Anatomy sem 4

• Spinal Cord


  • Superior cord is continuous with brain stem
  • At 3rd month of foetal life, the cord extend entire length of vertebral canal; at birth, cord end at level of 3rd lumbar vertebrae; at adult, cord end at level between L1/L2
  • Enlargement at: cervical and lumbar
  • Conus medullaris: caudal to lumbar enlargement
  • Spinal nerve: C1-C7 exit interverbral foramina above its level while C8 and below will exit below its level
  • Cauda equina: collection of spinal nerve that runs within the vertebral canal to reach its respective intervertebral foramina
  • Filum terminale (continuation of Pia matter): attach to tip of conus medullaris to 1st coccygeal vertebra

  
• Spinal Meninges


  • Dura (tough, outermost fibrous membrane): subdural space, epidural space (separated from bony wall of vertebral canal) filled with fat and internal vertebral venous plexus
  • Arachnoid (transclucent avascular membrane): subarachnoid space that contain CSF
  • Pia (innermost delicate vascular membrane): closely applied to surface of spinal cord and nerve root
  • Pia matter ends at coccus as filum terminal while arachnoid and dura continues inferior until S2 forming dural sac from L1-S2

  
• Lumbar puncture


  Needle can be inserted at L3/4 or L4/L5 because spinal cord in adult terminal at level of L1/L2 and dural sac is at L1-S2 which does not contain spinal cord
• Spinal Cord Lesions


  • Both UMN & LMN lesion: Amylotrophic lateral sclerosis (genetic degenerative disease)
  • Upper Motor Neuron lesion: Loss ability to send signal from brain down to spinal cord and because of that have dis-regulated innervation of muscle
  • Lower Motor Neuron Lesion: Loss innervation of muscle due to damage to alpha motorneuron or denervation of muscle
  • Spastic paralysis: due to intact monosynaptic arc
  • Flaccid paralysis: due to denervation of efferent component of reflex arc
  • Hypertonia (increase tone): increases resistance to passive movement and loss inhibitory effect from brain
  • Hypotonia: because alpha motorneuron the only one that can stimulate extrafusal ms fibres
  • Hyperreflexia: bend rapidly especially deep reflex while in superficial reflex absent
  • Hyporeflexia: absent of alpha motoreuorn cause loss of ms contraction
  • Babinski's sign +ve: toe going up which extensor plantar response
  • Babinski's sign -ve: toe gown down
  • Clonus: involuntary ms contraction due to sudden stretching of ms
  • Fasciculation: visible ms twitches because of spontaneous AP
• Lesion of dorsal column


  • Late manifestation of syphilis infection
  • Cause selective destruction/demyelination of dorsal spinal root and column of spinal cord
  • Unsteady gait: loss of touch and proprioception
  • Romberg's sign positive which unable to maintain steady posture while standing with feet together and eyes close
  • Hyporeflexia due to degeneration of afferent fibre component in reflex arc
• Lesion of spinothalamic tract


  • Central canal enlarge compressing spinothalamic tract as 2nd order neuron are damage because they decussate in anterior white commissure which close to central canal
  • Cause selective loss of pain and temperature
  • Intact discriminative touch, vibration and proprioception
• Incomplete lesion of spinal cord

  • Anterior Cord Syndrome: Damage to corticospinal tract: paraplegia which at level of lesion lead to LMN paralysis while at below level of lesion lead to UMN paralysis; Damage to spinal thalamic tract: bilateral thermoanasthesia (loss of pain and temperature); Damage to descending autonomic tract: loss of bladder and bowel control; Not damage to DCLM: intact propioception, vibration and fine touch
  • Central Cord Syndrome: Damage to corticospinal tract: paraplegia which at level of lesion lead to LMN paralysis while at below level of lesion lead to UMN paralysis (spastic paralysis but sacral sparing); Damage to spinal thalamic tract: bilateral thermoanasthesia (loss of pain and temperature) with sacral sparing
  • Brown-Sequard Syndrome (spinal cord semi section): At level of the lesion: Damage to ventral root: ipsilateral LMN paralysis; Damage to dorsal root: ipsilateral band cutaneous anaesthesia; At below level of the lesion: Ipsilateral UMN paralysis; Damage to DCLM: ipsilateral loss of proprioception, discriminative touch

