by prof. saeed abuel makarem. white matter of cerebrum each cerebral hemisphere consists of: each...
TRANSCRIPT
BYPROF.SAEED ABUEL MAKAREM
WHIT MATTER OF
THE CERBRUM
White matter of Cerebrum• Each cerebral hemisphere
consists of:• 1- Cerebral cortex: (outer layer of grey matter).• 2- White matter: (enormous mass of nerve
fibers).• 3- Basal ganglia: (collection of grey matter in
the white matter).• 4- Lateral ventricle: The cavity of the hemisphere.
WHITE MATTER OF CEREBRAL HEMISPHERE
• There are 3 types:• 1- Association fibers:• Interconnect cortical sites
lying within one hemisphere.• They are short or long fibers .• 2- Commissural fibers:• Connecting functionally
related gyri on both hemisphere.
• 3- Projection fibers:• Connecting the cortex with
the lower centers in thalamus brain stem, or spinal cord.
• They are ascending or descending.
• A- Short association fibers:
• Connect nearer gyri on the same hemisphere.
• B- Long association fibers:
• Connect distant gyri on the same hemisphere.
• Example:• 1-Superior
longitudinal fasciculus:
Association fibers
Association fibersExample:1-Superior longitudinal fasciculus:Connects the frontal & occipital lobes.It lies above the insula.It has a subsidiary bundle known as arcuate fasciculus, which connects the frontal & temporal lobes.It is important for language function
Association fibers• 2- Inferior longitudinal fasciculus:
• Connects the occipital & temporal poles.
• It is contributed in visual recognition.
• 3- Uncinate fasciculus:• U-shaped curved around
the bottom of the lateral sulcus.
• It connects the anterior & inferior parts of the frontal gyrus with the temporal gyri.
• It is important for behavioral regulation.
Association fibers• 4- Cingulum:• Begins in the anterior
perforated substance in the frontal lobe.
• Runs in cingulate gyrus.• Curves inferiorly to run
in the Parahippocampal gyrus.
• It is a part of the limbic system
• It terminates in the Uncus, (smell center).
COMMISSURAL FIBERS
• The major commissural fibers are:
• 1-Corps callosum.• 2-Anterior commissure. • 3-Hippocampal
commissure ( Commissure of the fornix).
CORPUS CALLOSUM• The greatest commissure
of brain.• It connects homologous
areas of the 2 cereral hemispheres
• Formed of 4 parts: Rostrum, genu, body & splenium.
• Lies in floor of great longitudinal fissure .
• Its inferior surface is attached to fornix by the septum pellucidum.
CORPUS CALLOSUM• Rostrum & genu interconnect the anterior part of the frontal lobe.
• The trunk interconnects the posterior part of the frontal & parietal & temporal lobes.
• The splenium interconnects the occipital lobes.
• The fibers of the rostrum & genu arch forward to form forceps minor.
• The fibers of splenium arch backward to form forceps major.
ANTERIOR COMISSURE
• Rounded commissure.• Lies behind the lamina
terminals.• Runs transversely in
front of the anterior column of fornix.
• Interconnects the middle & inferior temporal gyri.
• Also, it connects the olfactory regions of the 2 hemisphere.
HIPPOCAMPAL COMMISSURE
• Composed of transverse fibers .• Interconnects the posterior columns of the fornix.
PROJECTION FIBERS• These are fibers which connect the cortex to other areas in the brain stem & the spinal cord.
• Projection fibers are 2 types:
• A- Ascending (afferent),or corticopetal:
• Conveying fibers to the cortex
• 1- Thalamic radiation: connecting different thalamic nuclei with different parts of cortex.
• 2- Optic radiation.• 3- Auditory radiation.
PROJECTION FIBERS• B- Descending (Efferent), or
corticofugal:
• 1. Pyramidal: a. Corticospinal. b. Corticobulbar.
• 2. Corticopontine.
• 3. Corticoreticular.
• 4. Corticorubral
INTERNAL CAPSULE• Thick band of projection fibers, (porta cerebri).
• V-shaped with its concavity directed laterally in horizontal section
• Its concavity is related to Lentiform nucleus.
• It is formed of:• Anterior limb.• Genu.• Posterior limb.
INTERNAL CAPSULE• Anterior limb:• Between head of caudate
nucleus & lentiform nucleus.
• It contains:• 1-Anterior thalamic
radiation: From anterior & mediodorsal
thalamic nuclei, to the frontal cortex.
• 2-Frontopontine fibers: That project to pontine nuclei, in the basal part of the Pons.
INTERNAL CAPSULE• Genu of internal capsule:• Is the angle of the V which
points medially, between head of caudate nucleus and thalamus.
• It contains:• 1- Corticonuclear (Corticobulbar).• 2- Anterior part of sensory
(superior thalamic) radiation, from ventral anterior & ventral lateral nuclei to motor regions of the frontal lobe.
INTERNAL CAPSULE• Posterior limb:• A-Lenticothalamic part• Lies between thalamus &
lentiform nucleus.• Contains:• 1-Corticospinal fibers.• 2-Frontopontine.• 3-Frontorubral.• 4-Great part of sensory
(superior thalamic ) radiation, from the ventral posterior nucleus to the primary somatosensory cortex.
INTERNAL CAPSULE• B-Retrolentiular part:
• It contains fibers from medial & lateral geniculate nuclei of thalamus, which form the auditory & optic radiation.
• Optic radiation passes to visual cortex, around the calcarine sulcus (geniculoalcarine fibers).
• Auditory radiation passes to superior temporal gyrus.