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Home , Cerebral hemisphere

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 of the cerebral hemispheres

• Applied anatomy of the cerebral hemispheres

2 INTRODUCTION

CEREBRUM • Largest part of the • Situated in the anterior and middle cranial fossae of the skull • Occupying the whole concavity of the vault of the skull.

3

Coronal section 4 Coronal section SECTIONS

Sagital section 5 () 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 .

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 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

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• 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 . 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 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

• 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 lies anterior to the central sulcus, and above the posterior ramus of the lateral sulcus. (2) The 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 is the area lying behind the first imaginary line. (4) The 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. 2. Superior frontal gyri 3. 3. Middle frontal gyri 4. Inferior frontal gyri

IN THE FRONTAL LOBE

The anterior and ascending rami of the lateral sulcus extends into the 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 lies between them. The

• Superior and inferior frontal sulci are extending anteriorly from the precentral sulcus.

• The lies superior to the superior frontal sulcus, the 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 forms primary auditory area 29 IN THE PARIETAL LOBE

• Postcentral sulcus runs parallel & parallel to the central sulcus, and the • lies between them.

30 IN THE PARIETAL LOBE

• Running posteriorly from the middle of the postcentral sulcus is the .

• 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 .

• The part that arches over the is called the . • The part that arches over the posterior end of the is called the arcus temporooccipitalis 32 IN THE OCCIPITAL LOBE

• lies horizontally and divides the lobe into superior and inferior .

• The 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 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 . • The large anterior part is called the . 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

• - 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.

• - 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. : • 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. : • It is an irregular H-shaped sulcus • and divides the rest of the orbital surface into anterior, posterior, medial, and lateral . 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 & calcarine sulcus is . • The part medial to the collateral sulcus is the . • On the medial side of the temporal pole there is the . • The part medial to the rhinal sulcus is the .

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INSULA/ISLAND OF REIL (CENTRAL LOBE)

• The insula is the submerged (hidden) portion of the cerebral cortex in the floor of the lateral sulcus.

• Can be seen only when the lips of the lateral sulcus are widely pulled apart.

• Triangular in shape and surrounded all around by a sulcus, the circular sulcus, except anteroinferiorly

• at its apex called limen insulae which is continued with the anterior perforated substance. 47 ??????????

SEQ - Describe main sulci, gyri & lobes of cerebral hemisphere 48 SBA & MTF • Paracentral lobule is located on which surface of cerebral hemisphere 1. Medial 2. Suprolateral 3. Inferior

The following statements concern the central sulcus: (a) The central sulcus extends onto the medial surface of the cerebral hemisphere. (b) The frontal lobe lies posterior to it. (c) The parietal lobe lies anterior to it. (d) The central sulcus is continuous inferiorly with the lateral sulcus. (e) Demark the moor & sensory area. b, c, d

49 GRAY AND WHITE MATTER OF THE CEREBRAL HEMISPHERES

50 GRAY AND WHITE MATTER OF THE CEREBRAL HEMISPHERES • When sectioned, the , , and spinal cord show regions that are white (white matter) and gray (gray matter).

TS of cerebrum TS of spinal cord

WHITE MATTER OF THE CEREBRUM

• Consists chiefly of myelinated fibres which connect various parts of the cortex to one another and also to the other parts of the CNS.

• The nerve fibers may be classified into three groups according to their connections: (1) Commissural fibers (2) association fibers (3) projection fibers 54 COMMISSURE FIBERS Bridge

• Junction between 2 parts • Commissure fibers essentially connect corresponding/ identical regions of the two hemispheres.

• They are as follows: 1. Corpus callosum, 2. , 3. , 4. Habenular commissure, 5. Commissure of the . 55

COMMISSURAL FIBERS

56 CORPUS CALLOSUM

• Largest commissure • A massive C-shaped arched (10 cm long), interhemispheric bridge in the floor of the median longitudinal cerebral fissure connecting the medial surfaces of the two cerebral hemispheres. • The concave inferior aspect of corpus callosum is attached with the convex superior aspect of the fornix by . • Divided into the rostrum, the genu, the body, and the splenium

57 CORPUS CALLOSUM -PARTS

Genu: • is thick curved anterior extremity lies 4 cm behind the frontal pole. • Fibers connect frontal lobes, forming a fork like structure, the forceps minor. • Forms Ant. boundary of lateral ventricle Rostrum: • The genu extends downwards and backward as a thin prolongation to join the lamina terminalis. • Connects orbital surface of frontal lobes

• Forms floor of lateral ventricle 58

CORPUS CALLOSUM -PARTS

Trunk: • Is the main (middle) part. • Fibers connect frontal & ant. Parts of parietal lobes • Forms roof of lateral ventricle Splenium: • is the massive posterior end lying 6 cm in front of occipital pole. • Fibres connect post. Parts of parietal, temporal & occipital

lobes. 59 CORPUS CALLOSUM Fibres of Corpus Callosum

1. Rostrum -connects the orbital surfaces of the two frontal lobes. 2. Forceps minor is made up of fibres of the genu that connect the two frontal lobes. (Fork like structure) 3. Forceps major is made up of fibres of the splenium connecting the two occipital lobes. 4.Tapetum is formed by some fibres from the trunk and splenium of the corpus callosum. 60 • FUNCTIONS OF THE CORPUS CALLOSUM • Impulses across the corpus callosum keeps the 2 hemisphere of brain working to gather. Hence it helps in coordinating activities of the two hemispheres.

• APPLIED ANATOMY • Occasionally, congenital absence or sectioned surgically, does not produce any definite signs or symptoms • SPLIT BRAIN SYNDROME – if congenital absence or sectioned surgically each hemisphere become isolated & patient responds as if he or she has two separate . • Surgical section is attempted to prevent the spread of from one hemisphere to the other.

