Pons medulla relationship in human and sheep eyes

pons medulla relationship in human and sheep eyes

The brainstem consists of the medulla oblongata, pons, and midbrain. Human Brain with Cranial Nerves: Cranial nerves are nerves that emerge directly from the in relation to the pons, pituitary gland, spinal cord, pineal gland and cerebellum. They also have motor roles in eye movement, facial expressions, chewing. olfactory - smell; optic – vision; oculomotor- eye movements; trochlear- eye The sheep's kidneys function differently than human kidneys. The pons serves as a communications and coordination center between the two hemispheres of the brain. It connects the medulla to the.

Follow the dorsal columns rostrally until they just begin to disappear beneath the cerebellum; you will find two small mounds. These two swellings are the nucleus gracilis and the nucleus cuneatus. Remember from Lab 1 that nuclei are collections or clusters of cell bodies located within the CNS.

The axons in the dorsal columns synapse on cells located in the nucleus gracilis and nucleus cuneatus. The axons of the cells residing in the two nuclei then exit the nucleus, decussate cross the midline and project to the contralateral thalamus where they synapse on cells in the ventroposterolateral nucleus VPL. The axons of the cells located in VPL project to somatosensory cortex the post-central gyrus.

Before you continue, stop to draw a schematic of the path that somatosensory information takes from spinal cord to postcentral gyrus. Include the nucleus gracilis, nucleus cuneatus, VPL and postcentral gyrus in your drawing. Important features of the ventral surface. In Lab 1, you located a large fiber structure, the cerebral pedunclesjust anterior to the pons. The oculomotor nerves can be seen exiting from them. Recall that the cell bodies that give rise to the axons in the cerebral peduncles are found in motor cortex and that they are called pyramidal cells.

The fibers in the cerebral peduncles continue to the spinal cord. They can be seen on the ventral surface of the medulla, where they are known as the pyramidal tract. Stop, now, and mentally trace the pyramidal tract from cerebral cortex to spinal cord.

The pyramidal motor system, one of two major motor systems in the body is in control of fine, discrete and voluntary motor activities such as writing, typing, or playing the piano. Other motor systems are concerned with gross motor movements, such as, dancing, walking, or waving goodbye. This may be a good time to restate conventions concerning names of tracts in the CNS.

If you keep the rule 'from-to' in mind, you will always be able to tell the site of origin and destination for a given tract. The first name in the title indicates the site of origin of the tract, while the second name indicates the tract's destination. The tract known as the corticospinal tract, according to the rule, originates from neurons whose cell bodies reside in the cortex and project their axons to the spinal cord.

The trapezoid body consists of fibers carrying information from the right ear to left auditory cortex and information from the left ear to right auditory cortex. The trapezoid body is to the auditory system what the optic chiasm is to the visual system. Unlike somatosensory cortex, the auditory and visual cortices receive bilateral input, that is, each projection site receives information from both ears or both eyes, respectively.

If it has not been stripped away, you will find the VIII cranial nerve, the vestibulo-cochlear or auditory nerve at the most lateral extent of the trapezoid body.

On the ventral surface of your sheep brain, locate the very prominent swelling between the trapezoid body and the cerebral peduncles, the pons. Its name is derived from the Latin word, pons, which means 'bridge. Pyramidal tract fibers descending from motor cortex to their destination in the spinal cord are one example of these fibers of passage.

Immediately posterior to the the cerebral hemispheres, you find the cerebellum, a large, complex structure concerned with all levels of motor coordination. The cerebellar surface is characterized by intricate, extremely fine convolutions called folia. The folia are analogous to the gyri of the cerebral hemispheres. Like the cerebral hemispheres, the cerebellum has an inner core of white matter.

In the cerebellum this inner core of white matter is called the arbor vitae. Click on the image below for a larger view. The white-matter core consists of axons projecting to and from the cerebellar hemispheres, the spinal cord, sensory and motor cortices, and other regions of the brain.

The cerebellum sends information to the brain and spinal cord via axons that exit from the cerebellum. In this way, we have information coming into the cerebellum that helps guide cerebellar control of our motor behavior. Without an intact cerebellum, you would find it difficult to walk, maintain a sense of balance, or to perform a complex behavior, such as, hit a tennis ball with a tennis racket, an action that requires hand-eye coordination and timing.

