Development of brain
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  • 1. DEVELOPMENT OF BRAIN BRAIN VESICLES &FLEXURES
  • 2. BRAIN VESICLES• PRIMARY VESICLES APPEAR DURING THE 4th WEEK• SECONDARY VESICLES APPEAR DURING THE 5th WEEK
  • 3. BRAIN FLEXURES• 1 MIDBRAIN FLEXURE IN THE MIDBRAIN REGION• 2 CERVICAL FLEXURE B/W THE HINDBRAIN AND SP CORD—AT THE LEVEL OF SUPERIOR ROOT OF C1• 3 PONTINE FLEXURE PRODUCED AS A RESULT OF UNEQUAL GROWTH OF BRAIN B/W 1 & 2 IT IS IN THE OPPOSITE DIRECTION –RESULTS IN THE THINNING OF THE ROOF OF HINDBRAIN
  • 4. BRAIN FLEXURES• PRODUCE VARIATIONS IN THE OUTLINE OF TRANSVERSE SECTIONS AT DIFFERENT LEVELS OF THE BRAIN AND IN THE POSITIONS OF GRAY AND WHITE MATER• SULCUS LIMITANS EXTENDS CRANIALLY TO THE JUNCTION OF MIDBRAIN AND FOREBRAIN• ALAR AND BASAL PLATES ARE RECOGNIZABLE ONLY IN THE HINDBRAIN AND MIDBRAIN
  • 5. DEVELOPMENTOF HINDBRAIN [RHOMBENCEPHALON ]• MYELENCEPHALON [MEDULLA OBLONGATA ]• CAUDAL /CLOSED PART• ROSTRAL/OPEN PART• CAUDAL PART• RESEMBLES SP CORD DEVELOPMENTALLY AND STRUCTURALLY• LUMEN FORMS A SMALL CENTRAL CANAL
  • 6. DEVELOPMENT OF MEDULLA OBLONGATA• ROSTRAL PART• WIDE AND FLAT OPPOSITE THE PONTINE FLEXURE• PONTINE FLEXURE CAUSES LATERAL WALLS OF THE MEDULLA TO MOVE OUTWARD LIKE THE PAGES OF AN OPEN BOOK• ROOF PLATE IS ALSO THINNED AND GREATLY STRETCHED
  • 7. DEVELOPMENT OF MEDULLA• NEUROBLASTS IN THE BASAL PLATE• ORGANIZE INTO THREE COLMNS ON EACH SIDE-- -FROM MEDIAL TO LATERAL• 1 GENERAL SOMATIC EFFERENT—NEURONS OF HYPOGLOSSAL NERVE• 2 SPECIAL VISCERAL EFFERENT---NEURONS INNERVATING MUSCLES DERIVED FROM PHARYNGEAL ARCHES• 3 GENERAL VISCERAL EFFERENTS ---SOME NEURONS OF GLOSSOPHARYNGEAL AND VAGUS NERVE
  • 8. DEVELOPMENT OF MEDULLA• NEUROBLASTS IN THE ALAR PLATE• FORM NEURONS THAT ARE ARRANGED IN FOUR COLUMNS ON EACH SIDE FROM MEDIAL TO LATERAL• 1 GENERAL VISCERAL AFFERENT---RECEIVE IMPULSES FROM• 2 SPECIAL VISCERAL AFFERENT---RECEIVE TASTE FIBRES• 3 GENERAL SOMATIC AFFERENT---RECEIVE IMPULSES FROM THE SURFACE OF THE HEAD
  • 9. DEVELOPMENT OF MEDULLA• NEUROBLASTS IN THE ALAR PLATE [CONTD ]• 4 SPECIAL SOMATIC AFFERENT---RECEIVE IMPULSES FROM THE EAR• SOME NEUROBLASTS FROM ALAR PLATE MIGRATE VENTRALLY AND FORM NEURONS IN THE OLIVARY NUCLEUS
  • 10. •DEVELOPMENT OF PONS• RHOMBENCEPHALON CONSISTS OF—• MYELENCEPHALON –MEDULLA OBLONGATA• METENCEPHALON—PONS• ---CEREBELLUM• CAVITY OF THE METANCEPHALON FORMS THE UPPER PART OF 4th VENTRICLE
