Brain
The brain, with covers surrounding it is in a cavity of a cerebral skull. The top ventral surface of a brain under the form corresponds to an internal concave surface of a calvaria. The bottom surface - the brain basis, has the difficult relief corresponding to cranial fossas of the internal basis of a skull.
The mass of a brain of the adult person fluctuates from 1100 till 2000 gm an extent from 20 till 60 years mass and volume remain maximum and constant for each individual.
At survey of a preparation of a brain its three largest components are well appreciable. These are didymous hemicerebrums, a cerebellum and a cerebral trunk.
Hemicerebrums
Hemicerebrums at the adult person it is the strongest developed, the largest and is functional the most important part CNS. Departments of hemispheres cover with themselves all other parts of a brain. The right and left hemispheres are separated from each other by a deep longitudinal cleft of the big brain, reaching big soldering of a brain, or a corpus collosum.
In back departments the longitudinal cleft runs into a cross-section cleft of the big brain which separates hemispheres from a cerebellum.
On ventral, medial and bottom surfaces of hemispheres of a brain deep and fine sulcuses are located. Deep sulcuses part each of hemispheres on shares of the big brain. Fine sulcuses separate from each other gyruses of the big brain. The bottom surface, or the basis, a brain is formed by ventral surfaces of hemicerebrums, a cerebellum and ventral departments of a cerebral trunk.
The grey hillock which bottom departments are extended in the form of tube gradually narrowed to a bottom - funnels adjoins to a back surface of a visual decussation. On the bottom extremity of a funnel roundish formation - a pituitary body settles down. The grey hillock is adjoined by two white spherical eminences - mastoid bodies.
Behind from visual tracts two longitudinal white platens - brain legs between which there is an excavation - between-leg fossa are visible. Its bottom is formed by the back made a hole substance. The wide cross-section platen - the bridge further away settles down. Lateral departments of the bridge proceed in a cerebellum, forming its average cerebellar legs.
Departments of an oblong brain are more caudal the bridge are presented by medially located pyramids parted from each other by a forward middle cleft, and lateralis - olivas.
Survey of a medial surface of the hemicerebrums, some details of a cerebral trunk and cerebellum to become possible at carrying out of a middle cut on a longitudinal cleft of the big brain.
The extensive medial surface of hemicerebrums hangs over much smaller in the sizes a cerebellum and a cerebral trunk. On a medial surface of hemispheres, as well as on other surfaces, sulcuses which separate from each other gyruses are visible.
Sites of frontal, parietal and occipital shares are separated from a corpus collosum by the sulcus with the same name.
The middle part of a corpus collosum wears the trunk name. Its forward departments are bent to a bottom, forming a corpus collosum knee. Even more from top to bottom the corpus collosum thins and passes in a corpus collosum bill. Back departments of a corpus collosum in its average part the thin white plate named a body of a crest separates. Gradually separating from a corpus collosum and forming an arched flexure forward and from top to bottom, the body proceeds in a column of a crest which comes to an end with a mastoid body, behind - in crest legs. Between crest columns cross-section there passes the fascicle of nervous fibers appreciable on a section in the form of a white oval, is a forward soldering of a brain. As well as cross-section going fibers of a corpus collosum, they bind with each other hemicerebrums.
Crest columns surround a thin plate of cerebral substance - a transparent septum.
All listed formations of a brain concern a final brain.
The structures located more low, except for a cerebellum, concern a cerebral trunk (intermediate, average, back departments of a brain and an oblong brain).
The most forward departments of a cerebral trunk are formed by visual hillocks which are located to a bottom from a crest and corpus collosum body and behind crest columns.
On a brain midsection the medial surface of a back thalamus (a visual hillock) is visible only.
In posterosuperior departments of visual hillocks there is a pinus which anteroinferior departments grow together with a thin cross-section going band (back soldering).
Visual hillocks and the formations close to it described above, concern an intermediate brain.
The back surface of a visual hillock is adjoined by the formations concerning a mesencephalon.
Oblong brain
Oblong brain is immediate continuation of a spinal cord. The border between oblong and a spinal cord corresponds to level of edges of the big occipital aperture. The top border of an oblong brain on a ventral surface passes on back edge of the bridge.
Forward departments of an oblong brain in comparison with back thicken also this department of a brain gets the form of the truncated cone a little. Sulcuses of an oblong brain are continuation of sulcuses of a spinal cord and wear the same names. On both parties from a forward median cleft on a ventral surface of an oblong brain convex pyramids gradually narrowed to a bottom are located.
Lateral pyramids from both parties are oval eminences - olivas.