  
• Spinal Cord total section (complete transection of spinal cord)


  • Causes: vertebral fracture
  • At level of the lesion: LMN paralysis bilaterally and loss of sensation bilaterally
  • At below level of the lesion: UMN paralysis bilaterally and loss of sensation bilaterally

  
• Midbrain


  • CN III: exit from medial side of interpeduncular fossa
  • CN IV emerge below inferior coliculus
• Pons


  • CN V emerge from anterolateral side (small motor root & large sensory root)
  • CN VI, VII, VII emerge from groove between pons and medulla oblongata
• Medulla oblongata


  • CN IX, X, XI exit dorsolateral sulcus
  • CN XII exit from ventrolateral sulcus
  • Ventral aspect: anterior median fissure, pyramid, olive (produced by inferior olivary nuclei
  • Lateral aspect: ventrolateral sulcus (CN XII exit), dorsolateral sulcus (CN IX, X, XI exit), inferior cerebellar peduncle
  • Posterior aspect: Superior 1/2 of medulla oblongata (lower part of floor of 4th ventricle): median sulcus, vagal trigone, hypoglossal trigone, vestibular area, foramen Luschka, foramen Magendie (midline opening), striae medullaris; Inferior 1/2 of medulla oblongata: dorsal median sulcus, fasciculus gracilis & cuneatus, gracile & cuneate tubercle that represent nucleus gracilis and cuneatus
  • Nuclei of cranial nerve: nucleus ambiguous (motor)- CN IX, X, XI nerve while nucleus tractus solitarius (sensory): CN VII, IX, X
• Pons

  • Ventral aspect: middle cerebellar peduncle, basilar groove, CN V emerge from anterolateral side (small motor root & large sensory root), CN VI, VII, VII emerge from groove between pons and medulla oblongata
  • Dorsal aspect: upper 1/2 of floor of 4th ventricle, superior cerebellar peduncle, median sulcus, medial eminence, sulcus limitans, facial colliculus (fibres of facial nerve wind around the nucleus of abducent nerve), vestibular area
  • Internal features: Ventral part (basis point): descending tracts, transverse fibre, pontine nuclei; Dorsal part (tegmental part): CN V, VI, VII, VIII nucleus

  
• Midbrain


  • Ventral aspect: crus cerebri of cerebral peducle, interpeduncular fossa, optic tract skirt around each cerebral peducle, CN III exit from medial side of interpeduncular fossa
  • Dorsal aspect: Tectum (superior colliculi to lateral geniculate body for spinovisual; inferior colliculi to medial geniculate body for spino-auditory), CN IV emerge below inferior coliculus and wind around lateral aspect of midbrain
  • Internal features: creberal peduncle (crus cerebri: corticospinal fibres, frontopontine fibre, temperopontcne fibre; substantia nigra, tegmentum), tectum (nucleus of inferior and superior colliculi)

  
• Cerebellum


  • Function: posture, balance, motor coordination, precision and timing of movement, motor learning
  • Zones: vermis, intermediate zone, lateral cerebral hemisphere
  • Functional: cerebrocerebellum, spinocerebellum, vestibulocerebellum
  • Anatomical: anterior, posterior and floccunodular node
  • Gray matter: cerebellar cortex (arbor vitae, folia)
  • White matter: deep cerebellar nuclei (dentate, globose, emboliform, fastigial)
  • Venous drainage: transverse sinus, superior and inferior petrosal sinus and great cerebral vein

