Articulations & the Axial Skeleton PDF

Articulations & the Axial Skeleton Images from Human Anatomy 8th ed., © 2015, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 3rd ed., © 2015 by McKinley & O’Loughlin, denoted by “Mc”. 1 Articulations • occur wherever two bones meet • movement occurs at articulation...

Articulations & the Axial Skeleton Images from Human Anatomy 8th ed., © 2015, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 3rd ed., © 2015 by McKinley & O’Loughlin, denoted by “Mc”. 1 Articulations • occur wherever two bones meet • movement occurs at articulations; however: • not all articulations permit movement • classified structurally, by what tissue joins the articulating bones, OR • functionally, by the range of movement permitted – synarthroses (no movement) – amphiarthroses (little movement) – diarthroses (free movement) 2 Synarthroses are Immoveable A A. fibrous synarthroses: bones joined by dense irregular CT A • suture, e.g. between bones of skull, gomphosis between each tooth and its bony socket B. cartilagenous synarthroses: bones joined by cartilage B • C C. bony fusion: two bones become one • Ma8.1 synchondrosis, e.g. epiphyseal plate of a growing bone, first costosternal joint synostosis, e.g. skull, sacrum, hip bones, sternum, vertebrae, mature long bones 3 Amphiarthroses permit slight movement A. fibrous amphiarthrosis: bones joined by a ligament or band of CT A – B B. cartilaginous amphiarthrosis: bones joined by a wedge of cartilage – Ma8.1 syndesmosis, e.g. distal tibiofibular joint symphysis, e.g. intervertebral discs, symphysis pubis 4 Diarthroses (Synovial Joints) are Freely Moveable A. fibrous joint capsule encloses joint space Periosteum B. articular cartilages cover articular surfaces C. synovial membrane covers all internal, nonarticular surfaces; secretes synovial fluid D A D. joint cavity contains synovial fluid B – lubricant C Ma8.1 – shock absorber – medium for solute transfer between blood & cartilages 5 Synovial Joints: Accessory Structures A. articular discs or menisci, such as medial & lateral menisci of knee joint B. fat pads accommodate joint mvt C. tendons help to stabilize joint C D. bursae are sacks of synovial membrane containing synovial fluid – facilitate relative mvt between structures, B – eg. may be subcutaneous or subtendinous – when inflamed, result in bursitis A D Ma8.1 • intrinsic ligaments: thickenings of the joint capsule across certain aspects of the joint • extrinsic ligaments – intracapsular – extracapsular 6 Stability vs. Mobility • stability is inversely proportional to mobility Mc9.1 Mobility Most mobile Shoulder Immovable Hip Elbow Very unstable Intervertebral joints Suture Stability Most stable • stability / mobility is influenced by: – the shape of articulating surfaces – the capsule – ligaments – tone of surrounding muscles – other tissues around the joint 7 Functional Classification of Synovial Joints Types of Movement Initial position Linear motion Angular motion Circumduction Rotation Ma8.2 • linear motion: “gliding” • angular motion: uniaxial, biaxial, triaxial • circumduction a combination of angular motion around 2 axes • rotation: angular motion around the long axis 8 Structural Classification of Synovial Joints Gliding Joint eg. intercarpal joints Hinge Joint (uniaxial) eg. elbow joint Humerus Carpal bones Ulna Pivot Joint (uniaxial) eg. atlantoaxial joint Ellipsoidal Joint (biaxial) eg. radiocarpal joint Atlas Carpal bones Axis Saddle Joint (biaxial) eg. 1st carpometacarpal jt. Metacarpal of thumb Radius Ball-and-Socket Joint Humerus (triaxial) eg. shoulder joint Scapula III II I Ma8.2 Trapezium The Axial vs. Appendicular Skeleton The axial skeleton consists of: • The skull • The vertebral column – 24 vertebrae – the sacrum – the coccyx • The thoracic cage – 24 (12 paired) ribs – 1 sternum The appendicular skeleton consists of: • The pectoral girdles & upper limbs Ma6.1 • The pelvic girdles & lower limbs 10 The Skull • includes the 8 bones that form the cranium and the 14 facial bones A A. The Cranium • internally, the cranial cavity houses the brain • externally, provides muscular attachment • articulates inferiorly with the vertebral column B. Facial Bones B Ma6.2 • surround entrances to digestive and respiratory tracts • provides muscular attachment for muscles of facial expression and mastication 11 The Skull SKULL FACE 14 2 Maxillae Palatine bones Nasal bones Inferior nasal conchae 2 2 2 Zygomatic bones Lacrimal bones Vomer Mandible 2 2 1 1 CRANIUM 8 1 Occipital bone Parietal bones Frontal bone Temporal bones Sphenoid Ethmoid 2 1 2 1 1 ASSOCIATED BONES Hyoid bone 1 7 Auditory ossicles enclosed in temporal bones (detailed in Chapter 18) Hyoid bone Nasal bone Frontal bone Lacrimal bone Parietal bone Vomer Zygomatic bone Maxilla Ethmoid Temporal bone Auditory ossicles Sphenoid Mandible Ma6.2 Occipital bone 6 The Skull: Anterior View A. the frontal bone – forms forehead, roofs of orbits B. supraorbital foramen B C. the maxillae A D. infraorbital foramen F F D E. superior alveolar process G G C E C F. the nasal bones G. the zygomatic bones H. the mandible I. inferior alveolar process Ma6.3 I H J. mental foramen J 13 The Skull: Superior View A. the frontal bone B. the parietal bones A C. the coronal suture C D. the sagittal suture D B B F. the lambdoid suture F Ma6.3 E. the occipital bone E 14 The Skull: Posterior View A A B A. the parietal bones C B. the occipital bone C. the lambdoid suture D. external occipital protuberance D E. the mandible E Ma6.3 15 A. the occipital bone The Skull: Lateral View B. the parietal bone C. the frontal bone C B D. the maxilla J K A E I G H E. the nasal bone F. the mandible D G. head of the mandible H. the zygomatic bone (zygoma) F I. temporal process of ZB J. The sphenoid bone Ma6.3 K. the temporal bone 16 The Temporal Bone A. zygomatic process of TB B. squamous part D C C. squamous suture D. pterion B E. external acoustic meatus A G. mastoid process mastoid air cells E F G Ma6.3 H F. temporomandibular joint / TMJ H. styloid process 17 The Skull: Inferior View A. the occipital bone B. occipital condyles articulate with C1 H C. the parietal bones D D. the temporal bones F G B B E. mastoid process E F. styloid process C Ma6.3 C A G. mandibular fossa H. zygomatic process of TB 18 The Skull: Inferior View I. the zygomatic bone (zygoma) M L N O K D B B C I J H Q F G I J. temporal process of ZB K. the sphenoid bone L. the maxilla E M.palatine process C N. the palatine bone O. the volmer Ma6.3 A 19 Cavities within the Skull A coronal section through the skull A. the cranial cavity B. the orbits C. the nasal cavities A D B C E F The Paranasal Air Sinuses • continuous with nasal cavities, lined by mucous membrane D. frontal E. ethmoidal air cells F. maxillary G Ma6.16 • sphenoid G. The Oral Cavity 20 The Base of the Cranium A. frontal bone A B. parietal bones C. occipital bone D. foramen magnum F G E E. temporal bones D F. squamous part B G. petrous part C Ma6.4 H H. petrous ridge 21 M The Base of the Cranium I. sphenoid bone A K J J. greater wing I L. hypophyseal fossa or sella turcica L F G K. lesser wing M. ethmoid bone E D – the