Thelencephalon. Cerebral Cortex Flashcards
Telencephalon vesicles derives from
Rostral most prosencephalon: hypothalamo-telencephalic prosomeres hp1 and hp2
hp1-cerebral hemispheres
hp2-preoptic area
Telencephalic expansion or vesicles give rise to
Cerebral hemispheres
As the telencephalic vesicles develop, we distinguish 2 divisions within the vesicle
Pallium (roof and walls of the vesicle) - gives rise to cerebral cortex
Subpallium (floor of the vesicle) - gives rise to deep structures
Derivatives of the subpallium
Caudate nucleus
Putamen
Pallidal complex (Globus pallidus)
Derivatives of subpallium form
Basal ganglia
Location of caudate nucleus
Adjacent / lateral to the ventricle, forms its lateral walls and follows its shape during development
Developing of the caudate nucleus and putamen
Subpallium proliferates —> cortex fibers = projected to reach spinal cord (corticospinal & corticonuclear tracts)
These 2 tracts come together as they descend, = internal capsule, at 2 sides/lateral to thalamus. It passes through & pierces subpallium —> divided:
- Dorsal structure (C shape) = Caudate nucleus
- Ventral structure (circular) = the Putamen
Caudate nucleus + putamen =
Striatum
Striatum =
Caudate nucleus + putamen
Developing of Globus pallidus and location
From subpallium, a couple more structures develop (Globus pallidus) which divides into 2 nuclei: medial and lateral.
They are both medial to the putamen.
Hippocampus definition
Cortical structure derived from the pallium, but also ends up being subcortical.
Hippocampus origin
Cortical (medial wall of pallium) —> surrounds the ventricle.
It’s a piece of cortex that is also subject to shaping by ventricles. Fibres radiating from it (fornix) = C shape.
Amygdaloid complex origin
Mixed: from a set of nuclei which all together form it
- Part derive from the pallium
- Part of the subpallium
Amygdaloid complex location
Directly rostral to the hippocampus.
Cerebral cortex is derived from
The pallium
Cerebral cortex division according to location
Medial wall —> archicortex (becomes subcortical) —> hippocampal complex
Dorsal wall —> neocortex. The majority of cortex originates from dorsal pallium. It provides higher function.
Ventrolateral wall —> paleocortex, which’ll form the olfactory cortex. In the adult, we only see a very small area with that origin.
Archicortex
Very old. Its derivative is the hippocampus (memory.)
Key for life and survival.
Paleocortex
Very old. Olfaction is essential, greatly developed in animals. Very old in the phylogenetic scale.
Neocortex
Newest, phylogenetically recent.
Cerebral cortex division according to structure
Isocortex
Allocortex
Isocortex
Formed by 6 well differentiated layers of cells.
Phylogenetically recent.
It would correspond to the neocortex. In humans, 90-96% of the cortex is neocortex
Allocortex
Variable nº of layers (3-6).
Older phylogenetically speaking.
Corresponds to hippocampus and olfactory cortex. They are structurally different, both have an organizational structure that is different to the typical neocortex = “allo”
Cerebral lobes
Frontal lobe - until the central sulcus (Rolando sulcus)
Parietal lobe - from central to parieto-occipital sulcus. Clearly visible in the medial aspect, only hinted on the outside
Occipital lobe - form the parieto-occipital sulcus to the caudal end
Temporal lobe - Sylvian fissure or lateral sulcus. Where it joins to the parietal lobe, we extend a line = marks the boundary of the temporal lobe
Gyri
Development is so fast that the parenchyma has to fold on itself, forming gyri
Cingulate gyrus
Medial aspect: gyrus that surrounds the corpus callosum: cingulate gyrus.
Limbic lobe
Cingulate gyrus + the one continuous with it below
Parahippocampal lobe
The ventral part of the limbic lobe.
Contains the hippocampus within it (on the deep aspect).
Insular lobe
Another lobe hidden under the frontal, parietal and temporal lobes.
It has short and long gyri + central sulcus. What separates the gyri are the sulci.
White matter - short association fibers
Connect adjacent regions of the cortex, located in the same area.
White matter - long association fibers
Connect distant cortical areas within the same hemisphere
Bridging connections from one hemisphere to the other (within white matter)
Commissural fibers, biggest one = Corpus callosum. Also found anterior commissure and posterior commissure.
Corona radiata
Fibers in the cerebral white matter that are not corticocortical projections, but going to subcortical structures.
Fibers in the cerebral white matter that are not corticocortical projections, but going to subcortical structures.
Corona radiata
Corona radiata fibers come to form…
Internal capsule
Internal capsule will…
Form corticospinal and corticonuclear tracts
Separate the putamen from the caudate nucleus
Internal capsule will compress even more at the level of midbrain to form
Crus cerebri
Internal capsule will compress even more at the level of medulla to form
Pyramids
Parts of the internal capsule
Anterior limb
Genu
Posterior limb
Cells of the layers of the isocortex
Granular cells - layers 2 and 4
Pyramidal cells - layers 3 and 5
Only cells that project out of the cortex
Pyramidal cells = cortical projection neurons
(Granular cells = inter neurons)
Sensory nuclei specifically project to
Layer 4
Difference between each region of the cortex
Changes in their respective cell layers
Homotypical areas
6 typical layers are distinguishable
Heterotypical granular areas
Huge, developed layer 4
Heterotypical agranular areas
Almost no layer 4 and large pyramidal cells
Brodmann areas
Heterotypical agranular cortical areas = motor cortex. Originate the descending pathway
Heterotypical granular cortical areas = sensory cortex. Area for projections from primary nuclei in the thalamus
Something in between = association cortices, receiving projections from the association nuclei in the thalamus. Integrate info from primary or secondary areas, and have a different structure
Higher function correlates with
Increase in associative cortices