  
• Thalamus


  • Important relay to all areas of cerebral cortex, basal ganglia and all sensory pathway except swell
  • External Features: Anterior: narrow and rounded, form posterior boundary of interventricular foramen; Posterior: expanded, pulvinar (medial and lateral geniculate body); Medial: connected to opposite side by inter thalamic connection
  • Covering: superiorly by stratum zonale while lateral by external medullary lamina
  • Internal Features: Internal medullary lamina: Y shaped structure containing nerve fibre and divides gray matter into 3 parts (anterior, medial, lateral)
  • Relations: Superior: related to choroid plexus and forms floor part of body of lateral ventricle; Inferior surface: hypothalamic sulcus, separating it from hypothalamus; Medial surface: form lateral wall of 3rd ventricle; Lateral surface: internal capsule, separating it from lentiform nucleus
  • Subdivision of thalami nuclei: Anterior nuclei, Medial nuclei, Lateral nuclei (Dorsal tier, ventral tier)

  
• Basal Ganglia


  • Important for control of posture and voluntary movement which consist of corpus stratum, amygdaloid nucleus and claustrum
  • Corpus striatum: Caudate nucleus, Lentiform nucleus (Putamen and Globus pallidus)
  • Amygdaloid nucleus: in temporal lobe, part of limbic system. It influence the body's response to environment changes
  • Claustrum: separated from lentiform nucleus by external capsule, laterally is extreme external capsule/subcortical white matter of insula
  • Basal Ganglia Connection: Striatum (caudate nucleus and putamen) receives cortico-striate fibres from ipsilateral cerebral cortex; Send output to globus pallidus; Project into ventral anterior nucleus of thalamus then project first to supplementary motor cortex then to premotor & motor areas —> anterior horn of spinal cord; Controls movements of contralateral 1/2 of body

  
• White Matter Internal Capsule

  • Association fibres (connect one gyrus to another in the same hemisphere): Short association fibres, Long association fibres: superior and inferior longitudinal fasciculus, fronto-fronts-occipital fasciculus, uncinate fasciculus and cingulum
  • Commissural fibres (connect corresponding region of the 2 hemisphere): Anterior, posterior, habenular commissure, fornix, Corpus callosum (connect 2 cerebral hemispheres): head/rostrum, menu, body and splenium
  • Projection fibres (pass between cerebral cortex & subcortical structure): ascending and descending fibres
• White matter of insula

  • Basal Ganglia Connection

  
• Basal Ganglia Connection


  1. Striatum (caudate nucleus and putamen) receives cortico-striate fibres from ipsilateral cerebral cortex

  2. Send output to globus pallidus

  3. Project into ventral anterior nucleus of thalamus then project first to supplementary motor cortex then to premotor & motor areas —> anterior horn of spinal cord

  4. Controls movements of contralateral 1/2 of body

  
• White matter internal capsule


  • Association fibres (connect one gyrus to another in the same hemisphere)
  • Short association fibres
  • Long association fibres: superior and inferior longitudinal fasciculus, fronto-fronts-occipital fasciculus, uncinate fasciculus and cingulum
  • Commissural fibres (connect corresponding region of the 2 hemisphere)
  • Anterior, posterior, habenular commissure, fornix
  • Corpus callosum (connect 2 cerebral hemispheres): head/rostrum, menu, body and splenium
  • Projection fibres (pass between cerebral cortex & subcortical structure): ascending and descending fibres
• Projection fibres


  Cerebral cortex -> corona radiata then converge internal capsule -> subcortical area

  
• Internal capsule of white matter


  • Band of white matter, made up of projection fibres, pass to and from cerebral cortex
  • Medially: caudate nucleus (superior) and thalamus (inferior)
  • Laterally: lentiform nucleus (globus pallidus and putamen)
  • Superiorly: corona radiata
  • Inferiorly: crus cerebri of cerebral peduncle of midbrain

  
• Parts of internal capsule


  • Anterior limb
  • Genu
  • Posterior limb
  • Retrolentiform (posterior end of lentiform nucleus)
  • Sublentiform (below the lentiform nucleus)

  
• Descending fibres


  • Corticospinal fibres
  • Corticopontine fibres (fronto/parieto/temporo/occipital-pontine
  • Fibres from cerebral cortex to brainstem nuclei (cortico-bulbar/rubral/reticular/tectal fibres)
• Ascending fibres from thalamus


