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  • 1. The Brain I Gross Anatomy and Functional Localization (for dental students) Dr.Akram Abood Jaffar Assistant Professor of Anatomy M.B.Ch.B., M.Sc., Ph.D.Dr. Akram Jaffar Dr. Akram Jaffar
  • 2. Objectives he cerebrum escribe the gross anatomical features of the cerebral cortex on the lateral, medial and inferior surfaces of the cerebral hemishphere. dentify the poles (frontal, occipital and temporal poles) and the lobes of the cerebral hemisphere: frontal, parietal, temporal, and occipital. Locate the boundaries between the lobes. numerate fissures of the brain and the main sulci and gyri in each lobe. ifferentiate the central sulcus from the precentral and postcentral sulci. dentify: superior and inferior frontal sulci, supeiror, middle and inferior frontal gyri; interparietal sulcus; superior and inferior parietal lobules; superior and inferior temporal sulci; superior, middle and inferior temporal gyri; parahippocampal gyrus, collateral sulcus, gyrus rectus, rhinal sulcus, uncus, olfactory sulcus, anterior perforated substance, preoccipital notch, calcarine sulcus, parieto-occipital sulcus, cingulate gyrus, cingulate sulcus, paracentral lobule, H-shaped gyri. dentify, define, and describe the parts of the corpus callosum sagittal and coronal sections of the brain. escribe the position of the insula. iscuss the location of main functional areas of the cerebral cortex and the effect of their damage: primary motor area, profrontal area, motor speech area, sensory speech area, primary sensory area, visula area, olfactory area, auditory area. ppreciate that the representation in the cerebral cortex is related to the functional importance. Further reading iscuss the concept of cerebral dominance and its relation to handedness. he cerebellum:Dr. Akram Jaffar • Snell RS (2010): Clinical Neuroanatomy. 7th Ed. Lippincott, Williams and Wilkins. escribe the position of the cerebellum and the connection of its peducles with the brain stem. Baltimore. efine gross features of the cerebellum: folia, sulci, vermis, tonsil, vallecula Dr. Akram Jaffar
  • 3. Gross anatomy of the cerebral hemisphere • The cerebral hemispheres are covered superiorly by the bones of the vault of the skull. • Inferiorly they lie on the bones of the parietal anterior and middle cranial fossae. • The tentorium cerebelli separates the cerebral hemispheres posteriorly occipital from the cerebellum. frontal temporal cerebrum cerebellum Posterior cranial fossa Tentorium Anterior cranial cerebelli fossa Middle cranial fossa • Thus the tentorium cerebelli forms a tent for the cerebellum (a roof) and a floor forDr. Akram Jaffar the posterior part of the cerebral hemispheres. Dr. Akram Jaffar
  • 4. Gross anatomy of the cerebral hemisphere • The cerebral hemispheres lie on either side of the mid-sagittal plane. Cerebral hemisphere • Cerebral hemisphere The hemispheres are partly separated by the median longitudinal fissure Mid-sagitta Inferior view Median plane Longitudinal fissureDr. Akram Jaffar Superior view Dr. Akram Jaffar
  • 5. Median longitudinal fissure • A sickle-shaped fold of dura called the falx cerebri lies in the median longitudinal fissure. • The hemispheres are joined together by a band of nerve fibers called the corpus callosum. Corpus callosumDr. Akram Jaffar Coronal section Dr. Akram Jaffar
  • 6. Gross anatomy of the cerebral hemisphere • The hemispheres have an outer layer of grey matter called the cerebral cortex. • Most of the neurons in the CNS are found in the cortex. cortex nucleus • Collections of neurons situated deeply are called nuclei. White matterDr. Akram Jaffar grey matter Dr. Akram Jaffar
  • 7. Sulci and gyri • The cortex is greatly convoluted: the grooves are called sulci (Sing. = sulcus). • The sulci separate ridges of brain tissue called gyri (Sing. = gyrus). • The convolutions of the cortex increase its surface area so that about 2/3rd of the total surface area is hidden in the sulci. sulcus gyrus gyrusDr. Akram Jaffar Dr. Akram Jaffar
  • 8. Poles and surfaces of the hemisphere • Each hemisphere has frontal, • Each hemisphere has lateral, occipital and temporal poles. medial and inferior surfaces Frontal pole occipital temporal pole pole Lateral surface Medial surfaceDr. Akram Jaffar Inferior surface Dr. Akram Jaffar
