Neuroanatomy PDF - For Physiotherapy - M201

HUMAN ANATOMY For PHYSIOTHERAPY ‫اﻟﻔ‬ Neuroanatomy ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ By ‫ﻧﯾﺔ‬ Mohamed Bakry Hafiz Waly Saber Shona Hassan Heidar Professors of Anatomy Anatomy Department Faculty of Medicine Cairo University Staff Members:  Ehab Abdel-Aziz...

HUMAN ANATOMY For PHYSIOTHERAPY ‫اﻟﻔ‬ Neuroanatomy ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ By ‫ﻧﯾﺔ‬ Mohamed Bakry Hafiz Waly Saber Shona Hassan Heidar Professors of Anatomy Anatomy Department Faculty of Medicine Cairo University Staff Members:  Ehab Abdel-Aziz  Hassan Heider  Helana Labib  Hafiz Waly  Soheir El-Sharouny  Saber Shona  Mohamed Bakry  Emad Naguib  Wafik Halim  Nabila Yousef Abdel-Halim  Ibrahim Labib  Mohamed Emad  Sherif Galal  Mamdouh Mahmoud  Fayza Abdel-Raouf ‫اﻟﻔ‬  Abdel-Wakeel Essawy  Safwat Wadie  Al-Moatasem Bellah Al-Sherif  Maha Ashmawy ‫رﻗﺔ‬  Hoda Alaasar  Tarek Abdel-Salam  Mohamed Wahdan  Medhat Morsy  Sherif Zaki ‫اﻟﺛﺎ‬  Naglaa Ali  Ayman Abou El-Enein  Abeer Oueida  Inas Ahmed ‫ﻧﯾﺔ‬  Walaa Mohamed Sayed  Hanan Nabeh  Mogeda Mahdy  Sherif Fahmy  Ahmed Galal  Magdy Fouad  Ahmed Al-Zainy  Tamer Shawky  Rasha Abd El Khalek  Hosam Yehya  Bahaa Khaled  Doaa Mahmoud  Shereen Abdelfattah  Tarek Abdelgalil  Contents Page Introduction of Nervous System 1 Spinal Cord 2 Cerebral Meninges 14 Cerebrospinal Fluid 16 Brain Stem 18 Medulla 18 Pons 21 Midbrain 21 Fourth Ventricle 24 Cerebellum 27 Interpeduncular Fossa 30 Cerebral Hemisphere 32 ‫اﻟﻔ‬ Functional Areas of the Cerebral Hemisphere 42 Internal Structure of the Cerebral Hemisphere 46 White Matter of the Cerebral Hemisphere 46 Basal Ganglia ‫رﻗﺔ‬ 50 The Internal Capsule 52 Diencephalon 55 Blood Supply of the Brain 56 ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫ﻧﯾﺔ‬ ‫اﻟﺛﺎ‬ ‫رﻗﺔ‬ ‫اﻟﻔ‬ ‫‪NEUROANATOMY‬‬ ‫ﻧﯾﺔ‬ ‫اﻟﺛﺎ‬ ‫رﻗﺔ‬ ‫اﻟﻔ‬  Neuroanatomy Introduction of the Nervous System The nervous system (NS) consists of two types of cells: 1. Nerve cells proper (Neurons) are variable in size and shape but all of them have cytoplasmic processes (dendrites and axons). Dendrites carry impulses towards the nerve cell body (afferent) while axons carry impulses away from cell body (efferent). Most axons in the central nervous system are wrapped up in a fatty sheath called myelin sheath which is segmented and absent at constrictions called nodes of Ranviere. Myelin sheath is covered by neurolemma (Schwan's cell). ‫اﻟﻔ‬ 2. Neuroglia cells which are the connective tissue cells of the central nervous system. Organization of the Nervous System: ‫رﻗﺔ‬ 1. Central nervous system (CNS): Brain-spinal cord. 2. Peripheral nervous system (PNS): i. Cranial nerves (12 pairs, connected to the surface of cerebrum and brain stem). ‫اﻟﺛﺎ‬ ii. Spinal nerves (31 pairs; 8 cervical, 12 thoracic, 5 lumber, 5 sacral and one coccygeal). 3. Autonomic nervous system (ANS): ‫ﻧﯾﺔ‬ i. Parasympathetic (craniosacral) division: - Cranial part: related to cranial nerves III, VII, IX and X. - Sacral part: related to sacral spinal nerves 2, 3 and 4. ii. Sympathetic (thoracolumber) division: - Arises from the spinal cord (T1-L3). - Forms the sympathetic trunk with its ganglia. 1  Neuroanatomy Spinal Cord I. External Features  Site and Extent: a- It begins, above, at the lower border of foramen magnum as a continuation of the medulla oblongata. b- It ends, below, at the level of the disc between L1/L2 vertebrae. The lower end of the spinal cord tapers off into a conical extremity called conus medullaris i.e. the spinal cord occupies the upper 2/3 of the vertebral canal.  Length: It is about 45 cm in length (about 25 cm shorter than the length of ‫اﻟﻔ‬ the vertebral column).  Shape: The spinal cord is cylinderical, being slightly compressed antero- posteriorly. Its thickness is not uniform. It shows two enlargements: ‫رﻗﺔ‬ a- Cervical enlargement b- Lumbar enlargement  External features: The external surface of the spinal cord shows 6 longitudinal grooves or sulci: 1- Anterior median fissure or sulcus: is the deepest. 2- Posterior median sulcus. ‫اﻟﺛﺎ‬ 3- & 4- Two anterolateral sulci: Rt & Lt along which emerge the ventral (motor) roots of the spinal nerves. 5- & 6- Two posterolateral sulci: Rt & Lt along which enter the dorsal ‫ﻧﯾﺔ‬ (sensory) roots of the spinal nerve.  Segments: The spinal cord is divided into 31 segments, arranged as follows: ▪ 8 cervical segments. ▪ 12 thoracic segments. ▪ 5 lumbar segments. ▪ 5 sacral segments. ▪ 1 (one) coccygeal segment. Since the spinal cord is shorter than the vertebral column, so the segments of the spinal cord lies above their corresponding vertebrae:  The cervical region of the spinal cord ends at the level of the 6th cervical (C6) vertebra.  The thoracic region of the spinal cord ends at the level of the 9th thoracic (T9) vertebra. 2  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪3‬‬  Neuroanatomy  Spinal nerves:  Each segment of the spinal cord gives origin to a pair of spinal nerves (right and left). Accordingly, there are 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and one coccygeal nerves).  Each spinal nerve is attached to the side of its corresponding spinal segment by two roots: A- Ventral root (motor): emerges from the antero-lateral sulcus. It contains somatic efferent (motor) fibres, in addition to sympathetic and parasympathetic fibres in certain segments of spinal cord. B- Dorsal root (sensory): enters through the posterolateral sulcus. It consists of general somatic afferent (sensory) (pain, temperature, ‫اﻟﻔ‬ touch, pressure and proprioception) from the body below the head to enter the spinal cord. Each dorsal root carries the dorsal root or spinal ‫رﻗﺔ‬ ganglion. The nerve cells in this ganglion represent the 1 st order neurons in the pathways of the general somatic sensations from the body below the head. ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 4  Neuroanatomy  At the corresponding intervertebral foramen, the ventral and dorsal roots unite together forming the spinal nerve trunk which is mixed containing both motor and sensory fibres. It leaves the vertebral canal through the intervertebral foramen.  The spinal nerve trunk is very short. Once it emerges from the intervertebral foramen, it divides into two primary rami (anterior and posterior). Both rami are mixed and supply the anterior and posterior aspects of the body respectively.  Each root is covered by the pia, arachnoid and dura maters. At the intervertebral foramen, only the dural sheath continues outwards around the spinal nerve trunk. ‫اﻟﻔ‬  Length of the roots and the cauda equina: Since the spinal cord is shorter than the vertebral column; accordingly: - ‫رﻗﺔ‬ Therefore, the roots of the spinal nerves have to descend for some distances in the subarachnoid space to reach their intervertebral foramina. Accordingly, the roots of the spinal nerves become progressively longer and more oblique as we go downwards. - Below the end of the spinal cord (below L1 vertebra), the vertebral ‫اﻟﺛﺎ‬ canal is occupied only by a leash of the long lumbar and sacral nerve roots, surrounding the filum terminale together forming the cauda equine which float in the CSF filling the subarachnoid space. Lumbar ‫ﻧﯾﺔ‬ puncture can be safely done below L2 vertebra without any danger of injury of the spinal cord. 5  Neuroanatomy ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ Relation of segments of the spinal cord and spinal nerves to the vertebral column. The vertebral bodies are on the right side and the dorsal spines of the vertebrae on the left. 6  Neuroanatomy ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ Cauda Equina 7  Neuroanatomy  Coverings of the spinal cord; (Spinal Meninges):  The spinal cord as well as the brain (i.e. the CNS) are surrounded by three membranes called the meninges; from inside outwards they are: the pia, arachnoid and dura maters.  