ANATOMY OF THE SPINAL CORD, ASCENDING, DESCENDING, AND INTERSEGMENTAL TRACTS (PART 1)

SKIBIDI DOB DOB DOB YES YES

Support skull, pectoral girdle, upper limbs, and thoracic cage and through the pelvic girdle, transmit body weight to the lower limbs

VERTEBRAL COLUMN

What structures make the vertebral column flexible?

Intervertebral Discs (IV DISCS)

Enumerate all types of vertebra and how many are there per region.

7 cervical
12 thoracic
5 lumbar
5 sacral
4 coccygeal (fused lower 3)

PARTS OF THE VERTEBRA:

 most prominent, rounded anterior 

Vertebral body

 posterior

Arch / Vertebral Arch

Form the side of the arch

Pedicles

Extends from the pedicles; fuses to form spinous process

Lamina / Flattened lamina

How many processes are there in a vertebra?

7 :  1 spinous, 2 transverse, 4 articular 

VERTEBRAL LIGAMENTS

Above the spinous process; between tips of spines

Supraspinous Ligament
Key word: Tip to tip action

Connects adjacent spine

Interspinous Ligament
Key word: Shaft on shaft action

supraspinous & interspinous ligament on the neck region

Ligamentum nuchae

Level of the ligamentum nuchae

C1-6

Connects laminae

Ligamentum Flavum

ligaments on anterior portion of vertebral column

Anterior longitudinal ligament

ligaments on posterior portion of vertebral column

Posterior Longitudinal Ligament

Anterior and posterior longitudinal ligament extends from _____ to ______ (Hint: Skeleton parts)

Skull to sacrum

Which ligament is stronger and wider of the two longitudinal ligaments?

Anterior longitudinal ligament (Flexion>Extension)

INTERVERTEBRAL DISC PARTS

• Peripheral part

• Fibrocartilage

• Strongly attached to vertebral bodies and the anterior and posterior longitudinal ligaments

Annulus FibroSUS

• Central Part; Ovoid

• semifluid, gelatinous material

Nucleus PulpoSUS

Upper and lower surfaces of adjacent vertebral bodies are covered with thin plates of _________ cartilage

Hyaline

TRUE OR FALSE: IV discs are the thickest in the thoracic region where movement is most restricted

FALSE
IV discs are thickest where movement is greatest (cervical and thoracic)

SPINAL CORD

From _______ where it is continuous with the ______

Foramen magnum

Medulla oblongata

Terminates at what level for adults

Lower border of L1 vertebra

Terminates at what level for newborns

L3

Cone shaped termination of the spinal cord

Conus medullaris

Fusiformly enlarged at the areas that give off _____and _____plexus

Brachial and lumbosacral

Spinal nerves exiting at levels lower than L1

Cauda Equina

SPINAL CHORD MENINGES

• pial folds that stretch from the surface of cord to dural sheath midway between the dorsal and ventral roots

• Dura is NOT adherent to SC

• _________ anchor spinal cord to vertebral body

Denticulate ligaments 

Wrapped by ___ adherent to the SC 

• Covered by ___ until nerve roots

Pia

Enumerate all spinal chord segments

31 segments:

• 8 cervical

• 12 thoracic

• 5 Lumbar

• 5 Sacral

• 1 coccygeal

Dorsal and ventral roots join in the ___________ to form spinal nerve

Intervertebral foramen

True or false: spinal chord is inner gay outer whack

FALSE
Inner gray and outer white

PRACTICE NAMING SPINAL NERVES:

The next slides will give you a pair of vertebrae, name the spinal nerve in between them.

Above the atlas (C1), below foramen magnum

C1 spinal nerve

C4 and C5

C5 spinal nerve

T1 and C7

C8 spinal nerve

C2 and C3

C3 spinal nerve

L5 and L6

BUNYE
L5 and S1 = L5 spinal nerve

L4 and L5

L4 spinal nerve

PRACTICE NAMING SPINAL CHORD SEGMENTS

The next slides will give a spinal vertebra, name the corresponding spinal chord segment.

C1

C2 spinal segment

T6

T8 spinal segment

T9

T12 spinal segment

T10

L1-2 spinal segments

T11

L3-4 spinal segments

T12

L5 spinal segment

L1

Sacral and coccygeal spinal segments

DERMATOMES (Memorize them bozo)

MYOTOMES

Groups of muscles innervated by a single spinal cord segment

Spinal Cord Meninges

PAD: Pia, Arachnoid, Dura

Arranged from inner to outer

• Layer of pia closely adherent to the surface of the spinal cord

INTIMA PIA

• Layer of pia that carries blood vessels

• Denticulate Ligaments - Lateral flattened bands of _____ tissue

Epipia

Denticulate ligaments are epipial tissue

• Between pia and arachnoid

• Contains CSF

Subarachnoid Space

• Layer that’s closely adherent to Dura

Arachnoid

Potential space; there should be no space but there are bridging veins; susceptible to rupture =___________