cribriform plate & crista galli B – lateral masses contain the ethmoid air cells C Ma6.4 H – perpendicular plate contributes nasal septum 22 The Ethmoid Bone Crista galli Perpendicular plate Ethmoid bone, anterior view lateral masses contain the ethmoid air cells perpendicular plate contributes to the nasal septum Sphenoid bone Ethmoid bone Vomer Lateral mass containing ethmoid air cells Mc7.16 Palatine bone Mc7.15a Anterior view 23 The Cranial Fossae A A. Anterior cranial fossa B • houses frontal lobes of brain C B. The middle cranial fossa • houses temporal lobes of brain A B C. The posterior cranial fossa C • Mc7.17 houses the cerebellum 24 A C1 2 3 4 5 6 7 T1 Vertebral Regions A. Cervical region: 7 cervical vertebrae, C1 – C7 2 B. Thoracic region: 12 thoracic vertebrae, T1 – T12 3 4 5 B – articulate with ribs, contribute to bony thorax 6 7 8 C. Lumbar region: 5 lumbar vertebrae, L1 – L5 9 10 11 D. Sacral region: sacrum originates as 5 vertebrae, S1 – S5 12 L1 – fused in maturity 2 C 3 – contributes to bony pelvis 4 5 D E E. Coccygeal region: originates as 3 - 5 vertebrae, Co1 – Co5 S1 2 3 4 5 – fusion is variable Mc7.28 25 Spinal Curves A 1° curves: thoracic (B) & sacral (D) curves • develop prenatally 2° curves: cervical (A) & lumbar (C) curves B • develop postnatally C D Ma6.19 • cervical curve develops with the ability to hold the head up • lumbar curve develops with upright posture • lumbar curve critical in maintenance of balance 26 Anatomy of a Typical Vertebra D Inferior view F B E Posterior view A. vertebral body (anterior) – weight bearing B. vertebral arch (posterior) C G – pedicles G F E A Lateral and inferior view F E D – laminae C. vertebral foramen D. 1 spinous process A E. 2 transverse processes D G F. 2 sup. articular processes C Ma6.20 G. 2 inf. articular processes 27 Regional Variations in Vertebrae • structural variations in vertebrae reflect regional specializations in function in a rostrocaudal direction: • the size of the vertebral body increases – load increases • the diameter of the vertebral canal decreases – diameter of spinal cord decreases • regional differences in processes – reflect regional differences in function, movement – e.g. transverse foramina in cervical region, costal facets in thoracic region 28 Atlas (C1) Superior view A The Atlas and the Axis The Atlas A B A. superior articular facets B – articulate with the occipital condyles – “yes” Axis (C2) B. transverse foramina C D B – accommodate the vertebral arteries D The Axis C. dens originally the body of the atlas, absorbed by the axis D. superior articular facets B E C Posterosuperior views The Atlas and Axis Articulated E. the transverse ligament of the atlas – “no” Mc7.30 29 Intervertebral Articulations C A. vertebral canal houses the spinal cord B. intervertebral foramina accommodate spinal nerves C. zygapophyseal joints A B • join superior & inferior articular processes of adjacent vertebrae • plane synovial joints allowing slight gliding movements Ma8.7 30 Intervertebral Articulations D. intervertebral discs • symphyses, consisting of: E. fibrocartilagenous anulus fibrosus joins disc to adjacent vertebral bodies J F K E A F. gelatinous core, the nucleus pulposus is largely water intervertebral ligaments G H C D G. supraspinous ligament H. interspinous ligaments I B I. anterior & J. posterior longitudinal ligaments Ma8.7 K. ligamentum flavum 31 The Sacrum Anterior View • fxns: articulates with lower limb; muscle attachment; protects pelvic viscera • originates as 5 sacral vertebrae; fusion begins ~ puberty; complete in adulthood B Anterior view A. apex E B. base C C. transverse ridges D. ant. sacral foramina C D E. sacral promontory C The Coccyx (F) C A Mc7.31 F • originates as 3 – 5 coccygeal vertebrae • begin fusing in early adulthood • provides muscular and ligamentous attachment for perineum 32 The Sacrum Posterior View J F. coccyx G. median sacral crest K H. post. sacral foramina I. auricular surface articulates with pelvic girdle G I H J. sacral canal is the continuation of spinal canal K. superior articular processes Mc7.31 F 33 Nomenclature Images from Human Anatomy 8th ed., © 2015, by Martini, Timmins and Talitsch, denoted by “Ma”. The Importance of Precise Language Ma1.7 2 Superior: Above Cranial or Cephalic Toward the head “The thoracic region of the spinal column is cranial to the sacral region.” Posterior or Dorsal Posterior: Toward the back Dorsal: Toward the back (equivalent to posterior when referring to human body) Anterior or Ventral Anterior: Toward the front • the anatomical position • terms are usually* relative i.e. compare the positions of two structures Ventral: Toward the belly • (equivalent to anterior when referring to human body) “The navel is on the “The scapula (shoulder anterior (ventral) blade) is located posterior surface of the trunk.” to the rib cage.” Caudal Toward the tail (coccyx in humans) “The lumbar region of the vertebral column is caudal to its cervical region. Lateral view Ma1.10 The Anatomical Position & Directional Nomenclature Inferior: Below general terms – anterior vs. posterior (~ ventral vs. dorsal) – superior vs. inferior – cranial / cephalic vs. caudal – medial vs. lateral – median* is an absolute term – proximal vs. distal (re. limbs; also the digestive system, etc.) – superficial vs. deep • specialized terms – re. nervous system: rostral vs. caudal Right Left Proximal Closer to an attached base “The shoulder is proximal to the wrist.” The Anatomical Position & Directional Nomenclature • the anatomical position • terms are usually* relative i.e. compare the positions of two structures • general terms – anterior vs. posterior Lateral Medial (~ventral vs. dorsal) Away from Toward the the midline midline – superior vs. inferior Proximal Distal – cranial / cephalic vs. caudal Farther from an attached base – medial vs. lateral “The fingers are distal to the wrist.” – median* is an absolute term OTHER DIRECTIONAL TERMS – proximal vs. distal (re. limbs; Superficial Closer to the body surface also the digestive system, etc.) Distal “The skin is superficial to muscle.” – superficial vs. deep Deep Farther from the body surface “The bone of the thigh is deep to • specialized terms Anterior the surrounding skeletal muscles.” view – re. nervous system: rostral vs. Ma1.10 caudal Sectional Nomenclature Frontal or coronal plane Separates the body into anterior and posterior portions. Plane is oriented parallel to long axis Sectioning produces a 2D representation of a 3D structure Sagittal plane Separates the body into right and left portions. A midsagittal section passes through the midline, dividing the body into right and left halves. A parasagittal section misses the midline, creating right and left portions of unequal size. Plane is oriented parallel to long axis Transverse or crosssectional plane Plane is oriented perpendicular to long axis Ma1.11 In humans, is equivalent to the horizontal plane; separates the body into superior and inferior portions. Regional Nomenclature Frons or forehead Nasus or nose (nasal) (frontal) Oculus or eye (orbital or ocular) Cranium or skull (cranial) Cephalon or head (cephalic) Facies or face (facial) Oris or mouth (oral) Mentis or chin (mental) Axilla or armpit (axillary) Brachium or arm (brachial) Antecubitis or front of elbow (antecubital) Antebrachium or forearm (antebrachial) Carpus or wrist (carpal) Palma or palm (palmar) Pollex or thumb Digits or fingers (digital) Patella or kneecap (patellar) Crus or leg (crural) Tarsus or ankle (tarsal) Ma1.8 Digits or toes (digital) Hallux or great toe Auris or ear (otic) Bucca or cheek (buccal) Cervicis or neck (cervical) Shoulder Thoracis or thorax, (acromial) chest (thoracic) Dorsum or Mamma or breast back (dorsal) (mammary) Trunk Abdomen (abdominal) Umbilicus or navel (umbilical) Lumbus or loin Pelvis (pelvic) (lumbar) Cephalon or head (cephalic) Cervicis or neck (cervical) Upper limb Manus or hand (manual) Inguen or groin (inguinal) Gluteus or buttock (gluteal) Pubis (pubic) Popliteus or back of knee (popliteal) Femur or thigh (femoral) Sura or calf (sural) Calcaneus or heel of foot (calcaneal) Pes or foot (pedal) Planta or sole of foot (plantar) Lower limb The heart is ___________ to the lungs. The stomach is __________ to the heart. The elbow is ____________ to the hand. The breastbone is _________ to the vertebral column. The skin is __________ to bones. The bowels are ___________ to the esophagus. The lumbar region of the back is ___________ to the cervical region. The head is ____________ to the body. 7 1. The spleen is an unpaired, left-sided structure. It is possible to see the spleen in all of the following planes of section, EXCEPT: a) parasaggital b) coronal c) midsagittal d) horizontal 2. The kidneys are bilaterally paired structures not found in the midline. In which plane of section is it possible to see only one kidney? a) parasaggital b) coronal c) midsagittal d) horizontal 8 The Spinal Cord & Spinal Nerves Images from Human Anatomy 8th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Images from Neuroanatomy: An Atlas of Structures, Sections, and Systems, 7th ed., by Duane E. Haines, © 2007 indicated by “HA”. Cerebrum CNS = Brain + Spinal Cord Brain enclosed in cranium, consists of the: Brain stem Cerebellum 1. Cerebrum Spinal cord • bilaterally paired, anatomically symmetrical cerebral hemispheres 2. Brainstem • contains nuclei, white matter tracts, vital centers • continuous with spinal cord 3. Cerebellum Mc14.1 • bilaterally paired cerebellar hemispheres • concerned with coordination of movement, etc. Spinal Cord the elongated continuation of the brainstem enclosed in the vertebral column 2 PNS = Cranial Nerves, Spinal Nerves & Ganglia Cranial Nerves Cranial Nerves Spinal Nerves • arise from the brain & brainstem Ganglia • special senses: vision, hearing, balance, smell, taste • general sensation from the face • voluntary motor control of striated muscle in the face • parasympathetic outflow to targets in face (eyes, glands) as well as thoracic and abdominal viscera Spinal Nerves • arise from the spinal cord • general sensation from body and back of head • voluntary motor control of striated muscle in the body • all sympathetic outflow (thoracic and abdominopelvic viscera, skin, AND targets in face) • parasympathetic outflow to visceral organs of pelvis Ganglia Mc14.1 • associated with both cranial and spinal Ns 3 Dermatomes & Myotomes C2–C3 NV Dermatomes C2–C3 C2 C3 T2 C6 C8 C7 L1 L2 T1 L3 L4 L5 C4 C5 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 S2 • dermatome: the area of skin innervated by a given spinal level C3 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 L1 L2 L4L3 L5 C4 C5 T2 C6 T1 C7 • myotome: the group of muscles supplied by a given spinal level SS 43 L1 S1L5 S5 C8 L2 S2 • lesion of a given spinal nerve results in a stereotyped loss of sensory input and motor output L3 S1 L4 ANTERIOR Ma14.7 POSTERIOR 4 The Meninges Gray matter • within bony coverings, CNS enclosed in meninges White matter Spinal nerve • composed of three layers: Pia mater Arachnoid mater Dura mater – dura mater – arachnoid mater – pia mater • subarachnoid space contains cerebrospinal fluid (CSF) Ma14.2 5 VERTEBRAE Spinal nerves C1-C8 Spinal nerves T1-T12 Spinal nerves L1-L5 Spinal nerves S1-S5 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 1 2 3 4 5 Rostrocaudal Subdivisions of the Spinal Cord Cervical spinal segments C1-C8 • bilaterally paired spinal nerves are named according to their associated vertebra Thoracic spinal • C1 spinal nerves emerge from segments T1-T12 above the atlas…… • axons within a spinal nerve (or peripheral nerve arising from it) come from cell bodies located at a prescribed spinal level or segment Lumbar spinal segments L1-L5 Sacral spinal segments S1-S5 • the naming of a spinal segment corresponds to its spinal nerve 6 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 1 2 3 4 5 The Cauda Equina & Dural Sac A. spinal cord ends as the conus medullaris at vertebral level L2 • more caudal nerves must descend to exit between appropriate vertebrae B. mass of nerves below vertebral level L2 referred to as the cauda equina A B C • spinal cord (like the rest of the CNS) enclosed in meninges: dura, arachnoid & pia maters • pia covers the spinal cord faithfully C. dura & arachnoid form the dural sac which extends to vertebral level S2 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 1 2 3 4 5 The Lumbar Cistern A. subarachnoid space lies between arachnoid and pia maters, contains cerebrospinal fluid (CSF) B. pial filum terminale interna extends caudally from conus medullaris A C. at S2, filum terminale takes layers from sac forming filum terminale externa which extends to the coccyx B D. expanded subarachnoid space between vertebral D levels L2 & S2, is the lumbar cistern C • CSF sampled in a lumbar puncture 8 CONUS MEDULLARIS CAUDA EQUINA HA2.4 DURAL SAC FILUM TERMINALE INTERNA 9 Ma14.1 Cervical spinal nerves Thoracic spinal nerves C1 C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T9 T11 Lumbosacral enlargement L1 Conus medullaris T12 L2 L3 L4 L5 Sacral spinal nerves Coccygeal nerve (Co1) S1 S2 S3 S4 S5 • here, the vertebral laminae have been cut, thus opening the spinal canal • the dural sac is open, exposing the spinal cord in situ from the dorsal aspect T8 T10 Lumbar spinal nerves Cervical enlargement The Spinal Cord in Situ Cauda equina inc. filum terminale interna Filum terminale externa • the cauda equina & filum terminale interna are within the lumbar cistern • nerves arising from the spinal cord extend toward the intervertebral foramina to exit 10 between adjacent vertebra Fat and BVs Fill the Epidural Space • this is the site of injection of an epidural anesthetic • arachnoid held against dura by hydrostatic pressure of CSF • spinal nerves formed by the union of a dorsal and ventral root Epidural space POSTERIOR Spinous process of vertebra Dura mater Arachnoid Subarachnoid space Pia mater Spinal cord Ma14.2 Spinal nerve Intervertebral foramen Body of vertebra ANTERIOR 11 CSF is Sampled in a Lumbar Puncture Position of lumbar puncture needle in interspinous space L3 Cauda equina L4 Subarachnoid space Filum terminale interna Vertebral canal MIDSAGITTAL SECTION OF VERTEBRAL COLUMN AND LUMBAR CISTERN 12 CSF