ONE1_03_Spinal_Anatomy
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Transcript ONE1_03_Spinal_Anatomy
Dr. Michael P. Gillespie
Kyphosis – exaggeration of the thoracic curve
Lordosis – an exaggeration of the lumbar curve or
cervical curve
Lumbar spine stenosis – narrowing of the spinal
canal
Scoliosis – lateral bending of the vertebral column
Bony vertebrae
Meninges
Cerebrospinal fluid (produced in the brain)
The spinal cord is located within the vertebral canal of
the vertebral column.
The vertebral foramina form the canal.
The vertebrae form a shelter for the cord.
The vertebral ligaments, meninges and CSF also
provide protection.
White matter – contains the sensory and motor tracts
(“highways”).
Gray matter – site for integration (summing) of action
potentials.
Spinal nerves – connect the CNS to sensory receptors,
muscles, and glands.
Connective tissue coverings that encircle the spinal
cord and brain.
Spinal meninges.
Cranial meninges.
3 spinal meninges.
Dura mater (most superficial).
Epidural space – between dura mater and wall of vertebral canal.
Arachnoid mater (middle layer) – spider web
arrangement.
Subdural space – between dura and arachnoid.
Pia mater (innermost layer).
Subarachnoid space – between arachnoid and pia – contains
CSF.
Denticulate ligaments – extend from pia and fuse with
arachnoid.
Cervical enlargement – nerves to and from the upper
limbs
Lumbar enlargement – nerves to and from the lower
limbs
Conus medullaris – the spinal cord tapers to a conical
portion
Filum terminale – an extension of the pia mater that
anchors the spinal cord to the coccyx
Cauda equina “horse’s tail”
Spinal nerves – paths of communication between
the cord and the nerves innervating specific
regions of the body
Posterior (dorsal) root
Sensory nerve axons
Posterior (dorsal) root ganglion – swelling – cell bodies
Anterior (ventral) root
Motor nerve axons
Spinal tap (lumbar puncture).
Local anesthetic is given and a long needle is
inserted into the subarachnoid space.
Uses.
Withdraw CSF for diagnosis.
Introduce antiobiotics, contrast media, anesthetics.
Introduce chemotherapy.
Measure CSF pressure.
Anterior median fissure.
Posterior median sulcus.
Gray commissure – form the crossbar of the “H.”
Anterior (ventral) gray horns – cell bodies of somatic
motor neurons and motor nuclei.
Posterior (dorsal) gray horns - cell bodies of somatic
and autonomic sensory nuclei.
Lateral gray horns – cell bodies of autonomic motor
neurons that regulate smooth muscle, cardiac muscle
and glands.
Central canal – in the center of the gray
commissure.
White columns.
Sensory (ascending) tracts.
Motor (descending) tracts.
2 principle functions.
Nerve impulse propagation – white matter tracts.
Sensory impulses flow toward the brain.
Motor impulses flow from the brain.
Information integration – gray matter.
The name of the tract often indicates its position in
the white matter and where it begins and ends.
Lateral and anterior spinothalamic tracts.
Convey impulses for pain, warmth, tickling, itching,
deep pressure, and a crude sense of touch (poorly
localized).
Posterior columns.
Convey impulses for proprioception, discriminative
touch, 2 point discrimination, light pressure sensations,
and vibrations.
Direct pathways – convey precise voluntary
movements.
Lateral corticospinal.
Anterior corticospinal.
Corticobulbar.
Indirect pathways – govern automatic movements (I.E.
Reflexes).
Rubrospinal.
Tectospinal.
Vestibulospinal.
Reflex – a fast, unplanned sequence of actions that
occurs in response to a particular stimulus.
Location of integration.
Spinal reflex.
Cranial reflex – integration in brain stem.
Types of reflexes.
Somatic reflexes – contraction of skeletal muscles.
Autonomic (visceral) reflexes – responses of smooth
muscle, cardiac muscle, and glands.
Reflex arc (reflex circuit) - the pathway followed by
nerve impulses.
Sensory receptor.
Distal end of a sensory neuron.
Responds to a stimulus.
Sensory neuron.
Nerves terminate in the brain stem or spinal cord.
Integrating center.
Monosynaptic reflex arc - A synapse between a sensory
neuron and a motor neuron.
Polysynaptic reflex arc – one or more interneurons and a
motor neuron.
Motor neuron.
Effector.
The part of the body that responds to the motor nerve
impulse.
Somatic reflex – the effector is a skeletal muscle.
Autonomic reflex – the effector is smooth muscle, cardiac
muscle or a gland.
Reflexes are normally predictable.
They can provide information about the health of the
nervous system.
Damage or disease anywhere along the reflex arc can
cause the reflex to be absent or abnormal.
Somatic reflexes can be tested by tapping or stroking
the body surface.
