Spinal Cord and Brainstem organization

segment

a cross section of the SC giving rise to a spinal nerve on each side

where do dorsal rootlets enter the SC

in the posterolateral sulcus on either side of the posterior surface of the SC

what do dorsal rootlets merge into

dorsal roots (sensory)

dorsal root ganglion (DRG)

collection of cell bodies of sensory nerves entering the SC

DRG location 

just proximal to where the spinal nerve begins 

ventral rootlets location 

exit SC from the anterolateral sulcus on each side of the anterior surface of the SC 

what do ventral rootlets merge into

ventral roots (motor)

what joins to form a spinal nerve

a dorsal and a ventral root

what nkind of nerves are spinal nerves

mixed (carry sensory and motor fibers)

how many segments are there in the human SC

31

how many cervical vertebrae

7

what many thoracic vertebrae

12

how many lumbar vertebrae

5

how many sacral vertebrae

5 (fused in adulthood)

how many coccygeal vertebrae

about 4 (fused in adulthood)

how many pairs of cervical spinal nerves 

8 

how many pairs of thoracic spinal nerves 

12 

how many pair of lumbar spinal nerves

5

how many pairs of sacral spinal nerves

5

how many pairs of coccygeal spinal nerves

1

groups of functionally or structurally related cell bodies in the CNS 

nucleus 

groups of functionally or structurally related cell bodies in the PNS 

ganglion 

groiups of parallel axons in the CNS 

tracts 

groups of parallel axons in the PNS 

nerve 

groups of several parallel tracts in the CNS

funiculus

group of axons connecting one side of the brain with the other

commissure

groups of functionally related cells that form a layer

layer, stratum

spinal nerve 

dermatome 

the area of skin innervated by a single spinal cord segment 

C2 dermatome

back of head

T4 dermatome

nipple line

T10 dermatome

umbilicus

S5 dermatome

anal area

myotome def 

group of muscles innervated by a single spinal cord segment 

C5 myotome

elbow flexion

C6 myotome

wrist extension

C7 myotome 

elbow extension 

C8 myotome 

finger flexion 

T1 myotome

pinky abduction

L2 myotome

hip flexion

L3 myotome

knee extension

L4 myotome 

ankle dorsiflexion 

L5 myotome 

long toe extension 

S1 myotome

ankle plantarflexion

what does the cervical enlargement give rise to

spinal nerves for upper extremities 

what does the lumbar enlargement give rise to

spinal nerves for lower extremities

conus medullaris

cone-shaped caudal end of SC located around vertebral level L1-L2

in the thoracic, lumbar, and sacral regions, where do spinal nerves exit 

just below the vertebra of the same name 

where do spinal nerves exit in the cervical region 

just above the vertebra of the same name 

where does the 8th spinal nerve exit

just aboce the 1st throacic vertebra

how do dorsal and ventral roots compensate for spinal nerves exiting at their respective interverebral foramina

become progressively longer proceeding from cervical to sacral levels

lumbar cistern location

enlarged subarachnoid space from end of SC at vertebral level L1-2 to end of dural sheath at vertebral level S2 

what is the lumbar cistern filled with 

CSF and cauda equina 

clinical significance of lumbar cistern

safe for lumbar punctures

3 layers of meninges that cover and protect the SC

1. dura

2. arachnoid

3. pia mater

denticulate ligaments

lateral extensions f pia mater that span to arachnoid and then to the dura and help to suspend and laterally anchor SC 

filum terminale 

inferior extension of pia mater at conus medullaries aht is anchored caudally to the coccyx 

spinal segment

cross-sectional area of SC supplied by a pair of spinal nerves 

what does each spinal segment consist of

gray and white matter

gray matter of SC

central portion of SC; H shaped and can be divided into horns 

whtie matter of SC

external portion of SC that surrounds gray matter; can be divided into funiculi, or columns

image 1

image 2

posterior intermediate sulcus

where in theSC is the posterior intermediate sulcus found 

only at C and upper T levels

sulcus

posterolateral sulcus

image 3

central canal

anterior median fissure 

posterior median sulcus

anterolateral sulcus 

where do dorsal rootlets enter 

posterolateral sulcus 

where do ventral rootlets exit 

anterolateral sulcus

central canal of the SC

extension of central canla from medulla; filled with CSF 

what does the posterior horn receive

sensory input from dorsal roots

what does the posterior horn contain

mostly interneurons and projection neurons

2 primary parts of posterior horn

1. substantia gelatinosa

2. body 

substantia gelatinosa of posterior horn

caps posterior horn; deals mostly with pain and temp information 

body of posterior horn function

deals mostly with somatic and visceral sensory info 

posterior horn 

image 4

anterior horn

what does the anterior horn contain

cell bodies of motor neurons that supply skeletal muscle 

two names for motor neurons that supply skeletal muscle 

aplha or lower motor neurons 

what type of lower motor neurons are more medial 

clusters that innervate axial muscles 

what type of lower motor neurons are more lateral 

muscles of the limbs 

location of intermediate gray matter

lies between anterior and posterior horns

consequence of location of intermediate gray matter

contains features of both anterior and posterior horns; also contains spinal preganglionic autonomic neurons

location of intermediolateral cell column

present in T1-L3

what does the intermediolateral cell column contain

sympathhetic nervous system neurons in teh pointy lateral horn

how do axons leave in teh intermediolater cell column 

through ventral roots 

what is the sacral parasympathetic nucleus

intermediate gray matter of S2-S4 with no distinctlateral horn 

what does the sacral parasympathetic nucleus cotain 

parasympathetic neuorns 

how do axons leave the sacral parasympathetic nucleus 

through ventral roots 

what pathways does spinal white matter contain 

both ascending and descending pathways 

tracts def 

bundles of axons that have the same origin, course, and termination 

what is funiculus

collection of tracts

3 main funiculi of each half of the SC

1. posterior funiculus

2. lateral funiculus

3. anterior funiculus 

where is the posterior funiculus located

between posterior median sulcus and posterior horn 

two fiber tracts of posterior funiculus

1. fasciculus gracilis

2. fasciculus cuneatus 

fasciculus gracilis relative location

more medial

fasciculus cuneatus relative location

more laterally in part of SC