  • Anterior thalamic radiation
  • Superior thalamic radiation
  • Posterior thalami radiation
  • Inferior thalamic radiation
• Anterior thalamic radiation


  Fibres from hypothalamus and limbic structures, pass through anterior limb, fibres to frontal lobe
• Superior thalamic radiation


  Fibres to somatosensory area, pass through posterior limb
• Posterior thalami radiation


  Optic radiation from lateral geniculate body, fibres to occipital lobe, lie in retrolentiform
• Inferior thalamic radiation


  Auditory radiation from medial geniculate body, fibres to temporal lobe, pass through sublentiform
• Arteries supplying the brain


  • Internal Carotid Artery
  • Vertebral Artery
  • Basilar Artery

  
• Branches of internal carotid artery


  • Anterior cerebral artery
  • Middle cerebral artery
  • Posterior communicating artery
  • Anterior choroidal artery
  • Ophthalmic artery

  
• Branches of vertebral artery


  • Anterior spinal artery
  • Posterior spinal artery
  • Posterior inferior cerebellar artery
  • Medullary branches
  • Meningeal branches

  
• Branches of basilar artery


  • Superior cerebellar artery
  • Anterior inferior cerebellar artery
  • Posterior cerebral artery
  • Pontine artery
  • Labyrinthine artery

  
• Circle of Willis


  Lies in interpeduncular fossa at base of the brain, right and left anterior cerebral artery join together through anterior communicating artery, right and left internal carotid artery, right and left posterior cerebral artery, posterior communicating artery joining internal carotid artery & posterior cerebral artery

  
• Blood supply to nervous system

  • Spinal cord: anterior and posterior spinal artery (vertebral artery) and segmental arteries
  • Medulla oblongata: anterior and posterior spinal artery (vertebral artery), posterior inferior cerebellar artery and medullary branches (basillar artery)
  • Pons: basilar artery
  • Cerebellum: superior cerebellar artery and anterior inferior cerebellar artery (basillar artery) and posterior inferior cerebellar artery (vertebral artery)
  • Midbrain: anterior cerebral artery (internal carotid artery), superior cerebellar artery (basillar artery)
  • Thalamus: posterior cerebral artery (basillary artery)
  • Basal ganglia: anterior and middle cerebral artery (internal carotid artery)
  • Internal capsule: anterior and middle cerebral artery, anterior choroidal artery (internal carotid artery)

  
• Temporal fossa


  • Anterior: frontal and zygomatic bone
  • Supero-posterior: temporal line
  • Inferior: zygomatic arch (lateral) and infratemporal surface and crest of greater wing of sphenoid (medial)
  • Floor: zygomatic, frontal, parietal, sphenoid
  • Roof: temporalis fascia
• Contents of temporal fossa


  • Muscle: temporalis
  • Artery: deep temporal (maxillary), middle temporal artery (superficial temporal)
  • Nerve: deep temporal (mandibular), zygomaticotemporal (maxillary)
• Infratemporal fossa


  • Superior: infratemporal surface and crest
  • Inferior: attach to medial pterygoid muscle to angle of mandible
  • Anterior: posterior surface of maxilla
  • Posterior: mastoid, styloid process and tympanic plate
  • Medial: lateral plate of pterygoid process of palatine bone (anterior) and 2 muscles of soft plate & pharynx (posterior)
  • Lateral: ramus of mandible

  
• Temporomandibular joint (TMJ)


  • Upper compartment: glinding movement (protrusion, retrusion)
  • Lower compartment: hinge movement (elevation and depression)
  • TMJ is made up of mandibular fossa and condyloid process of mandible
  • Primary muscle for protrusion is lateral pterygoid muscle while for retraction is temporalis muscle
• Contents of infratemporal fossa

  • Muscle of mastication (temporalis, medial and lateral pterygoid)
  • Pterygoid venous plexus
  • Mandibular nerve
  • Maxillary artery
  • Otic ganglion and its associated nerve
  • Lesser petrosal nerve and chorda tympani nerve