Spinal Cord Anatomy and Function Quiz
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Questions and Answers

What does a dermatome indicate when it shows loss of sensation?

  • Injury to only the skin surface
  • Total loss of muscle function
  • Complete spinal cord injury
  • Potential damage to one or more spinal nerves (correct)

How is referred visceral pain connected to dermatomes?

  • It always indicates a muscle injury
  • It is unrelated to spinal nerves
  • It can travel through the same nerve pathways (correct)
  • It is only relevant for pain in the limbs

What effect does damage to a single spinal nerve have on muscle or skin regions?

  • Total loss of sensation in the area
  • Partial loss of innervation, preserving some function (correct)
  • Loss of innervation to the entire muscle
  • No effect whatsoever

Which of the following is NOT one of the main nerve plexuses?

<p>Thoracic plexus (A)</p> Signup and view all the answers

What is the primary function of a nerve plexus?

<p>To form a network of interweaving spinal nerves (B)</p> Signup and view all the answers

What is the function of the posterior horn in the spinal cord?

<p>It relays sensory information to the brain. (C)</p> Signup and view all the answers

Which structure primarily separates the left and right sides of the spinal cord?

<p>Anterior median fissure (A)</p> Signup and view all the answers

Where is the gray matter primarily located in the spinal cord?

<p>Surrounding the central canal (B)</p> Signup and view all the answers

Which part of the spinal cord anatomy is involved in autonomic functions?

<p>Lateral horn (B)</p> Signup and view all the answers

What does the term 'funiculus' in the spinal cord refer to?

<p>A section of white matter containing ascending and descending fibers. (A)</p> Signup and view all the answers

Which anatomical structure is NOT part of the central canal's surrounding gray matter?

<p>Lateral funiculus (A)</p> Signup and view all the answers

What type of matter primarily contains myelinated axons?

<p>White matter (C)</p> Signup and view all the answers

Which of the following is NOT part of the gray matter in the spinal cord?

<p>Central canal (B)</p> Signup and view all the answers

What structure is contacted first when performing a lumbar puncture?

<p>Skin (D)</p> Signup and view all the answers

Which letter identifies the cervical plexus branch responsible for innervating the diaphragm?

<p>C5 (D)</p> Signup and view all the answers

Which of the following contributes to the formation of the ansa cervicalis?

<p>C1 and C2 (A)</p> Signup and view all the answers

What condition is characterized by reactivation of the chickenpox virus?

<p>Shingles (C)</p> Signup and view all the answers

What is the primary purpose of prompt steroid administration after spinal cord injuries?

<p>To reduce function loss (D)</p> Signup and view all the answers

Which of the following does NOT describe a symptom of shingles?

<p>Muscle paralysis (B)</p> Signup and view all the answers

What is the advantage of using neural stem cells post-spinal cord injury?

<p>To regenerate CNS axons (B)</p> Signup and view all the answers

Which nerve responsible for sensory innervation is NOT part of the cervical plexus?

<p>Hypoglossal nerve (D)</p> Signup and view all the answers

What is the primary composition of gray matter in the spinal cord?

<p>Neuron cell bodies, dendrites, and unmyelinated axons (C)</p> Signup and view all the answers

Which section of the spinal cord contains autonomic motor neurons?

<p>Lateral horns only (B)</p> Signup and view all the answers

What do the dorsal rootlets primarily contain?

<p>Sensory neuron axons (A)</p> Signup and view all the answers

What structure connects the left and right sides of the gray matter in the spinal cord?

<p>Gray commissure (B)</p> Signup and view all the answers

Which type of nuclei in the posterior horn are responsible for receiving signals from skin and muscles?

<p>Somatic sensory nuclei (B)</p> Signup and view all the answers

The anterior funiculus of the spinal cord contains which types of tracts?

<p>Both ascending and descending tracts (A)</p> Signup and view all the answers

What shape does the gray matter in the spinal cord typically resemble?

<p>An 'H' or butterfly shape (B)</p> Signup and view all the answers

What is contained within the white matter of the spinal cord?

<p>Myelinated axons (D)</p> Signup and view all the answers

How many pairs of spinal nerves are present in the human body?

<p>31 pairs (D)</p> Signup and view all the answers

Which spinal nerves are considered part of the cervical plexus?

