Module 3 Flashcards
- Part of the Central nervous system (CNS)
- 43 cm long, about the index finger in diameter
- Extends after the foramen magnum up to about L1-L2 vertebrae
- Cervical and lumbar enlargements for innervations to the limbs
- Narrowest and roundest at the thoracic region
- Extends caudally to end at about the level of L1 or L2 vertebrae as the conus medullaris
- Extends to the sacrum as a thin stand of glial tissue called filum terminale
SPINAL CORD
- From C4-T1 segments of spinal cord
- Most of the ventral rami of spinal nerves arising from it form the brachial plexus of nerves that innervates the upper limbs
Cervical enlargement
- From T11-L1 segments of spinal cord
- The ventral rami of the spinal nerves arising from it make up the lumbar and sacral plexuses of nerves that innervate the lower limbs
- The spinal nerve roots arising from lumbosacral enlargement and the medullary cone form the cauda equina
Lumbosacral enlargement
- Cephalad to the spinal cord as the foramen magnum is the most distal portion of the brain
Medulla Oblongata
- the distal or most inferior part of the spinal cord
Conus medullaris
- A continuous canal up to the coccyx
- Composed of the adjacent vertebrae
- Superior 2/3: spinal cord + spinal nerves
- Inferior 1/3: spinal nerves only (arranged collectively as the cauda equina
Vertebral Canal
- bundle of spinal nerve roots running through the lumbar cistern
cauda equina
All the tissue of the nervous system can be divided into:
- Neurons
- Supporting tissue
- Glial connective tissue
Supporting tissue
Fibrous connective tissue contains:
Fibrocytes
Collagen and elastic fibers
Intercellular fluid
Various other cells (e.g. Schwann cells)
Glial connective tissue
Consists of cells and intercellular fluid Astrocytes Oligodendrocytes Microglia Ependyma
DIFFERENTIAL GROWTH: BONY SPINE VS. SPINAL CORD
- Early embryonic changes
Spinal cord extends up to the coccyx
Magkasing-haba sila End of 8th week Coccygeal cord atrophies which later becomes the filum terminale - Fetal stages
Bony spine grows faster than the cord (relative cord ascension)
Mas mabilis humaba yung bone than the cord kaya nagmumukhang pataas ang growth ng spinal cord - At birth- Cord ends at L2 or L3 vertebrae
- In adult - Cord ends at L1 or L2 vertebrae
- Vestigial cord
o Or vestigial coccygeal spinal cord
o Tail which holds the spinal cord to coccyx - Gial tissue
- Pierces the dural sac through sacral hiatus to attach to the dorsal coccyx
- Anchors the dural sac
FILUM TERMINALE
Three membranous connective tissue layers:
- Dura mater – next layer beneath the periosteum of the bone
- Arachnoid mater – next to the dura mater
- Pia mater – after subarachnoid space, intimately attached to gray matter
- Are continuous membranes that collectively make up the leptomeninx (G. slender membrane)
- Subarachnoid / Leptomeningeal space
Intermediate and internal layers (Arachnoid and pia mater)
- Clear liquid similar to blood in constitution
- Provides nutrients but has less protein and different ion concentration
- Formed by choroid plexuses of the 4 ventricles of the brain
Cerebrospinal fluid (CSF)
o Between periosteum and dura
o Fat, venous plexus
o Additional layer in spinal cord
o Epidura – above dura (sa buto na)
Epidural Space
o Thick, tough outer meningeal layer
o Encloses dural sac
o Continuous with cranial dura
o Dense, bilaminar membrane also called the pachymenix (G. pachy – thick; menix – membrane)
Dura Mater
o Long tubular sheath within vertebral canal, from foramen magnum and ends at about S2
o Extends laterally up to intervertebral foramen as root sleeves pierced by exiting spinal nerve roots
o Merges with connective tissue sheaths of peripheral nerves:
Dura – continuous with epineurium
Arachnoid – continuous with perineurium
Pia – continuous with endoneurium
o Caudally, anchored to the coccyx by the filum terminale
o Tension in the filum terminale stabilizes the spinal cord
Dural Sac
o Potential space
o Only gets filled after bleeding (hematoma formation)
o Pressure of CSF pushes the arachnoid to the dura. The space between the dura and arachnoid (subdural space) is only a potential space. Nagkakaspace lang siya if may blood from subdural hematoma.