The pia mater is closely adherent to the surface of the brain and the spinal cord. The pia mater is separated from the arachnoid mater by sub- arachnoid space which is a filled with cerebrospinal fluid (CSF). The arachnoid mater is separated from the dura mater by the narrow subdural space containing a thin film of serous fluid. ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 8  Neuroanatomy  The spinal dura mater is separated from the periostium of the vertebral canal by a space called the extradural (or epidural) space. A- Spinal Pia Mater: - It is a delicate membrane which is closely adherent to the surface of the spinal cord. - It is thickened to form two strong fibrous bands: a- Denticulate ligament: Are two thickened lateral extensions (Rt & Lt) arising from the pia mater at the side of the spinal cord; from the foramen magnum (above) till L1 vertebra (below). It lies midway between the ventral and dorsal spinal nerve ‫اﻟﻔ‬ root and its lteral border shows 21-teeth like processes which attached to the dura mater. b- Filum terminale: ‫رﻗﺔ‬ At the tip of the conus medullaris, the pia mater extends as a fibrous filament called the filum terminale, which descend in the centre of the cauda equina surrounded by the lower lumber and sacral nerves having a glistening silvery appearance. ‫اﻟﺛﺎ‬ It leaves the sacral canal through the sacral hiatus and gets attached to the periosteum on the back of the coccyx. B- Spinal Arachnoid Mater: It is a delicate membrane surrounding the pia mater and deep to ‫ﻧﯾﺔ‬ - the dura mater. - It is separated from the pia mater (inside it) by the subarachnoid space which is filled with CSF. - It is separated from the dura mater by a narrow subdural space which contains a thin film of serous fluid. - Above, it is continuous through the foramen magnum with the arachnoid mater of the brain. Below, it ends at the level of the 2 nd sacral vertebra where it is pierced by the filum terminale. - Subarachnoid space contains: Cerebrospinal fluid (CSF). Spinal blood vessels. Spinal nerve roots. Filum terminale. 9  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪10‬‬  Neuroanatomy - Lumbar puncture: is done by introducing a needle into the subarachnoid space, either to obtain a sample of CSF or to inject a drug, below the level of (L2) vertebra to avoid injury of the spinal cord. The nerve roots of the cauda equina, being floating in the CSF, they escape away from the lumbar puncture needle and are not injured. C- Spinal Dura Mater: - It is thick tough fibrous membrane representing the outermost of the three meninges. - It extends from the foramen magnum (above) down to the level of (S2) vertebra; (below). ‫اﻟﻔ‬ - It is separated from the arachnoid mater by the subdural space and is separated from the periosteal lining of the vertebral canal by ‫رﻗﺔ‬ the extradural (epidural) space which contains: Loose areolar tissue. Semiliquid fat. Internal vertebral venous plexus. Spinal nerve roots and trunks in their way to leave through the ‫اﻟﺛﺎ‬ intervertebral foramina. This space is used for the injection of the local anaesthesia.  Fixation of the Spinal Cord: The spinal cord is fixed in position by: i. The filum terminal, fixes the cord to the back of the coccyx. ‫ﻧﯾﺔ‬ ii. Denticulate ligaments: fixes the cord on both sides. iii. The dura mater itself which is attached above to the margin of the foramen magnum and on either side to the margins of the intervertebral foramina. 11  Neuroanatomy Blood Supply of the Spinal Cord A- Arterial Supply 1. Anterior Spinal Artery: (One median longitudinal trunk):  Formed by union of two branches from the 4th part of the vertebral artery inside the cranial cavity.  It leave the skull through the foramen magnum and continues in the subarachnoid space along the anterior median fissure of the spinal cord.  It supplies the anterior 2/3 of the thickness of the spinal cord. 2. Posterior Spinal Artery: (Two longitudinal arteries):  It arises from the 4th part of the vertebral artery inside the cranial cavity. ‫اﻟﻔ‬  Each artery leaves the skull through the foramen magnum and continues along the dorsal nerve roots (the posterolateral sulcus). ‫رﻗﺔ‬  Each artery divides into 2 branches, one in front and one behind the dorsal nerve roots.  They supply the posterior 1/3 of the spinal cord. Anastomosis between anterior and posterior spinal arteries occurs around the conus medullaris. 3. Radicular Spinal Arteries: ‫اﻟﺛﺎ‬  They arise from the vertebral arteries (in the neck), the posterior intercostal arteries (in the thorax), lumbar arteries (in the abdomen) and lateral sacral arteries (in the pelvis) on either side. ‫ﻧﯾﺔ‬  They enter the vertebral canal through the intervertebral foramina and divide into anterior and posterior branches which run along the ventral and dorsal spinal nerve roots.  They end on the surface of the spinal cord by anastomosing with both anterior and posterior spinal arteries forming a surface anastomosis supplying the superficial parts of the white matter. One of the radicular arteries is very large and supplies the lumbar enlargement and is called the arteria radicularis magna. B- Venous Drainage Veins corresponding to anterior, posterior and radicular spinal arteries drain into the internal vertebral venous plexus present in the epidural space. 12  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪13‬‬  Neuroanatomy Cerebral Meninges  The brain is surrounded by three membranes or coverings called the meninges.  From inside outwards these meninges are the pia mater, arachnoid mater and dura mater. A- The Pia Matter It is closely adherent to the surface of the brain and is carried into all its sulci surrounding the cerebral arteries. B- The Arachnoid Mater 1. It is a very thin and delicate membrane, between the pia and dura mater. ‫اﻟﻔ‬ 2. The arachnoid mater bridges over the various sulci on the surface of the brain, i.e. it does not enter the sulci of the brain; but it is carried into the ‫رﻗﺔ‬ median longitudinal fissure by the falx cerebri. 3. The subarachnoid space:  In most sites, the pia and arachnoid are close to each other; being separated from each other by the subarachnoid space which contains cerebrospinal fluid.  The blood vessels of the brain traverse the subarachnoid space; the ‫اﻟﺛﺎ‬ smaller vessels ramify in the pia mater before entering the substance of the brain. They enter the brain surrounded by prolongations of the subarachnoid space and carry with them sheaths of pia mater. ‫ﻧﯾﺔ‬ 4. The subarachnoid cisterns: Enlargement and dilatation of the subarachnoid spaces in certain sites; they are: a- The cerebellomedullary cistern: (cisterna magna) between the back of the medulla and the cerebellum b- The pontine cistern: infront of pons c- The interpeduncular cistern d- The cistern of lateral fissure 5. The arachnoid villi and granulations:  These are projections from the arachnoid mater into the superior sagittal sinus.  They increase in size and in number in old age.  They drain the CSF back to the blood stream. 14  Neuroanatomy C- The Dura Mater 1. It is firmly adherent to the endoperiosteal lining of the skull; the two layers cannot be separated from each other except at the dural venous sinuses. 2. The dura mater becomes folded to form double-layered septa e.g. the falx cerebri, tentorium cerebelli and falx cerebelli. 3. The subdural space. A capillary space between the dura and arachnoid mater, it contains serous fluid. 4. As the cranial and the spinal nerves leave the surface of the brain and spinal cord, they carry fine coverings of pia, arachnoid and dura mater. ‫اﻟﻔ‬ The Cavities of C.N.S. (Ventricles and Central Canals) ‫رﻗﺔ‬ The Ventricles: 4 ventricles (2 lateral V, 3rd V and 4th V).  