The cerebellum has other important functions; it is important for establishing skill memories and for the occurrence of classically conditioned responses. Nestled between the cerebellum and the cerebral hemispheres are two prominent elevations sitting symmetrically on either side of the midline. You may have to pull your cerebellum gently and caudally to reveal them.

Collectively, these four structures are called the corpora quadrigemina 'bodies of four twins'but it is easier to remember them in their pairwise configurations: This region of the midbrain is also called the tectum 'roof'because the colliculi 'little hills' form the roof, or upper boundary of the Aqueduct of Sylvius.

Look at the figure connected to this link to see the relationship between the colliculi tectum and the aqueduct of sylvius. The figure will clarify the location of the colliculi. If you are unable to see any of the structures named in this paragraph clearly and easily, seek help from the instructor, or lab assistant. On the ventral surface of the brain, at the midline just anterior to the oculomotor nerve, locate the small, but distinct, tissue that looks like the tip of a tongue.

Cells in the mammillary bodies are particularly vulnerable to alcohol. Autopsies have shown significant destruction of the mammillary bodies in chronic alcoholics suffering from a severe memory disorder known as Korsakoff's syndrome. Some neurologists believe that the mammillary bodies are involved in memory processes. While the mammillary bodies form the caudal limit of the hypothalamusits anterior border is marked by the optic chiasm.

The general outline of the hypothalamus from the ventral aspect, thus, assumes a diamond-like configuration. Although the hypothalamus is not a very large structure, it is quite complex.

The hypothalamus contains many different nuclei that are concerned with regulation of temperature, hunger and satiety, sexual behavior, and, perhaps, even sexual preference. The last structures to concern us are evolutionarily older, archi-cortex. On the ventral aspect of the brain, notice the moderately large, relatively smooth masses of cortical tissue just lateral to the cerebral peduncles. Follow the tissue from its most caudal limit near the lateral-most partof the pons to its most anterior limit near the olfactory bulbs.

This mass of tissue, the rhinencephalon or 'smell brain,' is easily visible in the sheep brain, but it is hidden from external view by the temporal lobe in human brain.

One important structure located in the rhinencephalon is the hippocampal gyrusa structure that is exremely important for development and maintenance of memories. It should not surprise you to learn that loss of cells in the hippocampus is one of the characteristics of Alzheimer's patients, individuals who suffer severe memory impairments.

The hippocampus is critical to the functioning of our declarative memory processes, among other behaviors. Declarative memory processes are those processes concerned with our memory for facts, for example, the capital of the state of California, or the name of the structure that is intimately involved in the development of memory hippocampus.

Blood supply and innervation. The hypophysis is supplied by a series of hypophysial arteries from the internal carotid arteries fig. The maintenance and regulation of the activity of the adenohypophysis are dependent on the blood supply by way of the hypophysial portal system. Neurons in the hypothalamus liberate releasing factors into the capillary bed in the infundibulum and that these substances are then carried by the portal vessels to the pars distalis of the gland, which they affect.

The neurohypophysis receives its main nerve supply from the hypothalamus by way of fibers known collectively as the hypothalamohypophysial tract fig. This contains two sets of fibers, arising from distinct hypothalmic nuclei, the supraoptic and paraventricular nuclei.

Cranial nerves The cranial nerves, that is, the nerves attached to the brain see fig. They are numbered and named as follows: Olfactory nerve see fig. Optic nerve see figs. Oculomotor nerve see fig. Trochlear nerve see fig. Trigeminal nerve see figs. Abducent nerve see figs. Facial nerve see figs.

Vestibulocochlear nerve see fig. Vagus nerve see figs. Accessory nerve see figs. Hypoglossal nerve see figs. The efferent fibers of the cranial nerves arise within the brain from groups of nerve cells termed motor nuclei.

The afferent fibers arise outside the brain from groups of nerve cells, generally in a sensory ganglion along the course of the nerve. The central processes of these nerve cells then enter the brain, where they end in groups of nerve cells termed sensory nuclei. The four functional types of fibers found in spinal nerves are present also in some of the cranial nerves: These four types are termed "general.

