White Matter of Cerebral Hemispheres Lecture Notes PDF

White Matter of Cerebral Hemispheres By Dr. Mariam Atef Lecturer of Anatomy  The cerebral hemisphere consists of: Outer grey matter (cortex)= (cell body of the neuron ). Inner white matter ( nerve fibres). Basal ganglia (grey matter embedded inside the white matter). ...

White Matter of Cerebral Hemispheres By Dr. Mariam Atef Lecturer of Anatomy  The cerebral hemisphere consists of: Outer grey matter (cortex)= (cell body of the neuron ). Inner white matter ( nerve fibres). Basal ganglia (grey matter embedded inside the white matter). Lateral ventricle. (cavity of the cerebral hemisphere) White matter of the cerebral hemisphere: it consists of all nerve fibers in the cerebrum, there are 3 types of fibers  Association fibers: Fibres connecting different cortical areas within same hemisphere.  Commissural fibers: (crossing midline) Fibres connecting same areas within different hemisphere.  Projection fibers: Fibres connecting higher centers (cerebral cortex) with lower centers ( subcortical areas).  Definition: Fibres which connect different cortical areas in the same hemisphere.  Types: Short association fibers.(connecting adjacent gyri) Long association fibers. (connecting distant lobes)  1- Short association fibres ◦ U shaped bands. ◦Pass immediately beneath the cortex & connect adjacent gyri together. (coordination) Connect the widely separated gyri. Superior longitudinal bundle. Fronto-occipital bundle. Inferior longitudinal bundle Uncinate bundle. Cingulum. Arcuate fasiculus 1- Superior longitudinal bundle (C-shaped)  Connects the different cortical areas of the supero-lateral surface together.  Begins in frontal pole passes over insula ends in the occipital lobe and temporal lobe 2- Inferior longitudinal bundle:  Lies on the inferior surface  Extends from the temporal pole to the occipital pole 3. Cingulum - C-shaped ,within the cingulate gyrus -begins below the rostrum of corpus callosum - Ends in uncus -Function: Connects cingulate gyrus with the hippocampus 4- Fronto-occipital bundle :  Begins in the frontal pole ends in the occipital pole  Medial to superior bundle 5-Uncinate bundle: sharply curved bundle Connects the orbital gyri with the temporal pole. 6- Arcuate fasciculus: Connects Broca's area with area of Wernicke's.  Definition: is a band of white matter connecting same areas of different hemispheres. There are many commisures but the most important one is corpus callosum Fornix   Corpus callosum (About 10 cm in length) ◦ Is the largest & main commissure of the brain. ◦ Connects nearly the same areas of the 2 hemispheres except the temporal lobes which are connected by the anterior commissure. It lies at the bottom of the median longitudinal fissure below the falx cerebri  Parts 1. Rostrum 2. Genu 3. Body 4. Splenium All parts of corpus callosum are supplied by Anterior cerebral artery except the splenium which is supplied by the posterior cerebral arteries  Callosal syndrome ( split-brain) : a disconnection syndrome between the two hemispheres of the brain. They constitute all the descending fibers from the cerebral cortex to the lower centers and all the ascending fibers from the thalamus to the cerebral cortex. They pass through a V-shaped structure called the Internal capsule.