Sinusitis

The brain of amphibians. Reptile brain

Muscular system. It differs from such fish mainly in the greater development of the muscles of the limbs and the greater differentiation of the trunk muscles, consisting of a complex system of individual muscles. As a result, the primary muscle segmentation is disrupted, although in some abdominal and dorsal muscles it still remains quite distinct.

Nervous system. The brain of amphibians differs from the brain of fish mainly in the greater development of the forebrain, the complete separation of its hemispheres and the underdeveloped cerebellum, which is only a small ridge of nerve substance covering the anterior part of the fourth ventricle. The development of the forebrain is expressed not only in its enlargement and differentiation, but also in the fact that, in addition to the bottom of the lateral ventricles, their sides and roof contain nerve matter, i.e. in amphibians a real brain vault appears - the archipallium (from modern fish the archipallium present in lungfishes). The olfactory lobes are only weakly delimited from the hemispheres. The diencephalon is only slightly covered from above by neighboring sections. The parietal organ is attached to its roof, and a well-defined funnel extends from the bottom, to which the pituitary gland is attached. Although the midbrain is a significant section, it is relatively smaller than that of fish. Underdevelopment of the cerebellum, as in lungfishes, is associated with the simplicity of body movements: amphibians are generally sedentary animals, but in those that, like frogs, can make rapid movements, they are limited to jumping, i.e., very simple movements. From the brain, like in bony fishes, only 10 pairs of head nerves depart; The XII pair (hypoglossal nerve) extends outside the cranium, and the XI pair (accessory nerve) is not developed at all.

. I - top; II - bottom; III - side; IV - in longitudinal section (according to Parker):

1 - forebrain hemispheres, 2 - olfactory lobe, 3 - olfactory nerve, 4 - diencephalon, 5 - optic chiasm, 6 -funnel, 7 - pituitary gland, 8 - midbrain, 9 - cerebellum, 10 - medulla oblongata, 11 - fourth ventricle, 12 - spinal cord, 13 - third ventricle, 14 - aqueduct of Sylvius,

III - X - head nerves, XII - hypoglossal nerve

, scheme (according to Gregory):

1 - cranium, 2 - medulla oblongata, 3 - auditory nerve, 4 - semicircular canals, 5 - middle ear cavity, 6 - eustachian tube, 7 - pharynx, 8 - eardrum, 9 - eardrum

The frog has 10 pairs of true spinal nerves. The three anterior pairs take part in the formation of the brachial plexus, which innervates the forelimbs, and the four posterior pairs take part in the formation of the lumbosacral plexus, which innervates the hind limbs.

The sympathetic nervous system of the frog, like that of all amphibians, is very well developed and is represented mainly by two nerve trunks, which stretch on both sides of the spine and are formed by a chain of nerve ganglia connected to each other by cords and connected to the spinal nerves.

Respiratory system

Interesting features of the internal structure of the frog also concern breathing. The fact is that, along with the lungs, the capillary-filled skin of the amphibian plays a huge role in the gas exchange process. The lungs are thin-walled paired bags with a cellular inner surface and an extensive network of blood vessels.

How does a frog breathe? The amphibian uses valves capable of opening and closing its nostrils and movements of the floor of the oropharynx. In order to inhale, the nostrils open, and the bottom of the oropharyngeal cavity drops, and the air ends up in the frog's mouth. To allow it to pass into the lungs, the nostrils close and the floor of the oropharynx rises. Exhalation occurs due to the collapse of the pulmonary walls and movements of the abdominal muscles.

In males, the laryngeal cleft is surrounded by special arytenoid cartilages, on which the vocal cords are stretched. High sound volume is ensured by the vocal sacs, which are formed by the mucous membrane of the oropharynx.

Excretory system

The internal structure of the frog, or rather, it is also very curious, since the waste products of the amphibian can be excreted through the lungs and skin. But still, most of them are secreted by the kidneys, which are located at the sacral vertebra. The kidneys themselves are oblong bodies adjacent to the back. These organs have special glomeruli that are capable of filtering waste products from the blood.

Urine is discharged through the ureters into the bladder, where it accumulates. After the bladder is filled, the muscles at the ventral surface of the cloaca contract and fluid is expelled through the cloaca.

Circulatory system

The internal structure of the frog is more complex than that of an adult frog; it is three-chambered, consisting of a ventricle and two atria. Due to the single ventricle, arterial and venous blood are partially mixed; the two circulation circles are not completely separated. The conus arteriosus, which has a longitudinal spiral valve, extends from the ventricle and distributes mixed and arterial blood into different vessels.

