Spinal Cord Gross Anatomy PDF

Professor Lindboom-Broberg (LB) Spinal Cord Gross Anatomy Spinal Cord Anatomy & Organization Spinal Meninges Spinal Nerves Spinal Reflexes Nervous System Independence Spinal Cord Organization  Adult length ~ 45 cm (18 in.) Ends at L1–L2  31 sets of spinal...

Professor Lindboom-Broberg (LB) Spinal Cord Gross Anatomy Spinal Cord Anatomy & Organization Spinal Meninges Spinal Nerves Spinal Reflexes Nervous System Independence Spinal Cord Organization  Adult length ~ 45 cm (18 in.) Ends at L1–L2  31 sets of spinal nerves: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Spinal Cord Structure  Conus medullaris Cone-shaped end of spinal cord at L1–L2  Cauda equina (horse tail) Extended anterior and posterior roots of spinal segments L2 to S5  Filum terminale Fibrous tissue strands from conus medullaris to S2 Longitudinal support to spinal cord Spinal Cord Structure Cross-sectional spinal cord anatomy  White matter: Superficial; myelinated axons  Gray matter: Deep; forms an H, or butterfly shape Mostly neuron cell bodies, neuroglia, unmyelinated axons  Central canal: Contains cerebrospinal fluid Spinal Cord Structure Cross-sectional spinal cord anatomy  Posterior median sulcus: Shallow, longitudinal groove on posterior surface  Anterior median fissure: Deep groove on anterior surface Spinal Nerves Spinal Nerve Structure  Anterior root contains axons of motor neurons  Posterior root contains axons of sensory neurons  Posterior root ganglion (spinal ganglion) contains cell bodies of sensory neurons in posterior root  Spinal nerve: Axons of sensory and motor neurons  Professor Lindboom-Broberg (LB) Spinal Meninges Central Nervous System Covering Spinal Cord Covering Spinal meninges  3 membranes surrounding the CNS  Functions Stability Shock absorption Carry blood supply (oxygen and nutrients) The layers PAD the CNS (P-A-D)  P – Pia Mater  A – Arachnoid Mater  D – Dura Mater Spinal Cord Covering Spinal meninges  Dura mater (dura, hard + mater, mother) Outermost covering Tough, fibrous Dense collagen fibers oriented along the longitudinal axis of the spinal cord Spinal Cord Covering Spinal meninges  Arachnoid mater (arachne, spider + mater, mother) Middle meningeal layer Connects dura and pia Spinal Cord Covering Spinal meninges  Pia mater (pia, delicate + mater, mother) Innermost meningeal layer Meshwork of elastic and collagen fibers Anchored to neural tissue Spinal Cord Covering Spinal Cord Covering Spinal meninges  Supporting ligaments maintain position of spinal cord  Lateral Movements Denticulate ligaments extend from pia mater through arachnoid mater to dura mater; prevent lateral movement  Vertical Movements Dural connections at foramen magnum and coccygeal ligaments at sacrum prevent superior–inferior movements Spinal Cord Covering Lumbar puncture, or spinal tap  Withdraw sample of cerebrospinal fluid  Needle inserted into subarachnoid space, lumbar region, below conus medullaris (L3–L4) to avoid spinal cord Sagittal view of the lumbar spine, showing proper placement of a lumbar puncture needle. X-ray of the lumbar vertebrae, showing the cauda equina  Professor Lindboom-Broberg (LB) Spinal Nerves Spinal Cord Extensions into PNS Spinal Nerves Spinal nerve anatomy  From the inside out… Neuron Neuron is wrapped in myelin (or not) Myelinated (or not) neuron is wrapped in endoneurium Multiple endoneurium wrapped neurons collected together into a fascicle Each fascicle is wrapped in perineurium Multiple fascicles are collected together and wrapped in epineurium This is a nerve Spinal Nerves Spinal nerve organization  Spinal nerve rami Each spinal neve divides to form rami which serve body regions – Posterior ramus: Serves posterior trunk – Anterior ramus: Serves lateral & anterior trunk; limbs – Rami communicantes: In spinal nerves T1–L2, carry motor output of sympathetic division of ANS (responsible for “fight- or-flight” response) Spinal Nerves Spinal nerve organization  Dermatome: A specific bilateral area of skin supplied by pair of spinal nerves  Shingles Attacks neurons in posterior roots and sensory ganglia Painful rash/blisters along dermatome of affected nerve Spinal Nerves Sensory information in  Anterior ramus: From ventrolateral surface, body wall, and limbs  Posterior ramus: From skin/skeletal muscles of back  Rami  spinal nerve  posterior root  spinal cord Spinal Nerves Motor commands out  Spinal cord  anterior root  spinal nerve  rami  Posterior ramus: Somatic/visceral motor fibers to skin/skeletal muscles of back  Anterior ramus: Ventrolateral body surface, body wall, limbs  Professor Lindboom-Broberg (LB) Spinal Reflexes Automatic Homoeostatic Reflex Arcs Spinal Reflex Reflexes Classification of reflexes  4 ways to classify reflexes: Development: Innate or acquired Nature of response: Somatic or visceral Complexity of circuit: Monosynaptic or polysynaptic Processing site: Spinal or cranial Reflexes Development of reflexes  Innate reflexes Basic neural reflexes formed before birth Appear in predictable developmental sequence from simplest to more complex Example: Sucking, palmar grasp, patellar  Acquired reflexes (conditioned reflexes) Rapid, automatic learned motor patterns Repetition enhances them Reflexes Nature of response  Somatic reflexes Involuntary control of skeletal muscles Immediate – important in emergencies Example: withdrawal, patellar  Visceral reflexes (autonomic reflexes) Control involuntary effectors – Smooth muscle – Cardiac muscle – Glands – Adipose tissue Reflexes Complexity of circuit  Monosynaptic reflexes (two neuron) No interneuron Fast response Example: Patellar  Polysynaptic reflexes (three neuron) 1+ interneuron Slower response Example: Withdrawal Reflexes Processing site  Spinal reflexes Processing occurs in spinal cord  Cranial reflexes Processing occurs in brain Reflexes The brain can influence reflexes  Can facilitate/reinforce or inhibit motor neurons or interneurons  Example: Jendrassik maneuver facilitates patellar reflex