Lateral ventricles: The cavity of cerebral hemisphere, it consists of body and 3 horns (anterior, posterior and inferior).  The third ventricle: The cavity of diencephalons. ‫اﻟﺛﺎ‬  The fourth ventricle: The cavity of the hind brain: medulla-pons and cerebellum.  The central canals: ‫ﻧﯾﺔ‬ 1. The central canal of mid brain (Aqueduct of Sylvius). 2. The central canal of spinal cord and medulla. Communication of the Ventricles and the Central Canals 1- Each lateral ventricle is connected with 3rd ventricle by an inter. ventricular foramen. 2- The 3rd ventricle is connected with 4th ventricle by the central canal of mid brain. 3- The 4th ventricle communicates with the central canal of medulla and spinal cord below and with the subarachnoid space through its median and lateral foramina. 15  Neuroanatomy The Cerebrospinal Fluid (C.S.F.) C.S.F. is clear watery fluid (135 cc) in amount, contains small amount of sugar, protein and electrolytes. It is continuously secreted and absorbed. 1- Production: By the choroids plexus of the ventricles but mainly in the lateral ventricle: The choroids plexus is formed of two parts: a- Plexus of capillaries within a fold of pia mater (Tela choroida). b- Very thin part in the wall of each ventricle which is lined by single layer of cuboidal epithelium. ‫اﻟﻔ‬ Situation of choroids plexus: a- In the medial wall of each lateral ventricle. b- In the roof of 3rd and 4th ventricles. ‫رﻗﺔ‬ 2- Circulation: a- From each lateral ventricle it passes to the 3rd ventricle via the inter ventricular foramen (F. of Monro). b- From the 3rd ventricle to the 4th ventricle by the central canal of mid brain. ‫اﻟﺛﺎ‬ c- From the 4th ventricle it reaches the subarachnoid space by 3 openings: one in the roof of 4th ventricle (in the middle) (F. of Magendi) and two lateral openings (F. of Luschks), in the lateral angles (recesses) of the 4 th ‫ﻧﯾﺔ‬ ventricle. So, the C.S.F. circulates inside the brain (in the cavities) and outside it (in subarachnoid space). The movement of C.S.F. and its flow upwards around the brain is due to the pulsation of large arteries present in the subarachnoid space. 3- Absorption: By means of Arachnoid villi and granulation into the superior sagittal sinus. 4- Function: a- Protection of the brain and spinal cord it acts as a protective water cushion. b- Regulation of the intra-cranial pressure. c- It is the principal medium for removal of the waste products of the nerve cells activity. 16  Neuroanatomy Lateral ventricle 3rd ventricle Aqueduct of Sylvius ‫اﻟﻔ‬ 4th ventricle Cisterna magna ‫رﻗﺔ‬ Central canal of spinal cord and closed medulla ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ Cavities of C.N.S. 17  Neuroanatomy Brain The brain consists of: 1. Cerebrum: (Rt. and Lt. cerebral hemispheres with the diencephalon in between). 2. Brain stem: From above downwards it is formed of: ▪ Midbrain. ▪ Pons. ▪ Medulla oblongata. 3. Cerebellum: (Rt. and Lt. cerebellar hemispheres connected together by vermis). BRAIN STEM ‫اﻟﻔ‬  From below upwards it is formed of medulla oblongata, pons and midbrain. ‫رﻗﺔ‬  Above it is directly continuous with the diencephalon.  Below it is directly continuous with the spinal cord. MEDULLA OBLONGATA ‫اﻟﺛﺎ‬ 1. It is 3 cm long and is continuous with the pons superiorly and with the spinal cord inferiorly at the lower border of the foramen magnum. ‫ﻧﯾﺔ‬ 2. It is related anteriorly to the basilar part of occipital bone of the skull. 3. Parts: It has 2 parts: a- Open medulla (upper 1/2): Its posterior surface forms the lower part of the floor of the 4th ventricle. b- Closed medulla (lower 1/2): Contains a central canal which is continuous above with the 4th ventricle and below with the central canal of the spinal cord. External features: a- Anterolateral surface: shows the following features: i. Anterior median fissure: Is a median longitudinal groove, (obliterated in its lower part by the pyramidal decussation). 18  Neuroanatomy ii. The pyramid: Is an elongated elevation lying on each side of the anterior median fissure. It is produced by the cortico-spinal tract. iii. The olive: Is a second oval elevation overlying the inferior olivary nucleus. It lies lateral to the pyramid on either side, being separated from the pyramid by the anterolateral sulcus; along which emerge the rootlets of the 12th (hypoglossal) nerve. iv. The inferior cerebellar peduncle: Is a bundle of nerve fibres connecting the medulla with the cerebellum. It projects on the dorso- lateral aspect of the medulla. It appears more laterally, being separated from the olive by the posterolateral sulcus; along which emerge the rootlets of the 9th (glossopharyngeal) nerve, 10th (vagus) ‫اﻟﻔ‬ nerve and the cranial root of the 11th (accessory) nerve. ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 19  Neuroanatomy b- Posterior surface: i. The posterior surface of the upper 1/2 of the medulla (open medulla): Forms the lower part of the floor of the 4th ventricle (see later). ii. The posterior surface of the lower 1/2 of the medulla (closed medulla): Is directly continuous with the posterior surface of the spinal cord and presents: - A posterior median fissure which is an upwards extension of that of the spinal cord. - The gracile and cuneate tracts of the spinal cord ascend as 2 distinct ridges on either side of the posterior median fissure and ‫اﻟﻔ‬ end on the posterior surface of the medulla just below the 4 th ventricle in slightly expanded elevations called the gracile (medially) and cuneate (laterally) tubercles. ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 20  Neuroanatomy PONS 1. It lies between the medulla (below) and the midbrain (above) and in front of the cerebellum. 2. The cerebral peduncles of the midbrain arise from its upper border while the 2 pyramids of the medulla emerge from its lower border. 3. Its convex anterior surface is related to the clivus of the skull. External features: a- Anterior surface: Is convex from side to side and from above downwards. It presents: i. A shallow median groove (basilar groove) in which the basilar artery ‫اﻟﻔ‬ lies. ii. On each side of the basilar groove there are many thick transverse pontine fibres which collect on either side to form the middle ‫رﻗﺔ‬ cerebellar peduncle which turns backwards to sink into the corresponding cerebellar hemisphere. iii. The large sensory (lateral) and the small motor (medial) roots of the 5th (trigeminal) nerve emerge from the lateral part of the front of the pons near its upper border. ‫اﻟﺛﺎ‬ iv. The 6th (abducent) nerve emerges from ponto-meduallary junction near the middle line. v. The 7th (facial) and 8th (vestibule-cochlear) nerves arise at the ponto- medullary junction more laterally where the pons merges into the ‫ﻧﯾﺔ‬ middle cerebellar peduncle. The region from which these 2 nerves emerge is called cerebello-pontine. b- Posterior surface: Forms the upper part of the floor of the 4th ventricle. MIDBRAIN 1. It is the shortest part of the brain stem which lies between the pons (below) and the diencephalon (above). 2. It connects the pons and the cerebellum to the subthalamic region. 3. It occupies the notch of the tentorium cerebelli and is mainly hidden by the cerebral hemispheres. 