Mixed blood collects in the right atrium: venous blood comes from the internal organs, and arterial blood comes from the skin. Arterial blood enters the left atrium from the lungs.

The atria contract simultaneously, and blood from both enters a single ventricle. Due to the structure of the longitudinal valve, it enters the organs of the head and brain, mixed - to organs and parts of the body, and venous - to the skin and lungs. Students may have a hard time understanding the internal structure of a frog. A diagram of the amphibian circulatory system will help you visualize how blood circulation works.

The circulatory system of tadpoles has only one circulation, one atrium and one ventricle, like in fish.

The structure of the blood of a frog and a person is different. have a core, oval shape, and in humans they have a biconcave shape, with no core.

Endocrine system

The endocrine system of the frog includes the thyroid, reproductive and pancreas glands, adrenal glands and pituitary gland. The thyroid gland produces hormones necessary to complete metamorphosis and maintain metabolism; the gonads are responsible for reproduction. The pancreas is involved in the digestion of food, the adrenal glands help regulate metabolism. The pituitary gland produces a number of hormones that affect the development, growth and coloring of the animal.

Nervous system

The nervous system of the frog is characterized by a low degree of development; it is similar in characteristics to the nervous system of fish, but has more progressive features. The brain is divided into 5 sections: midbrain, diencephalon, forebrain, medulla oblongata and cerebellum. The forebrain is well developed and is divided into two hemispheres, each of which has a lateral ventricle - a special cavity.

Due to monotonous movements and a generally sedentary lifestyle, the cerebellum is small in size. The medulla oblongata is larger. In total, ten pairs of nerves emerge from the frog's brain.

Sense organs

Significant changes in the sensory organs of amphibians are associated with the exit from the aquatic environment to land. They are already more complex than those of fish, since they must help navigate both in water and on land. Tadpoles have developed lateral line organs.

Pain, tactile and temperature receptors are hidden in the epidermis layer. Papillae on the tongue, palate and jaws serve as taste organs. The olfactory organs consist of paired olfactory sacs, which open through both the external and internal nostrils into the environment and the oropharyngeal cavity, respectively. In water, the nostrils are closed, the sense of smell does not function.

As a hearing organ, the middle ear is developed, in which there is an apparatus that amplifies sound vibrations thanks to the eardrum.

The structure of a frog's eye is complex, because it needs to see both underwater and on land. The eyes of adults are protected by movable eyelids and a nictitating membrane. Tadpoles do not have eyelids. The cornea of a frog's eye is convex, the lens is biconvex. Amphibians can see quite far and have color vision.

In fish the brain as a whole is small. Its anterior section is poorly developed. The forebrain is not divided into hemispheres. Its roof is thin, consists only of epithelial cells and does not contain nervous tissue. The base of the forebrain includes the striatum, and the olfactory lobes extend from it. Functionally, the forebrain is the highest olfactory center.

In the diencephalon, with which the pineal gland and pituitary gland are connected, the hypothalamus is located, which is the central organ of the endocrine system. The midbrain of fish is the most developed. It consists of two hemispheres and serves as the highest visual center. In addition, it represents the highest integrating part of the brain. The hindbrain contains the cerebellum, which regulates the coordination of movements. It is very well developed in connection with the movement of fish in three-dimensional space. The medulla oblongata provides communication between the higher parts of the brain and the spinal cord and contains the centers of respiration and circulation. A brain of this type, in which the highest center of integration of functions is the midbrain, is called ichthyopsid.

In amphibians the brain is also ichthyopsid. However, their forebrain is large and divided into hemispheres. Its roof consists of nerve cells, the processes of which are located on the surface. Like fish, the midbrain reaches a large size, which also represents the highest integrating center and center of vision. The cerebellum is somewhat reduced due to the primitive nature of the movements. Conditions of terrestrial existence reptiles require a more complex morphofunctional organization of the brain. The forebrain is the largest section compared to the rest. The striatum is especially developed in it. The functions of the highest integrative center are transferred to them. Islands of bark of a very primitive structure first appear on the surface of the roof; it is called ancient - archicortex. The midbrain loses its importance as a leading section, and its relative size decreases. The cerebellum is highly developed due to the complexity and variety of movements of reptiles. A brain of this type, in which the leading section is represented by the striatal bodies of the forebrain, is called sauropsid.

