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Cerebral Hemisphere and Basal Ganglia

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Cerebral Hemisphere and Basal Ganglia CEREBRAL HEMISPHERE DR. SANGEETA KOTRANNAVAR A S S I S TA N T PROFESSOR DEPARTMENT OF ANATOMY USM KLE IMP, BELGAUM CEREBRAL HEMISPHERES • OBJECTIVES • External features, lobes, sulci and gyri of the cerebral hemispheres • Gray and white matter of the cerebral hemispheres • Applied anatomy of the cerebral hemispheres 2 INTRODUCTION CEREBRUM • Largest part of the brain • Situated in the anterior and middle cranial fossae of the skull • Occupying the whole concavity of the vault of the skull. 3 gyrus sulcus Coronal section 4 Coronal section SECTIONS Sagital section 5 CEREBRAL CORTEX (GREY MATTER) Telencephalon WHITE MATTER Diencephalon BASAL NUCLEI Post. Horn of LATERAL VENTRICLE Each hemisphere has a covering of gray matter, the cortex and internal masses of gray matter, the basal nuclei, and a lateral ventricle. 6 Horizontal section CEREBRAL HEMISPHERES • Are separated by a deep median cleft, the longitudinal cerebral fissure. • The two hemispheres are linked by the fibers of the corpus callosum. 7 EXTERNAL FEATURES • POLES -3 • SURFACES-3 • BORDERS - 3 • SULCI • GYRI 8 POLES 1. FRONTAL POLE • Anterior end of hemisphere, more rounded. 2. OCCIPITAL POLE • Posterior end of hemisphere, more pointed. 3. TEMPORAL POLE • lies between the frontal and occipital poles, and points forwards and somewhat downwards. 9 1. Superiolateral surface SURFACES 2. Medial surface 3) inferior surface 10 SUPERIOLATERAL MEDIAL SURFACE SURFACE • Flat and vertical • Most convex • C shaped carpus callosum • Faces upwords and laterally 11 Inferior surface • Irregular • Anterior orbital surface • Posterior tentorial surface 12 BORDERS Superomedial border Inferomedial Border Sagittal section 1) Supero-medial border Coronal section through a cerebral 2) Infero-lateral border hemisphere to show its borders and 3) Infero-medial border surfaces. 13 BORDERS 1. Superio medial border 2. Inferiolateral border • Superciliary border 3. Inferiomedial border • Medial orbital border • hippocampal border • Medial occipital border 14 SULCI AND GYRI • Surface of each cerebral hemisphere is thrown into folds called gyri or convolutions. • Gyri are separated from each other by sulci or fissures. • Surface area -2000cm2 • Function-To increase the surface area of the cerebral cortex 15 MAIN SULCI 1. Central sulci 2. Parieto-occipital sulci 3. Lateral sulci 4. Calcarine sulci Sulcus-singular Sulci-plural 16 CENTRAL SULCUS • Begins by cutting the superomedial border of the hemisphere about 1 cm behind the midpoint between the frontal and occipital poles • Runs downwards and forwards, and ends just above the posterior ramus of the lateral sulcus. 17 CENTRAL SULCUS • Great importance • Anterior to it contains the motor cells that initiate the movements of the opposite side of the body • Posterior to it lies the general sensory cortex that receives sensory information from the opposite side of the body 18 LATERAL SULCUS • is a deep cleft • found on the inferior and lateral surfaces of the cerebral hemisphere. • consists of a short stem that divides into three rami. 19 LATERAL SULCUS • Stem arises on the inferior surface, and on reaching the lateral surface, it divides into the anterior horizontal ramus and the anterior ascending ramus and continues as the posterior ramus. 20 CALCARINE SULCUS • Is found on the medial surface of the hemisphere. • Starts posterior end of the corpus callosum and arches upward and backward to reach the occipital pole • Is joined at an acute angle by the parieto-occipital sulcus. 21 PARIETO-OCCIPITAL SULCUS • Begins on superomedial border of the hemisphere about 5 cm in front of the occipital pole • Passes downwards on medial surface to meet calcarine sulcus & may extend slightly onto the superolateral surface. 22 LOBES These main sulci forms boundaries for the division of the cerebral hemisphere into frontal, parietal, temporal, and occipital lobes 23 LOBES (1 )The frontal lobe lies anterior to the central sulcus, and above the posterior ramus of the lateral sulcus. (2) The parietal lobe lies behind the central sulcus. It is bounded below by the posterior ramus of the lateral sulcus and by the second imaginary line; and behind by the upper part of the first imaginary line. (3) The occipital lobe is the area lying behind the first imaginary line. (4) The temporal lobe lies below the posterior ramus of the lateral sulcus and the second imaginary line. It is separated from the occipital lobe by the lower part of the first imaginary line. 24 SULCI & GYRI ON SUPEROLATERAL SURFACE 25 IN THE FRONTAL LOBE • Frontal lobe – sulci • Frontal lobe – gyri 1. Precentral sulcus 1. Precentral gyri 2. Superior frontal sulcus 2. Superior frontal gyri 3. Inferior frontal sulcus 3. Middle frontal