Subdural Space
Rupture of subdural space = Subdural hematoma

DURA

• Attached to SC only at the level of the __________

• Otherwise it attaches to the __________

• Ensheath the ventral and dorsal roots DRG, and proximal portions of the spinal nerves

• Closest to vertebra

Foramen magnum

Epidural Space

• With adipose tissue and venous plexus

• Prone to hematoma

• Exists below level of foramen magnum

• REAL space

Epidural Space

SPINAL CORD FISSURES

deep longitudinal midline fissure anteriorly

Anterior Median Fissure

shallow furrow on posterior surface

Posterior Median Septum

site of entrance of dorsal roots

Posterolateral Sulcus

site of exit of ventral roots

Anterolateral Sulcus

• Separates fasciculus gracilis and fasciculus cuneatus

Dorsal/Posterior intermediate septum

TRUE or FALSE : The dorsal intermediate septum only exists at the level of T6 above

TRUE:

The dorsal intermediate septum separates the fasciculus gracilis and cuneatus but below T6 there is only gracilis.

Horns that are only present in levels T1-L3 (Outflow of sympathetic nerve fibers)

Lateral Horns

middle of anterior and posterior gray horns

Gray Commisure

contains CSF

• Divides into gray commissure into anterior and posterior commissure

Central Canal

GRAY MATTER
H-shaped pillar with anterior and posterior gray horns

United by gray commissure containing the central canal

Amount of gray matter is related to amount of muscles innervated (Greatest at ________ and _________)
__________-cell bodies that receive axons of DRG; sensory (Horn)

____________-seen in thoracic and upper lumbar segments; preganglionic SY nerve fibers that exit via ventral root

• Fibers from _______ join motor fibers and come out of ______ root

_________-motor; largest at cervical and lumbosacral

Cervical and Lumbosacral

Dorsal Horn

Lateral Horn / intermediolateral horn

Lateral horn joins motor fibers and comes out the ventral root

Ventral horn

ANTERIOR GRAY COLUMN NERVE CELL GROUPS

• Large and multipolar 

• Axons pass in the anterior roots of spinal nerves 

• Innervate skeletal muscles

α Efferents / α motor neurons

• Smaller and multipolar

• Axons pass in the anterior roots of spinal nerves

• Innervate intrafusal muscle fibers of neuromuscular spindles

𝜸 Efferents / 𝜸 motor neurons

Group that is present in most segments

Innervate skeletal muscle of neck, trunk, intercostal, and abdominal muscles 

Medial Group

Smallest group, present in cervical and lumbosacral segments

Central Group

Which nerve roots form the phrenic nucleus for the diaphragm?

C3-5

 Which nerve roots form the accessory nucleus (SCM and trapezius; axons form spinal part of accessory nerve)?

Upper 5 or 6 cervical segments (C1-5 / C1-6)

Which nerve roots form the lumbosacral nucleus?

L2-S1

Group that is present in cervical and lumbosacral segments

Innervate skeletal muscles

Lateral Group

POSTERIOR GRAY COLUMN NERVE CELL GROUPS

In the apex of posterior gray column

Composed of golgi type II neurons

Receives afferent fiber for pain, temperature, and touch from SRG (Sensory root ganglia / Dorsal root ganglia)

Substantia Gelatinosa Group

Anterior to SG

Main bulk of cells in posterior gray column

Receives fibers associated with proprioception, 2 point discrimination and vibration 

Nucleus Pulposus group (2nd red arrow)

At the base of PGC (Posterior gray column)

C8-L3-4

Associated with proprioceptive endings (neuromuscular spindles and tendon spindles

Nucleus Dorsalis (Clarke column)

situated lateral to nucleus dorsalis

T1-L3

Receives visceral afferent information

Visceral Afferent Nucleus

LATERAL GRAY COLUMN NERVE CELL GROUPS

situated lateral to nucleus dorsalis

T1-L3

Receives visceral afferent information 

Gives rise to preganglionic sympathetic fibers (focus on dis)

Intermediolateral Group

S2-S4 

Give rise to preganglionic parasympathetic fibers (focus on dis)

Dorsal Outpouching of Ventral Horn

GRAY COMMISSURE AND CENTRAL CANAL

Take a 5 min break and rehydrate

connects anterior and posterior gray columns

GRAY COMMISSURE

center of gray commissure

continuous with central canal of the 4th ventricle superiorly

Expands terminal ventricle in the conus medullaris inferiorly and terminates within the root of filum terminale 

Filled with CSF

CENTRAL CANAL

Central canal is lined with what type of cells?

 ciliated columnar epithelial cells or EPENDYMA

posterior to canal

Posterior gray commisure

anterior to the canal

Anterior Gray commisure

ZONES OF LAMINA

Summary:

1-6 Dorsal Horn 

7- Lateral or Intermediate Zone 

8-9 Ventral Horn 

10 - Surrounding Central canal

Break muna medyo marami na ung slides

part 2 coming soon