is Sampled in a Lumbar Puncture Conus medularis Subarachnoid space containing cerebrospinal fluid and spinal nerve roots Cauda eqina and filum terminale interna L5 vertebra Filum terminale externa Ma14.2 MRI, lateral view A Cross Section Through the Spinal Cord POSTERIOR Ma14.5 ANTERIOR Organization of the Spinal White Matter • located superficially, runs longitudinally • carries sensory info upward, motor info downward Sulci Delineate the White Matter into Columns Dorsal median sulcus White matter Dorsal funiculus (column) Lateral funiculus (column) Ventral funiculus (column) Mc16.5 Ventral median fissure Dorsal lateral sulcus (dorsal rootlets enter) Ventral lateral sulcus (ventral rootlets enter) 15 Organization of the Spinal Grey Matter • deep, forms a continuous column extending the length of the cord • at all levels, grey matter forms a butterfly in XS, divided into: – dorsal horns: primarily sensory Ns – ventral horns: primarily motor Ns • at certain levels, intermediolateral cell column (IML) present (next slide…) Grey matter Dorsal horn Ventral horn Mc16.5 LOWER CERVICAL Regional Variations in the Spinal Cord The ventral horns are enlarged at cervical and lumbar levels • cervical enlargement: ventral horns from C5 – T1 contain somatic motor Ns innervating the arms THORACIC • lumbosacral enlargement: ventral horns from L2 – S2 contain somatic motor Ns innervating the legs IML cell columns form lateral horns from T1 to L2 • contain cell bodies of sympathetic preganglionic Ns LUMBOSACRAL IML cell columns are present from S2 – S4 • contain cell bodies of parasympathetic preganglionic Ns • their axons form the pelvic splanchnic nerves S2 – S4 • because of large ventral horns, does not form a distinct “lateral horn” White matter • amount of white matter ↓ in rostrocaudal direction 17 Dorsal Roots Carry Sensory Information Neurons of the dorsal horn are sensory. • Neurons of the dorsal horn receive sensory information from body wall, limbs, viscera • cell bodies of sensory Ns located in dorsal root ganglia, DRG • sensory input conveyed by dorsal roots • in a lesion of a the dorsal root, sensory signs seen in a dermatomal distribution Dorsal root ganglion Sensory axon DH Dorsal root LH VH 18 Ventral Roots Carry Motor Information Neurons of the ventral horn are somatic motor. • Somatic motor Ns control striated muscle of the body wall & limbs Neurons of the IML cell column are visceral motor. • Visceral motor Ns control visceral targets • both somatic & visceral motor output conveyed by ventral roots • a lesion of a ventral root will manifest with motor signs in a myotomal distribution Dorsal root ganglion Sensory axon DH Dorsal root IML VH Ventral root Visceral motor axon Somatic motor axon 19 Spinal Nerves are Mixed Nerves • spinal nerves formed by union of dorsal & ventral roots • thus contain both sensory and motor fibres; i.e. they are mixed nerves • in a lesion of a spinal nerve, both sensory and motor signs may be seen Dorsal root ganglion DH Sensory axon Dorsal root Spinal nerve LH VH Ventral root Visceral motor axon Somatic motor axon 20 The Spinal Cord and Spinal Nerves in Context Deep muscles of back POSTERIOR Spinous process Dorsal root Dorsal root ganglion Spinal cord Dorsal ramus Ventral ramus Spinal nerve Ventral root Body of vertebra Rami communicantes Sympathetic Trunk ganglion Mc16.5 ANTERIOR 21 Spinal Cord: Anterior View Pia mater Denticulate ligaments Dorsal root of C4 Ventral root of C4 Spinal blood vessel Dura and Arachnoid mater (reflected) Ma14.2 Herniated Disc Compressed area of spinal nerve Area of distortion Nucleus pulposus Mc8.9 Spinal nerve Spinal cord Anulus fibrosus Herniated disc, superior view 23 Somatic Nerve Plexuses • a plexus is a “braid” • recall, dorsal & ventral rami are mixed nerves • ventral rami of some spinal nerves blend to create compound nerves carrying axons from 2 or more spinal segments • the overlapping network between the ventral rami and the final compound peripheral nerve is called a nerve plexus Ma14.8 • ∴ a muscle innervated by a compound nerve is controlled by more than one spinal segment 24 eg. the Brachial Plexus Ma14.10 25 Visceral Nerve Plexuses • viscera are controlled by the balance between the sympathetic and parasympathetic inputs at any point in time • sympathetic and parasympathetic outflow originate from different regions of the CNS • they overlap, prior to innervating their target, in a visceral plexus Ma17.9 26 Reflexes • reflex: an involuntary motor response (output) evoked by a specific stimulus (input) • stimulus (input) may be external or internal – external stimuli: – internal stimuli: • motor response (output) may involve skeletal, cardiac or smooth muscle – skeletal muscle – cardiac muscle – smooth muscle • thus, reflexes occur in both the somatic and visceral nervous systems • reflexes function to maintain homeostasis or the status quo • pathway from receptor to effector is a reflex arc • great variation in complexity between different reflex arcs 27 Meninges & the Cerebral Hemispheres Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. Organization of Lecture 1. Overview of the brain, cerebral meninges, dural venous sinuses (slides 3 - 15). 2. The ventricular system (slides 16 - 24). 3. Cerebral hemispheres and functional localization, the diencephalon (slides 25 - 38). 2 An Overview of the Brain A. Cerebral hemispheres • bilaterally paired; separated by the longitudinal fissure • anatomically ~ symmetrical • functionally asymmetrical A B B. Diencephalon • grey matter buried within the cerebral hemispheres • includes the paired thalami, hypothalamus, epithalamus C E D C. Brainstem • includes the midbrain, pons & medulla • contains vital autonomic centres, cranial nerve nuclei, white matter tracts Ma15.1 D. Cerebellum • consists of bilaterally paired cerebellar hemispheres • separated from the cerebral hemispheres by the transverse fissure (E) 3 Cerebral Cortex • a layer of grey matter (neuronal cell bodies) 4-6 mm thick • highly folded in sulci (grooves) and gyri (bumps) which ↑ surface area – sulcus (singular), gyrus (singular) – particularly deep sulci are called fissures • variability in sulci & gyri between brains and between hemispheres of the same brain • however, some sulci and gyri are fairly consistent between brains and are named • these are used as landmarks to divide the brain into anatomical regions, called lobes…. 