Spinal Anatomy Flashcards
How may vertebra?
33
Cervical vertebra?
Thoracic vertebra?
Lumbar vertebra?
- C1-C7
- T1-T12
- L1-L5
What do we hope to feel when palpating back for spinal/epidural?
Spinous process of the vertebra
What do intervertebral foramina allow for?
Passage of nerves - intervertebral discs can become damaged and compressed and pressure can be exerted on the nerves = pain/paresthesia
What forms facet joint when vertebrae are stacked?
Superior and inferior articulate surfaces and lateral notches
Which spinous processes are more angled and require more cephalad angle for needle?
Cervical and thoracic
Which vertebra are larger, have less overlap, larger gaps, and are easier to place needles?
Lumbar vertebra
What is the Sacral Hiatus? Where is it found?
Incomplete lamina of last vertebra, bridged only by ligaments
- Found in sacrum
What is the bony process of he sacrum that allows ID of sacral hiatus??
Sacral cornu
Why is the sacral hiatus and sacral Cornu useful?
Caudal block
What is a scoliosis?
Lateral curvature
What is a kyphosis?
Posterior curvature
What is a lordosis?
Anterior curvature
What is the strong cord like ligament that connects apices of spinous processes?
Supraspinous ligament
What is the major ligament of the cervical and upper thoracic regions?
Supraspinous ligament
What is the thin ligament that runs between adjacent spinous processes?
Intraspinous ligament
Which ligament is absent or poor quality in cervical region and can be extremely thin in lumbar?
Intraspinous
Which is the strongest ligament that joins the vertebral arches through vertical extensions from adjacent lamina?
Ligamentum Flavum
T/F: Ligamentum Flavum is paired ligaments that overlap between each lamina and appears as a contiguous ligament?
True
Which ligaments cover the anterior and posterior portion of the vertebrae?
Anterior and Posterior Longitudinal Ligaments
What is the space between the ligamentum flavum and the dura mater?
Epidural space
What is the depth of epidural space (potential space), for lumbar, thoracic, cervical?
- midlumbar = 5-6 mm
- thoracic = 3-5 mm
- cervical 1.5-2 mm
What 5 things are found in the epidural space?
- Veins
- Fat
- Lymphatics
- Segmental arteries
- Nerve roots
__A__ veins are valveless, form a plexus being most prominent __B__.
They become engorged during ___C___ and with ___D____.
A. Epidural
B. Laterally
C. Pregnancy
D. Obesity
How far is the epidural space from the distance of the skin?
Average 5 cm midlumbar approach
- varies with level and weight
Where does spinal cord start and end?
- Starts in medulla oblongata
- Ends in adults = L2
- Ends in peds = L3
What are the 3 meningeal layers of the spinal cord?
- Dura mater
- Arachnoid mater
- Pia mater
Which layer of spinal cord holds CSF?
Arachnoid mater
How many total pairs of spinal nerves?
- Cervical?
- Thoracic?
- Lumbar?
- Sacral?
- Coccygeal?
- 31 total pairs
- Cervical = 8
- Thoracic = 12
- Lumbar = 5
- Sacral = 5
- Coccygeal = 1
Where does the first spinal nerve exit?
Between the base of skull and atlas
Where does 8th cervical spinal nerve exit?
Between C7 and T1
Cervical spinal nerves correlate with vertebrae __A__ them. Thoracic spinal nerves correlate with vertebrae __B__ them.
Cervical spinal nerves = A. Below vertebrae
Thoracic spinal nerves = vertebra B. Above
Where does the brachial plexus in relation to the spinal cord?
C4-T1
Where is the lumbar and sacral plexus in relation to the spinal cord?
L2-S3
What consists of long roots of lumbar and sacral nerves and extends from L1-S5?
Cauda Equina
Where does the cauda equina extend from?
L1-S5
What regions is the spinal cord divided into (3)?
- Dorsal
- Ventral
- Lateral
What is contained in the “gray matter” of the spinal cord?
Neuronal cell bodies and unmyelinated fibers
What is contained by the white matter of the spinal cord?
Fiber tracts
What region of the spinal cord contains the sensory root?
Dorsal region (sensory = afferent = toward CNS)
What region of spinal cord contains the motor root?
