Missing Unit One Notes

Hi All,

These notes constitute the end of unit one material. See you in open lab on Friday!

Spinal Cord (from Ch. 16, pages 485-492)Spinal Cord (from Ch. 16, pages 485-492)

The spinal cord provides a vital link The spinal cord provides a vital link between the brain and the rest of the between the brain and the rest of the body. The spinal cord and its spinal body. The spinal cord and its spinal nerves:nerves:

1. Are the main pathway for sensory and 1. Are the main pathway for sensory and motor impulses.motor impulses.

2. Are responsible for reflexes which are 2. Are responsible for reflexes which are the quickest reactions to a stimulus.the quickest reactions to a stimulus.

Gross Anatomy of the Spinal CordGross Anatomy of the Spinal Cord

Length: 42 -45 cmLength: 42 -45 cm

Two longitudinal depressions on external surface:Two longitudinal depressions on external surface:• Posterior median sulcusPosterior median sulcus on posterior surface. on posterior surface.• Anterior median fissureAnterior median fissure on anterior surface on anterior surface

Gross Anatomy of the Spinal CordGross Anatomy of the Spinal Cord

• The spinal cord is shorter than the The spinal cord is shorter than the vertebral canal that houses it.vertebral canal that houses it.

• The tapering inferior end of the spinal The tapering inferior end of the spinal cord is called the cord is called the conus medullarisconus medullaris and and is the official “end” of the spinal cord, is the official “end” of the spinal cord, usually at the level of the first lumbar usually at the level of the first lumbar vertebra.vertebra.

Gross Anatomy of the Spinal CordGross Anatomy of the Spinal Cord

• Inferior to the conus medullaris groups of Inferior to the conus medullaris groups of axons called the axons called the cauda equinacauda equina project project inferiorly from the spinal cord.inferiorly from the spinal cord.

• Within the cauda equina is the Within the cauda equina is the filum terminalefilum terminale which is a thin strand of pia mater that helps which is a thin strand of pia mater that helps anchor the conus medullaris to the coccyx.anchor the conus medullaris to the coccyx.

Gross Anatomy of the Spinal CordGross Anatomy of the Spinal Cord

The spinal cord is associated with The spinal cord is associated with thirty-one pairs thirty-one pairs of spinal nerves that connect the CNS to of spinal nerves that connect the CNS to muscles, sensory receptors and glands.muscles, sensory receptors and glands.

Each side contains:Each side contains:• Eight cervical nerves (C1-C8).Eight cervical nerves (C1-C8).• Twelve thoracic nerves (T1-T12).Twelve thoracic nerves (T1-T12).• Five lumbar nerves (L1-L5).Five lumbar nerves (L1-L5).• Five sacral nerves (S1-S5)Five sacral nerves (S1-S5)• One coccygeal nerve (Co)One coccygeal nerve (Co)

Spinal Cord MeningesSpinal Cord Meninges

The spinal cord is protected and encapsulated by The spinal cord is protected and encapsulated by spinal cord meningesspinal cord meninges which are continuous which are continuous with the cranial meninges around the brain.with the cranial meninges around the brain.

Some of the spaces between the meningeal layers Some of the spaces between the meningeal layers have clinical significance.have clinical significance.

Spinal Meninges and Structure of Spinal Meninges and Structure of the Spinal Cordthe Spinal Cord

Spinal Cord MeningesSpinal Cord Meninges(dura mater, arachnoid mater, and pia mater)(dura mater, arachnoid mater, and pia mater)

The The epidural spaceepidural space::• Lies between the dura mater and the bone Lies between the dura mater and the bone

of the vertebrae.of the vertebrae.• Houses areolar connective tissue, blood Houses areolar connective tissue, blood

vessels, and adipose tissue.vessels, and adipose tissue.The The dura materdura mater::• Is the most external layer of meninges.Is the most external layer of meninges.• Fuses with the connective layers that Fuses with the connective layers that

surround the spinal nerves.surround the spinal nerves.

Spinal Cord MeningesSpinal Cord Meninges

A narrow A narrow subdural spacesubdural space separates the dura separates the dura mater from the arachnoid. This is really mater from the arachnoid. This is really only a potential space.only a potential space.

The The arachnoidarachnoid is deep to the dura mater and is deep to the dura mater and the subdural space. the subdural space.

The The subarachnoid spacesubarachnoid space is a real space filled is a real space filled with cerebrospinal fluid – the fluid with cerebrospinal fluid – the fluid surrounding the entire CNS (brain and surrounding the entire CNS (brain and spinal cord).spinal cord).

Spinal Cord MeningesSpinal Cord Meninges

The The pia materpia mater::• The innermost meningeal layer that adheres The innermost meningeal layer that adheres

directly to the spinal cord.directly to the spinal cord.• This delicate layer supports some of the This delicate layer supports some of the

blood vessels (mainly capillaries) supplying blood vessels (mainly capillaries) supplying the spinal cord.the spinal cord.