4 Lobes of the Cerebral Hemispheres CENTRAL SULCUS FRONTAL LOBE PARIETAL LOBE TEMPORAL LOBE LATERAL FISSURE Mc15.1 PARIETOOCCIPITAL FISSURE (on medial surface) OCCIPITAL LOBE PREOCCIPITAL NOTCH 5 Lobes of the Cerebral Hemisphere 6 7 A. skin Coverings of the Brain B. periosteum C. cranium Mc15.4 D. dura mater E. periosteal layer A B C E F I J K L M H F. meningeal layer G. dural reflection H. dural venous sinus D I. subdural space – “potential” space J. arachnoid mater K. subarachnoid space – contains CSF, BVs L. pia mater G M. cerebral cortex 8 Loose connective tissue and periosteum of cranium ANTERIOR Cranium Dura mater Epicranial aponeurosis Subarachnoid space Arachnoid mater Scalp Cerebral cortex covered by pia mater POSTERIOR Ma16.4 The Dural Reflections in a Coronal MRI A FN-C9 A. falx cerebri B. parietal lobe C B C. lateral fissure D. temporal lobe E. tentorium cerebelli D E F F. cerebellum 10 Midsagittal view Dural Reflections A • meninges form rigid folds in major fissures: A. falx cerebri in longitudinal fissure – separates right and left cerebral hemispheres B. tentorium cerebelli in transverse fissure B C – separates occipital lobe of cerebrum from cerebellum C. diaphragma sellae Pituitary gland Ma16.3 Sella turcica of sphenoid – stabilizes position of the pituitary gland in the skull base 11 The Dural Reflections in a Sagittal MRI A. frontal lobe FN-S1 D B. parietal lobe B A C. occipital lobe C E D. tentorium cerebelli F H E. brainstem G F. cerebellum G. foramen magnum H. spinal cord 12 Dural Venous Sinuses I B A Note the dural reflections, the falx cerebri and tentorium cerebelli. Note the related dural venous sinuses: • in margins of dural reflections; i.e. between periosteal and meningeal layers of dura mater C • drain venous blood from the brain into R & L internal jugular veins A. superior sagittal sinus D B. inferior sagittal sinus C. straight sinus D. confluence of sinuses Ma16.3 Note the dural reflections in bold. Note their related sinuses. Mc15.5 14 Dural Venous Sinuses and Cerebral Venous Drainage 2 4 Superior sagittal sinus Dura mater Subdural “space” Subarachnoid space Ma16.5 3 Subdural “space” Subarachnoid space Arachnoid mater Arachnoid trabeculae Pia mater Arachnoid granulation Falx cerebri Cranial Meninges Cerebral cortex Cerebral vein 1 Cerebral cortex Perivascular space D Dural Venous Sinuses II E A. confluence of sinuses F C B A B. transverse sinus C. sigmoid sinus to jugular foramen D. cavernous sinus receives ophthalmic veins from orbit D E F Ma6.11 A C B E. superior petrosal sinus F. inferior petrosal sinus Diaphragma sellae over pituitary gland Crista galli Tentorium cerebelli Ma16.23 Falx cerebri (cut) Tentorium cerebelli (cut edge) Superior view The Ventricular System • the nervous system originates from a hollow, fluid-filled tube, the neural tube • cells of tube wall proliferate, differentiate forming cells of the nervous system • enclosed fluid-filled space, the neural canal forms the ventricular spaces of the CNS • contains cerebrospinal fluid (CSF), produced by the choroid plexus within the ventricles 18 Choroid Plexus in the Lateral Ventricle Remember: TJs between the ependymal cells of the choroid plexus forms the blood-CSF barrier. Coronal section through the cerebrum Choroid plexus 19 Structural Characteristics of Neural Capillaries Remember: TJs between the endothelial cells of the cerebral BVs forms the blood-ISF barrier. Capillaries in neural tissue are of the continuous type. Capillaries in many other tissues are fenestrated. 20 B BBB Breakdown A • results in ↑ permeability of brain capillaries • causes vasogenic edema, which ↑ intracranial pressure and can act like a space occupying lesion C • in imaging, seen with contrast agent, that doesn’t cross intact BBB • BBB breakdown occurs in tumors, arteriovenous malformations, inflammation (2° to stroke, MS, etc.) A. Normal brain with contrast B. Gadolinium-enhanced MRI showing BBB breakdown in a glioblastoma multiforme. 21 C. Gadolinium-enhanced MRI showing BBB breakdown due to inflammation in active MS lesions. The Ventricular System • ventricular spaces are associated with subdivisions of the nervous system: CEREBRAL HEMISPHERES A. BILATERALLY PAIRED LATERAL VENTRICLES DIENCEPHALON B. THIRD VENTRICLE MIDBRAIN C. CEREBRAL AQUEDUCT PONS, MEDULLA, CEREBELLUM D. FOURTH VENTRICLE SPINAL CORD E. CENTRAL CANAL A A B B C C Lateral view Ma16.2 D D E Anterior view E 22 Continuity of the Ventricular System A B Ma16.2 C A D Lateral view E H F G A. R, L lateral ventricles B. interventricular foramen C. third ventricle D. cerebral aqueduct E. fourth ventricle F. central canal Fourth ventricle is continuous with the subarachnoid space through the median aperture (G) and the lateral apertures (H). A C B D E H F G (very) Schematic coronal section 23 Choroid plexus in lateral ventricle Arachnoid granulations The Circulation of CSF • CSF is produced by the choroid plexus, present in all ventricles • total volume CSF ~150 mL • produce ~ 500 mL / day Choroid plexus of third ventricle Aqueduct of midbrain Choroid plexus of fourth ventricle Subarachnoid space Central canal • ∴ turned over 3 times per day • CSF circulates through ventricles, enters subarachnoid space via median and lateral apertures of fourth ventricle • circulates in subarachnoid space Lumbar cistern Ma16.7 NEXT SLIDE Choroid plexus in lateral ventricle Arachnoid granulations The Circulation of CSF • CSF is returned to venous blood via arachnoid granulations in dural venous sinuses Dural venous sinus Choroid plexus of third ventricle Aqueduct of midbrain Choroid plexus of fourth ventricle • Also along the sheaths of cranial and spinal nerves to surrounding lymphatics Cranium Dura mater (endosteal layer) Central canal Arachnoid granulation Subarachnoid space Arachnoid trabecula Central canal Lumbar cistern Dura mater (meningeal layer) Cerebral cortex Ma15.6 Pia mater Subarachnoid space Arachnoid mater 25 MRI of normal ventricles MRI of ventricles in hydrocephalus 26 Midsagittal section Association tracts Parietal lobe Corpus callosum Commissural tracts (in corpus callosum) • cerebral hemispheres receive sensory information from, issue motor commands to, the opposite side of the body • the cerebral cortex is grey matter Frontal lobe Temporal lobe The Medullary Centre Occipital lobe Coronal section • subcortical white matter – carries afferent information toward neuronal cell bodies of cerebral ctx – carries efferent information away from neuronal cell bodies of cerebral ctx – may be association, commissural or projection fibres Cerebral nuclei • buried within are grey matter structures – the basal nuclei (ganglia) Projection tracts Mc15.13 Thalamus – diencephalon (thalamus, hypothalamus, epithalamus) 27 28 Functional Localization in the Cerebral Cortex Motor Output • movement is planned and initiated in specific dedicated cortical areas Sensory Input • all sensory modalities ultimately reach the cerebral cortex, most after a relay in the thalamus • each modality has an area dedicated to it’s perception, its 1º sensory cortex; e.g. 1° somatosensory ctx, 1° visual ctx, 1° auditory ctx, etc. • each modality has an area dedicated to it’s interpretation, its association cortex; e.g. somatosensory assn. ctx, visual assn. ctx, auditory assn. ctx. • input from the various sensory modalities are integrated in the multimodal association cortices 29 Major Sulci & Gyri of the Cerebral Hemispheres Lateral view B A C D M L J G I F H E K Ma15.9 Left lateral view 30 Lobes of the Cerebral Hemisphere 31 32 Functional Localization in the Cerebral Cortex I A. 1º Motor Cortex (precentral gyrus) Superior view B A • control of voluntary, skilled mvt Hip Knee Ankle Toes • somatotopic representation of the contralateral half of body, the motor homunculus • area ∝ precision of movement of body part, not its size Pharynx Coronal section through precentral gyrus B. Premotor