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Skin MS: Week 2 > Histology (11/6) > Flashcards

Histology (11/6) Flashcards

1
Q

Embryology of Nervous System

A

Neural crest
PNS: sensory neurons of spinal & cranial ganglia; motor neurons of autonomic ganglia; glia of the PNS; other “non-neuronal” cell types

Neural tube
Neurons & glia of CNS

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2
Q

Mitotic potential of NS cells

A

Neurons are non-mitotic

Glial cells maintain mitotic capability

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3
Q

White Matter

A

Aggregations of axons, includes nerves in PNS and tracts, columns, fasciculi of axons in CNS, white d/t myelination

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4
Q

Gray Matter

A

AGgregations of nerve cell bodies + neuropil
Ganglia in PNS, nuclei etc in CNS
Gray d/t little myelin

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5
Q

Neuropil

A

complex network of nerve cell processes, synapses, and glial cells occupying intervals between nerve cell bodies in gray

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6
Q

Constituents of Nervous Tissue: CNS

A

Nerve cells
Glia: Astrocytes, oligodendrocytes, Microglia, ependymal cells
Blood vessels

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7
Q

Constituents of Nervous Tissue: PNS

A

Nerve cells
Glia: Schwann cells, Satellite cells
Blood vessels
connective tisse

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8
Q

General Cytology/Components of Nerve Cell

A

Plasma membrane, cell body, Dendrites, (Sensory receptors), axon, end terminal

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9
Q

RER in nerve cells

A

Nissl bodies

Extensive - present throughout whole cell body + dendrites, absent from axon hillock + axon

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10
Q

Golgi in Neurons

A 
Just in cell body 
Package vesicles (full or empty) to send down axon
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11
Q

Neurofilaments

A

Type of intermediate filament found only in neurons - structural role - form neurofibrils - found in body and processes

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12
Q

Microtubules in neurons

A

Involved in transport of molecules/particles down axon (maybe growth and development)

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13
Q

Microfilaments in neurons

A

Specialized distribution (growth cones, some junctions)

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14
Q

Pigments in Neurons

A

Lipofuscin - insoluble remnants of lysosomes (product of digestion) - golden brown
Neuromelanin - naturally occuring in some areas, dark brown/black

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15
Q

Mitochondria in Neurons

A

Large numbers throughout cells, especially abundant in axons

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16
Q

Unencapsulated nerve endings (receptors)

A

Touch, pain (maybe hot/cold)

i.e. merkel cell (Touch)

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17
Q

Corpuscles of Ruffini + Krause’s end-bulbs

A

mechanoreceptors, glomerular (encapsulated)

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18
Q

Meissner’s Corpuscle

A

Touch
Fibrous capsule (encapsulated)
Found in hairless skin

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19
Q

Pacinian Corpuscle

A

Deep pressure, vibration
Lamellar corpuscle
Looks like onion

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20
Q

ABC grades of axons

A

A - large, myelinated
B - smaller, myelinated
C - smallest, not myelinated

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21
Q

Presynaptic dense projections

A

electron dense material on cytoplasmic side of membrane at axon end terminal
Vesicles approach and fuse with presynaptic membrane (guide into right place)

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22
Q

Axonal Transport : Slow

A

Only orthograde

Carries soluble macromolecules, small molecules not in vesicles, fibrillar components of axoplasm

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23
Q

Axonal Transport: Fast

A

Orthograde faster than retrograde (both much faster than slow), microtubules
Orthograde: vesicles, organelles, etc. - KINESIN –> plus end (faster)
Retrograde: Worn out membranes, etc. - DYNEIN –> minus end

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24
Q

Consequences of Retrograde transport

A

clinically: how viruses (i.e. rabies) get far into nervous system
developmentally: might be how axons are told to grow
experimentally: track process of marker molecules back to find cell bodies

