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Parts of the brain Sanjaya Adikari Department of Anatomy.

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Presentation on theme: "Parts of the brain Sanjaya Adikari Department of Anatomy."— Presentation transcript:

1 Parts of the brain Sanjaya Adikari Department of Anatomy

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3 Spinal cord Foramen magnum Central Nervous System (CNS)

4 Skull Vertebral column

5 Meninges Dura mater Arachnoid mater Pia mater

6 Dura mater Arachnoid mater Pia mater Ependymal cell layer Ventricle

7 = forebrain = midbrain = hindbrain Main divisions of the brain

8 1 6 Diencephalon 2 + Cerebellum 43 5 = brainstem midbrain pons medulla Cerebrum

9 Cerebral hemispheres –Left & right cerebral hemispheres Diencephalon –Consists of thalamus, hypothalamus etc. Cerebrum is the largest part of the brain. It is situated in the anterior and middle cranial fossae and the whole concavity of the vault of the skull Has two parts;

10 Diencephalon thalamus hypothalamus Spinal cord Mid-sagittal section of brain

11 Diencephalon thalamus hypothalamus Spinal cord

12 Cerebral hemispheres Largest part of the brain Separated by a deep mid-sagittal fisure called longitudinal cerebral fissure The fissure contains the falx cerebri and anterior cerebral arteries Tentorium cerebelli separates cerebral hemispheres from the cerebellum

13 Falx cerebri Tentorium cerebelli Dura mater Anterior cerebral arteries Corpus callosum

14 Sulci and Gyri To increase the surface area of the brain the cerebral hemispheres are thrown into folds - gyri The gyri are separated from each other by fissures - sulci Hemispheres are divided into lobes (named according to the cranial bones under which they lie) by main sulci –Central –Parieto-occipital –Lateral

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16 Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe Central sulcus Parieto- occipital sulcus Lateral sulcus

17 Cranial Fossae

18 Main gyri Precentral gyrus Postcentral gyrus Superior/middle/inferior frontal gyri Superior/middle/inferior temporal gyri Cingulate gyrus Parahippocampal gyrus

19 Superior, middle, inferior frontal gyri Superior, middle, inferior temporal gyri Precentral gyrusPostcentral gyrus

20 Cingulate gyrus Parahippocampal gyrus

21 Functional areas of the brain

22 Homunculus

23 Homework Draw a labelled line diagram to illustrate a mid- sagittal section of the brain including the brain stem. Draw a labelled line diagram to illustrate a horizontal section of the cerebrum through the head of the caudate nucleus. Study the above diagrams before you come for the next lecture on parts of the brain

24 Lecture II

25 Gray matter and white matter Gray matter White matter Gray matter consists of nerve cells White matter consists of nerve fibres

26 Gray matter of the cerebral cortex Five types of cells are organized into six cortical layers

27 Molecular layer External granular layer External pyramidal layer Internal granular layer Ganglionic layer (Internal pyramidal layer) Multiform layer

28 White matter Composed of myelinated nerve fibres Supported by neuroglia Classified into three groups according to their connections –Commissural fibers –Association fibers –Projection fibers

29 Commissural fibers Connects corresponding regions of the two hemispheres Corpus callosum, fornix, anterior and posterior commissures Corpus callosum, the largest commissure of the brain, is divided into rostrum, genu, body and the splenium

30 Corpus callosum Genu Rostrum Splenium Body

31 Association fibers Connects various cortical regions within the same hemispheres Divided into short and long groups Short association fibers lie immediately beneath the cortex and connect adjacent gyri Long association fibers are arranged into named bundles - fasciculi

32 Projection fibers Afferent and efferent nerve fibers passing to and from the brain stem to the cerebral cortex Internal capsule, corona radiata, optic radiation

33 Internal capsule Corona radiata Optic radiation Cerebral peduncle Optic tract Pyramidal tract Internal capsule and corona radiata

34 Cerebral peduncle Internal capsule Putamen Amygdala

35 Basal ganglia Basal ganglia are collection of masses of gray matter within the white matter of cerebral hemispheres Gray matter of cerebral cortex White matter of cerebrum Basal ganglia

36 Basal ganglia…..cont. Corpus striatum –Divided into two by internal capsule of white matter Caudate nucleus Lentiform nucleus (putamen & globus pallidus) Amygdaloid Claustrum

37 Basal ganglia…..cont.

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39 Anterior horn of lateral ventricle Head of caudate nucleus Tail of caudate nucleus Thalamus Lentiform nucleus (putamen) Internal capsule Claustrum External capsule Lentiform nucleus (globus pallidus)

40 Frontopontine Corticobulbar Corticospinal Thalamocortical Parieto/temporo/occipito pontine Visual & auditory Fiber tracts in the internal capsule

41 Basal ganglia…..cont. Some definitions include the following also under basal ganglia –Subthalamic nucleus –Substantia nigra Midbrain

42 Diencephalon Consists of the following –Thalamus –Subthalamus –Hypothalamus –Epithalamus Habenular nucleus Pineal gland

