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