The special afferent fibers comprise visual, auditory, equilibratory, olfactory, taste, and visceral reflex fibers. The first three are usually classified as somatic, and the last three as visceral. The special efferent fibers which are classified as visceral are those to skeletal muscles either known or thought to be derived from the pharyngeal arches muscles of mastication, facial muscles, muscles of pharynx and larynx, sternomastoid, and trapezius.

The cranial nerves may be grouped as follows: Nerve III also contains parasympathetic fibers to the smooth muscle of the sphincter pupillae and the ciliary muscle general visceral efferent. Trigeminal nerve V contains motor fibers to the muscles of mastication special visceral efferent and sensory fibers from various parts of the head, e. Many of the fibers to the pharynx and larynx are derived from nerve XI internal branch and travel by way of nerve X hence XI is "accessory" to the vagus.

Nerve X also supplies most of the smooth muscle of the respiratory and digestive systems, as well as cardiac muscle. Parasympathetic ganglia associated with cranial nerves see fig.

The ciliary, pterygopalatine, otic, and submandibular ganglia are associated with certain of the cranial nerves. In these ganglia, parasympathetic fibers synapse, whereas sympathetic and other fibers merely pass through. The chief features of the ganglia are summarized in table Because the two layers are indistinguishable except in a few areas, however, it is simpler to consider the dura as one layer, which serves as both endocranium and meninx. The dura is particularly adherent at the base and also at the sutures and foramina, where it becomes continuous with the pericranium.

Four folds or processes are sent internally from the dura: The falx cerebri, median and sickle shaped, occupies the longitudinal fissure between the two cerebral hemispheres. Anchored anteriorly to the crista galli, its superior and inferior borders enclose the superior and inferior sagittal sinuses, respectively. The tentorium cerebelli separates the occipital lobes of the cerebral hemispheres from the cerebellum. Its internal, concave, free border contributes to the tentorial notch.

The external, convex border encloses the transverse sinus where it attaches to the dura over the inside of the occiput. Beyond the "petrous ridge," the tentorium is anchored to the anterior and posterior clinoid processes.

The tentorial notch fig. Space-occupying intracranial lesions may cause herniation of the brain upward or downward through the notch, and distortion of the midbrain may ensue.


Near the apex of the petrous part of the temporal bone, the dura of the posterior cranial fossa bulges anteriorward beneath that of the middle cranial fossa to form a recess, the trigeminal cave, which contains the trigeminal ganglion.

The falx cerebelli, median and sickle shaped, lies below the tentorium and projects between the cerebellar hemispheres. The diaphragma sellae is the small, circular, horizontal roof of the sella turcica.

Meningeal Innervation and Vessels. The dura, like the scalp, is supplied by both cranial chiefly the trigeminal and cervical nerves. The brain itself is normally insensitive, and headaches are commonly either of vascular intracranial or extracranial or dural origin. The meningeal vessels are nutrient to the bones of the skull. These are outside the brain, between the skull and the dura. Small anterior and posterior branches are provided by the internal carotid and vertebral arteries, but the middle meningeal artery is of much greater significance.

The middle meningeal artery is clinically the most important branch of the maxillary artery, because, in head injuries, tearing of this vessel may cause extradural epidural hemorrhage. This may result in brain compression and contralateral paralysis and may necessitate trephining opening the skull.

From its origin in the infratemporal fossa see fig. The middle meningeal artery divides at a variable point on a line connecting the midpoint of the zygomatic arch with the posterior end of the pterion see fig. The meningeal vessels occupy grooves and sometimes canals in the bones. The branches include an anastomosis with the lacrimal artery see fig. These layers bound the subarachnoid space, which is limited externally by a water-tight layer of connective tissue, the arachnoid, and internally by a thinner layer, the pia mater.

The pia mater adheres intimately to the surface of the brain and spinal cord. There is a trabecular structure of connections between the arachnoid and the pia that bridges the subarachnoid space which is otherwise full of circulating C. The arachnoid surrounds the brain loosely and is separable from the dura by a potential space into which subdural hemorrhage may occur.

