Diencephalon

DIENCEPHALON

DEVELOPMENT

ANATOMY OF DIENCEPHALON

• CONSISTS OF THE THIRD VENTRICLE AND THE STRUCTURES THAT FORM ITS BOUNDARIES

• EXTENT• INTERVENTRICULAR FORAMEN--- ANTERIORLY

TO• THE POINT WHERE THE 3rd VENTRICLE

BECOMES CONTINUOUS WITH THE AQUEDUCT---POSTERIORLY

ANATOMY OF DIENCEPHLON

• INFERIOR SURFACE

• ONLY EXPOSED AREA• INCLUDES FROM ANTERIOR TO POSTERIOR----• OPTIC CHIASMA &OPTIC TRACT• INFUNDIBULUM WITH TUBER CINEREUM• MAMMILARY BODIES


• SUPRIOR SURFACE

• FORMED BY THE ROOF OF 3rd VENTRICLE• CONCEALED BY FORNIX---A THICK BAND OF

FIBRES----ARISES IN THE HIPPOCAMPUS---ARCHES OVER THE THALAMUS TO JOIN THE MAMMILARY BODIES


• MEDIAL SURFACE• FORMED BY—• THALAMUS AND• HYPOTHALAMUS• LATERAL SURFACE• BOUNDED BY• INTERNAL CAPSULE

DEVELOPMENT OF DIENCEPHALON

• DEVELOPS FROM FOREBRAIN VESICLE• ROOF AND FLOOR PLATES REMAIN THIN• LATERAL WALLS BECOME THICK• WITH THE CLOSURE OF THE ROSTRAL

NEUROPORE A DIVERTICULUM------THE OPTIC VESICLE APPEARS ON EACH SIDE OF THE FOREBRAIN

• PART OF BRAIN CAUDAL TO OPTIC VESICLE FORMS THE DIENCEPHALON


• RETINA AND OPTIC DISK DERIVED FROM OPTIC VESICLE AND STALK

• CAVITY OF DIENCEPHALON FORMS THE GREATER PART OF 3rd VENTRICLE

• SMALL PART OF THE CAVITY OF THE TELENCEPHALON ALSO CONTRIBUTES TO THE FORMATION OF 3rd VENTRICLE

DEVELOPMENT OF DIENCEPHALIN

• DIENCEPHALON CONSISTS OF---• A ROOF PLATE AND• TWO ALAR PLATES• ROOF SHOWS A SMALL DIVERTICULUM

IMMEDIATELY ANTERIOR TO MIDBRAIN WHICH WILL FORM THE PINEAL BODY

• REMAINDER OF THE ROOF WILL FORM THE CHOROID PLEXUS OF 3rd VENTRICLE


• THREE SWELLINGS DEVELOP IN THE LATERAL WALL OF 3rd VENTRICLE WHICH LATER BECOME THE---

• 1 EPITHALAMUS• 2 THALAMUS• 3 HYPOTHALAMUS


• THALAMUS SEPARATED FROM EPITHALAMUS BY EPITHALAMIC SULCUS

• THALAMUS SEPARATED FROM HYPOTHALAMUS BY HYPOTHALAMIC SULCUS

• PINEAL BODY• INITIALLY APPEARS AS AN EPITHELIAL THICKENING IN

MIDLINE• BY 7th WEEK BEGINS TO EVAGINATE• BECOMES A SOLID ORGAN ON THE ROOF OF

MESENCEPHALON


• THALAMUS• ARISES AS A THICKENING OF ALAR PLATE ON THE

LATERAL WALLS OF 3rd VENTRICLE• DEVELOPS RAPIDLY ON EACH SIDE• BULGES INTO THE CAVITY OF 3rd VENTRICLE REDUCING

IT TO A NARROW CLEFT• IN 70 % OF BRAINS THE THALAMI MEET AND FUSE IN

THE MIDLINE FORMING A BRIDGE OF GRAY MATER ACROSS THE 3rd VENTRICLE---THE INTERTHALAMIC ADHESION OR MASSA INTERMEDIA


• MEDIAL GENICULATE BODY AND• LATERAL GENICULATE BODY

• DEVELOP AS SOLID BUDS---- THE METATHALAMUS


• HYPOTHALAMUS• ARISES BY PROLIFERATION OF NEUROBLASTS

IN LOWER PART OF ALAR PLATE ON EACH SIDE OF 3rd VENTRICLE VENTRAL TO HYPOTHALAMIC SULCUS

• A NUMBER OF NUCLEI CONCERNED WITH ENDOCRINE ACTIVITIES AND HOMEOSTASIS DEVELOP


• MAMILLARY BODIES

• A PAIR OF NUCLEI

• FORM PEA-SIZED SWELLINGS ON THE VENTRAL SURFACE OF HYPOTHALAMUS


• THIRD VENTRICLE• DEVELOPS FROM THE---

• 1 CAVITY OF DIENCEPHALON AND• 2 SMALL PART OF THE CAVITY OF

TELENCEPHALON


• THIRD VENTRICLE [ CONTD ]

• ROOF PLATE OF DIENCEPHALON IS THIN MADE UP OF A SINGLE LAYER OF EPENDYMA COVERED BY VASCULAR MESENCHYME FORMING THE CHOROID PLEXUS

• ROOF EXTENDS FROM THE INTERVENTRICULAR FORAMEN TO HABENULAR COMMISSURE


• THIRD VENTRICLE [ CONTD ]• ANTERIOR WALL• FORMED BY THE LAMINA TERMINALIS • LATERAL WALL• FORMED BY THE THALAMI • FLOOR• EXTENDS FROM OPTIC RECESS ON THE SUPERIOR

SURFACE OF OPTIC CHIASMA INTO THE INFUNDIBULAR RECESS AND THEN ABOVE MAMILLARY BODY TO THE AQUEDUCT

THANK YOU

Health & Medicine

Diencephalon