Ctx, Supplementary Motor Area (adjacent portions of frontal lobe) • fxn. in programming of, preparation for, mvt and control of posture Mc15.12 Lateral Medial 33 Functional Localization in the Cerebral Cortex II Superior view C. 1º Somatosensory Cortex (postcentral gyrus) C D Hip Leg Foot Toes Genitals • perception of somatosensation • somatotopic representation of the contralateral half of body, the sensory homunculus • area ∝ density of sensory innervation of a given body part, not its size Coronal section through postcentral gyrus Intra-abdominal D. Somatosensory Association Cortex (adjacent portions of parietal lobe) • interpretation of somatosensation Medial Mc15.12 Lateral • conscious awareness of the contralateral half of the body 34 Coronal MRI 35 Functional Localization in the Cerebral Cortex III E. 1º Visual Cortex (on either side of the calcarine fissure in the occipital lobe) • functions in visual perception F. Visual Association Cortex (remainder of occipital lobe) • interpretation of visual images in the context of past experience • lesion causes deficit in visual interpretation and recognition G. 1º Auditory Cortex (portions of temporal lobe within lateral fissure) • conscious perception of sound • organized as a “tonotopic” map of cochlear duct H. Auditory Association Cortex (adjacent portions of temporal lobe) • interpretation of auditory input in the context of past experience, etc. • in dominant hemisphere, adjacent to sensory speech or “Wernicke’s” area • in the nondominant hemisphere, the corresponding area interprets prosidy 36 Functional Localization in the Cerebral Cortex IV I. Motor Speech Area (portions of frontal lobe ant. to precentral gyrus) • in the dominant (usually the left) hemisphere only; a.k.a. “Broca’s area” • functions in motor aspects of speech • in the nondominant hemisphere, the corresponding area controls prosidy J. 1 ° Gustatory Cortex (inf. part of postcentral gyrus and insula) • conscious perception of taste K. 1° Olfactory Cortex (temporal lobe) • conscious perception of smell Multimodal Association Cortices L. Prefrontal Cortex (frontal lobe) • integrates information from various assn. cortices • higher intellectual functions e.g. reasoning, prediction, emotion M. Inferior portions of parietal lobe • interface between somatosensory, visual and auditory association cortices 37 The Basal Nuclei A B • includes the A. caudate B. putamen C. globus pallidus or “pallidum” D. substantia nigra & subthalamus Functions • refine normal voluntary mvt. • not directly connected to spinal cord; i.e. do not directly control movement • diseases of basal nuclei present with: – hypokinesis (without paralysis) or hyperkinesis D Coronal section Mc15.14 C – altered posture and muscle tone – altered cognition, behavioural disturbances – eg. Parkinsonism 38 The Diencephalon I • thalamus, hypothalamus & epithalamus Thalamus: Functional Organization of Nuclei Sensory Nuclei • vision (lateral geniculate nucleus) • hearing (medial geniculate nucleus) • somatic sensation, conscious proprioception, taste (ventral posterior) Motor Nuclei Mc15.16 • associated with basal nuclei & cerebellum • movement planning & control (VA, VL) Limbic Nuclei Medial group Posteri • emotions, mood (ant. nuc. group) or group Anterior Lateral group MG group Association (multimodal) Nuclei LG • integrates sensory information; connects VA VL VP Ventral group with association cortices Intrinsic & diffuse-projecting Nuclei 39 Left anterolateral view • influences levels of arousal A. The Hypothalamus The Diencephalon II • maintains homeostasis via neural & hormonal means in response to interoceptive & limbic input B A • regulates reproductive, autonomic and instinctive functions, food & water intake, circadian rhythms, emotional aspects of behaviour…. B. The Epithalamus • includes the pineal gland – secretes melatonin Midsagittal section Mc15.15 – fxn. in circadian rhythm & onset of puberty 40 41 The Diencephalon in MRI A B A. B. C. D. Midsagittal section C D Thalamus Hypothalamus Epithalamus Area of subthalamus FN-S1 42 The Cerebral Hemispheres in Axon-Stained Section LATERAL VENTRICLES CEREBRAL CORTEX (grey matter) SUBCORTICAL WHITE MATTER THALAMUS (grey matter) BASAL NUCLEI (GANGLIA) (grey matter) THIRD VENTRICLE HYPOTHALAMUS (grey matter) CGS Coronal section 43 The Cerebral Hemispheres in Coronal MRI LATERAL VENTRICLES CEREBRAL CORTEX (grey matter) SUBCORTICAL WHITE MATTER DIENCEPHALON (grey matter) BASAL NUCLEI (GANGLIA) (grey matter) THIRD VENTRICLE FN-C15 44 Motor & Sensory Pathways Images from Neuroanatomy: An Atlas of Structures, Sections, and Systems, 7th ed., by Duane E. Haines, © 2007 indicated by “HA”. 1 Pathways • consist of a series of neurons which communicate at synapses cell bodies synapses axons cell bodies synapses axons cell bodies PATHWAY • number of neurons / pathway varies • neuronal cell bodies located in ganglia or nuclei • processing, modulation occurs within at synaptic relays • axons grouped to form nerves (in PNS) or tracts (in CNS) • in CNS, pathways are functionally segregated • in PNS, nerves are organized regionally, ie. no functional segregation • bilaterally paired, usually crossed • name often indicates origin & destination of tract 2 Somatic Motor Pathways Control Skeletal Muscle and Consist of a Two-Neuron Chain A B C CNS The upper motor neuron (UMN) D PNS A. cell body at higher centres (eg. cerebral hemispheres, brainstem) B. axon usually decussates, projecting to synapse onto: The lower motor neuron (LMN) C. cell body resides in the motor nucleus of a cranial nerve (face) OR in the ventral horn of the spinal cord (body) D. axon travels through either a cranial or a spinal nerve to synapse onto: Skeletal Muscle 3 CEREBRAL CORTEX Somatic Motor Pathways: LMNs • in the spinal cord, for control of skeletal muscle of the body: – cell bodies of LMNs are located in the ventral horn BRAIN STEM CERVICAL CORD – axons of LMNs reach their target muscle by travelling in the ventral root, spinal nerve, peripheral nerve to NMJ • in the brainstem, for control of skeletal muscle of the face: – cell bodies of LMNs are located in cranial nerve nuclei LUMBAR CORD – axons of LMNs reach their target muscle by travelling in a cranial nerve to the NMJ 4 The “Final Common Pathway”• Cerebral Cortex Vestibular Nuclei Reticular Formation Red Nucleus UMNs in several locations send signals to the LMN, however: • the LMN is the only neuron that contacts the muscle and therefore influences it BRAIN -STEM Lower Motor Neurons Muscle 5 • therefore, it is called the “final common pathway” (Charles Sherrington) • LMNs are typically large neurons with extensive dendritic trees that receive and integrate all the incoming signals BRAINSTEM LMNs Form Bilaterally Paired Motor Columns • brainstem: LMNs form a series of motor nuclei associated with certain cranial Ns • spinal cord: LMNs form the ventral horns CERVICAL CORD THORACIC CORD In the spinal cord: LMNs controlling axial musculature located at all spinal levels • innervate ipsilateral* axial muscles controlling posture & balance LMNs controlling distal limb muscles found in cervical and lumbosacral levels only • innervate ipsilateral distal limb muscles for skilled voluntary movement LUMBAR CORD • forms the lateral portion of the ventral horn, the “cervical (C5 – T1) and lumbosacral (L2 – S2) enlargements” Motor Columns of the Ventral Horn LOW CERVICAL THORACIC LUMBAR Axon-stained sections of the spinal cord 7 • Somatic Motor Pathways: UMNs A A B B LMNs are innervated by descending pathways consisting of upper motor neurons (UMNs) A. Lateral pathways: • UMNs descend in the lateral funiculus; include the lateral corticospinal tract (LCST) • innervate LMNs of the lateral dorsal horn to control distal limb muscles. • function in skilled voluntary movements B. Medial pathways: • UMNs descend in the ventral funiculus; inc. medial corticospinal tract (MCST) • innervate LMNs of the medial ventral horn to control axial and proximal limb muscles • function in the maintenance of posture and balance. 