  • 9. Lobes of the hemisphere • Each hemisphere has frontal, parietal, occipital, and temporal lobes. • The lobes are named after the closely related bones of the skull Parietal lobe Frontal lobe Occipital lobe Temporal lobe Frontal parietal bone bone temporal occipital bone boneDr. Akram Jaffar Dr. Akram Jaffar
  • 10. Features of the lateral surface • A deep lateral sulcus divides the frontal and parietal lobes from the temporal lobe. Central sulcus • The central sulcus divides the frontal and parietal lobes. frontal parietal lobe lobe temporal lobe Lateral sulcusDr. Akram Jaffar Dr. Akram Jaffar
  • 11. Features of the lateral surface • Precentral gyrus – anterior to the central sulcus. – in the frontal lobe. frontal parietal lobe lobe r us s – limited anteriorly by a gyru precentral sulcus that al gy runs parallel to the tr al central sulcus. ent r tcen Prec Pos • Postcentral gyrus – posterior to the central sulcus. – located in the parietal temporal lobe. lobe – limited posteriorly by a postcentral sulcus that runs parallel to the central sulcus.Dr. Akram Jaffar Dr. Akram Jaffar
  • 12. Features of the lateral surface • The parietal lobe posterior to the postcentral sulcus is divided by the intraparietal sulcus into a superior and inferior parietal lobules r us s Superior frontal Su gyru pe gyrus r io al gy rp ar ie parietal ta tr al frontal l lo ent r Middle frontal bu lobe lobe le tcen gyrus Inferior Prec parietal Pos lobule Inferior frontal gyrus temporal lobe • In the frontal lobe, two horizontal sulci divide the surface into superior, middle, andDr. Akram Jaffar inferior frontal gyri. Dr. Akram Jaffar
  • 13. Features of the lateral surface • In the temporal lobe, the sulci divide the surface into superior, middle and inferior temporal gyri. r us s Superior frontal Su gyru pe gyrus r io al gy rp ar ie parietal ta tr al frontal l lo ent r Middle frontal bu lobe lobe le tcen gyrus Inferior Prec parietal Pos lobule Inferior frontal gyrus temporal lobe Superior temporal Middle gyrus temporal gyrus inferiorDr. Akram Jaffar temporal gyrus Dr. Akram Jaffar
  • 14. The insula • The margins of the lateral sulcus overlap a buried (deeply placed) area of the cerebral cortex called the insula. Lateral sulcus Coronal section • The insula can be seen only when the lips of the lateral selcus are separated away from each other. insulaDr. Akram Jaffar Horizontal section Dr. Akram Jaffar
  • 15. Features of the medial surface • The corpus callosum is a band of nerve fibers joining the two cerebral hemispheres. • In midsagittal section, the corpus callosum, has the shape of a hook lying horizontally. body genu splenium rostrum • The pointed portion is the rostrum (beak) • The bend is the genu (knee) • The horizontal part is the body • The expanded posterior end is the spleniumDr. Akram Jaffar Dr. Akram Jaffar
  • 16. Features of the medial surface • The cingulate gyrus lies above Central sulcus and parallel to the corpus callosum. • The central sulcus, unlike the pre- and post-central sulci, extends on the medial surface. body genu splenium rostrumDr. Akram Jaffar Dr. Akram Jaffar
  • 17. Features of the medial surface • The calcarine sulcus extends horizontally Central sulcus Parieto- backwards from behind the splenium of the occipital corpus callosum to the occipital pole. sulcus body genu splenium rostrum occipital pole • The parieto-occipital sulcus passes obliquely Calcarine upwards from about the middle of the calcarine sulcus sulcus to the superior margin of the medial surface.Dr. Akram Jaffar Dr. Akram Jaffar
  • 18. The pre-occipital notch o On the inferior margin there is a notch produced by the petrous temporal bone called the preoccipital notch. o An imaginary line can be drawn from the superior margin (where the parieto-occipital sulcus extends) to the preoccipital notch on the inferior magin. o This imaginary line divides the occipital lobe from the parietal and temporal lobes Parieto- occipital Parieto-occipital sulcus sulcus parietal lobe temporal lobe occipital lobe Petrous temporal bone Preoccipital notch Pre-occipital notchDr. Akram Jaffar Dr. Akram Jaffar