43 Corpus callosum Fornix Thalamus Mamillary body

44 Thalamus Hypothalamus Epithalamus Subthalamus

45 Fornix Roof of 3 rd ventricle Interthalamic connection Lentiform nucleus Internal capsule Optic chiasma Pituitary Thalamus Hypothalamus Mammillary body

46 Thalamus Large ovoid mass of gray matter Forms large part of diencephalon Very important cell station Receives main sensory tracts (except olfactory pathway) Integrates information it receives and relays to the cerebral cortex and subcortical regions Integrates visceral and somatic functions

47 Thalamic nuclei

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49 Hypothalamus Part of the diencephalon that extends from the optic chiasma to the posterior border of the mammillary bodies Almost all physiological activities of the body are influenced by hypothalamus –Integration of autonomic functions –Regulation of endocrine functions –Maintaining body homiostasis –Regulation of body temperature and body fluids –Sexual behaviour, emosions, drive to eat and drink

50 Hypothalamus…. Contains some important cell groups –Supraoptic nucleus –Paraventricular nucleus These have axons running down into the posterior lobe of the pituitary gland Other cell groups deliver their neurosecretions into the hypothalamo-hypophyseal poryal system leading to the anterior lobe of the pituitary gland

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52 Pineal gland (Pineal body) Projects backwards from the diencephalon to lie posterior to the midbrain Progressive calcification with age becoming visible in x-ray Produces metatonin hormone in a circadian rhythm influenced by light Indirectly controls the function of other endocrine organs, including the pituitary

53 Lecture III

54 Development of the central nervous system Sanjaya Adikari Department of Anatomy

55 Neural tube & cavity

56 1 2 3 Prosencephalon (forebrain) Mesencephalon (midbrain) Rhombencephalon (hindbrain) 1a 2 3a 1b 3b Development of brain

57 1a 2 3a 1b 3b Telencephalon Cerebral hemispheres Diencephalon Midbrain tectum, tegmentum and cerebral pedunculi Metencephalon pons, upper medulla and cerebellum Myelencephalon lower medulla Thalamus, hypothalamus subthalamus, epithalamus

58 Lateral ventricle Foramen of Monro Aqueduct 4 th ventricle Central canal of SC 3 rd ventricle

59 Development of spinal cord and brain stem Mantle layer Marginal layer Neuroepithelial layer

60 Neuroepithelial cells Gliablast cells Neuroblast cells Neurons Glial cells 1 2 OligodendrogliaAstroglia MicrogliaEpendymal cells

61 Alar plate (sensory) Basal plate (motor) Sulcus limitans Mantle layer Marginal layer Neuroepithelial layer

62 Posterior horn Lateral horn Anterior horn Motor Sensory Motor Sensory

63 BE BA SE VE VA GSA

64 Brainstem Consists of midbrain, pons and medulla oblongata Broad functions –Conduit for ascending and descending tracts –Contains reflex control centers of respiratory and cardiovascular systems –Associated with control of consciousness –Contains nuclei of cranial nerves III to XII

65 Midbrain About 2 cm in length Connects the pons and cerebellum to forebrain by passing through the opening of tentorium cerebelli On the posterior surface are superior and inferior colliculi –SC: centers for visual reflexes. Connected to lateral geniculate body –IC:lower auditory centers. Connected to medial geniculate body On the anterior surface are crus cerebri. Contains cerebral aqueduct Contains cranial nerve nuclei III and IV

66 Transverse section of midbrain Tectum Tegmentum Crus cerebri or cerebral peduncles

67 Transverse sections of midbrain Cerebral peduncle Cerebral aqueduct Superior colliculus Red nuclues Substantia nigra

68 Pons Anterior to the cerebellum Bridges the two hemispheres of the cerebellum On the anterior surface many transverse fibers that go into the middle cerebellar peduncle Basilar groove in the midline anteriorly Motor and sensory roots of trigeminal nerve emerge from anterior surface Posterior surface contains the upper part of the floor of the 4 th ventricle above

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70 Medulla oblongata Connects to the spinal cord at the level of the foramen magnum, where the first cervical spinal nerve roots start Anterior surface contains the pyramids and the olives Posterior surface contains cuneate and gracile tubercles below and the lower part of the floor of the 4 th ventricle above Laterally are the inferior cerebellar peduncles

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72 Motor and sensory decussations of medulla sensorymotor Posterior surface Anterior surface

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74 Arrangement of cranial nerve nuclei in the flow of the 4 th ventricle Extensive lateral spread of 4 th ventricle during embryonic development has caused the alar plates to lie lateral to the basal plates Somatic motor (efferent) nuclei lie closer to the midline and somatic sensory (afferent) nuclei lie away from the midline Visceral nuclei lie in between, with visceral motor more closer and visceral sensory more distant from the midline

75 Cerebellum Lies posterior to the 4 th ventricle, pons and medulla Two cerebellar hemispheres joined by a narrow median vermis Connected to brain stem by superior, middle and inferior cerebellar peduncles

76 Cerebellum….. Has 3 lobes – anterior, middle and flocculonodular Primary fissure lies between anterior and middle lobes Uvulonodular fissure lies between middle and flocculonodular lobes Horizontal fissure lies within the middle lobe separating superior and inferior surfaces