<p>C1 to C8 (B)</p> Signup and view all the answers

Which number of thoracic nerves is present in the spinal cord?

<p>12 (A)</p> Signup and view all the answers

What is the correct identification for the coccygeal nerve?

<p>Co1 (C)</p> Signup and view all the answers

Which of the following correctly describes how C1 to C7 spinal nerves emerge?

<p>Above their corresponding vertebrae (B)</p> Signup and view all the answers

What does the term 'conus medullaris' refer to in the spinal cord anatomy?

<p>The termination of the spinal cord (B)</p> Signup and view all the answers

Which anatomical part is associated with lumbar plexus?

<p>L1 to L5 (C)</p> Signup and view all the answers

What type of axons do spinal nerves contain?

<p>Both sensory and motor axons (B)</p> Signup and view all the answers

What does 'filum terminale' refer to in spinal cord anatomy?

<p>The connective tissue that anchors the spinal cord (B)</p> Signup and view all the answers

Which of the following is true regarding the sacral plexus?

<p>It includes spinal nerves S1 to S5 (B)</p> Signup and view all the answers

Which cranial nerve is primarily responsible for sensation in the face?

<p>Trigeminal nerve (CN V) (B)</p> Signup and view all the answers

Which of the following dermatomes corresponds to the C6 nerve root?

<p>C7 (D)</p> Signup and view all the answers

According to Hilton's Law, what does a nerve serving a muscle that produces movement at a joint also innervate?

<p>The joint and the skin over that joint (D)</p> Signup and view all the answers

Which spinal nerve roots contribute to the upper limb sensation?

<p>C3 to T2 (C)</p> Signup and view all the answers

What is the primary function of the trigeminal nerve?

<p>Sensation of the face and motor control of chewing (B)</p> Signup and view all the answers

Which nerve root does NOT correspond to the lumbar region?

<p>S1 (B)</p> Signup and view all the answers

Which nerve fibers are responsible for transmitting sensory information from the skin over a joint?

<p>Somatic sensory fibers (C)</p> Signup and view all the answers

Which of the following best describes the innervation pattern of muscles and joints according to Hilton's Law?

<p>A muscle's nerve also supplies the joint it acts upon (B)</p> Signup and view all the answers

Which spinal nerve roots are primarily involved in providing sensation to the areas of the upper arm?

<p>C5 and C6 (B)</p> Signup and view all the answers

Which area is NOT typically supplied by the C5 nerve root?

<p>Medial forearm (B)</p> Signup and view all the answers

What region does the C8 nerve root primarily innervate?

<p>Medial forearm and hand (B)</p> Signup and view all the answers

In terms of dermatome mapping, which region is primarily supplied by T10?

<p>Abdomen (B)</p> Signup and view all the answers

Which of the following describes a typical consequence of an injury to the C7 nerve root?

<p>Loss of sensation in the lateral hand (C)</p> Signup and view all the answers

Hilton's law implicates which type of relationship between joint, muscle, and skin innervation?

<p>A shared nerve for all three structures (C)</p> Signup and view all the answers

Flashcards

Spinal Nerve Rami

Immediately after a spinal nerve emerges from the spinal cord, it branches into two main divisions called rami: the dorsal ramus and the ventral ramus.

Dorsal Root

The dorsal root carries sensory information from the body to the spinal cord. It contains axons of sensory neurons and the dorsal root ganglion.

Ventral Root

The ventral root carries motor commands from the spinal cord to muscles and glands. It contains axons of motor neurons.

Gray Matter in Spinal Cord

Gray matter in the spinal cord is made of neuronal cell bodies, dendrites, unmyelinated axons, and glial cells. It appears as an "H" or butterfly shape in cross-section.

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Anterior Horns

The anterior horns house the cell bodies of somatic motor neurons, which control voluntary movements of skeletal muscles.

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Lateral Horns

The lateral horns, only present in thoracic and lumbar regions (T1-L2), contain cell bodies of autonomic motor neurons, which control involuntary functions like heart rate and digestion.

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Posterior Horns

The posterior horns contain axons of sensory neurons and cell bodies of interneurons. They receive sensory information from the body.

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White Matter in Spinal Cord

White matter in the spinal cord consists of myelinated axons that transmit signals to and from the brain. It surrounds the gray matter.