gyri 4. Inferior frontal gyri IN THE FRONTAL LOBE The anterior and ascending rami of the lateral sulcus extends into the Inferior frontal gyrus and is divided into three parts: a)Pars orbitalis: below the anterior ramus b)Pars triangularis : between anterior and ascending ramus c)Pars Opercularis: posterior to ascending ramus 27 IN THE FRONTAL LOBE • Precentral sulcus -runs parallel to the central sulcus, and the precentral gyrus lies between them. The • Superior and inferior frontal sulci are extending anteriorly from the precentral sulcus. • The superior frontal gyrus lies superior to the superior frontal sulcus, the middle frontal gyrus lies between the superior and inferior frontal sulci. • The inferior frontal gyrus lies inferior to the inferior frontal sulcus. And divided into 3 parts by anterior and ascending rami of the lateral sulcus. 28 IN THE TEMPORAL LOBE • The superior and inferior temporal sulci run parallel to the posterior ramus of the lateral sulcus and divide the temporal lobe into the superior, middle, and inferior temporal gyri. • Sup. Surface of superior temporal gyrus forms primary auditory area 29 IN THE PARIETAL LOBE • Postcentral sulcus runs parallel & parallel to the central sulcus, and the • Postcentral gyrus lies between them. 30 IN THE PARIETAL LOBE • Running posteriorly from the middle of the postcentral sulcus is the intraparietal sulcus. • Superior to the intraparietal sulcus is superior parietal gyrus. • Inferior to the intraparietal sulcus is inferior parietal gyrus. 31 IN THE PARIETAL LOBE • The part that arches over the upturned posterior end of the posterior ramus of the lateral sulcus is called the supramarginal gyrus. • The part that arches over the superior temporal sulcus is called the angular gyrus. • The part that arches over the posterior end of the inferior temporal sulcus is called the arcus temporooccipitalis 32 IN THE OCCIPITAL LOBE • Lateral occipital sulcus lies horizontally and divides the lobe into superior and inferior occipital gyri. • The lunate sulcus runs downwards and slightly forwards just in front of the occipital pole. • The transverse occipital sulcus is located in the uppermost part of the occipital lobe. 33 SULCI & GYRI ON MEDIAL SURFACE 34 SULCI & GYRI ON MEDIAL SURFACE Cingulate sulcus – • Most prominent sulcus, curved coarse, parallel to the upper convex margin of the corpus callosum. • Begins beneath anterior end of corpus callosum & continues above it & extends till end. Posteriorly it runs upwards to reach the superiomedial border of the hemisphere a little behind the upper end of the central sulcus. • The area between cingulate sulcus and corpus callosum is termed cingulate gyrus. 35 SULCI & GYRI ON MEDIAL SURFACE • Callosal sulcus – it separates cingulate gyrus from the corpus callosum • The part of the medial surface of the hemisphere between the cingulate sulcus and the superomedial border consists of two parts. • The smaller posterior part which is wound around the end of the central sulcus is called the paracentral lobule. • The large anterior part is called the medial frontal gyrus. 36 SULCI & GYRI ON MEDIAL SURFACE • Paracentral lobule – highest center of micturition & defecation 37 SULCI & GYRI ON MEDIAL SURFACE • The calcarine sulcus begins a little below the splenium and runs towards the occipital pole. • parieto-occipital sulcus which reaches the superolateral surface. 38 SULCI & GYRI ON MEDIAL SURFACE • CUNEUS - is a triangular area of cortex bounded above by the parieto-occipital sulcus, inferiorly by the calcarine sulcus, and posteriorly by the superior medial margin. • PRECUNEUS - bounded anteriorly by the upturned posterior end of the cingulate sulcus and posteriorly by the parieto-occipital sulcus. 39 SULCI & GYRI ON MEDIAL SURFACE • A little below the genu there are two small anterior and posterior Para olfactory sulci • The paraterminal gyrus lies just in front of the lamina terminalis. • The parolfactory gyrus lies between the anterior and posterior parolfactory sulci. 40 SULCI & GYRI ON INFERIOR SURFACE - ORBITAL 1. Olfactory sulcus: • is a straight sulcus which runs anteroposteriorly close to the medial border of the orbital surface. • It lodges the olfactory bulb & tract. The area medial to this sulcus is called gyrus rectus. 2. Orbital sulcus: • It is an irregular H-shaped sulcus • and divides the rest of the orbital surface into anterior, posterior, medial, and lateral orbital gyri. 41 SULCI & GYRI ON INFERIOR SURFACE -TENTORIAL • 2 sulci runs anteroposteriorly. • Medial one is the collateral sulcus and the lateral is the occipitotemporal sulcus. • The part lateral to the collateral sulcus is divided into medial and lateral occipitotemporal gyri by the occipitotemporal sulcus. 42 SULCI & GYRI ON INFERIOR SURFACE -TENTORIAL • The area between posterior part of the collateral sulcus
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