Cerebrum PDF - University of Zambia School of Medicine

UNIVERSITY OF ZAMBIA SCHOOL OF MEDICINE HUMAN ANATOMY Topic: Cerebrum (Telencephalon) Dr. Mukape Mukape - UNZA (BSc.HB, MBChB, MSc, MMED) - ZACOMS Specialist Fellow in Obstetrics and Gynaecology - Honorary Specialist Obstetrician- Gynaecologist, UTH, Lusaka, Zamb...

UNIVERSITY OF ZAMBIA SCHOOL OF MEDICINE HUMAN ANATOMY Topic: Cerebrum (Telencephalon) Dr. Mukape Mukape - UNZA (BSc.HB, MBChB, MSc, MMED) - ZACOMS Specialist Fellow in Obstetrics and Gynaecology - Honorary Specialist Obstetrician- Gynaecologist, UTH, Lusaka, Zambia. 10/20/23 Dr. Mukape Mukape 1  Brain Divided into 3 parts: - Forebrain (prosencephalon) - Midbrain (mesencephalon) - Hindbrain (rhombencephalon) 10/20/23 Dr. Mukape Mukape 2  Brain Forebrain (Prosencephalon) Midbrain (Mesencephalon) - Cerebrum (telencephalon), made of 2 - From before cerebral aqueduct backwards cerebral hemispheres 1. Crus cerebri - Diencephalon (thalamencephalon): 2. Substantia nigra 1. Thalamus 3. Tegmentum 2. Hypothalamus 4. Tectum (2 superior and 2 inferior 3. Epithalamus colliculi, collectively called corpora quadrigemina) Hindbrain (Rhombencephalon) - Pons and cerebellum (metencephalon) - Medulla oblongata (myencephalon) 10/20/23 Dr. Mukape Mukape 3  Introduction The cerebrum is located within the bony cranium It extends from the frontal bone anteriorly to the occipital bone posteriorly Within the skull, the cerebrum fills the anterior and middle cranial fossae, and is located above the tentorium cerebelli inferoposteriorly The cerebrum is the largest part of the brain, located superiorly and anteriorly in relation to the brainstem Accounts for two-thirds of the total weight of the brain It consists of two cerebral hemispheres (left and right), separated by the falx cerebri of the dura mater The two cerebral hemispheres are connected by a white matter structure, called the corpus callosum Embryologically, the cerebrum is derived from the prosencephalon. One hemisphere, usually the left, is functionally dominant, controlling language and speech The other hemisphere interprets visual and spatial information 10/20/23 Dr. Mukape Mukape 4  Introduction The cerebral hemispheres consist of an inner core of myelinated nerve fibres, the white mater, and an outer cortex of gray mater The cerebral cortex is responsible for integrating sensory impulses, directing motor activity, and controlling higher intellectual functions The human cortex is several centimetres thick and has a surface area of about 2,000 square cm (310 square inches), largely because of an elaborate series of convolutions; the extensive development of this cortex in humans is thought to distinguish the human brain from those of other animals Nerve fibres in the white matter primarily connect functional areas of the cerebral cortex The gray matter of the cerebral cortex usually is divided into four lobes, roughly defined by major surface folds The frontal lobe contains control centres for motor activity and speech, the parietal for somatic senses (touch and position), the temporal for auditory reception and memory, and the occipital for visual reception Sometimes the limbic lobe, involved with smell, taste, and emotions, is considered to be a fifth lobe. 10/20/23 Dr. Mukape Mukape 5  External Structure of Cerebrum Numerous deep grooves in the cerebral cortex, called cerebral fissures or cerebral sulci, originate in the extensive folding of the brain’s surface The main cerebral sulci are: - Lateral sulcus of Sylvius, between the frontal and temporal lobes - Central sulcus of Rolando, between the frontal and parietal lobes, which separates the chief motor and sensory regions of the brain - Calcarine sulcus on the occipital lobe, which contains the visual cortex - Parieto-occipital sulcus, which separates the parietal and occipital lobes - Transverse