In the bottom part on a dorsal surface of an oblong brain the back middle sulcus lasts, on sides from which comes to an end with thickenings thin and sphenoidal fascicles of back funicles of a spinal cord. In these thickenings kernels of these fascicles from which the fibers forming a medial loop depart settle down. The medial loop at level of an oblong brain forms a decussation. Fascicles of this reticle are located more dorsally pyramids, in between-olivnom a layer. Here there pass fibers of a medial fascicle. Laterally olivas leave a back lateralis sulcus thin roots glossopharyngeal, wandering and the eleventh cranial nerves which kernels lay in dorsolateral departments of an oblong brain.
The grey substance of an oblong brain is presented in ventral departments by clumps of neurones which form bottom oviles cores. More dorsally pyramids along all oblong brain the reticular formation which is presented by an interlacing of nervous fibers and nervous cells laying between them settles down.
At level of an oblong brain there are such vital centres, as respiratory and circulations.
Bridge
Bridge on the basis of a cerebral trunk looks like cross-section located white platen which looks like cross-section located white platen which in caudal department borders on pyramids and olivas of an oblong brain, and in cranial - with brain legs.
Bridge continuation in a lateralis direction forms an average leg of a cerebellum.
The dorsal surface of the bridge is covered by a cerebellum and outside is not visible.
On a bridge cross-section in the central departments it is possible to see a thick fascicle of the fibers going cross-section concerning the spending way of an acoustic analyzer and forming a trapezoid body.
In the bottom departments of the bridge the clumps of grey substance named kernels actually of the bridge which act in a role of intermediaries in realisation of communications of a cortex of hemicerebrums with cerebellum hemispheres are appreciable.
In a dorsal part of the bridge fibers of the medial loop going from an oblong brain lay. Over which the reticular formation of the bridge is located. Laterally there pass fibers of an acoustical loop.
Cerebellum
Cerebellum makes larger, than the bridge, a part of a metencephal which fills with itself the most part of a back cranial fossa.
In a cerebellum distinguish the top and bottom surfaces, borders between which are forward and back edges.
The top surface of a cerebellum on the whole brain is covered by occipital shares of hemicerebrums and separated from them by a deep cross-section cleft of the big brain. In a cerebellum distinguish an unpaired middle part - a worm, two hemispheres. The worm is dismembered by cross-section sulcuses on fine gyruses which give it some similarity to an Annelida. Both surfaces of hemispheres and a worm are cut up by set of cross-section in parallel going fine grooves between which there are long and narrow gyruses of a cerebellum. Group of the gyruses separated by deeper sulcuses, form cerebellum lobes. Hemispheres of a cerebellum and a worm consist of the white substance located inside, and a thin layer of grey substance of a cortex of the cerebellum bordering white substance on periphery. The cerebellum cortex is presented by three layers of nervous cells. On a sagittal cut white substance of a cerebellum it is presented by three layers of nervous cells and looks like a branchy tree.
In a depth of white substance separate didymous clumps of nervous cells which form gear, probko-visible, ball-shaped kernels of a cerebellum and a tent kernel are found out.
In a cerebral trunk the following after the bridge department, small, but functionally important, is to the rhombencephalon reneck, consisting of the top legs of a cerebellum, the top cerebral sail and a triangular loop in which there pass fibers of a lateralis (acoustical) loop.
Mesencephalon
Mesencephalon consists of dorsal department of a roof of a mesencephalon and ventral - legs of a brain which are differentiated by a cavity - a brain waterpipe. The bottom border of a mesencephalon on its ventral surface is the bridge first line, the top visual tract and level of mastoid bodies. On a preparation of a brain four-holmija, or a mesencephalon roof, it is possible to see a plate only after excision of hemicerebrums.
On the basis of a brain the second part of a mesencephalon in the form of two thick white dispersing fascicles going to a tissue of hemicerebrums is well visible, are legs of a brain. An excavation between the right and left legs of a brain are called between-nozhkovoj a fossa, it leaves roots of third cranial nerves. Ahead about third cranial nerve kernels the kernel of a medial longitudinal fascicle lays. The largest kernel of a mesencephalon is the red kernel - one of the central coordination kernels of extrapyramidal system. Near to a waterpipe the reticular form of a mesencephalon lays.
On a cross-section the cranial substance which divides a brain leg into two departments is clearly visible: dorsal - a tyre cover of a mesencephalon and ventral - the basis of a leg of a brain. In a mesencephalon tyre cover kernels of a mesencephalon settle down and there pass ascending spending ways. Ventral departments of legs of a brain entirely consist of white substance, here there pass descending spending ways.
Functional value of a mesencephalon consists in that. That the subcortical centres of hearing and sight here are located; kernels of the head nerves providing an innervation cross-section-striatal and unstriated muscles of an eyeball: the kernels concerning extrapyramidal system, providing reduction of muscles of a body during automatic movements. Through a mesencephalon descending (impellent) and ascending (sensitive) spending ways follow. The mesencephalon area is also the location of the vegetative centres (the central grey substance) and a reticular formation.
