Anatomy - Unit 1 - Spine

4 tracts that enter spinal cord

- General Sensory Afferent (GSA) - somatic touch, pain, temp, and proprioception from skin to CNS - General Visceral Afferent (GVA) - sensory from organs to CNS - General Visceral Efferent (GVE) - motor to viscera - General Somatic Efferent (GSE) - motor to skeletal muscles

Spinal cord lesion at T5

- losing all dorsal column proprioception T5 down on side of injury - losing a lot of descending motor on side of injury - losing all info of pain and temp from T8 down on opposite side of injury (T6, T7 already crossed over) - Section of Lissaur compromised at T5 - loss from t5 to t8 on side of injury

Ribs will articulate at costal facet of body above and below

- rib # based on vertebrae below

Dura mater

- thick web like layer - outermost

How many columns located in white matter axons of spinal cord?

3 - Dorsal (Medial lemniscus system) - Lateral (Lateral corticospinal tract) - Ventral (Spinothalamic)

Veins of the vertebral column begin as plexus (that drains the spinal cord) How many posterior and anterior spinal veins?

3 posterior and 3 anterior - branches converge into segmental spinal vein

How many spinal nerves

31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

What percentage of head/neck rotation occurs at C1/C2?

50%

How many processes do typical vertebrae have?

7 2 transverse 1 spinous 4 articular (2 sup / 2 inf)

What is the subarachnoid space?

CSF

Dermatome and myotome segmentally innervate the back

Dermatome = sections of skin that are innervated by a single nerve Myotome = sections of muscles that are innervated by a single nerve

Groups of nerves within epineurium are called

Fascicles

Medial Lemniscus pathway (dorsal column) has tracts...

Fasciculus Gracilis (medial) - sensory form lower limb: legs, thorax and trunk Fasciculus Cuneatus (lateral - sensory from upper limb: hand, arms, and neck - exists only at cervical level ascending - touch and proprioception of joints ipsilateral - travels at same side that it enters ex.) left thigh info will travel up left side 3 neurons in pathway

Horns of spinal cord contain

Gray matter - Composed of nerve cell bodies, synapses

Pia mater

Innermost layer of the meninges - hugs spinal cord

Viscera

Involuntary - go to organs and blood vessels - Autonomic -- visceral motor

What level does the spinal cord end?

L1-L2

Which part of corticospinal tract has majority of fibers?

Lateral 85% - usually called Lateral Corticospinal Tract

2 main arteries supplying blood to spinal cord/vertebral column

Longitudinal spinal arteries: anterior and posterior Segmented spinal arteries: medullary and radicular

Dorsal column pathway carries what info

Medial Lemniscus system - ascending sensory info - touch and proprioception

Arachnoid layer

Middle layer - web like

Efferent

Motor, move from CNS to muscles/bones

Corticospinal tract (lateral and anterior )

Pyramidal tract - descending tract - voluntary motor control - ipsilateral pathway - 2 neurons (upper and lower motor) - upper = Inhibatory located in CNS - Lower = excitatory located in Anterior Horn of spinal cord

PNS

Sensory Motor

3 layers of intrinsic back muscles

Superficial - splenius capitus/cervicis Intermediate - erector spinae - primary back extensor muscles Transversospinalis group - all attach TP to SP - Semispinalis (4-6 segments) superficial - mutifidus (2-4 segments) - Rotatores (1-2) deepest

Common areas to know

T4 = nipple level T10 = umbilicus L1 = groin/inguinal L1-L2 = End of spinal cord

Cervical and lumbosacral enlargements

The nerves serving the upper and lower limbs emerge here

Defining characteristic of thoracic vertebrae

Transverse costal facets and demi costal facets

Lower motor neuron injury

Usually Excitatory so when damaged, have decreased function - flaccid muscle - major atrophy - decreased reflex - Fasciculations - spontaneous contractions under skin

Injury to upper motor neuron results in...

Usually inhibitory so if damage, causes increased function - increased muscle tone - minor atrophy - increased stretch reflex - Babinski = when bottom of foot stimulated, big toe goes up

Motor

Visceral motor - sympathetic (fight or flight) / parasympathetic (rest and digest) -involuntary responses Somatic motor - voluntary responses

Sensory

Visceral sensory Somatic Sensory

Somatic

Voluntary - go to muscles, and bones

A nerve is made up of?

a collection/group of axons

Filum Terminale

anchors spinal cord to coccyx covered in pia matter, one of only areas you can see pia matter

nucleus pulposus is surrounded by...

annulus fibrosus (ring)

Longitudinal spinal arteries give rise to

anterior and 2 posterior spinal arteries

Spinothalamic

ascending sensory info - pain and temp - ventral column - Lissauer's Tract

Lateral spinothalamic tract (Lissaur's Tract)

ascending tract - sensory pain and temp - contralateral pathway - axons come in, travel 3 levels up, THEN cross over - 3 neuron pathway

Dorsal root ganglion (DRG)

associated with the dorsal horns; cell bodies of sensory neurons are located here - of note, DRG branches into zygapophyseal joint (joint b/w articular processes on stacked vertebrae)

C1

atlas - no SP, no body - ring like - articulates with occipital bone and C2

C2

axis dens (odontoid process) - C1 rotates around C2 - Atlantoaxial joint - 50% of head rotation

Posterior intercostal artery

blood supply for erector spinae and transversospinalis gives rise to dorsal and ventral branches dorsal gives rise to intervertebral branches

CNS

brain and spinal cord

Secondary curvatures

cervical and lumbar

Cauda equina

collection of spinal roots below end of spinal cord and a spinal nerve, starting at L2