Subdural Space
o Fibrous and elastic tissue
o Avascular
o Thick and sturdy enough to be handled
o Lines dural sac
o Encloses CSF
o Pushed against the dura by CSF pressure
o G. arachne – spider; cobweb + eidos – resemblance
Arachnoid Mater
o Arachnoid granulations extend to the pia
o Filled with CSF
Subarachnoid Space
o “Pinakaloob”
o Delicate transparent layer of flatcells covering of the outer surface of the cord
o Ensheaths cord and vessels
o Continues as the filum terminale caudally
o Has lateral extensions between dorsal and ventral roots, the denticulate ligament to the dura seen from foramen magnum up to about L2
o Continues distally as the coccygeal portion of the spinal cord and when it atrophies early in life, it becomes your filum terminale
o Thinner membrane that is highly vascularized by a network of fine blood vessels
o When the cerebral arteries penetrate the cerebral cortex, the pia follows them for a short distance forming a “pial coat” and a “periarterial space
Pia Mater
– anchors pia mater; extends to the dura
Denticulate ligament
(Pia Mater)
- holds the spinal cord steady
Denticulate ligament + filum terminale
o Terminal portion of dural sac (L2-S2)
o Contains CSF and the cauda equina
o Access point for lumbar puncture procedures
Lumbar cistern
- Space between periosteum lining bony wall of vertebral canal and dura mater
- Position of extradural (epidural) herniation
- Contents: Fat (loose CT); Internal vertebral venous plexuses; Inferior to L2 vertebra, ensheathed roots of spinal nerves
Extradural (epidural)
- Naturally occurring space between arachnoid mater and pia mater
- Contents: CSF; Radicular, segmental, medullary and spinal arteries; Veins; Arachnoid trabeculae
Subarachnoid (leptomeningeal)
o Anesthetic directly into CSF
o Faster onset
o Shorter duration
Subarachnoid / Spinal Block
o Indwelling catheter inserted into epidural space
o Anesthetic bathes spinal nerves after they exit the dural sac
o Continuous
o Longer onset and duration
Epidural Block
31 pairs: o 8 cervical o 12 thoracic o 5 lumbar o 5 sacral o 1 coccygeal (may be absent)
SPINAL NERVES
BLOOD SUPPLY: 3 LONGITUDINAL ARTERIES
Ventral median artery (1): Anterior spinal artery
Paired dorso-lateral arteries (2): Posterior spinal arteries
o Receives segmental arteries (radicular arteries) at regular intervals from the aorta
– great anterior segmental medullary artery; the biggest feeder
Artery of Adamkiewicz
- Anterior 2/3 of cord
- Union of branches of the posterior inferior cerebellar and vertebral arteries
Anterior Median Artery
- Posterior 1/3 of cord
- Each is a branch of the ipsilateral posterior inferior cerebellar artery and vertebral artery
Paired Posterior Arteries
- Spinal cord plexus in the subarachnoid space
- Epidural (internal vertebra) plexus in the epidural space along the length of the vertebral column up to the foramen magnum
- External venous plexus along the outside of the vertebral column communicating freely with the epidural plexus
- Valveless, blood flow is bidirectional from spinal cord (away from the cord) - Regional network of veins of each spinal segment which eventually drain to the inferior vena cava
SPINAL VEINS: 3 LONGITUDINAL VENOUS SYSTEMS
Spread of Infection and Malignancy
- The usual route of spread of malignancy and infection between abdomino-pelvic cavity and the spine
- Pwede kumalat yung malignancy from spine to viscera and from viscera to the spine. Pero usually viscera to spine kaya common site ng metastasis and spine, both the cord and the bony vertebral column.