Intermediate brain
Intermediate brain is presented by following departments
- Area of visual hillocks (thalamic area) which is located in its dorsal sites;
- 1. A hypothalamus (under-talamicheskaja area), making ventral departments of an intermediate brain;
- 1. III ventricle which is looking like a longitudinal (sagittal) cleft between right both left visual by the hillocks and bridged through interventricular foramen with lateral ventricles.
In turn the thalamic area is sectioned into a thalamus (a visual hillock), a metathalamus (medealis and lateralis geniculate bodies) and an epithalamus (a pinus, leads, solderings of leads and ephithalamic soldering).
Visual hillocks consist of grey substance in which distinguish separate clumps of nervous cells (a kernel of a visual hillock), the parted thin layers of white substance. In connection with that that the most part of sensitive spending ways here is switched, the visual hillock actually is the subcortical sensitive centre, and its pillow - the subcortical visual centre.
The pinus joins a medial surface of visual hillocks by means of leads - an epiphysis.
The hypothalamus makes ventral department of an intermediate brain and participates in formation of a bottom of III ventricle. A hypothalamus concern a grey hillock with a funnel and a pituitary body - iron internal secretion, a visual tract, a visual decussation, mastoid bodies.
The hypothalamus represents continuation of legs of a brain in an intermediate brain. The grey substance under-thalamic areas settles down in the form of the kernels, capable to develop a neurosecretion and to transport it in a pituitary body, regulating endocrine work of the last.
Thus, the grey substance of an intermediate brain is made by the kernels concerning the subcortical centres of all kinds of sensitivity. In the field of an intermediate brain the reticular formation, the centres of extrapyramidal system, the vegetative centres regulating all kinds of a metabolism and nejro-confidential kernels are located.
The white substance of an intermediate brain is presented by spending ways of the ascending and descending directions providing a two-way communication of a cortex of a brain with subcortical formations and the centres of a spinal cord. Besides it, to an intermediate brain two glands of internal secretion - a pituitary body and a pinus which is taking part together with corresponding kernels of a hypothalamus and an epithalamus and formation hipo thalamic pituitary and epithalamic epiphyseal systems concern.
Final Brain
Final Brain consists of two hemicerebrums, each of which is presented by a raincoat, an olfactory brain and basal kernels. A cavity of a final brain are the lateral ventricles which are in each of hemispheres. Hemicerebrums are separated from each other by a longitudinal cleft of the big brain and bridged by means of a corpus collosum, forward and back solderings and a commissure of the fornix. The corpus collosum consists of cross-section fibers which in a lateralis direction proceed in hemispheres, forming radiance of a corpus collosum, bridging with each other sites of frontal and occipital shares of hemispheres, are arcually bent and lobbies - frontal and back - occipital forcepses form. To back and average parts of a corpus collosum from below adjacent the crest of the brain consisting of two arcually bent bands, adherent in an average part with the help forward brain solderings.
Cortex of Big Brain
Cortex of Big Brain is formed by white and grey substance. In a cortex allocate 6 layers of nervous cells, its various departments have a different thickness (from 1,5 to 5,0 mm, on the average 2-3 mm). Each of hemispheres has three surfaces: the most convex high-lateralis, flat, turned to an opposite hemisphere medial and having the difficult relief corresponding to the internal basis of a skull, - bottom, a surface of a hemisphere or the brain basis. The most acting sites of hemispheres have received the name of frontal, occipital, temporal poles. The surface of hemispheres is cut up by deep clefts, sulcuses. Complicate a relief the sites located between them - gyruses. Depth, extent of sulcuses, their form and a direction are very variable.
Clefts and sulcuses section hemispheres into frontal, parietal, temporal, occipital and insular shares. Last is not visible at the review of surfaces of hemispheres since the islet is at the bottom of a lateralis sulcus and is covered by sites of other shares.
On high lateralis surface of a hemisphere attracts attention a lateralis sulcus which is border between frontal, parietal and temporal shares and goes from the bottom surface of hemispheres back and upwards.
Other large sulcus - the central sulcus. Begins approximately from the middle of an upper edge of hemispheres and follows downwards and a little forward, but does not reach a lateralis sulcus. The central sulcus separates a frontal lobe from the parietal. The expressed border between parietal and occipital shares on a dorsolateral surface of hemispheres is absent.
Frontal lobe
Ahead from the central sulcus almost in parallel it the precentral sulcus which gives rise to two parallel sulcuses going to a frontal pole lasts. The named sulcuses divide a brain surface into a precentral gyrus laying before the central sulcus and horizontally going top, average and bottom frontal gyruses.