61 OTHER COMMISSURAL FIBRES

• 2. ANTERIOR COMMISSURE • is a small round bundle of white fibres which crosses the midline in the upper part of the lamina terminalis. • Connecting lower anterior parts of temporal lobes and olfactory regions of the two sides

62 OTHER COMMISSURAL FIBERS

3.POSTERIOR COMMISSURE - is a slender bundle of white fibres which crosses the midline through the inferior lamina of the stalk of , connecting the superior colliculi

4. HABENULAR COMMISSURE - is a slender bundle of white fibres which crosses the midline through superior lamina of stalk of pineal gland, connecting Habenular nuclei of 2 sides 5. COMMISSURE OF FORNIX (hippocampal commissure) connecting the crura of the fornix and thus the hippocampal formations of the two sides; 63

ASSOCIATION FIBERS

• Fibers interconnect the different regions of the cerebral cortex in the same hemisphere (intrahemispheric fibres). • Two types. • A. Short association fibres connect - adjacent gyri to one another.

• B. Long association fibres 64

ASSOCIATION FIBRES

Long association fibres - connect more widely separated gyri to one another

• Some examples are: 1. , connecting the temporal pole to the motor speech area and to the orbital cortex of frontal lobe 2. , connecting the cingulate gyrus to the parahippocampal gyrus; 3. Superior longitudinal fasciculus, connecting the frontal lobe to the occipital and temporal lobes; and 4. Inferior longitudinal fasciculus, connecting the occipital and temporal lobes. 65

Coronal section

PROJECTION FIBERS

• These fibers connect the cerebral cortex to subcortical centers such as (thalamus, brainstem) & spinal cord. • Examples: Mainly responsible for the sensory and • motor innervation of the opposite half of • Corona radiata the body • Fornix 66 Horizontal section INTERNAL CAPSULE

Location

• It is V shaped compact bundle of projection fibres between thalamus & caudate medially, and lentiform nucleus laterally. And concavity directed laterally 67 Horizontal section 68 Right side INTERNAL CAPSULE

• PARTS : 1. Anterior limb 2. Posterior limb 3. Genu 4. Retrolentiform - behind the lentiform nucleus 5. Sublentiform part—below the lentiform nucleus

69 CONSTITUENT FIBRES OF INFERNAL CAPSULE

• Motor fibers – originate from cerebral cortex relay to pons, spinal cord & striatum • Cortico-pontine fibers • Pyramidal fibers – forms pyramidal tract • Corticonuclear fibers- cortex to cranial nuclei, innervate head & neck muscle • Corticospinal fibers- cortex to ant. Horn cells of spinal cord, innervate limbs & trunk muscles • Extrapyramidal fibers- cortex to subcortical areas ex. corticorubral 70 CONSTITUENT FIBRES OF INFERNAL CAPSULE

• Sensory fibres – from thalamus to cortex – thalamocortical fibers • Ant. Thalmic radiation – connect ant. & dorsomedial nuclei of thalamus to frontal lobe • Sup. Thalmic radiation- connect ventral tier of thalamus to frontal & parietal lobe • Post. Thalmic radiation -connect lateral geniculate body to • Inf. Thalmic radiation-connect medial geniculate body to temporal (auditory area) lobe 72

CONSTITUENT MOTOR AND SENSORY FIBRES IN DIFFERENT PARTS OF THE INTERNAL CAPSULE

73 CORONA RADIATA • Is a mass of white matter composed of projection fibers

• Efferent /motor fibers converge from cortex to internal capsule or • Fan out (afferent/sensor y) from internal capsule towards cortex

74 75 ARTERIAL SUPPLY OF INTERNAL CAPSULE

76 LESIONS OF THE INTERNAL CAPSULE • The internal capsule is frequently involved in the cerebrovascular disorders. The most common cause of arterial hemorrhage is atheromatous degeneration of an artery in individuals suffering from high blood pressure.

• The hemorrhage commonly occurs due to rupture of the Charcot’s artery, the larger lateral striate branch of the (also called Charcot’s artery of cerebral hemorrhage), which supplies the posterior limb of the internal capsule.

• Damage to the internal capsule caused by hemorrhage or infarction, leads to loss of sensations & spastic paralysis of the opposite half of the body (contralateral hemiplegia). 77 FORNIX

• The fornix is a large bundle of projection fibres, which connects the with the mammillary body. • It constitutes the sole efferent system of the hippocampus

78 APPLIED ANATOMY OF CEREBRUM • DEGERATIVE DISORDERS – cerebral atropy • loss of neurons and the connections between them. • Causes – stroke, infections, diseases like Alzheimer's disease, multiple sclerosis.

• HEAD INJURY –

• HERNIATION OF BRAIN –  A is when brain tissue is moved or pressed away from their usual position inside the skull. factors that cause a mass effect and increase (ICP): these include traumatic brain injury, intracranial hemorrhage, or .

79 APPLIED ANATOMY OF CEREBRUM

• TUMOURS - two main types • Malignant or cancerous tumors and benign tumors. • Tumors may produce symptoms that vary depending on the part of the brain involved. These may include headaches, seizures, problem with vision, vomiting, and mental changes.

• Cerebrovascular accidents ( stroke) – it is sudden, focal neurological deficit resulting from impaired circulation of brain. It is associated with a cardiovascular disease such as thrombosis, embolism.

80 SUMMARY SULCI & GYRI ON SUPEROLATERAL SURFACE

81 82 83 ASSIGNMENT – LEARN DIAGRAMS

84 WHITE FIBERS

85 86 VIDEO LINK

• https://www.youtube.com/watch?v=zu_tIDkfBkU&t=3s • https://www.youtube.com/watch?v=o4JbIotpras&t=128s

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