Lecture #2: Spinal Cord, Spinal Nerves, Suboccipital Region, Thoracic Wall

How many pairs of spinal nerves are there?

31

How many pairs of cranial nerves are there?

12

The gray matter or the collection of nerve cell bodies in the CNS is called what?

Nucleus

The gray matter or the collection of nerve cell bodies in the PNS is called what?

Ganglion

The white matter or the collection of nerve cell bodies in the CNS is called what?

Tract

The white matter or the collection of nerve cell bodies in the PNS is called what?

Nerve

From what part of the body does the spinal cord descend from Caudally?

Brainstem/medulla Oblongata through the foramen magnum

What surrounds the spinal cord as it passes through the Vertebral Canal?

Dural (thecal) Sac

What purpose do the Lumbo-sacral enlargments serve along the spinal cord?

Gives rise to roots of spinal nerves for the brachial and lumbar plexuses (Upper and Lower extremities)

Where does the spinal cord end

L1-L2 in the conus medullaris

What nerve roots give rise to the Cauda Equina?

Lower lumbar, Sacral, and Coccygeal spinal nerves

Filum Terminae

a slender strand of fibrous tissue extending from the conus medullaris to the coccyx

How far does the dural sac extend?

S2

Dura

Projects laterally at each intervertebral level to encompass roots of spinal nerves

Arachnoid

Pressure of CSF keeps this layer attached to the Dura

Denticulate Ligaments

Found between emerging nerve roots, and penetrate arachnoid, and attach to the dura to stabilize the cord

Where arteries and veins lie to supply the spinal cord

Subarachnoid space

Choroid Plexus

Where CSF is produced in the brain

Venous Dural Sinuses

Where CSF is absorbed from subarachnoid space into the cranial network

CSF

clear, colorless liquid that fills the ventricles and canals of CNS; functions as a shock absorber; creates bouyancy for spinal cord

Lumbar Cistern

Where the subarachnoid space terminates caudally

Lumbar Puncture

Tightly flexed posture; needle inserted at L3/L4 or L4/L5; needle may encounter nerve roots but they will move out of the way

Spinal Anesthesia (Epidural)

tightly flexed posture, needle inserted into L3/L4 or L4/L5 however the needle does not go in as deep

Caudal Anesthesia

Needle enters through the sacral foramina and into the vertebral canal

Arteries that supply the spinal cord

anterior and posterior spinal arteries; Radicular and medullar spinal arteries that enter through the IV foramina

Anastomosis of vertical spinal vessels

communication between aorta and spinal vessels through the segemtnal medullar arteries in the sub-arachnoid space

Somatic Nerves

Part of the PNS; includes motor and sensory nerves

Somatic Motor Nerves (GSE)

Part of the PNS; carries outputs efferently from CNS to stimulate tonic, reflexive, and voluntary contraction of skeletale muscle

Somatic Sensory Nerves (GSA)

Part of the PNS; carries info afferently to the CNS through sensory ganglia for touch, pain, temperature from body wall; and pain/proprioception from muscles, tendons, and joints

Visceral Motor Nerves (GVE)

Part of the PNS, but make up the ANS; innervate smooth muscles, regulate glands, innervate cardiac muscle

Visceral Sensory Nerves (GVA)

Part of the PNS, but make up the ANS; visceral reflexes, convey visceral sensations (hunger, nausea); poorly localized pain; also responsible for referred pain

The amount of nerves between the CNS and either skeletal muscles innervated by GSE fibers OR sensory receptors innervated by GSA fibers

1 Nerve

Dermatome

A specific area of the body wall that GSA and GSE supply; area of skin supplied by the somatic afferents in one pair of spinal nerves; these also overlap each other

Myotome

A specific muscle mass in which the GSA and GSE fibers supply

What results from stimulus by Lower Motor Neurons in the brainstem or spinal cord?

Contraction of skeletal muscle

Which side do the lower motor neurons lie on when innervating their muscle?

Ipsilateral

Where are the cell bodies of lower motor neurons found?

Ventral horns of spinal gray

Dorsal Root

Comprised of somatic afferents carrying info from periphery to CNS

Ventral Root

Comprised of somatic efferents carrying info from CNS to periphery

Ganglion

collection of nerve cell bodies in the peripheral nervous system

Dorsal Ramus

MIXED spinal nerve in an Intervertebral foramen that splits into a smaller segment towards the back of the body

Ventral Ramus

MIXED spinal nerve in an intervertebral foramen that splits into a bigger segment towards the front of the body

Which root are ganglions located

Dorsal Root

Ventral Ramus Innervations

Anterolateral body wall; Hypaxial muscles; Extremities

Dorsal Ramus Innervations

Skin of back and posterior scalp; epaxial muscles (erector spinae muscles); Facet joints; posterior spinal ligaments

