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DIENCEPHALON I. Dr. Ahmed Fathalla Ibrahim. DIENCEPHALON. ORIGIN: from prosencephalon COMPONENTS: from dorsal to ventral: epithalamus, thalamus, subthalamus & hypothalamus CAVITY: third ventricle. EPITHALAMUS. SITE: above superior colliculus, dorsal to thalamus COMPONENTS:
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DIENCEPHALON I Dr. Ahmed Fathalla Ibrahim
DIENCEPHALON • ORIGIN: from prosencephalon • COMPONENTS: from dorsal to ventral: epithalamus, thalamus, subthalamus & hypothalamus • CAVITY: third ventricle
EPITHALAMUS • SITE: above superior colliculus, dorsal to thalamus • COMPONENTS: • Pineal gland: secretes melatonin that regulates onset of puberty • Habenular nuclei: a part of limbic system
THALAMUS SHAPE: • An oval mass of grey matter • Both thalami are joined by interthalamic adhesion
THALAMUS RELATIONS: • Superior: • Its lateral part is related to caudate nucleus • Its medial part forms the floor of lateral ventricle • Inferior: hypothalamus & subthalamus • Medial: forms the lateral wall of third ventricle • Lateral: posterior limb of internal capsule separating it from lentiform nucleus
CONNECTIONS OF THALAMUS ANTERIOR GROUP OF NUCLEI: • A part of limbic system • Concerned with recent memory, emotion, behavior Anterior group Cingulate gyrus Mammillary body Hippocampus
CONNECTIONS OF THALAMUS MEDIAL GROUP OF NUCLEI: • A part of limbic system • Concerned withcontrol of mood & emotion Hypothalamus Prefrontal cortex Medial group Prefrontal cortex
CONNECTIONS OF THALAMUS LATERAL GROUP OF NUCLEI: • Specific nuclei • Non specific nuclei
SPECIFIC NUCLEI VENTRAL POSTERIOR: • VENTRAL POSTERIOR LATERAL (VPL) • VENTRAL POSTERIOR MEDIAL (VPM) LATERAL GENICULATE BODY (LGB) MEDIAL GENICULATE BODY (MGB) VENTRAL ANTERIOR (VA) VENTRAL LATERAL (VL)
SPECIFIC NUCLEI Medial leminiscus Spinal leminiscus VPL Sensory cortex Trigeminal leminiscus Taste fibres VPM
SPECIFIC NUCLEI Optic tract LGB Visual cortex Inferior MGB Auditory cortex colliculus Globus Premotor & pallidus Motor cortex VA VL
NON SPECIFIC NUCLEI • LATERAL DORSAL • LATERAL POSTERIOR • PULVINAR They are connected to wide areas of cerebral cortex
CONNECTIONS OF THALAMUS INTRALAMINAR NUCLEUS (IL): • Control all level of activities of cerebral cortex Reticular formation Specific thalamic nuclei IL All cortical areas
CONNECTIONS OF THALAMUS RETICULAR NUCLEUS (RN): • Control mechanism of cerebral cortex over thalamus All cortical areas RN All thalamic nuclei
THALAMIC LESION THALAMIC SYNDROME: • Contralateral hemianaesthesia • Occurrence of spontaneous pain • Contralateral hemiparesis • Choreoathetosis