sulcus, which divides the cerebrum from the cerebellum - Lunate sulcus – groove located in the occipital cortex - Longitudinal sulcus, which divides the cerebrum into two hemispheres 10/20/23 Dr. Mukape Mukape 6  External Structure of Cerebrum The main gyri are: - Precentral gyrus – ridge directly anterior to central sulcus, location of primary motor cortex - Postcentral gyrus – ridge directly posterior to central sulcus, location of primary somatosensory cortex - Superior temporal gyrus – ridge located inferior to lateral sulcus, responsible for the reception and processing of sound 10/20/23 Dr. Mukape Mukape 7  Important Gyri 10/20/23 Dr. Mukape Mukape 8 10/20/23 Dr. Mukape Mukape 9 10/20/23 Dr. Mukape Mukape 10 10/20/23 Dr. Mukape Mukape 11 10/20/23 Dr. Mukape Mukape 12 10/20/23 Dr. Mukape Mukape 13 10/20/23 Dr. Mukape Mukape 14  Internal Structure of Cerebrum The cerebrum is comprised of two different types of tissue – grey matter and white matter: - Grey matter forms the surface of each cerebral hemisphere (known as the cerebral cortex), and is associated with processing and cognition - White matter forms the bulk of the deeper parts of the brain and consists of glial cells and myelinated axons that connect the various grey matter areas 10/20/23 Dr. Mukape Mukape 15  Layers of the Cerebral Cortex Grey matter of the cerebrum is called the neocortex The neocortex has six (6) layers From outside to inside: - Layer I: Molecular layer - Layer II: Outer granular layer - Layer III: Outer pyramidal layer - Layer IV: Inner granular layer - Layer V: Inner pyramidal layer - Layer VI: Pleomorphic/polymorphic/multiform/fusiform layer 10/20/23 Dr. Mukape Mukape 16  Layers of the Cerebral Cortex 10/20/23 Dr. Mukape Mukape 17  Layers of the Cerebral Cortex 10/20/23 Dr. Mukape Mukape 18  Layers of the Cerebral Cortex Pyramidal cells predominate in layers III and V Granule cells in layers II and IV 10/20/23 Dr. Mukape Mukape 19  Pyramidal cells Pyramidal cells have large apical dendrite and basal dendrites Axon projects downward into subcortical white matter; may have collaterals Pyramidal cell is the primary output neuron 10/20/23 Dr. Mukape Mukape 20  Internal Structure of Cerebrum 10/20/23 Dr. Mukape Mukape 21  Lobes of Cerebrum The cerebral cortex is classified into four lobes, according to the name of the corresponding cranial bone that approximately overlies each part These are: 1. Frontal lobe 2. Parietal lobe 3. Temporal lobe 4. Occipital lobe Each lobe contains various cortical association areas – where information from different modalities are collated for processing Together, these areas function to give us a meaningful perceptual interpretation and experience of our surrounding environment 10/20/23 Dr. Mukape Mukape 22  Lobes of the Cerebrum 10/20/23 Dr. Mukape Mukape 23  Lobes of the Cerebrum 10/20/23 Dr. Mukape Mukape 24  Brain 10/20/23 Dr. Mukape Mukape 25  Front lobe The frontal lobe is located beneath the frontal bone of the calvaria and is the most anterior region of the cerebrum It is separated from the parietal lobe posteriorly by the central sulcus and from the temporal lobe inferoposteriorly by the lateral sulcus. The association areas of the frontal lobe are responsible for: higher intellect, personality, mood, social conduct and language (dominant hemisphere side only) 10/20/23 Dr. Mukape Mukape 26  Simplified Presentation of Sulci and Gyri 10/20/23 Dr. Mukape Mukape 27  Parietal lobe The parietal lobe is found below the parietal bone of the calvaria, between the frontal lobe anteriorly and the occipital lobe posteriorly, from which it is separated by the central sulcus and parieto-occipital sulcus, respectively It sits superiorly in relation to the temporal lobe, being separated by the lateral sulcus Its cortical association areas contribute to the control of: language and calculation on the dominant