Parietal share
Behind from the central sulcus and almost in parallel it there passes a postcentral sulcus from which towards an occipital share the longitudinal intraparietal sulcus is referred. These two sulcuses divide a parietal share into a postcentral gyrus, and also on the top and bottom parietal lobes.
Temporal share
High a lateralis surface of a temporal share are presented by two sulcuses, going to in parallel lateralis sulcus which divide a brain surface into the top, average and bottom gyruses.
The grey substance of hemicerebrums is presented by a cortex and basal kernels of a final brain. Basal kernels concern the striatal body consisting from caudal and lentil-shaped of kernels; a fencing and an amygdaloid nucleus. Layers of white substance between them form external and internal capsules, and last represents the thick layer of white substance consisting of spending ways of a brain. In an internal capsule also allocate forward both back legs and a knee.
The striopallidal system
The striopallidal system represents the basic part of the impellent centres concerning extrapyramidal system. It is the centre controlling automatic movements and regulating a tonus of muscles. Besides it, the striatal body carries out function of the higher centre regulating processes of a thermoregulation and an exchange of carbohydrates. This centre occupies predominating position in relation to the vegetative centres similar to it which are located in subthalamic area.
The cortex of hemispheres of a brain is presented by the grey substance located on their periphery.
White Substance
The White Substance of HEMICEREBRUMS forms the white semioval centre which consists of huge number of nervous fibers. All nervous fibers are presented by three systems of spending ways of a final brain:
- The associative;
- The comissural;
- The projective.
Ascending (sensitive) proektsiono-spending ways in a place of the termination are sectioned on conscious and reflex.
Functioning and interrelation associative, comissural, and also ascending and descending ways provides existence of the difficult reflex arches allowing an organism to adapt to constantly varying conditions internal and an environment.
Lateral ventricles
Lateral ventricles are in a depth of white substance of hemicerebrums. The cavity of ventricles has the bizarre form in connection with that. That departments of each of them settle down in all shares of a hemisphere (except for an islet). Average - central - a ventricle part lies down from top to bottom from a corpus collosum, in a parietal share of a hemisphere. From the central part in all shares of a brain the processes of cavities named horns disperse: forward (a frontal horn) - in a frontal lobe, bottom (a temporal horn) - in temporal, back - (an occipital horn) - in an occipital share. The central part with the help between-zheludkovogo an aperture is bridged to III ventricle.
Brain cover
Brain cover
The brain, as well as spinal, is surrounded by three soedinitelno-woven leaves, or the covers which are continuation of covers of a spinal cord, each of which is separated from next by intercapsulate space.
Firm cover of a brain
Differs on a structure from a similar cover of a spinal cord. It is simultaneously a periosteum on an internal surface of bones of a skull to which it is bound unsteadily. In the field of the basis of a skull the cover gives a number of the processes getting into clefts and apertures of bones of a skull, than the big durability of an attachment here a firm cover of a brain speaks. Moreover, in places of an exit from a cavity of cranial nerves the firm cover of a brain on some extent continues to surround a nerve, forming its vagina and getting together with a nerve through an aperture outside.
On an internal surface of a firm cover distinguish some processes which get into a longitudinal cleft of the big brain and separate from each other its hemispheres. The back department of a sickle grows together with other process of a cover - with the drift of a cerebellum separating occipital shares of hemispheres from a cerebellum.
Falx cerebri continuation is the falcula getting from below between hemispheres of a cerebellum. One more process surrounds from above a Turkish saddle, forming its diaphragm and protecting a pituitary body from pressure of all overlying mass of a brain.
In certain sites of a firm cover of a brain there are splittings, inlay from within an endothelium, are sine of a firm cover of a brain on which venous blood flows off. Feature of sine is durability of walls that explains impossibility of their fall. Besides, sine are bridged to external veins of a head through emissary veins.
The web cover of a brain settles down inwards from firm cerebral and is separated from it by a subdural space.
The subarachnoid space of a brain in the field of the big occipital aperture is informed with subarachnoid space of a spinal cord.
In certain places, near to sine of a firm cover of a brain, the web cover forms original excrescences - granulation of a web cover. These excrescences press in sine of a firm cover. On an internal surface of bones of a skull in the location of granulations depressions and pits become perceptible.
The opinion on participation of granulation of a web cover in maintenance of outflow of a spinal liquid in a venous bed is conventional.
The soft (vascular) cover is most internal of brain covers. It consists of the connecting tissue forming two layers (internal and external) between which blood vessels lie down. The cover is adherent with external a surface of a brain and deeply gets into all its clefts and sulcuses. Blood vessels, leaving a vascular cover, are referred to a brain tissue, providing its food. In certain places the vascular cover gets into cavities of ventricles of a brain and forms the vascular plexuses projecting a spinal liquid.
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