8 The Lateral Corticospinal Tract • Allows for skilled asymmetric limb mvt. 1° motor cortex • The corticospinal tract (CST) originates in 1° motor cortex of the precentral gyrus, which contains the cell bodies of UMNs. Brain stem • Axons of UMNs traverse the subcortical white matter of the cerebral hemispheres & brainstem. Cervical Cord • At the junction of the medulla and spinal cord, most fibres of the CST decussate & thus descend contralaterally in the lateral funiculus as the LCST. • (The remainder descend ipsilaterally as the MCST.) • Axons of the LCST synapse on LMNs in the lateral ventral horn, which innervate distal limb musculature for discrete, skilled movement. LCST LCST Lumbar Cord 9 Sensory Pathways • carry information from receptors to the CNS • interoceptors concern themselves with our internal environment – chemosensors, baroreceptors, stretch receptors, etc. • exteroceptors concern themselves with our external environment – “special senses” (sight, hearing, smell, vestibular) – somatic sensation (modalities: touch, pressure, vibration, conscious proprioception, nociception, temperature) • conscious sensation – a small fraction of sensory input reaches modality-specific 1° sensory cortex in the contralateral cerebral hemisphere – here, determine the location, nature of sensation 10 Basic Rules of Somatosensory Pathways 1. They consist of a three neuron chain, 1°, 2°, 3°. R PNS CNS Midline 2. The 1° neuron is pseudounipolar. Its cell body is located in a ganglion in the PNS. – for the body, the axon travels in a peripheral nerve, spinal nerve & dorsal root, and its cell body is located in a DRG. 3. The cell body of the 2° neuron is either a) in the dorsal horn of the spinal cord OR b) a brainstem nucleus (depending on the somatosensory modality); its axon projects to the contralateral thalamus. ∴ it’s the axon of this 2° neuron that decussates. 4. The cell body of the 3° neuron is located in the VP nucleus of the thalamus. Its axon projects to 1° SS cortex. 11 Functional Localization in the Spinal White Matter: Somatosensory Pathways DORSAL COLUMNS Fasciculus gracilis: touch, vibration & cons. proprioception ~ T6↓ Fasciculus cuneatus: touch, vibration & cons. proprioception ~ T6↑ Spinothalamic tract pressure, pain & temperature 12 The Spinothalamic Tract: Pressure, Pain & Temperature from the Body THALAMI • 1° neurons: • cell bodies lie in dorsal root ganglia in the PNS • project to the CNS via dorsal roots to synapse onto: SL XS THRU LUMBAR CORD: 1° SS CTX BRAIN STEM CERVICAL CORD STT • • • • 2° neurons: STT cell bodies lie in the dorsal horn of the spinal cord axons decussate ascend in the spinothalamic tract (STT) of the ventrolateral funiculus, becoming the: • spinal lemniscus (SL) in the brainstem, synapsing onto: • 3° neurons: • cell bodies lie in the VP nucleus of the thalamus & project to: • 1° somatosensory cortex in the postcentral gyrus LUMBAR CORD 13 Somatotopy within the Spinothalamic Tract As you ascend the spinal cord, more and more axons are added to the STT XS THRU CERVICAL CORD: STT C Homework Assignment 1: How might each lesion present over time? Assume a slowgrowing spaceoccupying lesion. Cervical intramedullary lesion T L S/Co Cervical extramedullary lesion 14 Basic Rules of Somatosensory Pathways 1. They consist of a three-neuron chain, 1°, 2°, 3°. R PNS CNS Midline 2. The 1° neuron is pseudounipolar. Its cell body is located in a ganglion in the PNS. – for the body, the axon travels in a peripheral nerve, spinal nerve & dorsal root, and its cell body is located in a DRG. 3. The cell body of the 2° neuron is either a) in the dorsal horn of the spinal cord OR b) a brainstem nucleus (depending on the somatosensory modality); its axon projects to the contralateral thalamus. ∴ it’s the axon of this 2° neuron that decussates. 4. The cell body of the 3° neuron is located in the VP nucleus of the thalamus. Its axon projects to 1° SS cortex. 15 Functional Localization in the Spinal White Matter: Somatosensory Pathways DORSAL COLUMNS Fasciculus gracilis: touch, vibration & cons. proprioception ~ T6↓ Fasciculus cuneatus: touch, vibration & cons. proprioception ~ T6↑ Spinothalamic tract pressure, pain & temperature 16 Fasciculus Gracilis and Cuneatus Dorsal root ganglion Dorsal column C7 dorsal rootlets Sulci: Dorsal median Dorsal intermediate Dorsal lateral C7 dorsal root Fasciculus gracilis Fasciculus cuneatus HA2.2 Dorsal view of cervical cord 17 Dorsal Columns / Medial Lemniscus System: Touch, Conscious Proprioception, Vibration Sense from the Body 1° neurons: • cell bodies lie in dorsal root ganglia and project to the CNS via the dorsal roots • for the lower body, they ascend in the ipsilateral fasciculus gracilis (FG) to synapse on: XS THRU CERVICAL CORD: THALAMI NG FG 2° neurons: • cell bodies in the nucleus gracilis (NG) of the medulla • axons decussate, ascend contralaterally as the medial lemniscus (ML) through the brainstem, synapsing onto: 3° neurons: • cell bodies in the VP thalamus and project to • 1° somatosensory cortex in the postcentral gyrus. 1° SS CTX BRAIN STEM ML CERVICAL CORD FG LUMBAR CORD Dorsal Columns / Medial Lemniscus System: Touch, Conscious Proprioception, Vibration Sense from the Body 1° neurons: • cell bodies lie in dorsal root ganglia and project to the CNS via the dorsal roots • for the upper body, they ascend in the ipsilateral fasciculus cuneatus (FC) to synapse on: DRG XS THRU CERVICAL CORD: THALAMI FG FC 2° neurons: • cell bodies in the nucleus cuneatus (NC) of the medulla • axons decussate, ascend contralaterally in the medial lemniscus (ML) through the brainstem, synapsing onto: 3° neurons: • cell bodies in the VP thalamus and project to • 1° somatosensory cortex in the postcentral gyrus. 1° SS CTX NG NC FC BRAIN STEM ML CERVICAL CORD FG LUMBAR CORD Fasciculus Gracilis and Cuneatus Dorsal root ganglion Dorsal column C7 dorsal rootlets Sulci: Dorsal median Dorsal intermediate Dorsal lateral C7 dorsal root Fasciculus gracilis Fasciculus cuneatus HA2.2 Dorsal view of cervical cord 20 1° mCTX Brain stem Cervical Cord Thalami SL STT 1° SS CTX Brain stem Cervical cord Thalami NG NC FC 1° SS CTX Brain stem ML Cervical cord FG Lumbar Cord Lumbar cord Lumbar cord 21 1° SS CTX Describe the effects of the lesion BRAIN STEM CERVICAL CORD LESION LUMBAR CORD 22 Describe the effects of the lesion XS THRU CERVICAL CORD: STT XS THRU THORACIC CORD: LESION STT XS THRU LUMBAR CORD: STT The Autonomic Nervous System Images from Human Anatomy 6th ed., © 2009, by Martini, Timmins and Talitsch, denoted by “Ma”. Images from Human Anatomy, 2nd ed., © 2008 by McKinley & O’Loughlin, denoted by “Mc”. 