Spinal Cord - Lecture 3 - Anatomy - PDF

Spinal Cord Lecture 3  Organization of the Nervous System Central Nervous System Peripheral Nervous System Nerves emanating from Brain the brain and spinal cord Spinal Cord to all the areas...

Spinal Cord Lecture 3  Organization of the Nervous System Central Nervous System Peripheral Nervous System Nerves emanating from Brain the brain and spinal cord Spinal Cord to all the areas of the body (skin, muscle, internal organs etc.) Somatic = parietal = body wall Visceral = splanchnic = internal Ganglion - a collection of nerve cell bodies located outside the CNS Nucleus - a collection of nerve cell bodies located within the CNS  Nervous System Anatomical: Central Nervous Peripheral Nervous System (CNS) System (PNS) Functional: Somatic Nervous Autonomic Nervous System (SNS) System (sympathetic, (ANS) parasympathetic) Voluntary control Involuntary control to/from: to/from: - smooth muscles - skin - cardiac muscles - skeletal muscles - glands - joints  Spinal Cord Organization - External 31 pairs of spinal nerves 8 cervical (C1 – C8) 12 thoracic (T1 – T12) 5 lumbar (L1 – L5) 5 sacral (S1 – S5) 1 coccygeal (Co1) Spinal cord ends at vertebral level L1-L2 Conus – Conus medullaris (end of cord) medullaris – Below this is cauda equina “horse’s tail” Cauda Spinal nerve roots descending to exit as equina lumbar and sacral nerves  Due to rapid growth of the vertebral column the position of the caudal end of the spinal cord changes L2 L3 S1 S1 S1 S1 S2 8 24 weeks weeks Newbor Adul n t  Spinal Cord organization Cervical Spinal cord enlarges in two enlargeme area: nt Cervical enlargement for brachial plexus Around vertebral level C4-T1 Contains spinal segments supplying shoulder girdle and upper limb Lumbar enlargeme Lumbar enlargement for nt lumbosacral plexus Around vertebral level T9-T12 Contains spinal segments supplying pelvis and lower limb  Spinal Meninges Protective membranes covering the spinal cord Continuous with cranial meninges covering brain Made up of 3 layers (outer to inner):  Epidural space Dura mater 1. Dura mater (“Tough Mother”) Arachnoi  Subdural space (potential space) d mater 2. Arachnoid mater (“Spider web”)  Subarachnoid space (actual space with CSF) Pia mater Denticulate 3. Pia mater (“Gentle Mother”) ligament Lateral view of spinal canal  Clinical Applications Epi – “outside of” Sub – “beneath” Epidural anaesthesia Spinal anaesthesia (spinal block) Nerve block Epidural Anaesthesia Dura & Arachnoid mater Subarachnoid Epidur space containing al CSF space Pia mater  Epidural Anaesthesia Local freezing Insertion of catheter Hook-up to drug pump Drug delivery to the epidural space Spinal cord Epidur al space Dura Vertebr al lamina Spinal nerve Drug delivery to the subarachnoid space Nerve Block Nerve Block Pudendal nerve block What structure is the physician feeling for with her fingers in the vagina and why? -ischial spine which is near the pudendal nerve What other structure can be felt and used as a -landmark ischial for locating the pudendal n.? tuberosity Episiotomy Perineal body (central tendon of perineum)  Pia mater Filum terminale (pia mater) anchors the spinal cord inferiorly Conus to coccyx medullaris Arachnoid mater (dural sac) L2 End of cord extends past end of spinal cord @ L2 down to S2 Arachnoi Between L2 and S2 there is CSF d mater filled subarachnoid space with S2 End of dural cauda equina and filum terminale Filum sac @ S2 terminale – Clinical importance? Spinal tap / CSF collection Spinal Tap L2 L3 L4 Lumbar puncture L2 Best level L4 / L5 for LP S2 The skin covering the lower lumbar vertebrae is anesthetized and a lumbar puncture needle is inserted