21  Neuroanatomy External features: It looks like a cube with 4 surfaces (an anterior, a posterior and 2 lateral surfaces): a- The anterior surface: presents: i. Two cerebral peduncles which are 2 large bundles of fibres that emerge directly from the upper surface of the pons (below) and ascend to disappear in the substance of the corresponding cerebral hemispheres (above). ii. The interpeduncular fossa separate the Rt and Lt cerebral peduncles from each other in the median plane. From this fossa, the 3 rd (oculomotor) nerve emerges just medial to the cerebral peduncle. ‫اﻟﻔ‬ b- The posterior surface: presents: i. Four rounded elevations called the colliculi (or the corpora ‫رﻗﺔ‬ quadrigemina): They are: - Two superior colliculi (above): which lodge centres of the visual reflexes. - Two inferior colliculi (below): which are lower auditory centres. ii. Below each inferior colliculus arises a flattened band called the ‫اﻟﺛﺎ‬ superior cerebellar peduncle. The 2 superior cerebellar peduncles run downwards, backwards and laterally along the sides of the upper part of the 4th ventricle to enter the corresponding cerebellar hemisphere. ‫ﻧﯾﺔ‬ iii. In the median plane, the groove between the 2 inferior colliculi there is a thin sheet of white matter called the superior medullary velum which is stretched between the medial edges of the 2 superior cerebellar peduncles to form part of the roof of the 4th ventricle. iv. The 4th (trochlear) nerve emerges from the midbrain immediately below the inferior colliculi by piercing the superior medullary velum. It is the only cranial N. that emerges from the dorsal aspect of the brain stem. It then winds round the lateral aspect of the midbrain to reach the anterior aspect. 22  Neuroanatomy c- The lateral surface of midbrain: It is mostly the lateral surface of the cerebral peduncle:  From the superior and the inferior colliculi arise the superior and inferior brachia (quadrigeminal brachia) which run upwards and forwards on the posterior part of the lateral surface of the midbrain to end into the lateral and medial geniculate bodies respectively (lateral and medial geniculate bodies are parts of the diencephalon).  In addition the lateral surface of the midbrain (the cerebral peduncle) is also crossed: - Near it upper border by: 1- Optic tract. ‫اﻟﻔ‬ 2- Anterior choroidal artery (branch from internal carotid artery). 3- Basal vein. - ‫رﻗﺔ‬ Near its lower border by: 1- Posterior cerebral artery. 2- Trochlear nerve turning forwards. 3- Superior cerebellar artery. ‫اﻟﺛﺎ‬ The lateral surface is related the edge of the tentorial notch of the tentorium cerebelli. ‫ﻧﯾﺔ‬ 23  Neuroanatomy FOURTH VENTRICLE Site:  It is the cavity of the hindbrain.  It is situated between the cerebellum (behind), posterior surface of the pons and posterior surface of upper part of the medulla (in front). Shape:  It is diamond shaped when seen from behind but is tent-shaped when seen from the side. Lateral Boundaries:  Superior cerebellar peduncles...... (above and laterally).  Inferior cerebellar peduncles, cuneate and gracile tubercles…… (below ‫اﻟﻔ‬ and laterally). Angles and Communications: 4th ventricle has 4 angles: upper angle ‫رﻗﺔ‬ through which it continuous above with cerebral aqueduct of midbrain, lower angle through which it communicates below with the central canal of the medulla oblongata. Two lateral angles: Each lateral angle is prolonged laterally to form tubular prolongation called lateral recess. Each lateral recess opens in the subarachnoid space by the lateral aperature of the 4th ventricle or ‫اﻟﺛﺎ‬ (foramen of Luschka). Floor of 4th ventricle:  It is formed above by the posterior surface of the pons and below by the ‫ﻧﯾﺔ‬ posterior surface of the upper part of the medulla (open medulla).  The floor is divided into Rt. and Lt. longitudinal halves by a median vertical groove called the median longitudinal sulcus.  The floor is crossed at its widest point by the medullary stria, which divides the floor into upper (or pontine) part and lower (or medullary) part.  The upper (pontine) part: presents i. A smooth longitudinal elevation on either side of the median sulcus called the medial eminence. ii. On the medial eminence just above the medullary stria there is a small rounded elevation called the facial colliculus which is caused by the facial nerve fibres as they turn around the abducent nucleus. 24  Neuroanatomy iii. The facial colliculus is bounded laterally by a crescentic depression called-the superior fovea. iv. Pontine vestibular area: lies lateral to the superior fovea. It overlies superior, lateral and upper 1/2 of medial vestibular nuclei.  The lower (medullary) part: on either side of the middle line it presents: i. A small inverted V-shaped depression called the inferior fovea, placed with its apex directed upwards, close to the medullary stria. ii. The inferior fovea divides the medullary part into 3 triangular areas, from medial to lateral: a- Hypoglossal trigone: overlies the hypoglossal nucleus (12th ‫اﻟﻔ‬ nerve). b- Vagal trigone: overlies the dorsal nucleus of the 10th (vagus) nerve. ‫رﻗﺔ‬ c- Vestibular area: overlies the inferior and lower 1/2 of medial vestibular nuclei. The roof of the 4th ventricle: i. In its upper part it consists of: ‫اﻟﺛﺎ‬ - The medial borders of the 2 superior cerebellar peduncles. - The superior medullary velum (thin membrane) stretched between the medial borders of the 2 peduncles. ‫ﻧﯾﺔ‬ - Vermis of cerebellum cover the superior medullary velum. ii. The lower part of the roof is also divisible into 2 areas: - Upper area formed by the vermis of the cerebellum (in the median plane) and the inferior medullary velum on each side of the nodule. - Lower area consists of ependyma and pia mater in contact with each other. This thin area is invaginated into the cavity of the ventricle by the choroids plexus of the 4th ventricle. The lowest part of this area of the roof is pierced by a wide median aperture (foramen of Magendi) which connects the 4th ventricle to the subarachnoid space. 25  Neuroanatomy ‫اﻟﻔ‬ ‫رﻗﺔ‬ Floor of 4th Ventricle ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ Roof of 4th Ventricle 26  Neuroanatomy CEREBELLUM  It is the largest part of the hindbrain.  Site and Relations: The cerebellum lies in the posterior cranial fossa and is related: a- Above: To the tentorium cerebelli; separating the cerebellum from the cerebral hemispheres (occipital lobes). b- In front: To the back of pons and medulla being separated from them by the cavity of the 4th ventricle.  Parts of the cerebellum: It is composed of: ‫اﻟﻔ‬ i. Two large lateral cerebellar hemispheres (Rt. and Lt.): showing many gyri called folia separated by deep fissures (sulci). ‫رﻗﺔ‬ ii. Vermis: is a narrow median part joining the two cerebellar hemispheres. It is divided into superior and inferior vermis.  Shape: The cerebellum has a- Superior surface: showing: - Sloping outstretched upper surfaces of the right and left cerebellar ‫اﻟﺛﺎ‬ hemispheres. - Superior vemis: is a median longitudinal ridge connecting with the superior surfaces of the two cerebellar hemisphere without clear demarcation. ‫ﻧﯾﺔ‬ - Fissura prima (primary fissure): is a wide V-shaped fissure crossing the superior surface of the cerebellum. b- Inferior surface: shows: - Rounded inferior surface of each cerebellar hemisphere on each side separated from each other by a deep median longitudinal groove called the vallecula, containing the inferior vermis. - Flocculus is a small crenated portion, lying on either side, along the anterior border of the inferior surface of the cerebellar hemisphere. It is almost completely isolated from the main part of the cerebellar hemisphere by a fissure called the postero-lateral fissure. The two 27  Neuroanatomy flocculi are connected to the nodule (the most anterior part of the inferior vermis) in the median plane. - Tonsil: is a small circumscribed part of the cerebellar hemisphere. c- The anterior notch: is very wide and is related to the back of the brain stem. d- The posterior notch: is narrower and receives the falx cerebelli. e- Fissure of the cerebellum: 1- Postero-lateral fissure in the inferior surface. 2- Fissura prima (primary fissure) in the superior surface. 