  • 19. Features of the inferior surface • The inferior surface is separated from the midbrain by the hippocampal sulcus • The parahippocampal gyrus borders the hippocampal sulcus. uncus • The parahippocampal gyrus is separated laterally by the collateral sulcus from the rest of the cortex of the temporal lobe. midbrain • Anteriorly the parahippocampal temporal gyrus has a short recurved part lobe called the uncus. Hippocampal sulcus Collateral sulcusDr. Akram Jaffar Dr. Akram Jaffar
  • 20. Functional localization in the cerebral cortex • Different areas of the cerebral cortex are functionally specialized. • The simple division of cortical areas into motor and sensory areas is not exactly true, as these occupy only a small part of the total surface area. • The remaining areas are called association areas.Dr. Akram Jaffar Dr. Akram Jaffar
  • 21. Frontal lobe Primary motor area o The primary motor area is the major source of projection fibers to the low lying brain stem and spinal cord. o In the precentral r us gyrus and extends al gy to the medial surface of the frontal ent r cerebral hemisphere. lobe PrecDr. Akram Jaffar Dr. Akram Jaffar
  • 22. Frontal lobe Primary motor area • Somatotopic representation in the primary motor area is in the form of an inverted homunculus in which the size of the bodily regions is related to the motor skill involved rather than to the bulk of the body region. • Thus the tongue, larynx, face and hand areas are disproportionately large. • The trunk and lower extremities representation is small in proportion to the actual size and located superiorly and on the medial surface.Dr. Akram Jaffar Dr. Akram Jaffar
  • 23. Frontal lobe Primary motor area • The primary motor area controls voluntary movements on the contralateral side of the body • Destruction  paralysis • Excessive stimulation produces epileptic convulsions.Dr. Akram Jaffar Dr. Akram Jaffar
  • 24. Frontal lobe Prefrontal area • A large area in the anterior part of the frontal cortex. • Responsible for the makeup of the  personality, behavior, feeling, planning, and judgment.Dr. Akram Jaffar Dr. Akram Jaffar
  • 25. Frontal lobe Motor speech area • Situated in the inferior frontal gyrus of the dominant hemisphere, i.e. on the left side in right-handed individuals. Broca’s area • It forms the speech by its connections with the Paul Broca adjacent motor areas for 1824 - 1880 the muscles of the mouth, pharynx and larynx. • Its destruction results in paralysis of speech (motor aphasia) in which the language is understood but it cannot be expressed in speech or writing.Dr. Akram Jaffar Dr. Akram Jaffar
  • 26. Parietal lobe Primary sensory area • Occupies the postcentral gyrus, extending to the medial side of the cerebral hemisphere • Receives fibers originating from the contralateral side of the body. o The somatotopic s gyru representation is in the form of an parietal tr al inverted frontal homunculus. lobe lobe tcen Pos temporal lobeDr. Akram Jaffar Destruction cause  loss of sensation Dr. Akram Jaffar
  • 27. Parietal lobe Sensory speech area • Is located in the inferior parietal lobule. It is also called Wernicke’s area. • Like the motor speech area, it exists only on the dominant hemisphere. • It is concerned with understanding of language, written or spoken. parietal lobe Inferior • It receives impulses from the visual cortex parietal and the auditory lobule cortex (input), understand them Auditory Visual cortex (processing), and is cortex connected to the temporal motor speech area lobe (output). • Its damage results in sensory aphasia: the inability to understand written andDr. Akram Jaffar spoken language. The patient is able to see the words but is unable to understand them or to copy them. Dr. Akram Jaffar
  • 28. Temporal lobe Primary auditory area • The primary auditory area is located on superior temporal gyrus. • It receives auditory input bilaterally; thus a unilateral damage produces some (partial) deafness in both ears with the greater loss in the contralateral ear.Dr. Akram Jaffar Dr. Akram Jaffar
  • 29. Functional localization in the occipital lobe • The primary visual area lies in the walls and floor of the posterior part of the calcarine sulcus extending to the occipital pole.Dr. Akram Jaffar Dr. Akram Jaffar
