Lecture 1 CNS Histology Flashcards
How long is the lucid interval for epidural hematoma?
How long is the lucid interval for epidural hematoma?
What compose the coverings of the CNS?
From exterior to interior
- Skull
- Dura mater
- two layers of dense collagenous connective tissue with large venous sinuses
SUBDURAL (POTENTIAL) SPACE
- Arachnoid mater
- thin membrane containing a mixture of FIBROBLASTS and ARACHNOIDAL cells (meningothelial cells)
- adheres directly to dura
SUBARACHNOID (ACTUAL) SPACE
-CSF is found here
- Pia mater
- layer of cells tightly affixed to brain
- anchors arachnoid trabeculae
- Brain parenchyma
What does parenchyma mean?
The essential or functional elements of an organ
What are the Virchow-Robin spaces?
Essentially subarachnoid spaces (spaces in between the arachnoid and pia mater) that surround vessels within the brain
Pia mater adheres tightly to brain parenchyma
-brings arachnoid trabeculae, thus subarachnoid space, with it
What are arachnoid trabeculae?
Delicate strands of connective tissue that connect the arachnoid and pia mater
Where are sinuses located?
In the dura
What is the function arachnoid villi (aka arachnoid granulations)?
They allow CSF to diffuse into the sinuses for drainage
How do you identify arachnoid cells histologically?
Concentrated at tips of arachnoid villi
Oval nuclei
Can form prominent whorls or psammoma bodies
What is a psammoma body?
A round collection of calcium
What is the basis of meningioma?
Proliferation of arachnoid cells
What happens to the arachnoid as we age/are subjected to infection?
Clear arachnoid becomes OPACIFIED
-collagen deposition
What are the leptomeninges?
Means thin meninges
Refers to the pia and arachnoid mater
What are the main cellular elements of CNS histology?
- neurons
- glial cells
- astrocytes
- oligodendrocytes
- ependymal cells
- Microglia
- Choroid plexus cells
- blood vessels/blood cells (RBC/WBC)
- Meningothelial (arachnoid) cells
- Bone/cartilage
- Pituitary cells
What is a key histological feature of the cell body of neurons?
A prominent nucleolus
-surrounded by a large nucleus
What are Nissl bodies/Nissl substance?
-sites of protein synthesis, eg RER
Proteins can be visualized by cresyl violet aka Nissl stain
What is the delineating microscopic feature of the axon hillock?
The ABSENCE of Nissl substance
What are Neuropils?
Background of the CNS histology slide
Functional definition: pink shit that is in between the astrocytes, neurons and oligodendrocytes
“A feltwork of interwoven dendrites and axons and of neuroglial cells in gray matter of CNS”
What are delineating histologic features of astrocytes?
In cross section, small with a lot of nuclei
-in both white and grey matter
Are stained for GLIAL FIBRILLARY ACIDIC
PROTEIN (GFAP)
What is glial fibrillary acidic protein (GFAP)?
It is the intermediate filament in astrocytes that are stained
To ID astrocytes
What are delineating features of oligodendrocytes?
Egg shaped (nucleus with white shit surrounding it)
- in both white and grey matter
- one oligodendrocyte myelinates up to 50 axons (so a lot of Nissl substance
What are Ependymal Cells?
Lines the ventricles of the brain and the central canal of spinal cord Serve to absorb, secrete and propel CSF -Links the ventricular, vascular and The intraparenchymal compartments of CSF
What is the delineating histological feature
Of ependymal cells?
Cuboidal cells with microvilli ontop
-linked by tight junctions
What is the choroid plexus? Histological features?
Projectiosn of vascular stroma derived from meninges
Secretes CSF in ventricles
Cuboidal epithelium
How are neurons organized in the CNS
- Cortex
- neocortex
- Archicortex or Palleocortex (any cortical structure that has LESS than 6 layers)
- basal ganglia (deep gray nuclei)
- cerebellar cortex/nuclei
- brainstem nuclei
- spinal cord
What are the six layers of the neocortex?
- Molecular
- External Granular
- External Pyramidal
- axons point toward the pia
- Internal Granular
- Internal Pyramidal
- Plexiform
What are the areas of the cortex that have large pyramidal layers? Large granular layers?
M1 has large pyramidal layers
V1 has large granular layers
What are the cell layers of the cerebellar cortex?
- Molecular layer
- Purkinje cell layer
- Granular Cell layer
What does CA stand for in terms of hippocampus?
Cornu Ammonis (or Ammonis horn)
What region of hippocampus is most sensitive to Injury?
CA1 (aka Sommer sector
-sensitive to ischemia, seizure, Alzheimers
What are the characteristics of damage to neurons?
- acute ischemic injury (RED NEURONS)
- chronic injury (cell loss)
- neuronal inclusions like LIPOFUSCHIN
- Reactive gliosis
- Microglia and inflammatory infiltrates
What is the delineating feature of CNS that has gone acute ischemic injury?
Red Neurons
- intense cytoplasmic eosinophilia
- loss of Nissl substance
- nucleus is darkly stained w/o nucleolus
- shrunken cell body
What is the delineating factor of neuron aging?
Lipofuschin
Brown shit
-comes from oxidized fatty acids
What are the three pigmented nuclei of the brain?
- Substantia nigra
- DMX
- locus ceruleus
(catecholaminergic…dopamine for instance…neurons)
Pigmented = neuromelanin
Not to be confused with lipofuschin
What does a Lewy body look like?
A CYTOPLASMIC round INCLUSION
What is Glial Fibrillary Acidic Protein and what is its significance?
GFAP acts as a diagnostic marker for disease
- increased GFAP is indicator of hypertrophy and hyperplasia of astrocytes
- analagous to fibroblasts in injury
What is gliosis?
The inflammation of glial cells
More specifically, the hypertrophy/hyperplasia of astrocytes
What is the main effector of reaction to injury in the CNS?
Astrocytes
Via hypertrophy and hyperplasia cause gliosis
What happens to microglia in the event of injury?
Hyperplasia
Elongated nuclei
Increased elongated cytoplasmic processes