hemisphere side, and visuospatial functions (e.g. 2-point discrimination) on the non-dominant hemisphere side 10/20/23 Dr. Mukape Mukape 28 10/20/23 Dr. Mukape Mukape 29  Temporal lobe The temporal lobe sits beneath the temporal bone of the calvaria, inferior to the frontal and parietal lobes, from which it is separated by the lateral sulcus The cortical association areas of the temporal lobe are accountable for memory and language – this includes hearing as it is the location of the primary auditory cortex 10/20/23 Dr. Mukape Mukape 30 10/20/23 Dr. Mukape Mukape 31  Occipital lobe The occipital lobe is the most posterior part of the cerebrum situated below the occipital bone of the calvaria Its inferior aspect rests upon the tentorium cerebelli, which segregates the cerebrum from the cerebellum The parieto-occipital sulcus separates the occipital lobe from the parietal and temporal lobes anteriorly. The primary visual cortex (V1) is located within the occipital lobe and hence its cortical association area is responsible for vision 10/20/23 Dr. Mukape Mukape 32 10/20/23 Dr. Mukape Mukape 33 10/20/23 Dr. Mukape Mukape 34 10/20/23 Dr. Mukape Mukape 35  Insula lobe Also called island of Reil Present within the lateral sulcus of Silvius between temporal and frontal lobes The overlying cortical areas are called opercula formed from the parts of frontal, temporal and parietal lobe Functions linked to emotion and body’s homeostasis These functions include compassion, empathy, taste, perception, motor control, self-awareness, cognitive functioning and interpersonal experience In relation to these, it is involved in psychopathology The lobe is divided into two parts: - Larger anterior insula which is subdivided into there short gyri - Smaller posterior insula 10/20/23 Dr. Mukape Mukape 36 10/20/23 Dr. Mukape Mukape 37  Insula lobe 10/20/23 Dr. Mukape Mukape 38 10/20/23 Dr. Mukape Mukape 39 10/20/23 Dr. Mukape Mukape 40 10/20/23 Dr. Mukape Mukape 41 10/20/23 Dr. Mukape Mukape 42 10/20/23 Dr. Mukape Mukape 43  Korbinian Brodmann Areas Originally defined and numbered into 52 regions by the German anatomist Korbinian Brodmann in the early 1900’s Brodmann areas of the cerebral cortex are defined by its cytoarchitecture (histological structure and cellular organization) It is important to remember that the same Brodmann area numbers in humans and primates often do not translate to other species In addition, these Brodmann areas have been widely redefined, discussed, debated, and refined exhaustively based on cytoarchitecture, cortical functions, and brain plasticity 10/20/23 Dr. Mukape Mukape 44  Korbinian Brodmann Areas The Brodmann areas were initially based on the cytoarchitectural organization of neurons in the cerebral cortex Specifically, it was observed that they were organized in distinct groups once the cells were stained using the Nissl method (which consists of basic dyes, notably staining the rough endoplasmic reticulum—also known as Nissl substance—dark blue) Many of these areas of distinct neuronal organization have since been correlated to various cortical functions 10/20/23 Dr. Mukape Mukape 45  Korbinian Brodmann areas 10/20/23 Dr. Mukape Mukape 46  Korbinian Brodmann’s areas 10/20/23 Dr. Mukape Mukape 47  Important Brodmann Areas 10/20/23 Dr. Mukape Mukape 48  Korbinian Brodmann’s areas 10/20/23 Dr. Mukape Mukape 49  Korbinian Brodmann’s areas 10/20/23 Dr. Mukape Mukape 50  Korbinian Brodmann’s areas 10/20/23 Dr. Mukape Mukape 51  Korbinian Brodmann’s areas 10/20/23 Dr. Mukape Mukape 52  Cerebrum 10/20/23 Dr. Mukape Mukape 53 10/20/23 Dr. Mukape Mukape 54 10/20/23 Dr. Mukape Mukape 55 Broca’s area: pars opercularis (area 44) and pars triangularis (area 45) of inferior frontal gyrus 10/20/23 Dr. Mukape Mukape 56  Wernicke’s area (area 22, 39, 40) 10/20/23 Dr. Mukape Mukape 57  Corpus callosum Is only found in