Ventral region = motor = efferent = leaving CNS
What Rexed Lamina is very important to anesthesia? Name and why?
- Laminae II - “Substancia Gelatinosa”
- Laminae II involves spinothalamic Tract & dorsal tract
- spinothalamic tract relays information about PAINFUL stimuli to brain
- There are a large number of OPIATE RESPONSIVE neurons in Laminae II
Rexed Laminae I - VI contain what?
Afferent tracts = receive sensory information from periphery
Rexed Laminae VII - IX contain what (2)?
- Motor neurons
- interneurons involved in motor functions
T/F: Rexed Laminae are organized according to anatomical location
FALSE - Rexed Laminae are organized based on the types of functions of neurons in each lamina
When looking at a cross section of the spinal cord, how can you tell what is posterior and anterior?
- Posterior gray matter is “thinner winged” (containing room for dorsal column) also contains posterior medial sulcus
- Anterior contains anterior median fissure (gap between white matter)
What contains almost exclusively ascending sensory fiber tracts?
Dorsal white matter
What contains descending motor tracts?
Lateral and ventral white matter
What 6 things do sensory pathways transmit?
- Pain
- Temp
- Pressure
- Touch
- Vibration
- Proprioception
Are sensory pathways afferent or efferent?
Do they ascend or descend?
Sensory = afferent = ascend
Where are receptors for pain, and temp for sensory pathways located?
Epidermis and dermis
Where are receptors located for pressure, touch, vibration, and proprioception for sensory pathways?
Dermis
What are 2 types of receptors of sensory pathways to know?
- Exteroceptors= near surface of skin and oral mucosa
2. Proprioceptors = deeper skin layers, joint capsules, ligaments, tendons, muscles, and periosteum
Describe the path for Dorsal Column - Medial Lemniscus pathway?
- Carries signal in dorsal column tract (up toward the medulla)
- Crosses over at medulla
- Carries signal in medial lemniscus tract (through brainstem to thalamus)
- To brain to interpret
Where does signal cross over in dorsal column-medial lamniscus pathway?
at the medulla
Describe fibers for dorsal column-medial lemniscus pathway: size? Myelination? Speed? Spatial orientation
- Large
- Myelinated
- Conduction speed 30 - 110 m/sec
- High with respect to origin
What does dorsal column- medial lemniscus pathway provide (2)?
Spatial orientation and discrete types of mechanoreceptive sensations
Describe the anterolateral pathway:
- Originates in dorsal horn to Laminae I, IV, V, VI
- Synapse and immediately cross over in anterior commisure to anterior and lateral white columns
- Ascend to the brain through associated tract (anterior spinothalamic or lateral spinothalamic)
- Goes to brainstem or thalamus (for interpretation)
Describe the fibers of the anterolateral pathway: size? myelinated? Speed? Spatial orientation?
- Small
- Myelinated
- Few to 40 m/s
- Low with respect to origin
What type of sensations does anterolateral pathway detect?
Pain, warmth, cold, crude touch, sexual sensations
Which mentioned sensory pathway crosses over at the medulla?
Dorsal Column-Medial Lemniscus
Which mentioned pathway crosses over immediately in anterior commissary to anterior and lateral white columns?
Anterolateral pathway
What type of nerve fibers are preganglionic neurons of the SNS?
B fibers - small
Where do SNS preganglionic neurons originate?
Intermediolateral gray horn - between T1-L2/L3
How do the preganglionic SNS neurons exit the spinal cord?
Ventral nerve root — white rami communicans
What are the white rami communicans? Where are they located?
Carry preganglionic sympathetic fibers to the sympathetic chain —> contain both myelinated and unmyelinated preganglionic sympathetic fibers
- from each thoracic and L1 and L2
What are sympathetic trunks composed of?
Series of paired segmental paravertebral ganglia
What are paravertebral ganglia?
Interconnected autonomic ganglia that lie close to spinal nerves and vertebrae from low cervical/upper thoracic level, to sacral level of spinal cord
Define preganglionic:
Originates in brain stem or spinal cord
Define postganglionic
Lies outside of the CNS
What are the 4 stages of pain transmission?
- Transduction (noxious stimuli)
- Transmission (through primary afferent nocioreceptor)
- Modulation (synapse at dorsal horn gray matter)
Crosses to contralateral side and goes up spinothalamic tract - Perception (in the brain cortex)
What are the three divisions of Cervical Ganglia?