In mammals - mammalia brain type. It is characterized by a strong development of the forebrain due to the cortex, which develops on the basis of a small island of the reptile cortex and becomes the integrating center of the brain. It houses the higher centers of the visual, auditory, tactile, and motor analyzers, as well as the centers of higher nervous activity. The bark has a very complex structure and is called new bark - neocortex. It contains not only the bodies of neurons, but also associative fibers connecting its different parts. Also characteristic is the presence of a commissure between both hemispheres, in which the fibers that connect them together are located. The diencephalon, like other classes, includes the hypothalamus, pituitary gland and pineal gland. In the midbrain there is the quadrigemina in the form of four tubercles. The two front ones are connected to the visual analyzer, the two rear ones are connected to the auditory analyzer.

The main stages of the evolution of the central nervous system are also reflected in human ontogenesis. At the stage of neurulation, the neural plate is laid down, turning into a groove and then into a tube. The anterior end of the tube first forms three brain vesicles: anterior, middle and posterior. . Following this, the anterior vesicle is divided into two, differentiating into the forebrain and diencephalon - the middle cerebral vesicle develops into the midbrain, and the posterior vesicle into the hindbrain and medulla oblongata.

Monogenic type of inheritance. Examples.

Polygenic or multifactorial diseases. Features of inheritance.

Brain frogs, like other amphibians, are characterized by the following features compared to fish:

a) progressive development of the brain, expressed in the separation of the paired hemispheres by a longitudinal fissure and the development of the gray matter of the ancient cortex (archipallium) in the roof of the brain;

b) weak development of the cerebellum;

c) weak expression of the bends of the brain, due to which the intermediate and middle sections are clearly visible from above.

Diamond brain(rhombencephalon)

Medulla oblongata (myelencephalon, medulla oblongata), into which the spinal cord passes cranially, it differs from the latter in its greater width and the departure from its lateral surfaces of the large roots of the posterior cranial nerves. On the dorsal surface of the medulla oblongata there is diamond-shaped fossa (fossa rhomboidea), accommodating fourth cerebral ventricle (ventriculus quartus). On top it is covered with a thin vascular cap, which is removed along with the meninges. The ventral fissure, a continuation of the ventral fissure of the spinal cord, runs along the ventral surface of the medulla oblongata. The medulla oblongata contains two pairs of cords (bundles of fibers): the lower pair, separated by the ventral fissure, are motor, the upper pair are sensory. The medulla oblongata contains the centers of the maxillary and sublingual apparatus, the organ of hearing, as well as the digestive and respiratory systems.

Cerebellum located in front of the rhomboid fossa in the form of a high transverse ridge as an outgrowth of its anterior wall. The small size of the cerebellum is determined by the small and uniform mobility of amphibians - in fact, it consists of two small parts, closely connected with the acoustic centers of the medulla oblongata (these parts are preserved in mammals as fragments of the cerebellum (flocculi)). The body of the cerebellum - the center of coordination with other parts of the brain - is very poorly developed.

Midbrain(mesencephalon) when viewed from the dorsal side, it is represented by two typical optic lobes (lobus opticus s. tectum opticus), having the appearance of paired ovoid elevations forming the upper and lateral parts of the midbrain. The roof of the optic lobes is formed by gray matter - several layers of nerve cells. The tectum in amphibians is the most significant part of the brain. The optic lobes contain cavities that are lateral branches cerebral (Sylvii) aqueduct (aquaeductus cerebri (Sylvii), connecting the fourth cerebral ventricle with the third.

The bottom of the midbrain is formed by thick bundles of nerve fibers - cerebral peduncles (cruri cerebri), connecting the forebrain with the medulla oblongata and spinal cord.

Forebrain(prosencephalon) consists of the diencephalon and telencephalon, lying sequentially.

Diencephalon visible from above as a rhombus, with sharp angles directed to the sides.