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78 Cerebellum…cont. Has an outer cortex of cells. It has 3 layers – granular, purkinje and molecular layers Four intracerebellar nuclei – dentate, emboliform, globose and fastigial Afferent fibers enter through middle and inferior cerebellar peduncles Efferent fibers (axons of purkinje cells) synapse with cerebellar nuclei. Efferents from the nuclei leave through the superior cerebellar peduncle

79 Molecular cell layer Purkinje cell layer Granular cell layer

80 Dentate nucleus Middle cerebellar peduncle Emboliform nucleus

81 Function of the cerebellum

82 Cerebellar ataxia Diseases of the lateral cerebellar lobes –Limb ataxia –Gait broad-based and veered towards the side of the lesion Diseases of the cerebellar vermis –Truncal ataxia –Tendency to fall backwards/sideways –No limb ataxia

83 Limbic system Functionally important but not well defined anatomically Surrounds the corpus callosum and the diencephalon Deals with behaviour, imotion and memory

84 Components of the limbic system Cingulate gyrus Subcallosal gyrus Septal area and olfactory bulb Hippocampal formation –Hippocampal gyrus –Dentate gyrus –Parahippocampal gyrus Amygdaloid body and mammillary body Anterior nucleus of thalamus Hypothalamus

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86 Parts and connecting pathways

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88 Ventricular system of the brain

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90 Formation of CSF 1.Formed mainly in choroid plexus of the ventricles 2.Some is formed from the ependymal cells lining the ventricles and at perivascular spaces Blood-CSF barrier

91 Choroid plexus of lateral ventricle

92 Circulation of CSF Arachnoid granulations Foramina of Luschka & Magendie

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94 Functions of CSF 1.Functions as a cushion 2.Serves as a reservoir and regulates the contents of the cranial cavity 3.Nourishment of CNS 4.Way of removal of CNS metabolites 5.Serves as a pathway for pineal secretions to reach the pituitary gland

95 Lecture IV

96 How to draw different sections of the brain stem

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98 Anterior surface Posterior surface

99 Main nerve tracts in the spinal cord A B G C D E F

100 A.Posterior white columns B.Lateral corticospinal tract C.Anterior & posterior spinocerebellar tracts D.Anterior & posterior spinothalamic tracts E.Olivospinal, vestibulospinal, tectospinal tracts F.Anterior corticospinal tract G.Rubrospinal tract

101 Closed medulla at the level of decussation of pyramids Fasciculus gracilis Fasciculus cuneatus Nucleus gracilis Nucleus cuneatus Spinal tract of trigeminal nerve Spinal nucleus of trigeminal nerve Decussation of pyramids Pyramid Posterior spinocerebellar tract Anterior spinocerebellar tract Spinothalamic tract Spinal root of the accessory nerve Central canal Medial longitudinal fasciculus

102 Closed medulla at the level of decussation of medial lemnisci Fasciculus gracilis Fasciculus cuneatus Nucleus gracilis Nucleus cuneatus Spinal tract of trigeminal nerve Spinal nucleus of trigeminal nerve Decussation of medial lemnisci Pyramid Posterior spinocerebellar tract Anterior spinocerebellar tract Spinothalamic tract Hypoglossal nerve Spinal root of the accessory nerve Central canal Medial longitudinal fasciculus

103 Medulla Oblongata at the level of middle of the olivary nuclei Inferior medullary velum Cavity of 4 th ventricle Inferior cerebellar peduncle Vestibular & cochlear nuclei Olivary nucleus Olive Pyramid Anterior spinocerebellar tract Spinothalamic tract Spinal tract & nucleus of trigeminal nerve Vagus nerve Hypoglossal nerve Reticular formation Medial longitudinal fasciculus Tectospinal tract Medial lemniscus

104 Pons at the level of facial colliculus Superior medullary velum Cavity of 4 th ventricle Inferior cerebellar peduncle Spinal lemniscus Reticular formation Medial lemniscus Superior cerebellar peduncle Spinal tract & nucleus of trigeminal nerve Medial longitudinal fasciculus Facial colliculus Abducent nerve Facial nerve Pontine nuclei Transverse pontine fibres Corticospinal & corticonuclear fibres Vestibular nuclei

105 Midbrain at the level of inferior colliculus Trochlear nerve Inferior colliculus Cerebral aqueduct Medial longitudinal fasciculus Mesencephalic nucleus of trigeminal nerve Trigeminal lemniscus Spinal lemniscus Medial lemniscus Substantia nigra Cerebral peduncle Decussation of superior cerebellar peduncles Interpeduncular fossa Reticular formation Periaqueductal Gray Matter

106 Midbrain at the level of superior colliculus Oculomotor nerve Superior colliculus Cerebral aqueduct Medial longitudinal fasciculus Mesencephalic nucleus of trigeminal nerve Trigeminal lemniscus Spinal lemniscus Medial lemniscus Substantia nigra Cerebral peduncle Red nucleus Reticular formation Periaqueductal Gray Matter

107 PPRF = Paramedian pontine reticular formation Medial longitudinal fasciculus


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