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Spinal Cord Parts

The spinal cord is divided into five regions: cervical, thoracic, lumbar, sacral, and coccygeal. Each region contains nerves that control specific body functions.

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Cervical Plexus

A network of nerves formed by the first four cervical nerves (C1-C4). It supplies the neck, shoulders, and diaphragm.

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Brachial Plexus

A network of nerves formed by the lower four cervical nerves (C5-C8) and the first thoracic nerve (T1). It supplies the arms, hands, and shoulders.

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Lumbar Plexus

A network of nerves formed by the lumbar nerves (L1-L4). It supplies the lower abdomen, hips, thighs, and knees.

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Sacral Plexus

A network of nerves formed by the sacral nerves (S1-S4). It supplies the buttocks, legs, and feet.

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Cauda Equina

A bundle of nerves that extends from the end of the spinal cord in the lower lumbar and sacral regions. It resembles a horse's tail.

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Conus Medullaris

The tapered end of the spinal cord, located in the lumbar region.

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Filum Terminale

A thin, fibrous extension of the pia mater (innermost spinal cord membrane) that anchors the spinal cord to the coccyx bone.

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Spinal Nerves

31 pairs of nerves that emerge from the spinal cord. Each nerve contains both sensory and motor axons, responsible for communication between the brain and the body.

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Odd Numbering System

Cervical nerves C1 to C7 exit ABOVE the corresponding vertebra, while C8 exits BELOW the C7 vertebra.

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Gray Matter

Found in the spinal cord, it's made up of neuron cell bodies, dendrites, unmyelinated axons, and glial cells. It's responsible for processing information and generating responses.

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White Matter

Surrounding the gray matter in the spinal cord, it's made up of myelinated axons that transmit signals to and from the brain.

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Central Canal

A fluid-filled channel that runs the length of the spinal cord, it's filled with cerebrospinal fluid (CSF).

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Anterior Median Fissure

A deep groove on the ventral side of the spinal cord, it separates the two halves of the spinal cord.

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Posterior Median Sulcus

A shallow groove on the dorsal side of the spinal cord, it separates the two halves of the spinal cord.

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Dermatome

A specific area of skin innervated by a single spinal nerve. Damage to a spinal nerve can result in loss of sensation in the corresponding dermatome.

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Referred Visceral Pain

Pain originating from an internal organ that is perceived as coming from a different area of the body, usually a dermatome.

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Nerve Plexus

An intricate network formed by interweaving anterior rami (branches) of spinal nerves.

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Anterior Rami

The ventral branches of spinal nerves, responsible for supplying motor and sensory function to the limbs and trunk.

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Lumbar Puncture

A medical procedure involving inserting a needle into the subarachnoid space of the spinal cord to obtain cerebrospinal fluid (CSF).

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Spinal Cord Injuries

Damage to the spinal cord that can result in paralysis, sensory loss, and impaired bodily functions.

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Shingles

A painful viral infection caused by the reactivation of the chickenpox virus, which can cause a rash and blisters along the dermatome.

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Posterior Root Ganglia

Clusters of sensory neuron cell bodies located along the dorsal root of spinal nerves.

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Neural Stem Cells

Undifferentiated cells in the central nervous system that have the potential to develop into different types of nerve cells.

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What is a dermatome?

A dermatome is a specific area of skin that receives sensory input from a single spinal nerve root.

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Which spinal nerve root innervates the skin of the thumb?

The C6 spinal nerve root innervates the skin of the thumb.

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What is the dermatome for the little finger?

The C8 spinal nerve root innervates the skin of the little finger.

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Which dermatome covers the skin of the anterior thigh?

The L2 spinal nerve root covers the skin of the anterior thigh.

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What spinal nerve root innervates the skin of the big toe?

The L5 spinal nerve root innervates the skin of the big toe.

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Which dermatome covers the skin of the lateral calf?

The S1 spinal nerve root covers the skin of the lateral calf.

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What is Hilton's Law?

Hilton's Law states that a nerve supplying a muscle that moves a joint also innervates the joint and the skin overlying the joint.

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How does Hilton's Law relate to dermatomes?

Hilton's Law helps explain how different dermatomes overlap and contribute to sensory innervation of specific joint regions.

