Week 4 Lect The Spinal Cord PDF

PTY214 Applied Anatomy for Neurological Physiotherapy – The Spinal Cord fchs.ac.a  At the completion of this week it is expected that students will be able to:  identify and describe the key structural features of the external aspect of the s...

PTY214 Applied Anatomy for Neurological Physiotherapy – The Spinal Cord fchs.ac.a  At the completion of this week it is expected that students will be able to:  identify and describe the key structural features of the external aspect of the spinal cord  summarise the internal organisation of the spinal cord (common arrangement of grey and white matter)  describe the pathways and information conveyed in the following white matter tracts ◦ posterior (dorsal) columns ◦ spinothalamic tract (anterior and lateral) ◦ corticospinal (pyramidal) tract  CONT:  summarise the arterial supply and venous drainage of the spinal cord ▪ Functions: ▪ It carries signals between the brain and the rest of the body. ▪ The pathway for messages sent by the brain to the body and from the body to the brain. ▪ motor ▪ sensory ▪ autonomic information ▪ Acts as a reflex centre for basic reactions Eizenberg et al: An@tomedia: Regions: General Anatomy & Back modules: McGraw Hill Publishing www.anatomedia.com ▪ Located in back & neck regions ▪ Elongated Cylindrical shape ▪ Located in Vertebral canal ▪ ~45cm long ▪ Extends from Brainstem (medulla oblongata) (birth) ▪ Ends L2- Adult (L3 newborn) Eizenberg et al: An@tomedia: Regions: General Anatomy & Back modules: McGraw Hill Publishing www.anatomedia.com ▪ Enlargements ▪ a result of the increased volume of motor cells in the ventral horns of the grey matter. ▪ Cervical ▪ Lumbosacral ▪ Conus medullaris (ends L2) ▪ Cauda equina ▪ Filum terminale (ends Co1) ▪ Origin of Spinal nerves ▪ Anterior (ventral) nerve roots ▪ Posterior (dorsal) nerve roots ▪ Dura mater T1 ▪ Arachnoid Mater ▪ Pia Mater L5 S1 S5 Eizenberg et al: An@tomedia: Back module www.anatomedia.com  31 pairs of spinal nerves. Anterior (ventral) & Posterior (dorsal) Rootlets Anterior (ventral) & Posterior (dorsal ) Roots (motor) (sensory) Form MIXED Spinal Nerve in Intervertebral foramen Ventral (anterior) primary rami Dorsal (posterior) primary rami Anterior View  group of cell bodies responsible for the transmission of sensory messages from receptors such as thermoreceptors, nociceptors, proprioceptors, and chemoreceptors, to the CNS for a response.  Cauda Equina (horse’s tail) Lower nerve roots progressively elongated within the dural sac (to S2) Implications for Lumbar puncture- to diagnose serious infection, MS Epidural anaesthesia-pain relief Spinal Anaesthetic- the injection of numbing medicine directly into the fluid sac Eizenberg et al: An@tomedia: Back module (McGraw Hill) www.anatomedia.com  Composed of: ◦ Grey matter - centrally (‘H”) ◦ White matter - outside  Small central canal  Fissures ◦ Anterior Median Fissure ◦ Posterior Median Sulcus ◦ Posterolateral Sulcus  Central canal GREY MATTER - (cell bodies) Butterfly (‘H’-shaped) Connected by Grey commisures 4 extensions Ventral Horn (2) (motor neurons) Dorsal Horn (2) (sensory neurons) Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. New Jersey, Icon Learning Systems, 2003.  Grey matter ◦ subdivided into laminae (‘Rexed’s laminae) ▪ I – X (dorsal – ventral) ▪ IX most important - cell bodies of motor neurons to skeletal muscle Crossman’s Neuroanatomy: Chapter 8, p.72 White Matter- (axons) Highly organized ascending and descending nerve fibers running between the spinal cord and the brain Columns (funiculi) Tracts (fasciculi)  White matter is arranged into columns (funiculus) - Anterior (ventral) - Lateral - Posterior (dorsal) Columns are arranged into laminae -> partial spinal cord lesions can cause regional loss Eizenberg et al: General Anatomy: Principles & Applications, McGraw Hill 2008  Ascending tracts are sensory pathways that begin at the spinal cord and stretch all the way up to the cerebral cortex.  Descending tracts- the pathways by which motor signals are sent from the brain to lower motor neurons.  CUNEATE GRACILE Columns contain tracts sulcus CORTICOSPINAL - ascending (sensory) LATERAL - descending (motor) Anterior (ventral) columns - Corticospinal - Spinothalamic Lateral Columns - Corticospinal (lateral) fissure - Spinothalamic (lateral) (& spinocerebellar) CORTICOSPINAL TRACT Posterior (dorsal) Columns - Dorsal column tracts - Gracile Eizenberg et al: General Anatomy: - Cuneate Principles & Applications, McGraw Hill 2008  Lateral Corticospinal tract  Anterior Corticospinal tract  Corticobulbar tract Upper motor neurons (UMN’s): Cerebral Cortex→ LMN (via CS tract) (Spinal cord or brainstem) controls movement & inhibits muscle tone Lower motor neurons (LMN’s): Anterior horn in spinal cord (cranial nerve nuclei in