meninges the_spinal_cord

Meninges & The Meninges & The Spinal CordSpinal Cord

Chapter 9: Nervous SystemChapter 9: Nervous System

Unit 3: Integration and Unit 3: Integration and CoordinationCoordination

MeningesMeninges

Bones, membranes, and fluid Bones, membranes, and fluid surround the organs of the CNS.surround the organs of the CNS.

– Layered membranes called Layered membranes called MeningesMeninges lie between these bony lie between these bony coverings and the soft tissues of the coverings and the soft tissues of the CNS.CNS.

The meninges serve as protection for the The meninges serve as protection for the brain and the spinal cordbrain and the spinal cord

Layers of the Layers of the MeningesMeninges Meninges have three layers:Meninges have three layers:

– Dura MaterDura Mater

The outermost layer of the meningesThe outermost layer of the meninges

– Arachnoid MaterArachnoid Mater

The middle layer of the meningesThe middle layer of the meninges

– Pia MaterPia Mater

The innermost layer of the meningesThe innermost layer of the meninges

Dura MaterDura Mater

Dura materDura mater is composed is composed primarily of tough, white, fibrous primarily of tough, white, fibrous connective tissue. connective tissue.

– Contains many blood vessels and Contains many blood vessels and nerves.nerves.

Attached to the interior portion of the Attached to the interior portion of the skull and serves as the periosteum for skull and serves as the periosteum for the inside of the cranium.the inside of the cranium.

Also extends inward between the lobes of Also extends inward between the lobes of the brain (partitions and protection)the brain (partitions and protection)

More on Dura MaterMore on Dura Mater

Dura mater extends from the Dura mater extends from the cranium into the vertebral canal.cranium into the vertebral canal.

– It is a strong tubular sheath that It is a strong tubular sheath that surrounds the spinal cord.surrounds the spinal cord.

It is not attached to the vertebrae spinal It is not attached to the vertebrae spinal cord, but is separated by a space called cord, but is separated by a space called the the Epidural SpaceEpidural Space

Arachnoid MaterArachnoid Mater

The The Arachnoid MaterArachnoid Mater is a thin, is a thin, web-like membrane without blood web-like membrane without blood vesselsvessels

– Lies between the dura mater and the Lies between the dura mater and the pia materpia mater

– It spreads over the brain and the spinal It spreads over the brain and the spinal cordcord

Pia MaterPia Mater

The The Pia MaterPia Mater is very thin and delicate. is very thin and delicate. Contains many blood vessels that Contains many blood vessels that

nourish the cells of the brain and the nourish the cells of the brain and the spinal cord.spinal cord.

– This layer is connected to the surfaces of This layer is connected to the surfaces of both the brain and the spinal cord.both the brain and the spinal cord.

Separating the pia mater from the arachnoid Separating the pia mater from the arachnoid mater is the mater is the Subarachnoid SpaceSubarachnoid Space..

– This space contains the clear, watering This space contains the clear, watering Cerebrospinal Fluid (CSF)Cerebrospinal Fluid (CSF)

The Spinal CordThe Spinal Cord

The The Spinal CordSpinal Cord is a slender nerve is a slender nerve column that passes downward from column that passes downward from the brain into the vertebral canal.the brain into the vertebral canal.

– This structure is continuous with the This structure is continuous with the brain, but officially begins where brain, but officially begins where nervous tissue leaves the cranial nervous tissue leaves the cranial cavity (foramen magnum).cavity (foramen magnum).

Structure of the Spinal Structure of the Spinal CordCord The spinal cord consists of 31 segments The spinal cord consists of 31 segments

that each give rise to a pair of spinal that each give rise to a pair of spinal nerves.nerves.

– Spinal nervesSpinal nerves branch to different parts to branch to different parts to connect the CNS to the PNS.connect the CNS to the PNS.

– There are two spinal nerves that arise between There are two spinal nerves that arise between every vertebrae…one to each side of the bodyevery vertebrae…one to each side of the body

– Various parts of the spinal cord supply nerves to Various parts of the spinal cord supply nerves to specific parts of the PNS.specific parts of the PNS.

Spinal Cord Spinal Cord EnlargementsEnlargements The The Cervical EnlargementCervical Enlargement is is

found in the neck region of the found in the neck region of the spinal cord.spinal cord.

– Supplies nerves to the upper limbsSupplies nerves to the upper limbs

The The Lumbar EnlargementLumbar Enlargement is is found in the lower back region of found in the lower back region of the spinal cord.the spinal cord.

– Supplies nerves to the lower limbsSupplies nerves to the lower limbs

Spinal Cord AnatomySpinal Cord Anatomy

The human spinal cord has a very The human spinal cord has a very distinct appearance when viewed distinct appearance when viewed in cross sectionin cross section

The spinal cord is segmentedThe spinal cord is segmented– One segment per vertebraOne segment per vertebra– Each segment is nearly identical to Each segment is nearly identical to

all other segmentsall other segments


The spinal cord has both The spinal cord has both grey grey matter matter & & white matterwhite matter– White matter is composed of White matter is composed of

myelinated neuronal axonsmyelinated neuronal axons– Grey matter is unmyelinatedGrey matter is unmyelinated

Made mostly of neuron cell bodiesMade mostly of neuron cell bodies Makes up the central region of the Makes up the central region of the

spinal cordspinal cord Looks somewhat like a butterflyLooks somewhat like a butterfly


The Grey Matter “Butterfly”The Grey Matter “Butterfly”– The “top” of the butterfly is toward The “top” of the butterfly is toward

the posteriorthe posterior– The “bottom” of the butterfly toward The “bottom” of the butterfly toward

anterioranterior– The “wings” are called The “wings” are called hornshorns

posterior hornposterior horn anterior hornanterior horn


The anterior horns give rise to The anterior horns give rise to anterior rootsanterior roots– The anterior roots are composed of The anterior roots are composed of

the axons of the axons of motor neuronsmotor neurons– The axons of the anterior horn/root The axons of the anterior horn/root

join up with the axons of the join up with the axons of the posterior root to form a posterior root to form a spinal spinal nervenerve


The posterior horn gives rise to The posterior horn gives rise to posterior rootsposterior roots– These roots are made of the axons These roots are made of the axons

of of sensory neuronssensory neurons– Usually, there are Usually, there are gangliaganglia

associated with the posterior rootsassociated with the posterior roots GangliaGanglia (singular: (singular: ganglionganglion) are ) are

clumps of nerve cell bodies that allow clumps of nerve cell bodies that allow neurons to communicateneurons to communicate

meninges the_spinal_cord

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