3- Horizontal fissure (deep fissure cutting into the cerebellum along the margin which separates its superior from inferior surfaces). ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 28  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪29‬‬  Neuroanatomy CEREBRUM External Features The Inferior Surface of the Brain (Base of the Brain) Interpeduncular Fossa 1. Site: It occupies the central region of the base of the brain. 2. Boundaries: It is a diamond-shaped space bounded by:  The optic chiasma..............................(in front).  The optic tracts….............................. (antero-laterally).  The cerebral peduncles…....................(postero-laterally). ‫اﻟﻔ‬  The upper border of the pons…......... (posteriorly). 3. Contents: ‫رﻗﺔ‬ i. The tuber cinereum, behind the optic chiasma. ii. The infundibulum, connects the pituitary gland to the tuber cinereum. iii. Two mammillary bodies (the corpora mammilaria). iv. The oculomotor nerves which emerge from the posterior part of the fossa just medial to the cerebral peduncles. ‫اﻟﺛﺎ‬ v. The posterior perforated substance. ‫ﻧﯾﺔ‬ 30  Neuroanatomy The Anterior Part of the Base of the Brain (In Front of Interpeduncular Fossa) Shows: 1. Rt. and Lt. optic nerves: Join the antero-lateral aspect of the optic chiasma. 2. Anterior perforated substance:  Rt & Lt lies lateral to the optic chiasma and medial to the uncus of the temporal lobe.  It is pierced by the central branches of the anterior and the middle cerebral arteries which supply the internal capsule, the caudate nucleus and the putamen of the lentiform nucleus (corpus striatum). ‫اﻟﻔ‬ 3. The olfactory bulb and tract:  The olfactory bulb lies in contact with the orbital surface of the frontal ‫رﻗﺔ‬ lobe. Olfactory nerve filaments arise from the upper third of the nasal mucosa pass to enter the olfactory bulb.  The olfactory tract runs backwards from the bulb and ends by dividing into medial and lateral roots (striae).  The area between the two diverging roots sometimes forms a small ‫اﻟﺛﺎ‬ elevation called the olfactory pyramid (or trigone). Base of the Brain ‫ﻧﯾﺔ‬ 31  Neuroanatomy THE CEREBRAL HEMISPHERE 1. Position:  The 2 cerebral hemispheres are separated from each other by a median longitudinal cerebral fissure into which the falx cerebri projects down from the vault of the skull. At the floor of this fissure lies the corpus callosum which connects the 2 cerebral hemispheres together.  From before backwards; the frontal lobe occupies the anterior cranial fossa, the temporal lobe occupies the lateral part of the middle cranial fossa and the occipital lobe occupies the upper part of the posterior cranial fossa above the cerebellum with the tentorium cerebelli ‫اﻟﻔ‬ inbetween. 2. Surfaces: ‫رﻗﺔ‬ Each cerebral hemisphere has 3 surfaces: i. Lateral (supero-lateral) surface: convex. ii. Medial surface: flat. iii. Inferior surface: irregular. 3. Borders: ‫اﻟﺛﺎ‬ i. An arched superior (supero-medial) border: separates the lateral from the medial surfaces. ii. A curved superciliary border: separates the lateral from the inferior ‫ﻧﯾﺔ‬ surfaces in the anterior cranial fossa. iii. The inferior (infero-lateral) borders: separates the lateral from the inferior surfaces in the middle and posterior cranial fossae. A slight depression called the preoccipital notch is seen on this border about 2 inches in front of the occipital pole. 4. Division of the hemisphere into lobes: A- The sulci which divide the hemisphere into lobes: 3 major sulci or fissures: i. The central sulcus: - It runs obliquely downwards and forwards across the lateral surface of the hemisphere. 32  Neuroanatomy - It extends from a point in the middle of the superior border down to a point immediately above the middle of the posterior ramus of lateral fissure. - Its upper end usually cuts the upper border of the hemisphere and turns down a little on the medial surface of the hemisphere. - It separates the motor area (in the frontal lobe) from the sensory area (in the parietal lobe). ii. The lateral fissure: It extends laterally between the temporal and the frontal lobes to reach the lateral surface of the hemisphere where it divides into 3 rami: ‫اﻟﻔ‬ a- The posterior ramus: Is the longest; runs backwards on the lateral surface almost parallel to the inferior border. Its posterior end turns upwards cutting into the parietal lobe. ‫رﻗﺔ‬ b- The anterior horizontal ramus: 2 cm runs forwards in the frontal lobe. c- The anterior ascending ramus: 2 cm runs upwards in the frontal lobe. iii. The parieto-occipital sulcus: ‫اﻟﺛﺎ‬ - It is a deep sulcus found on the medial surface of the hemisphere, it extends for short distance on the lateral surface between the parietal and occipital lobes. B- Lobes of the cerebral hemisphere: ‫ﻧﯾﺔ‬ Each hemisphere is divided into 4 lobes and the insula. They are: i. The frontal lobe: Is bounded by: - The central sulcus…...................... (behind). - The superior border…................... (above). - The superciliary border….............. (below). - Frontal pole….............................. (in front). ii. The parietal lobe: Is a quadrilateral area bounded by: - The central sulcus…......................................... (in front). - The upper border…......................................... (above). - The upper 1/2 of the line joining the parieto-occipital sulcus and the pre-occipital notch…...................................... (behind). 33  Neuroanatomy - The posterior ramus of lateral fissure and an imaginary line joining the posterior ramus with the middle of the line between the parieto-occipital sulcus and the preoccipital notch…………………. (below). iii. The occipital lobe: Forms the posterior extremity of the lateral surface of the hemisphere; it lies behind an imaginary line drawn from the upper end of the parieto-occipital sulcus down to the preoccipital notch. It is bounded posteriorly by the occipital pole. iv. The temporal lobe: Is bounded by: - The inferior border…........................................ (below). - The posterior ramus of the lateral fissure… (above). ‫اﻟﻔ‬ - The lower 1/2 of the line joining the parieto-occipital sulcus and the pre-occipital notch…............................................ (behind). - ‫رﻗﺔ‬ Temporal pole................................................. (in front). v. The insula: Is a submerged part of the cortex which lies in the bottom of the posterior ramus of the lateral fissure. 5. Sulci and gyri of the cerebral cortex:  The surface of the cerebral hemisphere are interrupted by a large ‫اﻟﺛﺎ‬ number of sulci, which separate various gyri. ‫ﻧﯾﺔ‬ Lobes of the Cerebral Hemisphere 34  Neuroanatomy A- The Sulci and Gyri on the Lateral Surface I. Frontal Lobe:  Sulci: 1- The precentral sulcus: Is parallel to the central sulcus and a finger's breadth anterior to it. 2- The superior frontal sulcus: It runs forwards nearly parallel to the upper border. 3- The inferior frontal sulcus: It runs forwards and then downwards.  Gyri: 1- The precentral gyrus: Lies between the central and the precentral sulci. ‫اﻟﻔ‬ 2- The remaining part of the frontal lobe: Is divided into superior, middle and inferior frontal gyri by the superior and inferior frontal sulci. ‫رﻗﺔ‬ 3- The inferior frontal gyrus: Is subdivided, by the anterior horizontal and the anterior ascending rami of the lateral fissure, into 3 parts: a- Orbital part: Below the anterior horizontal ramus. b- Angular or triangular part: Between the 2 rami. c- Opercular part: Between the anterior ascending ramus and the ‫اﻟﺛﺎ‬ precentral sulcus. It covers part of the insula. II. Parietal Lobe:  Sulci: 1- The postcentral sulcus: Runs parallel to the central sulcus and a ‫ﻧﯾﺔ‬ finger's breadth behind it. 2- The intraparietal sulcus: Begins from the postcentral sulcus and runs backwards, nearly parallel to the upper border, towards the occipital lobe.  