brainstem) → skeletal muscle controls movement by directly innervating muscle Eizenberg et al: An@tomedia: General Anatomy: Principles & Applications McGraw Hill 2008  UMN & LMN Lesions Lesions of all motor neurons lead to loss of voluntary movement, UMN lesions → spastic paralysis (↑ tone & hyperreflexia, no wasting) LMN lesions → flaccid paralysis (↓ tone & reflexes, long-term wasting) Spinal cord & Brainstem lesions - damage LMN’s at the level of the lesion - damage UMN’s of all levels below the lesion - also lose all sensory input at and below level of lesion  Eizenberg, Briggs, Adams & Ahern. General Anatomy. Principles & Applications: Left cerebral hemisphere controls movement or Right side of body Motor Decussations - Main (lateral) corticospinal tracts decussate at medulla (pyramids) McGraw Hill, 2007, Chapter 9. - Motor fibres of cranial nerves decussate at level of their nuclei 2 Neurones, 1 Synapse ◼ Corticospinal Voluntary skilled movements Starts Cortex (pre-central gyrus) Forms pyramids on medulla Motor (brainstem) P Lateral (L): L 75-95% CS fibres Decussate in medulla (pyramids) A L To reach anterior horn in SC L Anterior (A) Decussate at spinal cord segment (not in pyramids) To reach anterior horn SC A Carries axons primarily from the motor cortex of the brain to the spinal cord, where they synapse with motor neurons  Axons remain ipsilateral  Cross over to the other side of the body anterior to the gray matter of the spinal cord  These fibers provide motor innervation to the back as well as the proximal portions of the extremities  Important role in maintaining posture  Axons decussate in the medulla at the pyramidal decussation  Supply motor innervation to the distal parts of extremities like the hand  Conducts impulses from the brain to the cranial nerves  Axons do not enter the spinal cord  Synapse onto the nuclei of CN III, IV, V, VI, VII, IX, X, XI, XII ◦ Contain motor fibers for the muscles of your eyes, face, muscles of mastication and some muscles of the neck  Also called corticonuclear tract  Spinothalamic tract  carries information to the brain about pain, temperature, itch, and general or light touch sensations.  Lateral- pain, temperature Spinocerebellar tract From SC to the cerebellum – proprioceptive information Gracile & Cuneate tracts-fibers that convey proprioceptive, tactile, and vibratory information from the ipsilateral side of the body Left cerebral hemisphere receives sensation from right side of body: Sensory Decussations -Spinothalamic tracts decussate within a few levels of their entry into the spinal cord (pain) - Dorsal column tracts decussate at the medulla unilateral spinal cord lesions may have differing bilateral sensory effects 3 neurones, 2 synapses (1 in thalamus) Spinothalamic L Pain, Temperature (in L) P (crude) touch & pressure (in A) A ◼ Primary afferent neuron enters dorsal horn (1st synapse) ◼ Fibres Decussate in Spinal cord (via white commissure) ◼ Travels to Thalamus (2nd synapse) L ◼ then to Somatosensory Cortex ◼ Highly organised ◼ Divides into: ◼ Lateral pathway (temperature and pain) ◼ Anterior pathway (crude touch and pressure)  Proprioception, discriminative (fine) touch & vibration P Gracile tract= lumbosacral Cuneate tract= thoracocervical Primary afferent neuron enters Ldorsal L horn to medulla (1st synapse) 2nd neuron decussates in Medulla travels to thalamus (2nd synapse) 3rd neuron reaches Somatosensory cortex A  Arterial Supply Anterior (1) and posterior (2) spinal arteries Lumbar arteries (abdominal aorta) Artery of Adamkiewicz- supplies the lower spinal cord by reinforcing the anterior Adamkiewicz artery ▪ Veins are numerous, tortuous & valveless ▪ Venous drainage of spine (& spinal cord) via internal vertebral venous plexus ▪ occurs along nerve roots in both anterior & posterior An@tomediaTM Back module. Melbourne, McGraw-Hill, 2004, ISBN: 0734-02676-5. Eizenberg, Briggs, Barker & Grkovic, ▪ Valveless veins drain pelvis and lumbar spine -> potential route for metastasis SC INJURY ◦ Effects of Cx fracture-dislocation + complete SC transection. ◦ Injury at other levels?  Facet joint Degeneration  Disc Prolapse  Spinal Stenosis  Spinal cord Compression  Spinal Metastases  Useful Texts /Resources Crossman & Neary (2010). Neuroanatomy- An illustrated colour text. 4th ed. Edinburgh, Elsevier Churchill Livingstone. Introduction p.11-12 Chapter 8: Spinal Cord Moore & Dalley (2014). Clinically Oriented Anatomy (7th Ed) LWW Pg 496-507 Eizenberg et al (2008) General Anatomy: Principles & Applications, McGraw Hill Ch 9: Nerves p.108-118 An@tomedia Back and General Anatomy modules (Systems: Nervous) Waxman,S.G (2009) Clinical Neuroanatomy McGraw Hill – Online access see MOODLE  http://neuroanatomy.ca/  http://www.handwrittentutorials.com/vi deos.php ◦ Look for neuroscience tutorials on tracts