The arachnoid dips into the longitudinal interhemispheric fissure but not into the sulci. Near the dural venous sinuses, the arachnoid has microscopic projections, termed arachnoid villi, which are believed to be concerned with the absorption of C.

Enlargements of the villi, known as arachnoid granulations, enter some of the sinuses especially the superior sagittal and their associated lateral lacunae and are visible to the naked eye. Both the granulations and the lacunae lie in granular pits on the internal aspect of the calvaria. The pia covers the brain intimately and follows the brain into the gyri of the cerebral hemispheres and the folia of the cerebellum.

pons medulla relationship in human and sheep eyes

The subarachnoid space The subarachnoid space contains the C. The subarachnoid space communicates with the fourth ventricle by means of apertures: At certain areas on the base of the brain, the subarachnoid space is expanded into cisternae fig. The most important of these is the cerebellomedullary cisterna or cisterna magnawhich can be "tapped" by a needle inserted through the posterior atlanto-occipital membrane, a procedure known as cisternal puncture see fig.

Cisternae that include important vessels are found on the front of the pons basilar arterybetween the cerebral peduncles arterial circleand above the cerebellum great cerebral vein. Blood supply of brain Arteries figs. The former supply chiefly the frontal, parietal, and temporal lobes, the latter the temporal and occipital lobes, together with the midbrain and the hindbrain.

On the inferior surface of the brain the four arteries form an anastomosis, the arterial circle circulus arteriosus, of Willis. The tissues that intervene between the blood and the neurons include capillary endothelial cells and their basement membraneswhich form the "blood-brain barrier. The petrous part of the artery first ascends and then curves anteriorward and medially. It is closely related to the cochlea, the middle ear, the auditory tube, and the trigeminal ganglion.

pons medulla relationship in human and sheep eyes

The subsequent directions of the petrous, cavernous, and cerebral parts of the vessel may be numbered from 5 to 1, as follows fig. At the foramen lacerum, the petrous part of the internal carotid artery ascends to a point medial to the lingula of the sphenoid bone.

pons medulla relationship in human and sheep eyes

The artery then enters the cavernous sinus where its surface is covered by an endothelial lining and surounded by the venous blood in the sinus see fig. This is the cavernous part of the artery.

Chapter 43: The brain, cranial nerves and meninges

In the sinus the vessel passes anteriorward along the side of the sella turcica. It next turns dorsally and pierces the dural roof of the sinus between the anterior and middle clinoid processes. The cerebral part of the internal carotid artery turns posteriorward in the subarachnoid space just inferior to the optic nerve. The U-shaped bend, convex on its anterior aspect and formed by parts 2, 3, and 4 is termed the "carotid siphon" fig.

The artery finally ascends and, at the medial end of the lateral sulcus, divides into the anterior and middle cerebral arteries.

The internal carotid artery and its branches, including the cerebral arteries, are surrounded and supplied by a sympathetic plexus of nerves, derived from the superior cervical ganglion. Branches of the internal carotid artery fig The internal carotid artery gives no named branches in the neck.

Within the cranial cavity, it supplies the hypophysis, the orbit, and much of the brain. The carotid siphon gives off three branches: The ophthalmic artery is described with the orbit see fig. The posterior communicating artery connects the internal carotid artery with the posterior cerebral artery and thereby forms a part of the arterial circle. The anterior choroid artery passes backward along the optic tract and enters the choroid fissure.

It gives numerous small branches to the interior of the brain, including the choroid plexus of the lateral ventricle. The anterior choroid artery is frequently the site of thrombosis. The terminal branches of the internal carotid artery are the anterior and middle cerebral arteries. The anterior cerebral artery passes medially just superior to the optic chiasma and enters the longitudinal interhemispheric fissure of the brain.

Here it is connected with its fellow of the opposite side by the anterior communicating artery which is frequently double and which sometimes gives off a median anterior cerebral artery. It then runs successively in a rostral, then dorsal, and finally caudal direction.

pons medulla relationship in human and sheep eyes

It usually lies on the corpus callosum, and ends by turning dorsally on the medial surface of the hemisphere just before reaching the parieto-occipital sulcus. The middle cerebral artery, the larger terminal branch of the internal carotid artery, is frequently regarded as the continuation of that vessel.