Ganglia

collections of neuron cell bodies outside brain or spinal cord (CNS) Autonomic ganglia = collections of post synaptic cell bodies

Gray and white rami are

communicating rami White rami = preganglionic sympathetic axons to trunk gray rami = postganglionic sympathetic axons back to nerve

Extrinsic muscles

connect upper limb to thorax - they DO NOT move back of trunk, ONLY move axillary limbs

Ligamentum Flavum

connects the laminae of adjacent vertebrae - posterior to spinal cord - yellow

autonomic

controls involuntary action of visceral motor

Upper motor neuron travels from

cortex down to ventral horn Lower motor neuron - goes from Ventral horn out to muscles

Thoracic vertebrae special feature

costal facets: transverse and demi - vertical articular facets that allow for rotation and lateral flexion

What are the wings off the pia mater called?

denticulate ligaments - made of pia mater

Lateral corticospinal tract

descending efferent motor control

Sensory Afferent info into which part of spinal cord?

dorsal - efferent = motor info out of Ventral

What is the blood supply branch for spinal cord, meninges, and vertebral arch?

dorsal branch of posterior intercostal artery

Rootlets converge to form

dorsal or ventral roots

Intrinsic muscles all innervated by...

dorsal rami of spinal nerves

Conus medullaris

end of spinal cord at L1-L2

Individual nerve fibers (axons) are surrounded by

endoneurium

Layers of skin

epidermis - skin dermis - skin hypodermis - superficial fat / subcutaneous tissue

Denticulate ligaments

extensions of pia mater that secure cord to dura mater - mostly seen in thoracic region of spinal cord

Fibers off the spinal cord are called

filaments or rootlets

Somatic Stretch Reflex

flexion - withdrawal reflex

Blood supply of back muscles

from intercostal muscles and segmentally supplied - all dorsal branches

Kyphosis

hunchback - excessive thoracic curvature (primary)

Parasympathetic nervous system found...

in brain, brain stem, and sacral gray S2-4

Sympathetic nervous system starts...

in lateral horns of spinal gray matter T1-L2 - Thoracolumbar

Cervical curvature forms when...

infant is able to hold head upright and stand - other curvatures form when able to stand

Dorsal rami innervates

intrinsic muscles and skin of back

Medullary branch connects directly to

longitudinal spinal artery

Segmented spinal arteries has two branches

medullary and radicular

Rami are...

mixed nerves - carry sensory and motor and autonomic ( visceral motor)

Posterior Longitudinal Ligament (PLL)

more narrow than ALL - widens over discs then narrows at body - located just posterior to body - Mainly see on inside of vertebral column

Ventral rami innervate

most of the body, including limbs EXCEPT head and parts of trunk

Ventral roots carry

motor info

General Visceral Efferent (GVE)

motor innervation to organs, smooth muscle, heart muscle, and glands

General Somatic Efferent (GSE)

motor to skeletal muscles

Motor nerves are uni or multipolar

multipolar - meaning single axon BUT multi dendrites for communication

Intrinsic muscles

muscles entirely within confines of back - cause motion at back/trunk

presynaptic neuron

neuron that sends the signal

Lumbar vertebrae

no transverse foramen. no costal facets - mammillary process on tip of superior articulating process - main movement is flexion/extension and very limited rotation

What is in the subdural space?

nothing. No actual space there unless trauma/bleeding occur ex. subdural hematoma

Inner part of IV disc is called?

nucleus pulposus - gelly like substance that takes the force and transmits it outwards to the ring

Epineurium

outermost layer of a nerve - connective tissue surrounding blood vessels

What is in the epidural space?

outside dura. Fat and veins

Fascicles surrounded by

perineurium

Where do sensory and motor roots enter spinal cord?

posterolateral sulcus - dorsal sensory entry anterolateral sulcus - ventral motor exit

Disc herniation tends to be in which direction?

posterolaterally - from nucleous to ring - commonly at L4. L5, AND S1

paravertebral ganglia

postsynaptic ganglia on the sympathetic chain ganglia

Radicular branch connects to

roots and rootlets

Where does the cauda equina sit?

sacral canal (superior part of sacrum) sacral hiatus - inf sacrum

General Visceral Afferent (GVA)

sensory from organs to CNS

Dorsal roots carry

sensory info

afferent

sensory, move towards CNS

Typical Cervical Vertebrae (C3-C7)

smaller bodies - larger vertebral foramina - *transverse foramen* - only cervical vertebrae have these - C2-6 bifid spinous processes - horizontal articular facets that allow for large range of movement

Anterior Longitudinal Ligament (ALL)

starts at occipital bone and descends to sacrum - *only lig to resist extension*

Lordosis

swayback - excessiver secondary lumbar curvature

prevertebral ganglia

sympathetic ganglia which lie between the paravertebral ganglia and the target organ - in periphery around some major blood vessels

Facet joints are what type of joint?

synovial - Zygapophyseal - plane joints - capsule and fluid

post-synaptic neuron

the neuron on the receiving end of the synapse

Nuchal ligament

thickened supraspinous ligament only in cervical region where trapezius muscle attaches - combo of interspinous and supraspinous ligs

Primary curvatures of spine

thoracic and sacral

General Sensory Afferent (GSA)

touch, proprioception, pain and temp from joints and muscles (somatic) to the CNS

Median fissure is located on which side of spinal cord?

ventral - opp side is dorsal median sulcus, dorsolateral sulcus, dorsal intermediate sulcus

C7

vertebra prominens - longest cervical spinous process and not a bifid spinous process

what travels through transverse vertebral foramen?

vertebral artery - which supplies occipital triangle, erector spinae and transversospinalis

Dark area of spinal cord contains

white matter - all axons