1 Fxns of the Autonomic Nervous System (ANS) Functionally maintains homeostasis • regulates body temperature via control of sweat glands and vascular smooth muscle • regulates the activity of body systems: – cardiovascular – respiratory – digestive – excretory – reproductive systems • monitors and adjusts body fluids, fine-tuning concentrations of – electrolytes – nutrients – dissolved gases 2 The ANS differs from the Somatic NS Anatomically: • in the somatic NS, neurons in the CNS synapse directly onto effectors: Brain stem or spinal cord (CNS) Somatic motor neuron Skeletal muscle Peripheral nerve • in the ANS, the CNS controls effectors via a two neuron chain: Brain stem or spinal cord (CNS) Preganglionic neuron Autonomic ganglion Postganglionic neuron Peripheral nerve Smooth or cardiac muscle or glands • The somatic NS and the ANS may share a given peripheral nerve • there are two subdivisions of the ANS, the sympathetic nervous system (SyNS) and the parasympathetic nervous system (PsyNS) 3 The SyNS & PsyNS Differ Functionally • the PSyNS predominates during resting conditions: “rest & digest” • the SyNS predominates during exertion or emergencies: “fight or flight” • within a given system, the two divisions usually oppose each other – e.g. SyNS  HR, PSyNS  HR – e.g. PSyNS  digestion, SyNS  digestion • occasionally they work independently – SyNS alone controls most vascular smooth muscle and all smooth muscle in the limbs & body wall (BVs, erector pili muscle, glands) 4 The SyNS & PSyNS Differ Anatomically The two divisions differ in the locations of their: A Preganglionic neuron Autonomic ganglion Postganglionic neuron B Peripheral nerve Smooth or cardiac muscle or glands A. preganglionic neuronal cell bodies in the CNS • SyNS (“thoracolumbar division”): spinal cord, T1-L2 levels • PSyNS (“craniosacral division”): brainstem cranial nerve nuclei & spinal cord, S2-S4 levels B. postganglionic neuronal cell bodies in the PNS • sympathetic ganglia located near the spinal cord in either the paired sympathetic chain ganglia or unpaired preaortic ganglia • parasympathetic ganglia located in or near effector organs 5 Organization of the Spinal Grey Matter • deep, forms a continuous column extending the length of the cord Gray matter White matter Ventral root • at all levels, grey matter forms a butterfly in XS, divided into: Spinal nerve Dorsal root ganglion Dorsal root – dorsal horns: sensory, receives input via spinal nerves and dorsal roots – ventral horns: somatic motor, conducts output via ventral roots, spinal Ns Ma14.2 • at certain levels, (T1-L2 & S2-S4) intermediolateral cell column (IML), contains autonomic preganglionic motor neurons, conducts output via ventral roots, ensuing nerves 8 The Sympathetic Division targets: A. smooth muscle of limbs & body wall B. viscera of head & thorax C. viscera of abdomen & pelvis preganglionic neurons (for ALL targets) • cell bodies located in lateral gray horns, T1-L2; • axons travel via ventral roots, spinal nerves, synapse onto: postganglionic neurons • cell bodies located in sympathetic ganglia near the vertebral column, either: – in bilaterally paired sympathetic chain ganglia (targets A&B) or – in unpaired prevertebral (preaortic) ganglia (targets C) • postganglionic axons innervate the target organ 9 Somatic Innervation of the Body Wall & Limbs • somatic motor neurons innervate skeletal muscle – cell bodies in the ventral grey horn of the spinal cord • sensory Ns monitor skin, joints, skeletal muscle – cell bodies in dorsal root ganglia (DRG), axons convey info to dorsal grey horn of spinal cord • their axons form peripheral nerves A. Dorsal horn B. Lateral horn H E G I C. Ventral horn D F A D. Dorsal root B E. DRG C F. Ventral root G. Spinal nerve H. Dorsal ramus XS through spinal cord between T1 and L2 I. Ventral ramus 10 A. Sympathetic Innervation of the Body Wall & Limbs • the body wall & limbs are innervated by postganglionic sympathetic neurons located in the paravertebral or sympathetic chain ganglia • target organs are smooth muscle of erector pili, BVs, glands in ALL dermatomes of body Rami communicantes Paravertebral ganglion XS through spinal cord between T1 and L2 11 Preganglionic sympathetic fibres can ascend or descend within the sympathetic chain before synapsing. In this way, sympathetics are distributed to dermatomes* ABOVE T1 and BELOW L2 *dermatome: the area of skin innervated by a specific spinal segment and nerve 12 Summary: The Sympathetic Nervous System PONS Dermatomes C2–C3 NV C2–C3 Cervical Superior sympathetic Middle ganglia Inferior C2 C3 Gray rami to spinal nerves T2 C6 L1 L2 C8 Postganglionic fibers to spinal Ns (innervating BVs, sweat glands, erector pili muscles, adipose tissue) C7 T1 L3 L4 L5 Sympathetic chain ganglia C3 C4 C5 T2 3 T1 T T4 T2 T T3 T5 T4 T67 T5 T8 T6 T9 T7 T10 T8 T11 T9 T L12 T10 L21 T11 L4L3 T12 L5 S2 C4 C5 T2 C6 C7 T1 SS 4 3 L1 S5 S1L5 C8 L2S2 L3 S1 Ma17.4 Preganglionic Ns Ganglionic Ns Coccygeal ganglia (Co1) fused together (ganglion impar) L4 ANTERIOR POSTERIOR 13 B. Sympathetic Innervation of Thoracic Viscera & Face Thoracic viscera & targets in the face are innervated by postganglionic sympathetic Ns located in the paravertebral or sympathetic chain ganglia. For targets in the thorax: Axons of postganglionic Ns form splanchnic Ns (cardiac, pulmonary, esophageal splanchnic Ns) which contribute to autonomic plexuses (cardiac, pulmonary, esophageal plexuses) that innervate targets in the thorax. For targets in the face: Axons of postganglionic Ns form autonomic plexuses, which “hitch a ride” with arteries to reach their targets. Named for artery, eg. carotid plexus. 14 Summary: The Sympathetic Nervous System Eye PONS Salivary glands Cervical Superior sympathetic Middle ganglia Inferior Gray rami to spinal nerves Heart Cardiac and pulmonary plexuses Lung Postganglionic fibers to spinal Ns (innervating BVs, sweat glands, erector pili muscles, adipose tissue) Sympathetic chain ganglia Ma17.4 Preganglionic Ns Ganglionic Ns 15 C. Sympathetic Innervation of Abdominopelvic Viscera Abdominopelvic viscera are innervated by postganglionic sympathetic neurons located in the prevertebral ganglia, eg. the celiac, superior mesenteric and inferior mesenteric ganglia. Axons of postganglionic neurons contribute to autonomic plexuses, which “hitch a ride” with arteries to reach their target organs. The plexuses are named by the BV, ie. celiac, superior and inferior mesenteric plexuses. 16 The Adrenal Medulla • is a modified sympathetic ganglion • is innervated by preganglionic sympathetic neurons of the lateral gray horns • postganglionic “neurons” of the adrenal medulla release epinephrine & norepinephrine which is picked up by blood vessels for systemic distribution • consequences?