It passes laterally in the lateral fissure and gives rise to numerous branches on the surface of the insula. Small, central branches lenticulostriate arteries enter the anterior perforated substance, supplying deeper structures of the hemispheres and are liable to occlusion lacunar strokes or rupture Charcot's "artery of cerebral hemorrhage". It supplies the motor and premotor areas and the sensory and auditory areas. It also supplies the language areas in the dominant hemisphere.

Occlusion of the middle cerebral artery causes a contralateral paralysis hemiplegia and a sensory defect. The paralysis is least marked in the lower limb territory of anterior cerebral artery.

When the dominant usually left side is involved, there are also disturbances of language aphasia. The general distribution of the cerebral arteries is shown in figure B and C. The chief branches of the internal carotid artery are summarized in table The branches to the brain stem are functionally end-arteries so occlusion usually results in a stroke. The vertebral artery, a branch of the subclavian artery, may be considered in four parts: The suboccipital part of the vertebral artery perforates the dura and arachnoid and passes through the foramen magnum see fig.

The intracranial part of each vertebral artery procedes rostrally and medially to reach a position anterior to the medulla. At approximately the caudal border of the pons, the two vertebral arteries unite to form the basilar artery see fig. The vertebral artery, which gives off muscular and spinal branches in the neck, supplies chiefly the posterior part of the brain, both directly and, of greater importance, by way of the basilar artery.

The anterior spinal artery runs caudally just anterior to the medulla and unites with the vessel of the opposite side to form a median trunk. This contributes to the supply of the ventral side of the medulla and spinal cord. The posterior inferior cerebellar artery winds dorsally around the olive and gives branches to the lateral medulla, the choroid plexus of the fourth ventricle, and the cerebellum.

The posterior spinal artery is usually a branch of the posterior inferior cerebellar artery, but it may come directly from the vertebral artery. The basilar artery is formed by the union of the right and left vertebral arteries.

It begins at approximately the caudal border of the pons and ends near the rostral border by dividing into the two posterior cerebral arteries fig. It passes through the pontine cistern and frequently lies in a longitudinal groove on the ventral pons. Branches of the basilar artery are distributed to the pons, cerebellum, internal ear, midbrain, and cerebral hemispheres. The paired anterior inferior cerebellar arteries pass dorsally on the inferior surface of the cerebellum and supply the cerebellum and pons.

The paired labyrinthine internal auditory arteries may arise from either the basilar or the anterior inferior cerebellar artery, more commonly the latter.

Each enters the corresponding internal acoustic meatus and is distributed to the internal ear. The paired superior cerebellar arteries pass laterally just inferior to the oculomotor and trochlear nerves and are distributed to the cerebellum.

The two posterior cerebral arteries are the terminal branches of the basilar artery. They supply much of the medial temporal and most of the occipital lobes see fig.

Each is connected with the corresponding internal carotid artery by a posterior communicating artery; occasionally the posterior cerebral arises as a branch of the internal carotid artery an arrangement referred to as trifurcation of the internal carotid artery or persistnat fetal circulation. The posterior cerebral artery runs posteriorward, superior and parallel to the superior cerebellar artery, from which it is separated by the oculomotor and trochlear nerves.

Among the branches are the posterior choroidal branches, which supply the choroid plexuses of the third and lateral ventricles. The arterial system in the brain, therefore, is not strictly terminal. However, in the event of occlusion, these microscopic anastomoses are not capable of providing an alternate circulation for the ischemic brain tissue. The arterial circle, described by Thomas Willis inis an important polygonal anastomosis between the four arteries that supply the brain: It is formed by the posterior cerebral, posterior communicating, internal carotid, anterior cerebral, and anterior communicating arteries.

The circle forms an important means of collateral circulation in the event of obstruction of a major vessel. Variations in the size of the vessels that constitute the circulus are very common.