  • 11. DEVELOPMENT OF PONS• ARISES FROM THE ANTERIOR PART OF METANCEPHALON• ALSO RECEIVES CELLULAR CONTRIBUTIONS FROM ALAR PART OF MYELENCEPHALON• PONTINE FLEXURE CAUSES DIVERGENCE OF LATERAL WALLS OF PONS AND SPREADS GRAY MATER IN THE FLOOR OF 4th VENTRICLE• NEUROBLASTS IN EACH BASAL PLATE DEVELOP INTO MOTOR NUCLEI AND ORGANIZE INTO 3 CLUMNS ON EACH SIDE
  • 12. DEVELOPMENT OF PONS• NEURONS OF BASAL PLATES FORM THE MOTOR NUCLEI OF CRANIAL NERVES 5,6 & 7• NEURONS OF VENTROMEDIAL PART OF EACH ALAR PLATE FORM THE• 1 MAIN SENSORY NUCLEUS OF CR N 5• SENSORY NUCLEUS OF CR N 7• VESTIBULAR NUCLEUS OF CR N 8• COCHLEAR NUCLEUS OF CR N 8• PONTINE NUCLEI
  • 13. DEVELOPMENT OF PONS• AXONS OF PONTINE NUCLEI GROW TRANSVERSELY AND ENTER THE DEVELOPING CEREBELLUM OF THE OPPOSITE SIDE TO FORM THE TRANSVERSE PONTINE FIBRES AND MIDDLE CEREBELLAR PEDUNCLE
  • 14. DEVELOPMENT OF CEREBELLUM• DEVELOPS FROM THE POSTERIOR PART OF ALAR PLATES OF METENCEPHALON• ON EACH SIDE THE ALAR PLATES BEND MEDIALLY TO FORM THE RHOMBIC LIP• IN THE CAUDAL PART OF THE METANCEPHALON THE RHOMBIC LIPS ARE WIDELY SEPARATED• IMMEDIATELY BELOW THE MESENCEPHALON THEY APPROACH EACH OTHER IN THE MIDLINE
  • 15. DEVELOPMENT OF CEREBELLUM• PONTINE FLEXURE DEEPENS• RHOMBIC LIPS COMPRESS TO FORM THE CEREBELLAR PLATES• PLATES FUSE IN THE MIDLINE• DURING FUSION THEY OVERGROW THE ROSTRAL ½ OF THE 4th VENTRICLE AND OVERLAP THE PONS AND MEDULLA• THE FUSED PLATE SHOWS VERMIS IN THE MID LINE ANDTWO HEMISPHERES LATERALLY
  • 16. DEVELOPMENT OF CEREBELLUM• AT ABOUT THE END OF 4th MONTH FISSURES DEVELOP ON THE SURFACE AND THE FOLIA OF ADULT CEREBELLUM GRADUALLY DEVELOP• A TRANSVERSE FISSURE SEPARATES THE NODULE FROM THE VERMIS AND THE FLOCCULUS FROM THE HEMISPHERES• FLOCCULONODULAR LOBE IS THE MOST PRIMITIVE PART—THE ARCHICEREBELLUM –• CONNECTED TO VESTIBULAR APPARATUS
  • 17. DEVELOPMENT OF CEREBELLUM• VERMIS AND ANTERIOR LOBE FORM THE• PALEOCEREBELLUM ASSOCIATED WITH SENSORY DATA FROM THE LIMBS• POSTERIOR LOBE FORMS THE NEOCEREBELLUM CONCERNED WITH SELECTIVE CONTROL OF LIMB MOVEMENTS
  • 18. DEVELOPMENT OF CEREBELLUM• HISTOGENESIS• NEUROBLASTS DERIVED FROM THE CELLS IN THE VENTRICULAR ZONE MIGRATE TO THE SURFACE OF THE CEREBELLUM TO FORM THE EXTERNAL GRANULAR LAYER• THESE CELLS RETAIN THE ABILITY TO DIVIDE AND FORM A PROLIFERATIVE ZONE ON THE SURFACE OF THE CEREBELLUM
