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DIENCEPHALON

DIENCEPHALON.  . 4 th year. DIENCEPHALON. Site:- It is the part of the forebrain which lies above the midbrain & between the lower parts of the 2cerebral hemispheres. It consists of: Thalamus :-the large oval mass of grey matter Sub thalamus:- it lies directly above midbrain

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DIENCEPHALON

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  1. DIENCEPHALON  4th year

  2. DIENCEPHALON • Site:- It is the part of the forebrain which lies above the midbrain & between the lower parts of the 2cerebral hemispheres. • It consists of: • Thalamus :-the large oval mass of grey matter • Subthalamus:- it lies directly above midbrain • hypothalamus : lies infront of subthalamus • Metathalamus : formed by lateral & medial geniculate body • Epithalamus: Formed of pineal body, 2 habenular nuclei & commissures &posterior commissure. The thalamus :Is the main sensory relay station on the pathway of all sensations (except smell) to the cerebral cortex.

  3. The thalamus It consists of 2 ends & 4 surfaces 1) Narrow anterior end: behind the interventricular foramen 2)expanded posterior end: called pulvinar The surfaces of the thalamus: • The superior surface is related medially to the tella choroida, fornix &laterally it form the floor of the central part of the lateral ventricle • The inferior surface: anteriorlyit lies on hypothalamus,  on its middle part on the subthalamus but  on the posterior part it is free and has lateral & medial geniculate bodies.

  4. c) The medial surface: forms the upper part of the lateral wall of the 3rd ventricle &it is separated from the hypothalamus by hypothalamic sulcus. Here the 2 thalami are connected by inter thalamic adhesion. d) The lateral surface: related to the posterior limb of internal capsule separating it from the lentiform nucleus

  5. The internal structure of the thalamus • It is divided by a Y-shaped sheet of white matter • Called internal medullary lamina into 3 main parts. 1) anterior part: between the 2 anterior limbs 2) medial part : lying medial to the posterior limb of medullary lamina & lateral part lying lateral to it. • The thalamic nuclei • The medial group in the medial part of the thalamus • Anterior group in the anterior part • The lateral part is divided by imaginary horizontal plane into • a) small dorsal part • b) Large ventral part • nuclei of dorsal part • a) lateral dorsal n. • b) Lateral posterior n. • Nuclei of ventral part 3 nuclei • a) Ventral Anterior • b) ventral Intermediate • c) ventral Posterior ventral Posterolateral n V. P. L.N ventral Posteromedial n V. P. M.N

  6. The hypothalamus • It lies anterior inferior to the thalamus. • It form the floor & lower part of the lateral wall of the third ventricle. • It includes the following structure: • optic chiasma & supra optic nuclei • tuber cinerium &infandibulum • mammilary body • posterior perforated substances

  7. SUBTHALAMUS • It lies between the thalamus & tegmentum of the midbrain • It contains 1) 3 nuclei (upper end of red nucleus, • upper end of substantia nigra • subthalamic nuclei) 2) bundles of projection fibers

  8. THANK YOU

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