in the midline between the spinous processes of L4 and L5 at the supracristal line (dotted line). After 4-6cm the needle “pops” through the ligamentum flavum and then “pops” again when penetrates the dura to enter the lumbar cistern. Lumbar puncture is not performed in the presence of increased intracranial pressure. Lumbar Puncture NB Needle is directed Cephalad ie headwards  Spinal Cord Organization Cord made up of two types of tissue: – Inner gray matter – cell bodies of neurons and glial cells – outer white Dorsal hornmatter – myelinated axons, neural (sensory) “highways” White Lateral horn matter (sympathetic- motor) Ventral horn Gray (motor) matter Meninges P.A.D.  Spinal Cord Organization Dorsal rootlets Dorsal root Dorsal ramus (sensory) (sensory) Spinal (mixed) nerve Ventral Ventral Ventral rootlets (mixed) root ramus (motor) (motor) (mixed) Dorsal Dorsal root rootlets ganglion Dorsal Dorsal root ramus Ventral ramus Ventral root Spinal Ventral nerve rootlets Grey and white rami communicantes  Spinal Nerves and Their Path Dorsal ramus Ventral ramus Spinal nerve exits through intervertebr al canal Anterior Posterior  Spinal Nerves and Their Path CV1 C1 between skull and C1 C1 vertebra (above same number vertebra) C2 to C7 exit above same number vertebra C7 C8 exits above T1 vertebra Transitio CV7 (acts as C8 for counting since n in no C8 vertebra exists) T1 naming TV1 From T1 to end of cord, nerves exit from the spinal canal TV2 through the intervertebral foramen below the same number vertebra)  Spinal Nerves and Their Path Dorsal (Posterior) ramus – Dorsal ramus supplies intrinsic back muscles Ventral ramus (motor) and skin over that area (sensory) Ventral (Anterior) ramus - supplies all other muscle (motor) and skin over that area (sensory) Sympathetic chain ganglia run down the length of the vertebral column lateral to vertebral bodies (bilateral) Sympathetic chain ganglia communicate with spinal nerve via grey (unmylinated) and white (myelinated) rami communicantes Dermatomes A dermatome is an area of skin innervated by a single spinal nerve Dorsal rami Ventral rami  Dermatomes Because of overlap between adjacent spinal nerves, sensory (cutanous) loss results only if two or more consecutive spinal nerves are lesioned. T4 T5 T6 T6 dermatome T7 T8 Herpes Zoster (shingles ) T 9  Spinal Nerves Recap Dorsal root (sensory) Dorsal horn (sensory) Dorsal root ganglion (cell bodies) Lateral Spinal nerve Spinal horn nerve Dorsal Dorsal (motor) ramus ramus Ventral Ventral ramus ramus White ramus Ventral Gray r.c. communicans Ventral root horn (motor) (motor) Sympathetic chain ganglion Sympathetic nervous system (Next Lecture Topic)  Muscles of the back Motor neuroblast (from basal plate of intermediate layer) forming somatic Muscles motorneuron of the body wall and limbs  Sweat glands, vascular smooth muscle and hair follicle smooth muscle Motor neuroblast Motor neuroblast (from (from neural basal plate of crest) forming intermediate layer) visceral forming visceral motorneuron motorneuron (pre- (post- ganglionic sympathetic) ganglionic sympathetic)  Skin of the back Sensory neuroblasts (from neural crest) in DRG forming primary sensory nerves Skin of the body wall and limbs  Spinal Nerves Recap Dorsal root (sensory) Dorsal root ganglion (cell bodies) Skin and intrinsic muscles of back plus sympathetics Skin and muscles of body Ventral root (motor) wall and limbs Spinal plus nerve sympathetics (mixed) A spinal nerve and its branches contain mixed fibers (sensory/motor/autonomics  References Moore KL, Dalley AF, Clinically Oriented Anatomy, Seventh Edition. 2014. Frank H. Netter. Atlas of Human Anatomy 6th, 2014