  • 19. DEVELOPMENT OF CEREBELLUM• HISTOGENESIS [ CONTD ]• OTHER NEUROBLASTS REMAIN CLOSE TO THE VENTRICULAR SURFACE AND DIFFERENTIATE INTO---• 1 DENTATE NUCLEUS• 2 EMBOLIFORM NUCLEUS• 3 GLOBOSE NUCLEUS• 4 FASTIGIAL NUCLEUS
  • 20. DEVELOMENT OF CEREBELLUM• HISTOGENESIS [CONTD ]• IN THE 6th MONTH THE EXTERNAL GRANULAR LAYER GIVES RISE TO VARIOUS CELL TYPES• LAYERS OF CORTEX• 1 OUTER MOLECULAR LAYER• 2 MIDDLE PURKINJE LAYER• 3 INNER GRANULAR LAYER
  • 21. DEVELOPMENT OF CEREBELLUM• HISTOGENESIS [ CONTD ]• MOLECULAR LAYER• TWO TYPES OF CELLS• 1 STELLATE• 2 BASKET CELLS• PURKINJE CELL LAYER• LARGEST NEURONS OF CNS [ GOLGI TYPE I ]• GRANULAR LAYER• TWO TYPES OF CELLS• 1 GRANULE CELLS—MOST NUMEROUS,SMALLEST AND ONLY EXCITATORY NEURONS• 2 GOLGI TYPE 2/INNER STELLATE
  • 22. DEVELOPMENT OF CEREBELLUM• CEREBELLAR CORTEX REACHES ITS DEFINITVE SIZE AFTER BIRTH• DEEP NUCLEI REACH THEIR FINAL POSITION BEFORE BIRTH
  • 23. DEVELOPMENT OF CHOROID PLEXUS OF 4th VENTRICLE• THIN EPENDYMAL ROOF IS COVERED EXTERNALLY BY PIA MATER• TELA CHOROIDEA FORMED BY THESE TWO LAYERS• TELA CH CONTAINS TUFTS OF BLOOD VESSELS• TELA CHOROIDEA INVAGINATES THE VENTRICLE AND DIFFERENTIATES INTO CHOROID PLEXUS
  • 24. DEVELOPMENT OF CHOROID PLEXUS• CHOROID PLEXUS SECRETES CSF• THIN ROOF EVAGINATES IN THREE LOCATIONS• THESE OUTPOUCHINGS RUPTURE TO FORM THREE FORAMINA• 1 FORAMEN OF MAGENDIE--- MEDIAN• 2 FORAMINA OF LUSHKA---LATERAL
  • 25. FUNCTIONAL COMPONENTS OF SPINAL & CRANIAL NERVES• CELL COLUMNS OF OF BASAL PLATE• THREE ELONGATED BUT INTERRUPTED COLUMNS FROM MEDIAL TO LATERAL• 1 GENERAL SOMATIC EFFERENT• CONTINUOUS WITH THE ANTERIOR GRAY COLUMN OF SP CORD• IN THE CAUDAL PART OF HINDBRAIN REPRESENTED BY HYPOGLOSSAL NUCLEI• REAPPEARS AT HIGHER LEVELS AS THE NUCLEI OF CN6,CN4 &CN3
  • 26. FUNCTIONAL COMPONENTS OF SPINAL &AND CRANIAL NERVES• CELLS OF BASAL PLATE [ CONTD ]• 2 SPECIAL VISCERAL EFFERENT• REPRESENTED IN UPPER PART OF SP CORD AND LOWER BRAIN STEM [MEDULLA & PONS ]• FOR THE SUPPLY OF PHARYNGEAL AND POST PHARYNGEAL MUSCLES• CAUDAL BRAIN STEM PART GIVES FIBRES TO CN9,CN10,CN11 AND FORM THE ELONGATED NUCLEUS AMBIGUUS [SUPPLIES LARYNX ,SOFT PALATE ,PHARYNX AND UPPER OESOPHAGUS ]
  • 27. FUNCTIONAL COMPONENTS OF SPINAL AND CRANIAL NERVES• CELLS OF BASAL PLATE [CONTD ]• SPECIAL VISCERAL EFFERENT CONTD• NUCLEUS AMBIGUUS CONTINUES INTO THE CERVICAL PART OF THE SP CORD AS THE ORIGIN OF SPINAL ACCESSORY NERVE• AT HIGHER LEVELS GIVES ORIGIN TO MOTOR NUCLEI OF CN7 & CN5