Gyri: 1- The postcentral gyrus: Lies between the central and the postcentral sulci. 2- The remaining part of the parietal lobe: Is divided by the intraparietal sulcus into: - A smaller superior parietal lobule. - A larger inferior parietal lobule. 35  Neuroanatomy 3- The inferior parietal lobule: contains 2 gyri, they are: a- The supramarginal gyrus: It surrounds the upturned posterior end of the posterior ramus of lateral sulcus. It is the most convex part of the lateral surface of the brain. b- The angular gyrus: It surrounds the upturned posterior end of the superior temporal sulcus. III. Temporal Lobe:  Sulci: 1- The superior temporal sulcus: Begins near the temporal pole and runs backwards nearly parallel to the posterior ramus of lateral fissure, a finger breadth below it. Its posterior end turns up cutting into the parietal ‫اﻟﻔ‬ lobe where it is surrounded by the angular gyrus. 2- The inferior temporal sulcus: Is an interrupted sulcus which runs ‫رﻗﺔ‬ parallel to the superior temporal sulcus, a finger breadth below it.  Gyri: 1- The superior temporal gyrus: Lies between the posterior ramus of lateral fissure and the superior temporal sulcus. 2- The middle temporal gyrus: Lies between the superior and inferior ‫اﻟﺛﺎ‬ temporal sulci. 3- The inferior temporal gyrus: Lies below the inferior temporal sulcus. ‫ﻧﯾﺔ‬ IV. Occipital Lobe:  The main part of the occipital lobe is found on the medial surface. 36  Neuroanatomy B- Sulci and Gyri on the Inferior Surface  The anterior 1/3 of the inferior surface (frontal lobe) rests of the orbit called the orbital surface; it faces down and laterally.  The posterior 2/3 is called the tentorial surface as it rests on the tentorium cerebelli. It represents the inferior surface of the temporal and occipital lobes. The tentorial surface faces down and medially; that is why it is described with the medial surface of the hemisphere. Sulci and Gyri of the Orbital Surface ‫اﻟﻔ‬ 1. The olfactory sulcus: Is a straight deep sulcus near the medial border and parallel to it. The olfactory tract (with the olfactory bulb at its anterior end) lies in this sulcus. ‫رﻗﺔ‬ 2. The straight gyrus (gyrus rectus): Lies medial to the olfactory sulcus. 3. The remaining part of the orbital surface: Is divided into anterior, posterior, medial and lateral orbital gyri by an H-shaped orbital sulci. ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 37  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪38‬‬  Neuroanatomy C- Sulci and Gyri on the Medial and Tentorial Surface  The medial surface of the cerebral hemisphere is marked by the corpus callosum.  The corpus callosum consists of 4 parts, from in front backward: the rostrum, genu, body and splenium.  Sulci: 1- The callosal andHippocampal sulci:  The callosal sulcus: forms an arch over the genu, body and splenium to become continuous with the hippocampal sulcus on the tentorial surface.  The hippocampal sulcus: It is the continuation of the callosal sulcus on the tentorial surface. It is a shallow groove passing forwards from ‫اﻟﻔ‬ the splenium to end between the uncus and parahippocampal gyri. 2- The Cingulate sulcus:  It follows the curvature of the corpus callosum about a finger's ‫رﻗﺔ‬ breadth from the callosal sulcus.  It ends by dividing into 2 branches: a- The marginal sulcus. b- The subparietal sulcus. 3- The calcarine sulcus: Begins below the splenium of the corpus ‫اﻟﺛﺎ‬ callosum and runs backwards and upwards to meet the postcalcarine sulcus at the lower end of the parieto-occipital sulcus. It is a deep sulcus. 4- The postcalcarine sulcus: Begins from the occipital pole and runs forwards and upwards to meet the calcarine sulcus at the lower end of ‫ﻧﯾﺔ‬ the parieto-occipital sulcus. 5- The parieto-occipital sulcus:  Starts from the junction of the calcarine and the postcalcarine sulci, passes upwards to end about 2 inches in front of the occipital pole.  Together with the calcarine and postcalcarine sulci, it forms a Y- shaped sulcus. 6- The collateral sulcus:  It extends from the occipital pole to the temporal pole, on the tentorial surface.  Its middle part is very deep.  A shallow groove called the rhinal sulcus extends forwards and medially from a point near the anterior end of the collateral sulcus to complete the outline of the uncus. 39  Neuroanatomy 7- Occipito-temporal sulcus: It is interrupted sulcus, lies lateral and parallel to the collateral sulcus.  Gyri: 1. The cuneus:  It is the triangular area of the cortex which lies above the postcalcarine sulcus and behind the parieto-occipital sulcus, on the medial surface of the occipital lobe.  It contains parts of the visual cortical area. 2. The lingual gyrus:  It lies between the calcarine and postcalcarine sulci and the posterior part of the collateral sulcus.  Anteriorly it becomes continuous with the para-hippocampal gyrus. It lies ‫اﻟﻔ‬ between the marginal and subparietal sulci. 3. The precuneus:  It is a quadrilateral area on the medial side of the parietal lobe. ‫رﻗﺔ‬  It forms the medial surface of the parietal lobe. 4. The paracentral lobule:  Quadrilateral area surrounds the upper end of the central sulcus which appears on the medial surface.  It contains the motor and sensory areas for the leg, foot and perineum. ‫اﻟﺛﺎ‬ 5. The medial frontal gyrus:  Lies above the cingulated gyrus and in front of the paracentral lobule.  It forms the medial surface of the superior frontal gyrus. 6. The cingulated gyrus: ‫ﻧﯾﺔ‬  Lies between the cingulated and callosal sulci.  Posteriorly this gyrus becomes continuous with the isthmus of the limbic lobe. This isthmus is continuous in front with the parahippocampal gyrus and uncus. 7. The parahippocampal gyrus and uncus:  It lies between the hippocampal and collateral sulci.  Its anterior end is continuous with the uncus.  Its posterior end is connected to the cingulated gyrus by the isthmus of the limbic lobe and also with the lingual gyrus. 8. Medial occipito-temporal gyrus: (The fusiform gyrus):  It lies between the collateral and occipito-temporal sulci. 9. Lateral occipito-temporal gyrus: lies lateral to occipito-temporal sulcus represents the inferior temporal gyrus. 40  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪41‬‬  Neuroanatomy Functional Areas of the Cerebral Hemisphere I. Frontal Lobe 1. The motor area; (or area 4):  It occupies the precentral gyrus and extend over the anterior part of the paracentral lobule on the medial surface.  It is the somato motor area for the movements of the opposite 1/2 of the body, gives origin to the pyramidal tract (cortico-spinal and lateral cortico-bulbar fibres).  The motor area (4) is the pyramidal area for all the body except the eye. ‫اﻟﻔ‬  In the motor area (4) the body is represented in an inverted position. 2. The premotor area; (or area b): ‫رﻗﺔ‬ It lies infront to and parallel to the motor area, it is wide above and narrow below. It is the extrapyramidal area of the body except the eye. 3. The frontal eye field; (or area 8):  It lies in front of the premotor area in the posterior end of the middle frontal gyrus. ‫اﻟﺛﺎ‬  It is the pyramidal motor area for the eyes. It gives origin to the medial corticobulbar fibres (a part of the pyramidal tract). 4. Broca's area; (or the motor speech center; or area 44): ‫ﻧﯾﺔ‬  It lies in the inferior frontal gyrus in the left hemisphere in Rt. handed person and is necessary for speech.  It control the movements of tongue, lips and vocal cords of the larynx. 5. Prefrontal area (frontal association area): It forms the most anterior part of the frontal lobe. It is concerned with emotion, behavior and the place where problems area solved. 