1. DEVELOPMENT OF BRAIN
BRAIN VESICLES &FLEXURES

3. BRAIN VESICLES
• PRIMARY VESICLES APPEAR DURING THE 4th
WEEK
• SECONDARY VESICLES APPEAR DURING THE
5th WEEK

4. 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

6. 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

7. 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

9. 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

10. 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

12. 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

13. 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

15. •DEVELOPMENT OF PONS
• RHOMBENCEPHALON CONSISTS OF—
• MYELENCEPHALON –MEDULLA OBLONGATA
• METENCEPHALON—PONS
• ---CEREBELLUM
• CAVITY OF THE METANCEPHALON FORMS THE
UPPER PART OF 4th VENTRICLE

16. 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

18. 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

19. 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

21. 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

23. 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

25. 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

28. 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

29. 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

30. 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

31. 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

33. 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

34. DEVELOPMENT OF CEREBELLUM
• CEREBELLAR CORTEX REACHES ITS DEFINITVE
SIZE AFTER BIRTH
• DEEP NUCLEI REACH THEIR FINAL POSITION
BEFORE BIRTH

35. 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

37. 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

38. 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

39. 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 ]

40. 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

41. 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

42. 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

43. 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

44. 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

45. 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

46. 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

47. 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

49. 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

50. 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

51. THANK YOU