Autonomic reflexes cannot be tested easily because
the visceral receptors are deep inside the body.
Stretch reflex
Tendon reflex
Flexor (withdrawal) reflex
Crossed (extensor) reflex
A stretch reflex causes contraction of a skeletal
muscle in response to stretching of the muscle.
Monosynaptic reflex arc.
Ipsilateral reflex.
This reflex helps avert injury by preventing
overstretching of a muscle.
Reciprocal inhibition – when the stretched muscle
contracts, the antagonistic muscle(s) relax.
The tendon reflex controls muscle tension by causing
muscle relaxation before muscle forces become so
great that they tear tendons.
Ipsilateral reflex.
Sensory receptors – tendon (Golgi tendon) organs.
Causes withdrawal from a painful stimulus.
This reflex causes contraction of the flexor
muscles with causes withdrawal from a painful
stimulus.
Ipsilateral reflex.
Several motor units at different levels of the spinal
cord are recruited – intersegmental reflex arc.
Reciprocal innervation occurs.
Helps you maintain balance.
Contralateral reflex arc.
Reciprocal innervation occurs.
The plantar flexion reflex is elicited by stroking
the lateral outer margin of the sole.
The normal response is curling under of the toes.
Babinski sign – the great toe extends – this
indicates damage to the descending motor
pathways.
The babinski sign is normal in children under 18
months due to incomplete myelination of the
axons.
The spinal nerve has two connections to the cord: a
posterior root and an anterior root.
The posterior and anterior roots unite to form a spinal
nerve at the intervertebral foramen.
The posterior root contains sensory axons and the
anterior root contains motor axons; Therefore, the
spinal nerve is a mixed nerve.
Endoneurium – surrounds individual axons.
Perineurium - surrounds bundles of axons called
fascicles.
Epineurium – surrounds the entire nerve.
After passing through the IVF, the spinal nerve forms
rami (branches).
Posterior (dorsal) ramus.
Anterior (ventral) ramus.
Meningeal branch.
Rami communicantes – serves the autonomic nervous
system.
A network of axons.
Principle plexuses:
Cervical plexus.
Brachial plexus.
Lumbar plexus.
Sacral plexus.
Coccygeal plexus.
The nerves have branches named for the
structures they innervate.
The cervical plexus supplies the skin and muscles of
the head, neck, and superior part of the shoulders and
chest.
The phrenic nerves arise from the cervical plexus and
innervates the diaphragm.
“C3, 4 & 5 keep the diaphragm alive.”
The brachial plexus provides the entire nerve supply of
the shoulders and upper limbs.
Major nerves:
Axillary nerve – supplies deltoid and teres minor mm.
Musculocutaneous nerve – supplies arm flexors.
Radial nerve – supplies posterior arm and forearm mm.
Median nerve – supplies anterior forearm mm and some
hand mm.
Ulnar nerve – supplies anteromedial mm of the forearm
and most of the hand muscles.
Known as “waiter’s tip position”.
Results from forceful pulling away of the head from
the shoulder.
Caused by improper intramuscular injections into the
deltoid or when the cast is applied too tightly around
the mid-humerus.
Indicated by wrist drop.
Numbness, tingling, and pain in the palm and fingers.
Inability to pronate the forearm.
Weak wrist flexion.
Inability to abduct or adduct the fingers.
Atrophy of the interosseous mm of the hand.
“Clawhand”.
Loss of sensation over the little finger.
Paralysis of the serratus anterior mm.
The scapula protrudes.
“Winged scapula”.
The lumbar plexus supplies the anterolateral
abdominal wall, external genitals, and part of the
lower limbs.
Femoral nerve injury.
Can be caused by a stab or gunshot wounds.
Inability to extend the leg and lost sensation.
Obturator nerve injury.
Complication of childbirth.
Paralysis of the adductor muscles of the leg and loss of
sensation.
The sacral plexus supplies the buttocks, perineum and
lower limbs.
The sciatic nerve originates here.
The coccygeal plexus supplies a small patch of skin in
the coccygeal region.
Injury to the sciatic nerve causes sciatica – pain the
extends from the buttock, down the posterolateral
aspect of the leg and to the foot.
Damage to the fibular nerve can cause:
Footdrop.
Equinovarus – inverted foot.
Calcaneovalgus – injury of the tibial portion of the
sciatic nerve resulting in dorsiflexion.
Specific segments of skin that are innervated by
specific spinal segments or specific cranial nerves.
The nerve supply in adjacent segments overlaps
somewhat.
Knowing which spinal segments supply each
dermatome allows us to determine the location of
nerve damage.
Meningitis – inflammation of the meninges.
Nerve block – loss of sensation in a region due to
injection of a local anesthetic.
Neuralgia – pain along the course of a sensory nerve.
Neuritis – inflammation of the nerves.
Paresthesia – abnormal sensation.