42  Neuroanatomy II. The Parietal Lobe 1. The main somato sensory area; (or area 3, 1 and 2):  It lies in the postcentral gyrus.  It contains the higher centres for general somatic sensations for the opposite half of the body. The body is represented in inverted up-side down sensory area. 2. Parietal association area: It occupies the remaining part of the parietal lobe. It is the region in which we can know the meaning of the sensation we feel. 3. Supramarginal and angular gyri (the second speech area of ‫اﻟﻔ‬ Wernicke) (area, 40 and 39) or the sensory speech center. Damage of this area leads to sensory aphasia: inability to understand spoken or written words. ‫رﻗﺔ‬ III. The Paracentral Lobule  It contains the motor and sensory areas for (leg, foot and perineum). ‫اﻟﺛﺎ‬  It is also concerned with voluntary control sphincters of defecation and micturation reflexes. ‫ﻧﯾﺔ‬ IV. The Temporal Lobe 1. The auditory sensory area; (or area 41 and 42):  It is found in the middle of the superior temporal gyrus (Heschl's gyrus).  It receives the auditory radiation from the medial geniculate body. 2. The auditory association area; (or area 22):  Surrounds the Hesch's gyrus and occupies the rest of the superior temporal gyrus.  It is responsible for knowing the meaning of the received sounds. If this area is damaged, the patient will still hear the sounds but can not understand their meaning. 43  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪44‬‬  Neuroanatomy V. The Occipital Lobe 1. The visual sensory area; (or area 17):  Is found mainly on the medial surface of the occipital lobe; it lies on the lips of the postcalcarine sulcus (in the cuneus and lingual gyri).  It receives the visual radiation from the lateral geniculate body. 2. The visual association area; (or area 18 and 19):  Surrounds the visual sensory area in the cuneus and the lingual gyrus, in the occipital lobe.  It is responsible for knowing the meaning of the pictures seen. Damage ‫اﻟﻔ‬ of this area does not cause blindness; the objects can be seen but not understand. ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ 45  Neuroanatomy Internal Structure of the Cerebral Hemisphere Each cerebral hemisphere consists of:  Gray matter (cerebral cortex) on the surface.  White matter forming the core.  Basal ganglia (collections of gray matter embedded in the white matter core near the base of the brain).  Lateral ventricle (cavity). White Matter of the Cerebral Hemisphere ‫اﻟﻔ‬ It consists of all nerve fibers in the cerebrum. There are 3 types of fibers: ‫رﻗﺔ‬ 1. Association Fibres The fibers which connect the different parts of the cerebral cortex in the same hemisphere. ‫اﻟﺛﺎ‬ Types: I. Short Association Fibers: U-shaped hands the beneath the cerebral cortex, and connect the adjacent gyri together. ‫ﻧﯾﺔ‬ II. Long association fibers: Connect the widely separated gyri or connect the anterior and posterior pole together. They are: 1- Superior longitudinal bundle: C-shaped bundle, connects the different parts of the superolateral surface. It begins in the frontal pole, passes backwards above the insula, then curves behind it to enter the temporal lobe where it ends in the temporal pole. 2- Fronto-occipital bundle: It begins in the frontal pole, passes posteriorly medial to superior long-bundle to end in the occipital pole. 46  Neuroanatomy 3- Inferior longitudinal bundle: It lies in the inferior surface extending from the temporal pole anteriorly to the occipital pole posteriorly. 4- Uncinate bundle: Sharply curved bundle across the floor of the stem of the lateral sulcus connects the orbital gyri with the temporal pole. 5- Cingulum: C-shaped bundle, runs within the cingulated gyrus, begins below the rostrum of Corpus callosum (infront) and ends in the uncus (behind). It connects the cingulated gyrus with the hippocampus. 2. Commissural Fibres ‫اﻟﻔ‬ The fibers which cross the midline and connect the corresponding parts of the two cerebral hemispheres. ‫رﻗﺔ‬ There are many commissures but the most important one is corpus callosum. The Corpus Callosum:  It is the largest and chief commissure connecting nearly all areas of the two ‫اﻟﺛﺎ‬ cerebral hemispheres.  It lies at the bottom of the median longitudinal fissure and is placed nearer to the anterior (frontal) than to the posterior (occipital) end of the brain. ‫ﻧﯾﺔ‬  It consists of: rostrum (lower part), genu (anterior part), body (trunk) and splenium (posterior part). 3. Projection Fibres  They constitute all the descending fibers from the cerebral cortex to the lower centres and all the ascending fibers from the thalamus to the cerebral cortex.  They pass through a L. or V-shaped space called internal capsule. 47  Neuroanatomy ‫اﻟﻔ‬ ‫رﻗﺔ‬ Sub. longitudinal ‫اﻟﺛﺎ‬ and fronto-occipital bundle ‫ﻧﯾﺔ‬ 48  Neuroanatomy ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ Transverse Section at the Level of Corpus Callosum 49  Neuroanatomy Basal Ganglia 1. Definition: Subcortical mass of gray matter, deeply placed inside the cerebral hemisphere, near the base of the brain. 2. Components: a- The caudate nucleus. b- The lentiform nucleus. c- The amygdaloid nucleus…........ (a smell centre). d- The claustrum…...................... (unknown function). A- The Caudate Nucleus ‫اﻟﻔ‬  It is arched nucleus consists of 3 parts: (1) a head, ‫رﻗﺔ‬ (2) a body, (3) a tail. B- The Lentiform Nucleus  A biconvex mass consists of 2 parts: ‫اﻟﺛﺎ‬ 1- A larger darker lateral part; the putamen. 2- A smaller pale medial part; the globus pallidus. The 2 parts are separated by a whitish streak. 1- The lateral surface of the nucleus is gently convex and is related to ‫ﻧﯾﺔ‬ the external capsule which separates it from the claustrum. 2- The medial surface of the nucleus is markedly convex or angulated and is related to the internal capsule which separates the lentiform nucleus from the thalamus and the caudate nucleus except inferiorly where the anterior end of the putamen becomes continuous with the head of caudate and the anterior perforated substance. The lentiform nucleus lies between the internal and external capsules. 50  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪51‬‬  Neuroanatomy C- The Amygdaloid Nucleus  It is a small round mass which lies mostly in the uncus, at the anterior end of the tail of the caudate nucleus. D- The Claustrum  Is a thin layer of gray matter between the lentiform nucleus and insula with the external capsule inbetween.  Its function is unknown. ‫اﻟﻔ‬ The Internal Capsule ‫رﻗﺔ‬ Definition and site:  It is a broad projection bundle of white matter, lies medial to the lentiform nucleus and separates it from the thalamus and caudate nucleus (medially). Shape, parts and relations: ‫اﻟﺛﺎ‬  In a horizontal section the internal capsule has a wide V-shaped appearance, having: a- A short anterior limb: Lies between the lentiform nucleus (laterally) ‫ﻧﯾﺔ‬ and the head of caudate nucleus (medially). b- A longer posterior limb: Lies between the lentiform nucleus (laterally) and the thalamus (medially). c- An apex (genu): Is the angle at the junction of the anterior and the posterior limbs. d- A retro-lenticular part: Lies behind the lentiform nucleus. e- A sub-lenticular part: Lies below the lentiform nucleus. 52  Neuroanatomy Fibres passing through the internal capsule:  It contains all the fibres which descend from the cerebral cortex to the midbrain or parts below it (pyramidal and extra-pyramidal tracts) and in addition, most of the fibres which ascend from the thalamus to the cortex (thalamo-cortical fibres or radiations). Arrangement of the fibres in the internal capsule: A- The anterior limb: Is occupied by the fibres from and to the prefrontal area:  Fronto-pontine tract (descending).  