Number of Cervical spinal nerves

8 pairs

Posterolateral herniated Lumbar disc

will usually compress the roots of the spinal nerve emerginf through the next intervertebral foramen DOWN

Posterior Herniation of Lumbar disc

May affect multiple nerve roots in the cauda equina

Irritative Peripheral Nerve Injuries

Caused by acute or chronic mechanical trauma or inflammation; if Sensory fibers stimulated: pain, or parasthesia (altered sensation); if Motor fibers stimulated: spasm, twitching of skeletal muscles

Destructive Peripheral Nerve Injuries

Trauma or neuropathy; Motor symptoms: paralysis or paresis of skeletal muscles; Sensory symptoms: Anesthesia or hypesthesia (diminished sensation), also pain or dysesthesia

Articular Columns

Cervical facet joints stacked ontop of each other

Nuchal Lines

site where muscles of the posterior neck and back attach to the skull

Occipital Condyles

Articulates with C1 (Atlas) which is why C1 has no body

External Occipital Protuberance

attachment for neck and back muscles positioned most posteriorly

Atlanto-Occipital Joints

Joints on the Atlas segment where superior articular facets allow the occipital condyles to rest; the "Yes" joint; Jefferson Fracture

lateral atlantoaxial joint (Right and Left)

Inferior articular facets of the Atlas; Part of the "No" joints

median atlantoaxial joint

the Anterior articular facet on the Dens helps to form this joint; part of the "No" joints

Tectorial Membrane

Continuation of PLL connecting the Atlas to the Occipital bone aong the anterior side of foramen magnum

Cruciform Ligament

Transverse and Longitudinal portions; lies deep to the Tectorial membrane

Transverse Ligament of the Atlas

Forms a collar around the Dens; maintaining median atlantodental joint; Rupture may lead to injury of spinal cord by wandering Dens

Alar Ligaments

Extend from Dens to occipital condyles; each limit rotation and lateral bending of the head; Hyperflexion injury

Ligamentum Nuchae

Runs from External Occipital Protuberance down to C7; provides surface for attachment of posterior cervical muscles that maintain head position

Actions of Posterior Neck Muscles (Nuchal Musculature)

Resist flexion of the head; and reposition sense organs in the skull

C1 Dorsal Ramus Innervations

Sub occipital muscles (obliquus capitis superior, Obliquus capitis inferior, Rectus capitis posterior major, and Rectus capitis posterior minor

contents of suboccipital triangle

Vertebral Artery, Sub-Occipital Nerve, Posterior arch of atlas

The greater Occipital Nerve

Supplies the skin overlaying the triangle and posterior scalp

Atlanto-Occipital membrane

Where vertebral arteries pass through to enter the foramen magnum (membrane); ossification of this can lead to LOC in elderly patients with their head back

Mediastinum

Mid-line soft tissue that separates pulmonary cavities

Superior Thoracic Aperture

Transmits abundant viscera and neurovascular between thorax and neck

Manubrium

Literally meaning "Handle"; top portion of the sternum; articulates with the clavicles and costal cartilages of the first ribs

Body (Gladius)

Articulates with costal cartilages of ribs 3-7; middle portion of sternum

Xiphoid Process

Embedded in anterior wall musculature; inferior tip of sternum

Sternal Angle

Ridge between manubrium and body at second rib (Palpable); in line with spine at T4-T5 vertebrae

True Ribs

Ribs 1-7; articulate with sternum via their own costal cartilages

False Ribs

Ribs 8-10; have cartilages that articulate with the next highest one

Floating Ribs

Ribs 11-12; No sternal articulation

Head of Ribs

Part of the rib that connects to the vertebrae at costal facets

Costal Groove

Contains and Protects intercostal neurovasculature bundle

Rib 1

Surface features of this rib includes scalene tubercle and grooves for subclavian vessels

Scalene Muscles

run between cervical spine and upper ribs; serve as accessory muscles for breathing

Primary Cartilaginous joint (Joint 1)

immobile, thin layer of hyaline cartilage; closer to the midline of the body

Costochondral Joints (Joints 2-7 on the rib cage)

Allows gliding of the ribs to assist in breathing; plane synovial joints

External interocostals

Run Anteroinferiorly from the rib above to the rib below; most active during inspiration to ELEVATE the ribs

internal intercostals

Run Inferoposteriorly from floor of costal grooves to ribs below; most active during expiration to DEPRESS the ribs

innermost intercostals

Same action as internal intercostals; helps to house the neurovasculature bundle between it and the muscle layer above it

Transversus Thoracis

Limited to the anterior chest wall; Origin: ribs 2-6 inner layer of intercostal cartilage; Insertion: surface of sternum and xiphoid process; Action: Lowers ribs; Innervation: 2-7th intercostal nerves

Direction of neurovasculature bundle Superior to Inferior

Veins, Arteries, nerves