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What is the trigeminal nerve (CN V)?

The trigeminal nerve is the fifth cranial nerve, responsible for sensation in the face and motor control of chewing muscles.

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How does the trigeminal nerve relate to dermatomes?

The trigeminal nerve doesn't follow a dermatome pattern like spinal nerves, but its branches do provide sensation to specific facial regions.

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What happens if a spinal nerve root is damaged?

Damage to a spinal nerve root can lead to sensory loss in the corresponding dermatome, weakness or paralysis in the muscles it innervates, and potentially reflex changes.

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Why are dermatomes clinically important?

Dermatomes help diagnose neurological conditions like spinal cord injuries, nerve compression, and certain diseases like shingles.

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What is the difference between sensory and motor dermatomes?

A sensory dermatome corresponds to the area of skin innervated by a single spinal nerve root for sensory information. A motor dermatome refers to the muscles innervated by that same spinal nerve root.

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What is the clinical significance of overlapping dermatomes?

The overlap between dermatomes help protect against complete sensory loss if one nerve root is damaged, as other nearby nerve roots can take over some of the function.

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How can you test a patient's dermatomes?

You can test a patient's dermatomes by lightly touching or pricking different areas of skin and asking the patient if they feel it. This helps assess sensory function of various nerve roots.

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Study Notes

Chapter 14: Spinal Cord and Spinal Nerves

  • Spinal cord provides a vital link between the brain and body
  • Spinal cord exhibits functional independence from the brain
  • Spinal cord and spinal nerves are a pathway for sensory and motor nerve signals
  • Spinal cord and spinal nerves are responsible for reflexes and quick reactions to stimuli
  • Spinal cord extends from brain through vertebral canal to L1 vertebrae
  • Spinal cord has rootlets that form spinal nerves
  • Some spinal nerves form nerve plexuses

Words to Know

  • Neuro = nerve
  • Epi = above
  • Sub = below
  • Inter = between
  • Myelo = spinal cord
  • -plegia = paralysis
  • Encephalo = brain
  • Duro = dura mater

Organization of the Nervous System

  • Central nervous system (CNS): brain and spinal cord
  • Peripheral nervous system (PNS): nerves and ganglia
  • Sensory nervous system: detects stimuli and transmits information from receptors to CNS
  • Motor nervous system: initiates and transmits information from the CNS to effectors
  • Somatic sensory: consciously perceived input
  • Visceral sensory: not consciously perceived input from blood vessels and internal organs
  • Somatic motor: consciously or voluntarily controlled motor output (skeletal muscle)
  • Autonomic motor: not consciously controlled motor output; involuntary (cardiac muscle, smooth muscle, glands)

Synapses

  • Presynaptic neuron: neuron sending signals
  • Postsynaptic neuron: neuron receiving signals
  • Chemical synapse: uses neurotransmitters (EPSP= excitatory postsynaptic potential, IPSP= inhibitory postsynaptic potential)

Nervous System Terms

  • Ganglion: cluster of neuron cell bodies in PNS
  • Center: group of CNS neurons with common function
  • Nucleus: CNS center with distinct anatomic boundaries
  • Nerve: bundle of axons in PNS
  • Nerve plexus: nerve network
  • Tract/fasciculi: CNS axon bundle with similar function and common origin and destination
  • Funiculus: groups of tracts in the spinal cord
  • Pathway: centers with their associated tracts
  • Decussation: tract that crosses between sides of the CNS

Spinal Cord Gross Anatomy

  • Spinal cord extends inferiorly from brain through vertebral canal
  • Ends at the level of L₁ vertebra
  • Rootlets come off spinal cord, forming spinal nerves
  • Some spinal nerves form interweaving nerves (plexuses)
  • Cervical, thoracic, lumbar, sacral, and coccygeal subdivisions
  • Cervical part: superiormost part of spinal cord; continuous with medulla oblongata; contains neurons contributing to cervical spinal nerves
  • Thoracic part: inferior to cervical part; contains neurons for thoracic spinal nerves
  • Lumbar part: short section inferior to thoracic; contains neurons for lumbar spinal nerves
  • Sacral part: inferior to lumbar; contains neurons for sacral spinal nerves
  • Coccygeal part: most inferior part of spinal cord; contains neurons for single pair of coccygeal nerves