placental mammals Largest band of commissural fibres which connects wide areas of neocortex except lower and ant parts of temporal lobe Enables communication between the two cerebral hemispheres Well developed in man - 300 million finely myelinated fibres - 10 cm long Location : - Anterior end : 4cm behind frontal pole - Posterior end : 6cm in front of occipital pole 10/20/23 Dr. Mukape Mukape 58  Corpus callosum Parts: 1. Rostrum 2. Genu 3. Body (trunk) 4. Splenium Rostrum is continuous below with the lamina terminalis, named so because it resembles a bird’s beak Isthmus is the narrow part between body and splenium Splenium is the thickest part, means bandage in Greek 10/20/23 Dr. Mukape Mukape 59  Relations of corpus callosum On either side of fibers radiate in the white matter and pass to the various parts of the cerebral cortex Those curving forward from the genu into the frontal lobe constitute the forceps minor (also forceps anterior) Those curving backward from the splenium into the occipital lobes, form the forceps major (also forceps posterior) Between these two parts is the main body of the fibers which constitute the tapetum and extend laterally on either side into the temporal lobe, and cover in the central part of the lateral ventricle The tapetum and anterior commissure share the function of connecting left and right temporal lobes The anterior cerebral arteries are in contact with the under surface of the rostrum, they arch over the front of the genu and are carried along the trunk, supplying the front four-fifths of the corpus callosum 10/20/23 Dr. Mukape Mukape 60 10/20/23 Dr. Mukape Mukape 61 10/20/23 Dr. Mukape Mukape 62 10/20/23 Dr. Mukape Mukape 63 10/20/23 Dr. Mukape Mukape 64  Summary of blood Supply to Cerebrum The blood supply to the cerebrum can be simply classified into 3 distinct paired arterial branches: - Anterior Cerebral Arteries – branches of internal carotid arteries, supplying the anteromedial aspect of the cerebrum - Middle Cerebral Arteries – continuation of internal carotid arteries, supplying most of the lateral portions of the cerebrum - Posterior Cerebral Arteries – branches of the basilar arteries, supplying both the medial and lateral sides of the cerebrum posteriorly. Venous drainage - Via a network of small cerebral veins - These vessels empty into the dural venous sinuses – endothelial lined spaces between the outer and inner layers of dura mater 10/20/23 Dr. Mukape Mukape 65 10/20/23 Dr. Mukape Mukape 66  Simplified Course of ACA/PCA 10/20/23 Dr. Mukape Mukape 67  Superior/Inferior Divisions of MCA 10/20/23 Dr. Mukape Mukape 68  Lenticulostriate Arteries 10/20/23 Dr. Mukape Mukape 69  Superficial Territories of Major Cerebral Arteries 10/20/23 Dr. Mukape Mukape 70  Blood Supply to Basal Ganglia/Thalamus 10/20/23 Dr. Mukape Mukape 71  Blood Supply to Internal Capsule/Globus Pallidus 10/20/23 Dr. Mukape Mukape 72 10/20/23 Dr. Mukape Mukape 73 10/20/23 Dr. Mukape Mukape 74 10/20/23 Dr. Mukape Mukape 75  Summary of Superficial/Deep Blood Supply to Cerebral Hemispheres (Coronal View) 10/20/23 Dr. Mukape Mukape 76  Summary of Superficial/Deep Blood Supply to Cerebral Hemispheres (Axial View) 10/20/23 Dr. Mukape Mukape 77  Supratentorial Vascular Territories of the Major Cerebral Arteries via the level of the Basal Ganglia and Thalami Red: MCA - Lateral aspects of the hemispheres, including the lateral frontal, parietal, and anterior temporal lobes; insula; and basal ganglia Blue: ACA - Medial frontal and parietal lobes Green: PCA - Thalami and occipital and inferior temporal lobes Yellow: anterior choroidal artery: - Posterior limb of the internal capsule and part of the hippocampus Left: axial view extending to the anterior and superior surface of the occipital horn of the Right: coronal view lateral ventricle 10/20/23 Dr. Mukape Mukape 78  END 10/20/23 Dr. Mukape Mukape 79