  • 28. FUNCTIONAL COMPONENTS OF SPINAL AND CRANIAL NERVES• 3 GENERAL VISCERAL EFFERENT• ALSO INTERRUPTED• REPRESENTED IN THE SP CORD BY THE LATERAL GRAY COLUMN• CAUDAL PART FORMS SOME OF THE DORSAL NUCLEUS OF VAGUS---MOTOR NEURONS SUPPLYING INVOLUNTARY MUSCLES• CRANIAL PART FORMS THE SALIVATORY NUCLEUS
  • 29. FUNCTIONAL COMPONENTS OF SPINAL CRANIAL NERVES• CELL COLUMNS OF ALAR PLATE• FOUR INTRRUPTED COLUMNS FROM MEDIAL TO LATERAL• 1 GENERAL VISCERAL AFFERENT• REPRESENTED BY A PART OF DORSAL NUCLEUS OF VAGUS RECEIVING IMPULSES FROM THE VISCERA
  • 30. FUNCTIONAL COMPONENTS OF SPINAL AND CRANIAL NERVES• CELL COLUMNS OF ALAR PLATE [CONTD ]• 2 SPECIAL VISCERAL AFFERENT• REPRESENTED BY THE NUCLEUS OF TRACTUS SOLITARIUS RECEIVING TASTE FIBRES• 3 GENERAL SOMATIC AFFERENT• REPRESENTED BY THE AFFERENT NUCLEI OF CN5 RECEIVING IMPULSES FROM THE SURFACE OF THE HEAD
  • 31. FUNCTIONAL COMPONENTS SPUNAL AND CRANIAL NERVRS• CELL COLUMNS OF ALAR PLATE [ CONTD ]• 4 SPECIAL SOMATIC AFFERENT• REPRESENTED BY THE NUCLEI OF VESTIBULOCOCHLEAR NERVE RECEIVING IMPULSES FROM THE EAR
  • 32. DEVELOPMENT OF MIDBRAIN• DEVELOPS FROM MESENCEPHALON• NEURAL CANAL NARROWS AND BECOMES THE CEREBRAL AQUEDUCT WHICH CONNECTS THE 3rd & 4th VENTRICLES• SULCUS LIMITANS SEPARATES THE ALAR PLATE FROM THE BASAL PLATE
  • 33. DEVELOPMENT OF MIDBRAIN• BASAL PLATE• CONTAINS TWO GROUPS OF MOTOR NUCLEI• 1 SOMATIC EFFERENT• REPRESENTED BY CN3 & CN4 WHICH INNERVATE THE MUSCLES OF EYE• 2 GENERAL VISCERAL EFFERENT• REPRESENTED BY THE NUCLEUS OF EDINGER WESTPHAL WHICH INNERVATES THE SPHINCTER PUPILLAE MUSCLE
  • 34. DEVELOPMENT OF MIDBRAIN• BASAL PLATE [CONTD ]• MARGINAL LAYER OF EACH BASAL PLATE ENLARGES AND FORMS THE CRUS CEREBRI• CRURA SERVE AS PATHWAYS FOR CORTICOPONTINE,CORTICOBULBAR AND CORTICOSPINAL FIBRES• NEUROBLASTS POSSIBLY DIFFERENTIATE INTO NEURONS FORMING THE NUCLEI OF RED NUCLEUS,SUBSTANTIA NIGRA AND RETICULAR FORMATION
  • 35. DEVELOPMENT OF MIDBRAIN• ALAR PLATE• TWO ALAR PLATES AND THE ORIGINAL ROOF PLATE FOPRM THE TECTUM• NEUROBLASTS DIFFERENTIATE INTO SENSORY NEURONS OF SUP AND INF COLLICULI• COLLICULI APPEAR ON THE POSTERIOR SURFACE OF THE BRAIN
  • 36. DEVELOPMENT OF MIDBRAIN• ALAR PLATE [CONTD ]• SUP COLLICULI---ASSOCIATED WITH VISUAL REFLEXES• INF CILLICULI---ASSOCIATED WITH AUDITORY REFLEXES• CELLS OF ALAR PLATE MIGRATING VENTRALLY MAY GIVE RISE TO SUBSTANTIA NIGRA WHICH IS A BROAD LAYER OF GRAY MATER ADJACENT TO CEREBRAL PEDUNCLES
  • 37. THANK YOU