  • 30. Primary visual area • There is an inverted representation of the visual fields: – the left visual field projects to the right visual cortex and vice versa. – the upper visual field projects to the lower part of the visual cortex and vice versa. • The region of the retina concerned with highest visual resolution (macula) has an extensive representation and occupies the posterior third of the primary visual area.Dr. Akram Jaffar Dr. Akram Jaffar
  • 31. Cerebral dominance left right – Most of the functions of the cerebral cortex are related equally to both cerebral hemispheres. – Language tend to be lateralized: the hemisphere that is more important for the comprehension and production of language is called the dominant hemisphere. – The non-dominant hemisphere although inferior in language functions is superior in other functions.Dr. Akram Jaffar Dr. Akram Jaffar
  • 32. Cerebral dominance left right – In most individuals the left hemisphere is dominant. – The dominant hemisphere is concerned with handedness (writing) and speech (more than 90% of people are right- handed). But the majority of the left handers are left dominant. – The dominant hemisphere is concerned with language, mathematical and analytical functions – The non-dominant hemisphere is concerned with spatial and pictorial concepts and the recognition of faces and music.Dr. Akram Jaffar Dr. Akram Jaffar
  • 33. The CerebellumDr. Akram Jaffar Dr. Akram Jaffar
  • 34. Position & peduncles of the cerebellum • Lies in the posterior cranial fossa inferior to the tentorium cerebelli. Tentorium cerebelli • Is attached to the back of the Cerebellum brain stem by three paired bundles of fibers: superior, middle, and inferior cerebellar peduncles. 4th ventricle Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle CerebellumDr. Akram Jaffar Dr. Akram Jaffar
  • 35. Gross appearance of the cerebellum • Two cerebellar hemispheres joined by a narrow median vermis. • The inferior surface shows a deep groove, the vallecula, the floor of which is formed by the inferior aspect of the vermis. • The tonsil is a partly detached lobule overhanging the inferior vermis on each side. vermis vermis tonsilDr. Akram Jaffar vallecula Ventral view Dorsal view Dr. Akram Jaffar
  • 36. Gross appearance of the cerebellum • The cortex, which is greatly convoluted. • The sulci are parallel and the ridges between them are called the folia. • In some places deep fissures are present. • The cerebellum forms the roof for the fourth ventricle. 4th ventricle cortex 4th ventricle sulcus folium FissureDr. Akram Jaffar Horizontal section of the cerebellum at the middle cerebellar peduncle Dr. Akram Jaffar
  • 37. Cerebellar nuclei • Four pairs of nuclei. • The largest is the dentate nucleus. • Cerebellar afferents project to the cerebellar cortex, whose output is mostly to the cerebellar nuclei in which efferent fibers originate. Dentate nucleusDr. Akram Jaffar Dr. Akram Jaffar
  • 38. Fissures & lobes of the cerebellum Dorsal view • Primary fissure: – Located on the superior surface. Primary fissure – Separates the anterior lobe from Anterior lobe the middle (posterior) lobe. • Horizontal fissure – Located posteriorly within the Middle lobe middle lobe. • The uvulo-nodular fissure – Located on the inferior surface. – Separates the middle lobe from the flocculo-nodular lobe. Uvulo-nodular fissure Flocculo-nodular lobe Horizontal fissureDr. Akram Jaffar Ventral view Dr. Akram Jaffar
  • 39. Functional lobes of the cerebellum Dorsal view • Vestibulocerebellum: – Flocculonodular lobe mainly. spinocerebellum – Maintains equilibrium. • Spinocerebellum: – Anterior lobe mainly. – Concerned with unconscious pontocerebellum proprioception. • Pontocerebellum: – Middle lobe mainly. – Coordination of fine movements. vestibulocerebellumDr. Akram Jaffar Ventral view Dr. Akram Jaffar
  • 40. Cerebellar control and dysfunction • Each cerebellar hemisphere controls the same side of the body either because of ipsilateral projection cerebellum of some fibers or because other fibers cross twice. • Since the cerebellum is concerned with: – Coordination of muscular activity ≠ ataxia (in-coordination of movement) – Proprioception ≠  hypotonia and tremor – Equilibrium ≠  vertigo. Spinal cordDr. Akram Jaffar Ataxia Vertigo Tremor Dr. Akram Jaffar

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