function Ventral root – motor function 6.Dorsal root – sensory functionVentral root – motor functionDorsal RootFigure 7.22Ventral root
22Dorsal root – sensory function Ventral root – motor function
23Cervical Plexus-Important nerve= phrenic nerve which serves the diaphragm and muscles of shoulder and neck
24Major Peripheral Nerves of the Upper Limbs The brachial plexus branches into 5 major peripheral nerves of the upper limbs :AxillaryRadialMedianMusculocutaneousUlnarFigure 7.26a
25Major Peripheral Nerves of the Lower Limbs The nerves from the lumbar plexus serve the abdominal region and the anteromedial thigh.Important nerves:FemoralObturatorFigure 7.26b
26Major Peripheral Nerves Lower Limbs Sacral plexus – supply buttock, posterior thigh, and almost all leg and foot.Important Nerves:The sciatic nerve – largest nerve in the body; divides into common fibular nerve and tibial nerve.Superior and Inferior GlutealFigure 7.26c
30Spinal CordFunctions to transmit messages to and from the brain (white matter) and to serve as a reflex center (gray matter).extends about 17”diameter of your thumbThicker at the neck and end of the cord (cervical and lumbar enlargements) b/c of the large group of nerves connecting these regions of the cord w/ the arms and legs.
31Spinal CordThe cord does not extend the entire length of the vertebral column – so a group of nerves leaves the inferior spinal cord and extends downward. It resembles a horses tail and is called the cauda equina.
32Spinal Cord Notice the gross features of the spinal cord on the right. 31 pairs of spinal nerves attach to the cord by paired roots and exit from the vertebral canal via the intervertebral foramina.
33Cross Sectional Anatomy of the Spinal Cord Flattened from front to back.Anterior median fissure and posterior median sulcus partially divide it into left and right halves.Gray matter is in the core of the cord and surrounded by white matter.
34Resembles a butterfly.2 lateral gray masses connected by the graycommissure.Posterior projections are the posterior or dorsal horns.Anterior projections are the anterior or ventral horns.In the thoracic and lumbar cord, there also exist lateral horns.
35Gray Matter Posterior horns contain interneurons. Anterior horns contain someinterneurons as well as the cellbodies of motor neurons.These cell bodies project their axons via the ventral roots of the spinal cord to the skeletal muscles.The amount of ventral gray matter at a given level of the spinal cord is proportional to the amount of skeletal muscle innervated.
36Gray MatterLateral horn neurons are sympathetic motor neurons serving visceral organs.Their axons also exit via the ventral root.Afferent sensory fibers carrying info from peripheral receptors form the dorsal roots of the spinal cord. The somata of these sensory fibers are found in an enlargement known as a dorsal root ganglion.The dorsal and ventral roots fuse to form spinal nerves.
37White Matter Myelinated nerve fibers. Allows for communication btwn the brain and spinal cord or btwn different regions of the spinal cord.White matter on each side of the cord is divided into columns or funiculi.Typically, they are ascending or descending.What does that mean?
38Spinal NervesThe 2 roots join to form a spinal nerve prior to exiting the vertebral column.Roots are short and horizontal in the cervical and thoracic regions while they are longer and more horizontal in the sacral and lumbar regions.Almost immediately after emerging from its intervertebral foramen, a spinal nerve will divide into a dorsal ramus, a ventral ramus, and a meningeal branch that reenters and innervates the meninges and associated blood vessels.
39Each ramus is mixed.Joined to the base of the ventral rami of spinal nerves in the thoracic region are the rami communicantes.Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the rest of the body trunk and the limbs.