internal structures of hemispheres
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Internal structures of hemispheres
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Fibers
white matter fibers White matter is composed of
myelinated axons (nerve fibers) + neuroglial cells + blood capillaries.
actively affects how the brain learns and functions. While grey matter is primarily associated with processing and cognition, white matter modulates the distribution of action potentials, acting as a relay and coordinating communication between different brain regions
Typescommissural
fibers
projection fibers
Association fibers
Types connects region of the 2 hemispheres. example:1-corpus callosum (largest bundle).2- anterior commissure .3- posterior commissure .
commissural fibers
Typescommissural
fibers
projection fibers
Association fibers
Types Links different cortical area of the same
hemisphere. 2 types: 1- short association fibers:small bundle of fibers that connect adjacent gyri 2- long association fibers :For distant gyri, bundled together to make named structures.Example: Cingulum within cingulate gyrus Connects frontal and parietal lobes with temporal lobe .
Association fibers
Typescommissural
fibers
projection fibers
Association fibers
Types fibers that pass from the brainstem reaching
various regions. Exampels :Cut the braincut in the middle of the hemispherefibers will look like a fan and these projection fibers
projection fibers
Exampels : 1- corona radiata :Fibers which are dorsal (above ,superior)to the basal ganglia and close to the cortex .divided into (radiations)-Eg. optic radiation, auditory radiation.
2- A.internal capsule B. external capsule C.extreme capsule
projection fibers
Fibers travelling between “around” basal ganglia
Basal nuclei masses of grey matter embedded in white
matter.
Cotrex ???
thin line of grey matter its function isn't well known
Basal nucleiClaustrum barrier
Thalamus sensory station of the body not a part of basal nuclei used as a landmark to define different
projection fibers .
The fibers travelling between lentiform nucleus and caudate and between lentiform and thalamus is called
Between 2 limbs there is a structure like a knee»» the genu of internal capsule .
projection fibers
internal capsule
projection fibers The fibers travelling between lentiform
nucleus and claustrum is called
external capsule
The bundle between the claustrum and insula is called
projection fibers
extreme capsule
Insula
Other internal structures of cerebral hemisphere :❶septum pellucidum : double membrane) delicate membrane “part of anterior horn of
lateral ventricle”. bounded by corpus callosum superiorly and
fornix inferiorly.
Fornix(bundles of fibers that originate from hippocampus.
Other internal structures of cerebral hemisphere :❶septum pellucidum : double membrane) delicate membrane “part of anterior horn of
lateral ventricle”. bounded by corpus callosum superiorly and
fornix inferiorly. Inner surface of septum pellucidum composed of
ependymal cell, because this surface considered as part of the wall of the lateral ventricle.
we have 2 septum pellucidum (cavumpellucidum separate between them).
composed of both gray and white matter . (although it appears white in fresh specimen of brain ) .
❷corpus callosum : the largest bundle of commissural fibers . Covered with:-1.rostrum (the smallest) 2.genu(most anterior)3.body( the largest) 4.splenium(most posterior) .
Other internal structures of cerebral hemisphere :
Ventricles Four CSF-filled cavities located within the
brain . Lined by ependymal cells . Contain specialized vascular structures
called :choroid plexuses »» synthesis of CSF .
3rd ventricle in diencephalon 4th in hindbrain cerebral aqueduct in midbrain .
❶Lateral ventricles C-shaped of lateral ventricle to allow it to
extend to all lobes of brain. Each lateral ventricle is connected to 3rd
ventricle by foramen of monro . 2 in number
3rd ventricle connected to 4th by cerebral aqueduct then continue as centralcanal of spinal cord .
Does not contain choroidplexus .
Body » in parietal lobe . Ant.horn » in frontal lobe . Post. Horn » in occipital lobe . Inf. Horn » in temporal lobe .
Interthalamic connection : Bridge of tissue running through the 3rd ventricle connecting the 2 thalami .
❶Lateral ventricles
4th ventricle Tent shaped cavity Anterior to cerebellum, Posterior to pons and
medulla oblongata Communicates with subarachnoid space
through:-foramen of magendie(1 in number) » central .-foramen of luschka (2 in number ) » lateral .
MRI
Choroid plexuses Invagination of pia matter with blood
capillaries inside it, found through ventricles Components :-Endothelial layer(fenestrated)-Pial membrane.-Choroidal epithelial cells :form the blood -CSF barrier and responsible of active transport of the substances in and out of CSF
CSF
We have 150 ml of CSF in our body due to high turnover. “subarachnoid space”
Only 20 ml of CSF in ventricles (less than 50%).
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