May be due to:
o Interruption (rupture)
o Compression (trauma, malignancy)
o Ischemia
Manifests as (depending on part of cord affected and may be complete or incomplete):
o Loss of sensation
o Loss of motor power
o Loss of autonomic function (e.g. bowel/bladder control)
LOSS OF SPINAL CORD FUNCTION
- Lumbar spine nerves increase in size from superior to inferior, whereas the IV foramina decrease in diameter
- L5 spinal nerve roots are the thickest and their foramina is the narrowest.
- This increases the chance that these nerve roots will be compressed if osteophytes (bony spurs) develop, or herniation of an IV disc occurs
Compression of the Lumbar Spinal Nerve Roots
- A radiopaque contrast procedure that allows visualization of the spinal cord and spinal nerve roots
- CSF is withdrawn by lumbar puncture and replaced with a contract material injected into the spinal subarachnoid space and its extensions around the spinal nerve roots within the dural root sheaths.
Myelography
Possible causes: o Fractures o Dislocations o Fracture-dislocations Can lead to: muscle weakness and paralysis
Ischemia of Spinal Cord
- Transection of the spinal cord results in loss of all sensation and voluntary movement inferior to the lesion
Spinal Cord Injuries
(Spinal Cord Injury)
- No function below head level
- A ventilator is required to maintain respiration
C1-C3
(Spinal Cord Injury)
- Quadriplegia (no function of upper and lower limbs)
- Respiration occurs
C4-C5
(Spinal Cord Injury)
- Loss of lower limb function combined with a loss of hand and a variable amount of upper limb function
- May be able to self-feed or propel a wheelchair
C6-C8
(Spinal Cord Injury)
- Paraplegia (paralysis of both lower limbs)
- The amount of trunk control varies with the height of lesion
T1-T9
(Spinal Cord Injury)
- Some thigh muscle function, which may allow walking with long leg braces
T10-L1
(Spinal Cord Injury)
- Retention of most leg muscle function
- Short leg braces may be required for walking
L2-L3
- Divided into left and right hemispheres
- Corpus callosum – commissural fibers that join the cerebral hemispheres
- Median longitudinal fissure – incompletely separates the two hemispheres
CEREBRUM
Remember:
CEREBRAL CORTEX – GRAY MATER
CEREBRAL MEDULLA – WHITE MATER
LAYERS OF CEREBRUM (From superficial to deep)
- Molecular / Plexiform Layer - Horizontal cells of Cajal – spindle shape
- External Granular Layer - Small pyramidal cells, stellate and granulated cells
- External Pyramidal Layer - Medium-sized pyramidal cells
- Internal Granular Layer - Large pyramidal cells; Band of Ballerger
- Internal Pyramidal Layer
- Multiform / Polymorphic / Fusiform Layer - Inverted cells of Martinotti
(Classification of the Cerebral Cortex)
- 90% of cerebral cortex
- Also known as isocortex
- Composed of 6 layers
Neocortex or isocortex
(Classification of the Cerebral Cortex)
Includes the cingulate gyrus and hippocampus
Mesocortex
(Classification of the Cerebral Cortex)
- 10% of cerebral cortex
- Composed of:
o Paleocortex – olfactory cortex
o Archicortex – hippocampus, dentate gyrus
Allocortex
- Largest lobe
- 1/3 of hemispheric’s surface
- Lies anterior to the central sulcus of Rolando
- Superior to the lateral fissure of Sylvius
Frontal Lobe
- Primary motor area (BA 4)
- 1/3 of corticospinal tract (CST) arises here
- Function: Contralateral movements of face, arm, leg and trunk
Pre-central Gyrus
Manifestations of lesion in Pre-central Gyrus
o Monoplegia or hemiplegia
o Initial flaccid paralysis
o (+) Babinski reflex
- Premotor area (BA 6)
- Anterior to pre-central gyrus
- 1/3 of Cortico Spinal Tract fibers originates here
