9 - Spinal Cord Organizaiton Flashcards
1
Q
Three Germ Layers in Embryo
A
- Endoderm
- Mesoderm
- Ectoderm
2
Q
Endoderm
A
- Innermost germ layer
- Develops into GI tract & lungs
3
Q
Mesoderm
A
- Middle embryonic layer
- Forms connective tissue, muscle, bone, and urogenital & circulatory systems
4
Q
Ectoderm
A
- Outermost of 3 primary germ layers
- Forms epidermis, nervous tissue, sense organs
- Forms neural plate
5
Q
Neurulation
A
Neural plate folds up and the lateral edges fuse dorsally forming the neural tube
6
Q
Sulcus Limitans
A
Separates the dorsal alar plate and ventral basal plate
7
Q
Alar Plate
A
- Dorsal
- Broadly sensory
- Separated from basal plate by sulcus limitans
8
Q
Basal Plate
A
- Ventral
- Broadly motor
- Separated from alar plate by sulcus limitans
9
Q
Neural Crest Destiny
A
- Primary sensory neurons (DRG)
- Post-ganglionic autonomic neurons
10
Q
Anencephaly
A
- Failure of the anterior neuropore to close
- Results in major portion of the brain, skull, and scalp being absent
- Generally incompatible with life
- Infants delivered with this disorder do not live more than a few hours or days
11
Q
Rachischisis
A
- Failure of the posterior neuropore to close
- Results in motor and sensory deficits, chronic infections, and disturbances in bladder function
- Often cooccurs with anencephaly
12
Q
Spina Bifida
A
- Incomplete formation of the vertebrae and meninges surrounding the spinal cord
- Essentially a less severe form a Rachischisis
- Three types:
- Occulta
- Meningocele
- Meningomyelocele
13
Q
Spina Bifida Occulta
A
- Defect limited to vertebrae
- Mesodermal signaling that builds the vertebrae is disrupted, so something about the spinal processes doesn’t form well
- Often is a little dimple in the back
14
Q
Spina Bifida Meningocele
A
- Involves meninges
- Spinal cord and rootlets generally remain in the space they’re supposed to be in
- But meninges now lie eight below the skin
- CSF balloons up right below the skin surface
15
Q
Spina Bifida Meningomyelocele
A
- Involves meninges and nervous tissue
- Meninges AND spinal cord and rootlets lie right beneath the skin
16
Q
of Cervial Vertebrae
A
7
17
Q
of Thoracic Vertebrae
A
12
18
Q
of Lumbar Vertebrae
A
5
19
Q
of Sacral Vertebrae
A
5, fused
20
Q
Denticulate Ligaments
A
- Pial adaptation in the spine
- Projections come off and form scallop-shaped regular attachments to the dura
- Provide stability
21
Q
Spinal Cord Protection
A
- Central position of spinal cord
- Epidural fat, CSF, and meninges cushion
- Attachment of dural sheaths on spinal roots
22
Q
Spinal Cord Segments
A
31
23
Q
Spinal Nerve Pairs
A
31
24
Q
Spinal nerve definition
A
- Merged dorsal and ventral root that arises from each spinal cord segment
- IS created at the intervertebral foramen
25
Cervical Spinal Nerves
8
26
Thoracic Spinal Nerves
12
27
Lumbar Spinal Nerves
5
28
Sacral/Coccygeal Nerves
6
29
Spinal Cord Segment definition
Block of gray and white matter related to a particular spinal nerve
30
Ventral Root
* Conveys motor information
* Is efferent
* Brings info from ventral gray horn to periphery
31
Dorsal Root
* Afferent
* Sensory info
* Uses pseudounipolar DRG
* One axon in periphery, one in CNS
32
Rami
* Proceed from spinal nerve (splits into two; dorsal and ventral)
* Carry mixed motor and sensory to the body wall
* Ventral is bigger
33
Plexus
Aggregation of ventral rami in the periphery
34
Myotome Organization
* Proximal to distal down the cord
* Segmental overlap = several segments would need to be damaged to take out an entire muscle
35
1. Postero-marginal nucleus (most dorsal)
2. Substantia gelatinosa
3. Nucleus proprius (most anterior)
All in dorsal horn, at every level of spinal cord
37
Pain and temp DRG sensory neurons enter...
...at dorsal horn
38
Neurons for sensory info other than pain and temp enter the dorsal horn at the...
...dorsal columns
39
Reticular core of spinal cord
* In intermediate zone
* Contained interneurons for lower motor neuron pattern generators
40
Dorsal Nucelus of Clarke
* In intermediate gray area
* Present at levels C8-L3
* Receives signals from certain muscle proprioceptors
41
Lateral Horn
* T1-L2
* Contanis intermediolateral cell collumn (preganglionic **sympathetic** GVE)
42
Intermediolateral cell column T1-L2 (IML)
* Located in lateral horn
* Preganglionic GVE sympathetic cell bodies
43
Intermediolateral Cell Column S2-S4
* Preganglionic parasympathethic cell bodies
* Does NOT form a lateral horn (too small)
44
GSE Motor Neuron Organization in SC
* Medial = trunk
* Lateral = limbs
* Dorsal = flexor
* Ventral = extensor
45
3 important independent motor nuclei in SC Ventral Horn
1. Spinal accessory nucleus
2. Phrenic nucleus
3. Onuf's nucleus
46
Spinal Accessory Nucleus
* Independent motor nuclei in SC ventral horn
* C1-C5
* Origin of accessory nerve (XI)
* Somatomotor control of trapezius and sternocleidomastoid muscles
47
Phrenic Nucleus
* Independent motor nucleus of SC ventral horn
* C3-C5
* Origin of phrenic nerve for somatomotor control of diaphragm
48
Onuf's Nucleus
* Independent motor nucleus of SC ventral horn
* S1-S4
* Origin of the pudendal nerve for somatomotor (voluntary) control of the urethral and anal sphincters
49
Spinal lesions above T12 result in...
* Spastic bladder (reflexive voiding)
* Afferent bladder info is coming in
* Descending brainstem control to sympathetic preganglionic neurons in cord levels L1/L2 is disrupted
* Descending upper motor neuron control to Onuf's nucleus is also disrupted
50
Spinal lesions below T12
* flaccid (atonic) bladder
* Both afferent and efferent are damaged because it's after the end of the spinal cord
51
SC Nuclei with restricted levels
* Clarke's nucleus C8-L3
* IML T1-L2
* Lateral group LMN C4-T1, L2-S2
52
3 major spinal cord tracts (ascending vs descending)
1. Lateral corticospinal tract: descending (motor)
2. Dorsal column system: ascending (sensory)
3. Spinothalamic tract: ascending (sensory)