The blood vessels of the brain may be demonstrated radiographically by cerebral angiography figs. Venous drainage Veins of Brain see fig. The superior cerebral veins drain into the superior sagittal sinus. The superficial middle cerebral vein follows the lateral fissure, sends superior and inferior anastomotic veins to the superior sagittal and transverse sinuses, respectively, and ends in the cavernous sinus.

The inferior cerebral veins drain the inferior aspect of the hemispheres and join nearby sinuses. The basal vein is formed by the union of several veins, including those that accompany the anterior and middle cerebral arteries. It winds around the cerebral peduncle and ends in the great cerebral vein.

The single great cerebral vein see fig. It receives, directly or indirectly, a number of vessels from the interior of the cerebral hemispheres and also the basal veins.

It ends in the straight sinus. Venous Sinuses of Dura Mater fig. The superior sagittal sinus see fig. From its commencement near the crista galli, the sinus runs posteriorward and, near the internal occipital protuberance, enters in a variable manner one or both transverse sinuses. It receives the superior cerebral veins and communicates with lateral lacunae that contain arachnoid granulations. The confluence of the sinuses or torcular is the junction of the superior sagittal, straight, and right and left transverse sinuses fig.

It is situated near the internal occipital protuberance. The pattern of the constituent sinuses varies, and dominance of one side in drainage e. The inferior sagittal sinus lies in the concave, free border of the falx cerebri the blade of the sickle and ends in the straight sinus, which also receives the great cerebral vein.

The straight sinus runs posteriorward between the falx and tentorium, and joins the confluence. The transverse sinuses begin in the confluence, and each curves laterally in the convex border of the tentorium, where it attaches to the skull. At the petrous part of the temporal bone, the transverse becomes the sigmoid sinus see fig.

Smaller channels petrosal sinuses connect the cavernous sinus with the transverse sinus and jugular vein. The cavernous sinus comprises one or more venous channels sometimes a plexus. In addition to the venous channels, the dural compartment contains outside the endothelium the internal carotid artery, sympathetic plexus, abducent nerve, and, further laterally, the oculomotor, trochlear, and ophthalmic nerves fig.

The cavernous sinus extends posterorly from the superior orbital fissure to the apex of the petrous part of the temporal bone. It receives several veins superior ophthalmic, superficial middle cerebral, and sphenoparietal sinus and communicates by the petrosal sinuses with the transverse sinus and internal jugular vein, as well as with the opposite cavernous sinus. The facial vein via the superior ophthalmic vein communicates with the cavernous sinus and hence allows infection around the nose and upper lip "danger area" to spread to intracranial structures.

Lateral lacunae see fig. The lacunae receive 1 emissary veins, 2 diploic veins, 3 meningeal veins, and 4 occasionally some cerebral veins. It should be noted that the emissary veins, which pass through foramina in the skull, connect the deeper vessels with the veins of the scalp and hence also allow infection to spread from the scalp to intracranial structures.

Differences Between Human and Sheep Brains

Additional reading Blinkov, S. Haigh, Basic Books, New York, Aspects macroscopiques de l'encephale. Editions Offidoc, Paris, Beautiful photographs of the brain. Saunders Company, Philadelphia, A good introduction to the nervous system. Excellent photographs of superb dissections. Thomas, Springfield, Illinois, Questions Review the major divisions of the brain.

These fibers actually connect one cerebellar hemisphere with the contralateral half of the pons. They are a part of the corticopontocerebellar pathway.

Intermediate fibers are probably accessory to the motor root R. Each peduncle consists of crus cerebri, substantia nigra, and tegmentum see fig. The lateral fissure Sylvius, seventeenth century is evident see fig. The central sulcus Rolando, nineteenth century is not as easily identified.

It begins on the medial surface of the hemisphere, where it can be detected by following the cingulate sulcus backward and upward and then finding the next groove anteriorly see fig. Brodmann in on a somewhat arbitrary histological basis.

Areas 1,2,3 sensory areas4,6,8 motor areas17, 18, 19 visual areas22 receptive language area of Wernicke41, 42 auditory projection area of Heschland 44 motor language area of Broca are functionally the most important see fig.