Spinal Cord Subdivisions (Continued)

  • Conus medullaris: tapering end marking end of spinal cord proper
  • Cauda equina: nerve roots projecting inferiorly from the cone
  • Thin strand of pia mater anchors conus medullaris to coccyx

Spinal Nerves (31 pairs)

  • Contain sensory and motor axons
  • Identified by first letter of spinal cord part and number (e.g., C1-C8, T1-T12, L1-L5, S1-S5, Co1)

Odd Numbering System

  • C1-C7 emerge above the vertebrae named for
  • All others emerge below their named vertebrae

Spinal Cord Features

  • Cervical enlargement: wider part of spinal cord in cervical region, due to neurons that innervate the upper limbs
  • Lumbosacral enlargement: wider part of spinal cord in lumbar region, due to neurons that innervate the lower limbs

Protection and Support of the Spinal Cord

  • Spinal meninges encapsulate the spinal cord (continuous with cranial meninges)
  • Vertebra
  • Epidural space
  • Dura mater
  • Subdural space
  • Arachnoid mater
  • Subarachnoid space
  • Pia mater

Spinal Nerves

  • Dorsal/posterior root: sensory (afferent) fibers
  • Ventral/ anterior root: motor (efferent) fibers
  • Spinal nerves are short, combining dorsal/ posterior and ventral/ anterior roots

Sectional Anatomy of Spinal Cord

  • Gray matter: neuron cell bodies, dendrites, unmyelinated axons, and glial cells
  • Looks like an "H" or butterfly
  • Masses of gray matter project from center of spinal cord (anterior horns, lateral horns, posterior horns)
  • Anterior horns house somatic motor neurons
  • Lateral horns house autonomic motor neurons
  • Posterior horns house axons of sensory neurons and cell bodies of interneurons

Gray Matter and White Matter Organization in the Spinal Cord

  • White matter: myelinated axons to and from the brain
  • Regions of white matter: posterior funiculus, lateral funiculus, anterior funiculus

Spinal Cord Conduction Pathways

  • Conduction pathways characteristics: includes paired tracts, composed of multiple neurons, common locations of neuronal bodies and axons, and decussation
  • Sensory pathways (ascending): signals from sensory receptors to the brain
  • Motor pathways (descending): signals from the brain to muscles or glands

Sensory Pathways

  • Primary neuron: first neuron in sensory pathway, axon projects to secondary neuron within CNS
  • Secondary neuron: interneuron, projects to thalamus or cerebellum, axon projects to tertiary neuron
  • Tertiary neuron: interneuron residing in thalamus, axon projects to primary somatosensory cortex

Motor Pathways

  • Upper motor neuron: within cerebral cortex or brainstem nuclei; innervates lower motor neuron
  • Lower motor neuron: within anterior horn of spinal cord or brainstem nuclei; exits CNS and projects to skeletal muscles, always excitatory

Spinal Cord Conduction Pathways: Motor

  • Direct/pyramidal pathways: use chain of 1 or 2 motor neurons to communicate signals, lateral and anterior corticospinal tracts
  • Indirect pathways: responsible for subconscious or unconscious control, regulates and controls precise, discrete movements, related to flexor and extensor muscles

Spinal Nerves Characteristics, Distribution, and Rami

  • Spinal nerves are formed from multiple roots.
  • Contain motor and sensory axons, enveloped in connective tissues.
  • Posterior ramus: smaller, innervates deep muscles of back, skin of back
  • Anterior ramus: larger, innervates anterior and lateral trunk, upper limbs and lower limbs
  • Rami communicantes: connect spinal nerves to sympathetic trunk ganglion and sympathetic nervous system
  • Dermatomes: specific segment of skin supplied by a single spinal nerve
  • Hilton's Law: nerve serving a muscle that produces movement also innervates the joint and skin over the joint.

Clinical Views

  • Lumbar puncture
  • Spinal cord injuries (may lead to paralysis and loss of sensation)
  • Shingles (reactivation of chickenpox virus)

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Description

Test your knowledge on spinal cord anatomy, including the significance of dermatomes, nerve plexuses, and gray matter. This quiz covers crucial functions of different spinal structures and their impact on sensation and autonomic functions. Ideal for students or enthusiasts in anatomy and physiology!

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