Thalamo-cortical fibres; the anterior thalamic radiation (ascending). ‫اﻟﻔ‬ B- The genus: Contains the medial and lateral cortico-bulbar tracts (the pyramidal tract to the head) (motor descending fibres). ‫رﻗﺔ‬ C- The anterior 1/2 of the posterior limb: Contains the cortico-spinal tract (the pyramidal tract, motor to the body below the head). The fibres are arranged from before backwards as follows: neck, upper limb, trunk and lower limb. D- The posterior 1/2 of the posterior limb: Contains ‫اﻟﺛﺎ‬  Somato sensory radiation from the PVNT to the main sensory area (3, 1 and 2) in the postcentral gyrus (sensory ascending fibres).  Fronto-pontine fibres (descending fibres). E- Retro-lentiform part: Contains the optic radiation from the lateral ‫ﻧﯾﺔ‬ geniculate body to the visual sensory area (17) in the occipital lobe. It also contains parieto-occipito-pontine fibres (descending fibres). F- Sub-lentiform part: Contains the auditory radiation from the medial geniculate body to the auditory sensory area (41 and 42) in the temporal lobe. It also contains parieto-temporo-occipito-pontine fibres (descending fibres). Arterial supply of the internal capsule: See arterial supply of the brain (Figure). 53  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪54‬‬  Neuroanatomy Diencephalon Site: Lies between the lower parts of the cerebral hemispheres. Above the midbrain. Surrounds the 3rd ventricle. Subdivisions: 5 parts: a- Thalamus: Is the largest part. It is the secretary of the cerebral cortex; all impulses (except smell) have to synapse in the thalamus before reaching the cerebral cortex. b- Metathalamus: Is formed of the lateral and medial geniculate bodies which are attached to the lower surface of the posterior part of the ‫اﻟﻔ‬ thalamus. c- Subthalamus: Is a motor nucleus lies above the midbrain of extrapyramidal function. ‫رﻗﺔ‬ d- Hypothalamus: Lies in front of the subthalamus; it contains certain autonomic nuclei. e- Epithalamus: Is formed of the 2 habenular nuclei (trigones), the habenular commissure and the pineal body. It is a relay station of smell centres in the ‫اﻟﺛﺎ‬ cerebral hemisphere to the tegmentum of the midbrain. Shape and relations: ‫ﻧﯾﺔ‬  Diencephalons is wedge-shaped inside the cerebral hemisphere.  The lateral surface: is related to the internal capsule separates it from the lentiform nucleus.  The lower surface: is divided into 3 parts: a- The middle; the largest part; is the subthalamus which lies over the midbrain. b- The anterior part: consists of the hypothalamus and is connected to the pituitary gland. c- The posterior part composed of the metathalamus (medial and lateral geniculate bodies). 55  Neuroanatomy Blood Supply of the Brain Comes from 2 systems: I- Vertebrobasilar system: the Rt and Lt vertebral arteries unite at the lower border of the pons to form the basilar artery, which ascends infront of the pons in the middle line, at the upper border of pons it divides into 2 posterior cerebral arteries. II-Internal carotid system: Ends at the base of the brain into 2 terminal branches: A- Anterior cerebral artery (small). B- Middle cerebral artery large. ‫اﻟﻔ‬ The Circulus Arteriosus ‫رﻗﺔ‬ (The Arterial Circle of Willis)  It is an arterial circle lies in the interpeduncular cistern.  The circle of Willis is formed from:  The six large arteries (paired Rt and Lt) are: ‫اﻟﺛﺎ‬ 1- Rt. and Lt. anterior cerebral arteries. 2- Rt. and Lt. internal carotid arteries (ICA). 3- Rt. and Lt. posterior cerebral arteries.  The communicating arteries are: ‫ﻧﯾﺔ‬ i. Posterior communicating arteries (Rt and Lt): connects the ICA with the posterior cerebral artery of its same side. ii. Anterior communicating artery (single): connects the 2 anterior cerebral arteries. Function: It acts as an important arterial link between the internal carotid and the vertebrobasilar system of the arterial supply of the brain. 56  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪57‬‬  Neuroanatomy Arterial Supply of the Different Parts of the Brain 1. Lateral surface of the cerebral hemisphere: a- Middle cerebral artery supplies the main part. b- Anterior cerebral artery supplies a strip about one inch adjoining the upper border from the frontal pole till the parieto-occipital sulcus. c- Posterior cerebral artery supplies:  The occipital lobe.  A narrow strip of the temporal lobe adjoining the lower border. 2. Medial surface of the cerebral hemisphere: a- Anterior cerebral artery supplies the medial surface from the frontal pole almost to the parieto-occipital sulcus. b- Posterior cerebral artery supplies the area behind this sulcus (occipital ‫اﻟﻔ‬ lobe). 3. Tentorial surface of the hemisphere: a- Posterior cerebral artery supplies the main part. ‫رﻗﺔ‬ b- Middle cerebral artery supplies the temporal pole. 4. Orbital surface of the hemisphere: a- Its medial 1/2: by anterior cerebral artery. b- Its lateral 1/2: by middle cerebral artery. 5. Corpus callosum: ‫اﻟﺛﺎ‬ a- Rostrum, genu and body are supplied by anterior cerebral artery. b- Splenium is supplied by posterior cerebral artery. 6. Choroid plexuses of the ventricles: a- Lateral ventricle: ‫ﻧﯾﺔ‬ - Choroid plexus of the central part (body): is supplied by the posterior choroidal artery (branch of posterior cerebral artery). - Choroid plexus of the inferior horn: is supplied by the anterior choroidal artery (branch of internal carotid artery). b- Third ventricle: posterior choroidal artery. c- Fourth ventricle: posterior inferior cerebellar artery (branch of 4th part of vertebral artery). 7. Corpus striatum and the internal capsule: a- Anterior part of corpus striatum and anterior part of the anterior limb of the internal capsule are supplied by central branches of the anterior cerebral artery. 58  ‫‪Neuroanatomy‬‬ ‫اﻟﻔ‬ ‫رﻗﺔ‬ ‫اﻟﺛﺎ‬ ‫ﻧﯾﺔ‬ ‫‪59‬‬  Neuroanatomy b- The rest of corpus striatum, posterior part of anterior limb, the genu and the anterior part of the posterior limb of the internal capsule are supplied by central (striate) branches of the middle cerebral artery. c- The posterior part of the posterior limb, the retrolentiform part and the sublentiform part of the internal capsule are supplied by the anterior choroidal branch of ICA. 8. Thalamus: Is supplied mainly from posterior cerebral artery: a- Posterior cerebral artery: (terminal branch of basilar artery) through its posterior choroidal branch, medial and lateral central branches. b- Posterior communicating artery: branch from internal carotid artery. c- Anterior choroidal artery supplies the lateral geniculate body (LGB). 9. Hypothalamus: Is supplied from all arteries forming the circle of Willis. 10. The cerebellum: ‫اﻟﻔ‬ a- The superior surface: is supplied by superior cerebellar branch of basilar artery. b- The inferior surface: is supplied by: ‫رﻗﺔ‬  Posterior inferior cerebellar branch of vertebral artery (supplies the major posterior part).  Anterior inferior cerebellar branch of basilar artery supplies a small anterior part. 11. The midbrain: Central branches of posterior cerebral artery (terminal branch of basilar artery) helped by superior cerebellar artery and the ‫اﻟﺛﺎ‬ posterior communicating artery. 12. The pons:  Anterior part (basis pontis): is supplied by the pontine branches of the ‫ﻧﯾﺔ‬ basilar artery.  Posterior part (tegemntum): a- In lower pons: by the posterior inferior cerebellar artery. b- In upper pons: by the superior cerebellar artery. 13. The medulla oblongata: It is supplied by branches of the vertebral artery:  Anterolateral surface: is supplied by medullary branches of: a- Anterior spinal artery (medially). b- 4th part of the vertebral artery (laterally).  Posterolateral surface: is supplied by the posterior inferior cerebellar artery.  Gracile and cuneate tracts and nuclei: are supplied by the posterior spinal artery. 60