ANA 305 Histology of the Cerebrum Flashcards
Describe the gray matter and white matter of the brain
In the brain, the grey matter forms an outer covering or cortex, while the white matter forms an inner core or medulla
Islands of grey matter called nuclei are
found in the deep portions of the cerebrum and cerebellum
Describe the cerebral cortex
The cerebral cortex that forms the outermost layer of the brain contains abundant nerve cell bodies, unmyelinated initial portion of axons, dendrites, and central glial cells, and it is the site of synapse
Aggregates of neuronal cell bodies forming islands of grey matter embedded in the white matter are called_________
nuclei
Discuss the white matter
The main components of white matter are myelinated axons and the myelin-producing oligodendrocytes
* It contains microglia plus the associated glial cells and blood vessels (axons in fresh preparations appear white)
* These axons travel from one part of the nervous system to another
functionally related bundles of axons are called_______
tracts
What the layers of the cerebral cortex
Molecular layer
External granular layer
External pyramidal layer
Internal granular layer
Internal pyramidal layer (Ganglionic layer)
Multiform (polymorphic layer)
The type of cells present in this layer include:
I. Pyramidal cells
II. Fusiform
III. Stallete
IV. Cells of martinotti
V. Horizontal cells of cajal
Molecular layer (plexiform layer)
- This is the most superficial layer
- These fibres are derived from the:
apical dendrites of the pyramidal cells and fusiform cells
the axons of the stellate cells, and the cells of Martinotti
Scattered among these nerve fibres are occasional horizontal cells of Cajal - This is the most superficial layer of the cortex clearly where large numbers
of synapses between different neurons occur
External granular layer
- This layer contains large numbers of small pyramidal cells and
stellate cells
The dendrites of these cells terminate in the molecular layer,
and the axons enter deeper layers, where they terminate or pass on
to enter the white matter of the cerebral hemisphere
External pyramidal layer
- This layer is composed of pyramidal cells, whose cell body size increases from the superficial to the deeper borders of the layer
- The apical dendrites pass into the molecular layer, and the axons enter the white matter as projection, association, or commissural fibres
Internal granular layer
- This layer is composed of closely packed stellate cells
- There is a high concentration of horizontally arranged fibers
known collectively as the external band of Baillarger
Ganglionic layer (internal pyramidal layer)
- This layer contains very large and medium-size pyramidal cells
- Scattered among the pyramidal cells are stellate cells and cells of
Martinotti - In addition, there are a large number of horizontally arranged
fibers that form the inner band of Baillarger
Multiform layer (layer of polymorphic cells)
- Although the majority of the cells are fusiform, many of the cells
are modified pyramidal cells, whose cell bodies are triangular or
ovoid - The cells of Martinotti also are conspicuous in this layer 10
- Many nerve fibers are present that are entering or are leaving
the underlying white matter
Layers of the cerebellar cortex
an outer molecular layer,
a central layer of very large neurons called Purkinje cells,
and an inner granule layer
Describe the anterior and posterior grey commissure
- The part of the gray commissure that is situated posterior to thecentral canal is often referred to as the posterior gray commissure
- the part that lies anterior to the canal is called the anterior gray commissure