- Superior
- Medial
- Inferior
What occurs with stimulation of SNS fiber in the Superior Cervical ganglia?
- Myadriasis (radial muscle of iris contraction = dilated pupil)
- Relaxation of the ciliary muscle (eye)
- Constriction of blood vessels in the head
What causes Horne’s Syndrome (3)?
- Damage to superior cervical ganglia
- Central SNS damage
- Injury to other cervical paravertebral ganglia
What are the symptoms of Horner’s syndrome?
- Miosis (small pupil)
- Ptosis (drooping eyelid)
- Anhydrosis (lack of sweating)
What are the 2 components of the Stellate ganglia? Where is it located?
Inferior cervical ganglia + first thoracic ganglion
Located C5-C6
What fibers are part fo the reflex response to pain and temp?
- Dorsal horn branches synapse with internuncial (messenger) neurons
- Synapse with motor neurons in ventral horn
- Able to cross over and travel up or down before synapsing
Do dermatomes involve afferent or efferent neurons?
Afferent from limited areas of the skin
T-4 dermatome
Nipple line
T-6/7 dermatome:
Xiphoid process
T-10 dermatome
Umbilicus
Describe a basic motor pathway:
Efferent (exit) - info from brain to voluntary muscles, smooth and cardiac muscles and some glands
What does the corticospinal tract supply?
Where does it originate?
- Supplies: voluntary muscles of TRUNK and EXTREMITIES
- Originates: Large, upper motor neurons in the precentral gyrus
The Corticospinal tract travels from the __A__ through the __B__ (__C__) through the __D__ to the __E__
A. Precentral gyrus B. Internal capsule C. Anterior limb D. Midbrain E. Medulla
Corticospinal tract is sometimes referred to as:
The pyramidal tract
What happens after the Corticospinal tract crosses over in the medulla
Descend the spinal cord
Enter ventral horn
Synapse with lower motor neurons at designated level
__A__% of the Corticospinal tract crosses in the __B___ forming ___C___
A. 90%
B. Medulla
C. Pyramids of medulla
What happens to the 10% of neurons of Corticospinal tract that dont’ cross at the medulla?
They continue down the ventral Corticospinal tract
Where do the ventral Corticospinal tract neurons cross over?
What do the travel in to innervate voluntary muscle?
- before synapsing with lower motor neurons in the gray matter
- travel in spinal nerves to innervate voluntary muscle
What do the few Corticospinal tract runeurons that are located anterior to the precentral gyrus do?
They have inhibitory effects on the lower motor neurons to prevent excessive discharge
Damage to inhibitor Corticospinal tract neurons can cause what 2 things?
- Hyperreflexia = over firing
2. Spasticity = firing simultaneously
What 3 things happen with upper motor neuron paralysis?
- Reflexes remain intact
- Suppressor fibers impeded
- Hyperreflexia occurs
What happens when lower motor neurons are damaged?
Produce flaccid type paralysis
Which tract do cerebral palsy and ALS effect?
Corticospinal tract
What is the pain and temperature spinal tract?
Ipsilateral or contralateral? Where?
Lateral spinothalamic
- contralateral
- crosses dorsal gray to lateral white (2nd neuron)
What is the light touch and pressure tract?
Ipsilateral/contralateral? Where?
- anterior spinothalamic tract
- contralateral
- crosses at dorsal gray to anterior white (2nd neuron)
What is the discriminatory touch, vibration, proprioception pathway?
Ipsilateral/contralateral? Where?
“Dorsal Column Tract” aka f. Gracilis and cuneatus tract (post. White)
- ipsilateral - ascends up dorsal gray (same side) then crosses at brain stem (synapse)
- also synapses with 3rd neuron in thalamus to cerebral cortex
Where do all 3 ascending pathways end in the brain?
Cerebral cortex (opposite side of stimulation) in the somatosensory area
What is the motor/efferent, descending tract?
Contralateral/ipsilateral side?Where?
Corticospinal tract
- contralateral side
- crosses at lower medulla (pyramids) to the lateral white tract
- 1st order neuron goes from brain and descends to anterior gray horn at level of innervation