It should be noted that the olfactory bulbs and tracts are parts of the cerebral hemispheres and are not cranial nerves. The lateral ventricles communicate with the third ventricle by the interventricular foramina Monro, The fourth ventricle communicates with the subarachnoid space by median Magendie, and lateral Luschka, apertures. The end of each recess opens as the lateral aperture.

Differences Between Human and Sheep Brains | Animals - az-links.info

It permits passage of the midbrain see fig. Middle meningeal hemorrhage is usually caused by an injury potentially trivial usually although not always associated with fracture of the temporal bone. The most frequent cause is a blockage of the normal circulation of C. The term carotid Gk, karos, heavy sleep refers to the stupor that may result from compression of the carotid arteries.

Under good conditions, however, one internal carotid artery can be occluded without any residual symptoms. Vascular disease of this dorsolateral part ofthe medulla may result in widespread signs and symptoms Wallenberg's syndrome, Beautiful illustrations of normal and abnormal cerebral circulation can be found in M.

Little, Brown, Boston, In certain mammals e. For variations see H. The confluence was formerly called the torcular L. Detailed accounts are available, and these include H. Figure legends Figure The brain stem, anterior aspect, showing the cranial nerves. Figure Posterior aspect of the brain stem and the rostral part of the spinal cord after removal of the cerebellum, which displays the floor of the fourth ventricle.

The vertebral artery is visible on each side, together with certain cranial and spinal nerves. Figure The cerebellum, inferior aspect. In the inset, the brain stem has been removed by sectioning of the cerebellar peduncles. Figure A, The lobes of the brain, left lateral aspect.

B and C, The territories supplied by the cerebral arteries, lateral and medial aspects of the left cerebral hemisphere.

A, B, and C: In B, T represents the cut surface of the thalamus. The chief speech area of Broca is mainly area 44 and is usually on the left side of the brain. A receptive speech area of Wernicke is found mainly in area Figure The interpeduncular fossa and surroundings, antero-inferior aspect. The left half of the hypophysis has been removed. From a photograph by David Bassett, M. Figure Craniocerebral topography.

The middle meningeal artery proceeds from the middle of the zygomatic arch upward dotted line about 4 to 5 cm to the pterion P. The external acoustic meatus is shown in black. B, bregma; I, inion; L, lambda; XY, orbitomeatal plane. After von Lanz and Wachsmuth.

Figure Cast of the ventricles of the brain, left lateral aspect. In this brain, the right occipital horn is considerably longer than the left. The key drawing indicates related solid structures in parentheses.

Courtesy of David Tompsett, Ph. Figure Computerized axial tomograms of the head, showing the ventricular system as seen in horizontal sections. A and B are from the same subject. A shows the body and posterior horn of each lateral ventricle.

The median white line indicates the falx cerebri. The following structures are visible in B, from anterior to posterior: In C, the lesser wings of the sphenoid bone and the petrous portions of the temporal bones delimit the cranial fossae.

The dorsum sellae appears as a white band between the shadows of the temporal lobes. Between the cerebellar hemispheres, the fourth ventricle is visible as a dark, inverted U. Courtesy of Giovanni Di Chiro, M. In D, the approximate planes of section are indicated. XY, the orbitomeatal plane. Figure The course of the cerebrospinal fluid C. Arrows lead from the choroid plexuses of the lateral and third ventricles toward the aqueduct. The fluid thereby formed is joined by that produced in the fourth ventricle and passes through the median aperture to the cerebellomedullary cistern of the subarachnoid space.

The fluid then extends 1 dorsally around the brain and 2 caudally around the spinal cord. The inset a coronal section at the sagittal suture shows the drainage of the C. Various adjacent vessels are also included. A, cerebral artery; C, cerebral vein; D, diploic vein; E, emissary vein; M, meningeal vein; 3 and 4, third and fourth ventricles.

The lowermost part of the figure shows the caudal end of the spinal cord. Figure The hypophysis cerebri. A and B illustrate the terminology. C shows the blood supply. Arteries in the hypophysial stalk break up into capillary loops, which drain into hypophysial portal vessels. These, on reaching the pars distalis, drain into sinusoids, which enter the venous sinuses around the gland.

D illustrates schematically the hypothalamohypophysial tract. Figure The meninges and associated vessels.