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25
Neuroglia of CNS
Astrocytes, Microglia, Oligodendrocytes, Ependymal cells | Outnumber neurons
26
Macroglia
Astrocytes + Oligodendrocytes
27
Types of Astrocytes
Fibrous or Protoplasmic (Golgi staining vs. H&E) - either due to functional states or location
28
Golgi stain appearance of astrocytes
Cell body usually obscured by mass of processes, found near blood vessels/surfaces of brain
29
H&E/Nissl Stain Astrocytes
Nucleus - oval, large
30
Functions of Astrocytes
Terminal end feet --> pervasive between neurons and processes --> End on blood vessels (maybe induce blood brain barrier) End on inner surface of pia mater - external glial limiting membrane End on basal surface of ependymal cells to form internal glial limiting membrane Structural support, uptake potassium after activity, phagocytosis, Isolation from other neurons, regulation of environment
31
Appearance of Oligodendrocytes
Fewer processes than astrocytes | Nucleus (Nissl stain) - round, smaller, dense staining
32
Functions of oligodendrocytes
Myelination of CNS axons, maybe nutritive/maintenance
33
Microglia
5% or less of all glial cells, derived from monocytes - actively phagocytic
34
Ependymal cells
Line central canal of spinal cord, ventricles of brain Simple cuboidal, columnar epithelial - ciliated Beat CSF to brain, secretion into ventricles Modified to be choroidal epithelium - control composition of CSF in ventricles of brain
35
Epineurium
External layer, tough, dense collagen
36
Perineurium
Envelopes bundles or fascicles of fibers Intermediate in character between epi and endoneurium inner aspect has epithelioid like cells
37
Endoneurium
around individual axons delicate collagen contacts basement membrane of schwann cells which cover axon
38
Unmyelinated fibers of PNS consist of ____
Axon + Sheath of Shwann
39
Development of Sheath of Schwann
Schwann cells from neural crest - travel along axons Each SC embraces a small number of axons Trough, remain outside even though engulfed
40
Function of Sheath of Schwann in unmyelinated axons
unknown
41
Mesaxon
region where lips of schwann cell cytoplasm meet (gap)
42
Bundle of Remak
Collective term for a group of unmyelinated fibers encompassed by single schwann cell
43
c fibers
term for unmyelinated axons axons of most post-ganglionic autonomic neurons axons of small sensory neurons in Dorsal root ganglia Not usually seen d/t not stained
44
Myelinated fibers of PNS
Axon, myelin, sheath of schwann | Largest axons have thickest myelin, fastest conducting
45
Myelin content
High lipid content (protein)
46
Appearance of myelin
Fresh: white d/t lipids Osmium stained: Black empty rings H&E: see the residual protein (neurokeratin) EM: Black
47
Nodes of Ranvier
Periodic breaks in myelin sheath space between adjacent schwann cells Highest conc. Na channels
48
schmidt lantermann clefts
oblique clefts in myelin, faults in smooth wrapping myelin lamellae, light areas = trapped portions of schwann cell cytoplasm
49
Myelination via Jelly-roll theory
Myelin formed by spiral wrapping of SC membrane around nerve fiber Cytoplasm of SC squeezed out --> compaction --> intraperior and major dense lines Nucleus of SC in cytoplasm of final wrap
50
Intraperiod Line
former outer surfaces of schwann cell -- fuse to become very thin
51
Major dense line
Former cytoplasmic surfaces of schwann cell
52
Internal and external mesaxons
regions where schwann cell meets itself as it encircles axon initially (internal) and where it overlaps on last turn (external)
53
Myelinated Fibers of CNS
Oligodendrocytes responsible for myelination, may myelinated more than one axon = little cytoplasm, never a nucleus near axon (remain distant, tongue)
54
Nodes of Ranvier in PNS
Cytoplasm of Schwann cell covers, basement membrane out SC inside endoneurium Collateral branches, en passage synapses occur
55
Nodes of Ranvier in CNS
``` Shorter internodal distance Node exposed to extracellular space No basement membrane outside myeline No SL clefts No Connective tissue ```
56
Sensory Ganglia (PNS)
``` Light and dark cells No synapses in ganglia Satellite cells (capsule cells) Fibroblasts C.t. capsule Nuclei in middle of cells ``` Dorsal root ganglia and cranial nerve ganglia
57
Satellite Cells
Very small cells which form covering around each ganglion neuron, may be schwann cells, may play role in metabolism of ganglion neurons peripheral glia
58
Connective tissue capsule (PNS ganglia)
surround entire ganglia, continuous with perineurium/epineurium, extend into ganglion to separate nerve cell bodies into groups
59
Autonomic ganglia
Synapses Pre - Type B (myelinated) Post - Type C (small, not myelinated) Satellite cells and schwann cells
60
Wallerian or Orthograde Degeneration
Portion of axon separated from cell body changes Axon/terminals/myelin disintegrate Schwann cell + CT remain in PNS (none in CNS) Phagocytosis of debris
61
Retrograde Degeneration
Changes in cell body/portion of axon still attached Degeneration for short time toward cell body Chromatolysis (cell body/nucleus swell, moves to side, RER disintegrate) Death of cell with or without chromatolysis MAYBE Or maybe no change at all
62
Regeneration
Successful only in PNS Multiple sprouts emerge from central stump of axon --> one must get through surviving tube of schwann cells Remyelination
63
Specificity of Reinnervation
Will innvervate any sensory receptor/muscle - sensation/motions less critical
64
Traumatic neuroma
Large heterogeneous mass of entangled nerve fibers, schwann cells, ct cells, etc Regen. neurons unable to overcome obstacle Afferents may still send messages --> painful
65
CNS regeneration
Abortive No guiding tube (oligodendrocytes) Scar tissue by astroglia barrier
66
Plasticity
REcovery after CNS injury Collateral sprouting - new connections OR unmasking of other connections

Skin MS: Week 2 (12 decks)

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