• Has paired lateral extensions called Has paired lateral extensions called denticulate ligamentsdenticulate ligaments which attach the which attach the spinal cord to the dura mater.spinal cord to the dura mater.

Sectional Anatomy of the Spinal Sectional Anatomy of the Spinal CordCord

The spinal cord is partitioned into an inner The spinal cord is partitioned into an inner gray matter region and an outer white gray matter region and an outer white matter region:matter region:

Gray matterGray matter – made mainly of cell bodies – made mainly of cell bodies and dendrites of neurons (nerve cells).and dendrites of neurons (nerve cells).

White matterWhite matter – made of myelinated – made of myelinated (myelin-covered) axons.(myelin-covered) axons.

Gray and White Components of Gray and White Components of Spinal CordSpinal Cord

Location and Distribution of Gray Location and Distribution of Gray MatterMatter

Gray Matter:Gray Matter:• Centrally located in spinal cord.Centrally located in spinal cord.• Cross-section shape resembles butterfly.Cross-section shape resembles butterfly.Subdivided into:Subdivided into:• Anterior Horns.Anterior Horns.• Lateral Horns.Lateral Horns.• Posterior Horns.Posterior Horns.• Gray CommissureGray Commissure..

Location and Distribution of Gray Location and Distribution of Gray MatterMatter

Anterior hornsAnterior horns house the cell bodies of house the cell bodies of somatic somatic motor neuronsmotor neurons which innervate which innervate skeletal muscle tissue.skeletal muscle tissue.

Lateral hornsLateral horns::• Contain cell bodies of autonomic motor Contain cell bodies of autonomic motor

neurons which innervate cardiac muscle, neurons which innervate cardiac muscle, smooth muscle and glands.smooth muscle and glands.

Location and Distribution of Gray Location and Distribution of Gray MatterMatter

The The posterior hornsposterior horns contain axons of contain axons of sensory sensory neuronsneurons and cell bodies of interneurons. and cell bodies of interneurons.

The The gray commissuregray commissure is the gray matter is the gray matter between right and left sides. It houses the between right and left sides. It houses the smallsmall central canal central canal..

Neuron Pathways and Nuclei Neuron Pathways and Nuclei LocationsLocations

Location and Distribution of Location and Distribution of White MatterWhite Matter

The white matter of the spinal cord is external to The white matter of the spinal cord is external to the gray matter and is partitioned into three the gray matter and is partitioned into three portions, each called a portions, each called a funiculusfuniculus::

• Posterior funiculusPosterior funiculus• Lateral funiculusLateral funiculus• Anterior funiculusAnterior funiculusThe anterior funiculi are interconnected by the The anterior funiculi are interconnected by the

white commissurewhite commissure..The axons within each funiculus are organized The axons within each funiculus are organized

into tracts.into tracts.

Gray and White Components of Gray and White Components of Spinal CordSpinal Cord

Spinal NervesSpinal Nerves

• Each anterior and posterior root unite Each anterior and posterior root unite within an intervertebral foramen to within an intervertebral foramen to become a spinal nerve.become a spinal nerve.

• Each spinal nerve contains both motor Each spinal nerve contains both motor (efferent) and sensory (afferent) (efferent) and sensory (afferent) neurons.neurons.

Spinal Nerve DistributionSpinal Nerve DistributionAfter leaving the intervertebral foramen, a typical After leaving the intervertebral foramen, a typical

spinal nerve splits into branches called rami. spinal nerve splits into branches called rami. Each ramus contains both sensory and Each ramus contains both sensory and motor neurons!motor neurons!

The The posterior (dorsal) ramusposterior (dorsal) ramus is the smaller of is the smaller of the two main branches and innervates intrinsic the two main branches and innervates intrinsic muscles of the back and the skin of the back.muscles of the back and the skin of the back.

The The anterior (ventral) ramusanterior (ventral) ramus is the larger of the is the larger of the two main branches. Each innervates the body two main branches. Each innervates the body wall tissues and makes up the nerves of the wall tissues and makes up the nerves of the Peripheral Nervous System (PNS). Peripheral Nervous System (PNS). Examples: Sciatic N, Superior gluteal NExamples: Sciatic N, Superior gluteal N

Spinal Nerve DistributionSpinal Nerve Distribution

• Additional rami, the Additional rami, the rami rami communicantescommunicantes, extend between the , extend between the spinal nerves and the paired spinal nerves and the paired sympathetic trunks. These provide sympathetic trunks. These provide communication between somatic and communication between somatic and autonomic parts of the nervous system.autonomic parts of the nervous system.