- Function:
o Contralateral head and eye turning
o Assumption of posture
o Complex patterned movements infrequent rapid incoordinate movements
Superior Frontal Gyrus
Manifestation of lesion in Superior Frontal Gyrus
- Contralateral paralysis of the head and eye movements
- Head and eyes turn “toward” the diseases hemisphere
- Spasticity
- Increased tendon reflex added to primary motor lesion
- Fontal eye field (BA 8)
- Function:
o Conjugate deviation of the eyes to the other side
Manifestation of lesion:
o Difficulty in voluntarily moving the eyes to the opposite side
Middle Frontal Gyrus
- Broca’s Area - Pars orbitale and triangularis (BA 44 & 45)
o Function:
- Expressive center for speech in the dominant hemisphere
- Patterns of movement for muscles producing speech
- Control motor speech
o Manifestation of lesion: Broca’s or motor aphasia
Inferior Frontal Gyrus
- BA 9-12
- Areas of higher cortical function
- Lies rostral to the premotor and frontal eyefield areas
- Has connections with the dorsomedial nucleus of the thalamus, hypothalamus, limbic lobe, anterior temporal area, and association areas of the parietal and occipital lobes
- Function: Personality; Abstract thinking; Mature judgment; Foresight; Tactfulness; Self-control; Initiative; Socialization of certain autonomic functions and emotions; Monitor cortical plan of behavior
Prefrontal Area
Manifestation of lesion in Prefrontal Area
o Witzelsucht – inappropriate jocularity
o Akinetic mutism – severe loss of initiative with disinterest and unconcern
o Primitive reflexes – e.g. grasp, pout
o Frontal ataxia – disturbance of gait
o Paratonia – resistance to passive movements of limbs
- Anteriorly bounded by the paracentral sulcus
- Posteirorly bounded by the marginal branch of cingulate gyrus
- Function: Cortical inhibition of bladder and bowel voiding
- Manifestation of lesion: INCONTINENCE OF URINE AND FECES
Paracentral Lobule
- An infection of the brain or spinal cord cuased by the spirochete Treponema palladium
- Usually occurs in people who have had chronic, untreated syphilis, usually about 10-20 years after first infection
- Develops in about 25-40% of persons who are not treated
- Manifestation:
o Lack of general sense of responsibility
o Sloppiness in habits
o Vulgar speech
o Clownish behavior
Neurosyphilitic Frontal Atrophy
- Posterior to central sulcus
- Anterior to parieto-occipital sulcus
Parietal Lobe
- PRIMARY SENSORY OR GRANULAR CORTEX (BA 3, 1, 2)
- Concerned with tactile and kinesthetic sense from superficial and deep receptors and converge
- Somatopically represented
- Function: RECEIVES AFFERENT PATHWAYS FOR APPRECIATION OF POSTURE, TOUCH AND PASSIVE MOVEMENTS
Postcentral Gyrus
Manifestation of lesion in Postcentral Gyrus
o Contralateral impairment of touch, pressure and proprioception
o Disturbed postural and passive movement sensation
o Disturbed localization of touch with loss of 2-point discrimination
o Astereognosis – impaired appreciation of size, shape, texture and weight
o Preceptual rivalry – sensory inattention
- Lies posterior to BA 3,1, 2 along superior border of Sylvian fissure
- Manifestation of lesion: Impaired pain sensation
Secondary Somesthetic Area
- Cortical association areas
- Mnemonic constellations for understanding and interpreting sensory signals
Inferior Parietal Lobule
- BA 40
- Function: Understanding and interpreting sensory signals
Supramarginal Gyrus
Manifestation of lesion in Supramarginal Gyrus
o Lesion on dominant hemisphere:
Tactile and proprioceptive agnosia
o Lesion on non-dominant hemisphere:
Confusion in left-right discrimination
Body image disturbance
Apraxia