WHITE MATTER OF THE CEREBRUM

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WHITE MATTER OF THE CEREBRUM:

WHITE MATTER OF THE CEREBRUM Dr Pankaj Maheria

Types of Fibre:

Types of Fibre Association fibres. Commissural fibres. Projection fibres.

Association fibres:

Association fibres

Association fibres:

Association fibres The association fibres interconnect the different regions of the cerebral cortex in the same hemisphere ( intrahemispheric fibres ). Types : Short association fibres ( arcuate or 'u' fibres) Long association fibres

Long association fibres:

Long association fibres Uncinate fasciculus Cingulum Superior longitudinal bundle

Long association fibres:

Long association fibres Uncinate fasciculus Cingulum Superior longitudinal bundle Inferior longitudinal bundle Fronto -occipital bundle

Commissural fibres:

Commissural fibres

Commissural fibres:

Commissural fibres Corpus callosum . Anterior commissure . Posterior commissure . Hippocampal commissure ( commissure of fornix). Habenular commissure .

Corpus callosum:

Corpus callosum The largest commissure of the brain connecting the cerebral cortex of the two cerebral hemispheres. Enormous size in man. 10 cm long Consists of about 300 million fibres. Connects all the parts of neocortex of two hemispheres except for the lower and anterior parts of temporal lobes which are connected by the anterior commissure .

External features and relations:

External features and relations Massive, arched, interhemispheric bridge flooring the midline longitudinal fissure and roofing both the lateral ventricles. Two end: Anterior Posterior In sagittal section of cerebrum: C-shaped mass of white fibres on the medial surface of the hemisphere Forming the roof of the lateral ventricle

External features and relations:

External features and relations Inferior surface: Attached with the convex superior aspect of the fornix by the septum pellucidum Superior surface: Anterior cerebral vessels often lie on the pia mater covering its superior aspect of corpus callosum . Covered on each side by cingulate gyrus from which it is separated by a callosal sulcus .

Parts:

Parts Genu

Parts:

Parts Genu Rostrum

Parts:

Parts Genu Rostrum Trunk/body

Parts:

Parts Genu Rostrum Trunk/body Splenium

Tapetum :

Tapetum Thin lamina of white fibres (2 cm thick) Forms: Roof and lateral wall of the posterior horn Lateral wall of the inferior horn of the lateral ventricle. Formed by those fibres of the trunk and splenium of corpus callosum which are not intersected by the fibres of corona radiata .

Function :

Function Interhemispheric transfer of information which is essential for bilateral responses and in learning processes.

Applied Anatomy:

Applied Anatomy Split-brain (Split-brain syndrome)

Anterior commissure:

Anterior commissure Two components Large posterior neocortical component Smaller anterior paleocortical component

Posterior commissure:

Posterior commissure A slender bundle of white fibres which crosses the midlifie through the inferior lamina of the stalk of pineal gland. Interconnects : Superior colliculi Pretectal Interstitial nuclei of two sides.

Habenular commissure:

Habenular commissure A slender bundle of white fibres which crosses the midline through the superior lamina of the stalk of pineal gland. Interconnects Habenular nuclei of the two sides.

Hippocampal commissure (commissure of fornix):

Hippocampal commissure ( commissure of fornix) Interconnects: Crura of fornix and thus the hippocampal formations of the two sides

projection fibres:

projection fibres

PowerPoint Presentation:

Two types: Corticofugal fibres Corticopetal fibres

Internal capsule:

Compact bundle of projection fibres between the thalamus and caudate nucleus medially and the lentiform nucleus laterally. Rostrally : corona radiata Caudally : crus cerebri of the midbrain. The ascending ( corticopetal / sensory) and descending ( corticofugal / motor) fibres of internal capsule chiefly interconnect the cerebral cortex with the brainstem and spinal cord. These fibres are mainly responsible for the sensory and motor innervation of the opposite half of the body. Internal capsule

Parts:

Parts Anterior limb Posterior limb Genu Retrolentiform part Sublentiform part

Shape and boundaries:

Shape and boundaries In a horizontal section of the cerebral hemisphere A V-shaped compact bundle of white fibres with its concavity directed laterally Boundaries : Medial: caudate nucleus and thalamus Lateral : lentiform nucleus.

Constituent of fibres : Motor fibres:

Constituent of fibres : Motor fibres Corticopontine fibres

Constituent of fibres : Motor fibres:

Constituent of fibres : Motor fibres Corticopontine fibres Pyramidal fibres Corticonuclear fibres Corticospinal fibres

Constituent of fibres : Motor fibres:

Constituent of fibres : Motor fibres Corticopontine fibres Pyramidal fibres Corticonuclear fibres Corticospinal fibres Extrapyramidal fibres

Constituent of fibres: Sensory fibres :

Constituent of fibres: Sensory fibres Thalamocortical fibres

Constituent of fibres: Sensory fibres :

Constituent of fibres: Sensory fibres Thalamocortical fibres Anterior thalamic radiation Superior thalamic radiation

Constituent of fibres: Sensory fibres :

Constituent of fibres: Sensory fibres Thalamocortical fibres Anterior thalamic radiation Superior thalamic radiation Posterior thalamic radiation Inferior thalamic radiation

Constituent of fibres:

Constituent of fibres Anterior limb Genu Posterior limb Retrolentiform part Sublentiform part

Arterial supply:

Arterial supply Great clinical significance, due to high incidence of vascular lesions of internal capsule (called capsular lesions). Medial and lateral striate branches of the middle cerebral artery. Striate branches of anterior cerebral artery.

Arterial supply:

Arterial supply Central branches of the anterior choroidal artery supply the sublentiform part. Some direct branches from the internal carotid artery supply the genu . Central branches of the posterior communicating artery. Posterolateral central branches of the posterior cerebral artery

Applied Anatomy :

Applied Anatomy Damage to the internal capsule, due to haemorrhage or infarction leads to loss of sensations and spastic paralysis of the opposite half o f the body ( contralateral hemiplegia ). Involvement of recurrent artery of Huebner (due to thrombosis/rupture) results in paralysis of the face and upper limb on the opposite side Lesions of the posterior one-third of the posterior limb, and sublentiform and retrolentiform parts of the internal capsule lead to visual ( hemianopia ) and auditory (loss of hearing) defects. These lesions usually occur due to thrombosis of the anterior choroidal artery , a branch of internal carotid artery.

Thank you…:

Thank you…

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