Parts of the diencephalon lie around a vertically located wide fissure third cerebral ventricle (ventriculus tertius). Lateral thickening of the walls of the ventricle - visual cusps or thalamus. In fish and amphibians, the thalamus is of secondary importance (as coordinating sensory and motor centers). The membranous roof of the third cerebral ventricle - the epithalamus or epithalamus - does not contain neurons. It contains the superior medullary gland - pineal gland (epiphisis). In amphibians, the pineal gland already serves as a gland, but has not yet lost the features of the parietal organ of vision. In front of the epiphysis, the diencephalon is covered with a membranous roof, which orally turns inward and passes into the anterior choroid plexus (choroid tectum of the third ventricle), and then into the endplate of the diencephalon. Inferiorly the ventricle narrows, forming pituitary funnel (infundibulum), the inferior medullary gland is attached to it caudoventrally - pituitary gland (hypophisis). In front, on the border between the bottom of the terminal and intermediate sections of the brain, there is chiasma nervorum opticorum). In amphibians, most of the fibers of the optic nerves are not retained in the diencephalon, but go further to the roof of the midbrain.

Telencephalon its length is almost equal to the length of all other parts of the brain. It consists of two parts: the olfactory brain and two hemispheres, separated from each other sagittal (arrow-shaped) fissure (fissura sagittalis).

Hemispheres of the telencephalon (haemispherium cerebri) occupy the posterior two-thirds of the telencephalon and hang over the anterior part of the diencephalon, partially covering it. There are cavities inside the hemispheres - lateral cerebral ventricles (ventriculi lateralis), caudally communicating with the third ventricle. In the gray matter of the cerebral hemispheres of amphibians, three areas can be distinguished: dorsomedially there is the old cortex or hippocampus (archipallium, s. hippocampus), laterally - ancient bark(paleopallium) and ventrolaterally - the basal ganglia, corresponding striata (corpora striata) mammals. The striatum and, to a lesser extent, the hippocampus are correlative centers, the latter associated with olfactory function. The ancient cortex is an exclusively olfactory analyzer. On the ventral surface of the hemispheres, grooves are visible that separate the striatum from the ancient cortex.

Olfactory brain (rhinencephalon) occupies the anterior part of the telencephalon and forms olfactory lobes (bulbs) (lobus olfactorius), soldered in the middle with each other. They are separated from the hemispheres laterally by the marginal fossa. The olfactory lobes anteriorly contain the olfactory nerves.

10 pairs extend from the frog's brain cranial nerves. Their formation, branching and zone of innervation are not fundamentally different from those in mammals

Structure of the brain of bony fish

The brain of bony fishes consists of five sections typical for most vertebrates.

Diamond brain(rhombencephalon)

the anterior section extends under the cerebellum, and at the rear, without visible boundaries, it passes into the spinal cord. To view the anterior part of the medulla oblongata, it is necessary to turn the body of the cerebellum forward (in some fish the cerebellum is small and the anterior part of the medulla oblongata is clearly visible). The roof of this part of the brain is represented by the choroid plexus. Underneath lies a large widened at the anterior end and passing behind into a narrow medial fissure, it is a cavity The medulla oblongata serves as the origin of most of the brain nerves, as well as a pathway connecting various centers of the anterior parts of the brain with the spinal cord. However, the layer of white matter covering the medulla oblongata in fish is quite thin, since the body and tail are largely autonomous - they carry out most of the movements reflexively, without reference to the brain. In the bottom of the medulla oblongata in fish and tailed amphibians lies a pair of giant Mauthner cells, associated with acoustic-lateral centers. Their thick axons extend along the entire spinal cord. Locomotion in fish is carried out mainly due to rhythmic bending of the body, which, apparently, is controlled mainly by local spinal reflexes. However, the overall control over these movements is exercised by Mauthner cells. The respiratory center lies at the bottom of the medulla oblongata.

By viewing the brain from below, you can discern the origins of some nerves. Three round roots extend from the lateral side of the anterior part of the medulla oblongata. The first, lying most cranially, belongs to V and VII nerves, middle root - only VII nerve, and finally, the third root, lying caudally, is VIII nerve. Behind them, also from the lateral surface of the medulla oblongata, the IX and X pairs extend together in several roots. The remaining nerves are thin and are usually cut off during dissection.

Cerebellum Quite well developed, round or elongated, it lies over the anterior part of the medulla oblongata directly behind the optic lobes. With its posterior edge it covers the medulla oblongata. The part that protrudes upward is body of the cerebellum (corpus cerebelli). The cerebellum is the center for the precise regulation of all motor innervations associated with swimming and grasping food.

Midbrain(mesencephalon) - part of the brain stem penetrated by the cerebral aqueduct. It consists of large, longitudinally elongated optic lobes (they are visible from above).

Optic lobes, or visual roof (lobis opticus s. tectum opticus) - paired formations separated from each other by a deep longitudinal groove. The optic lobes are the primary visual centers for sensing stimulation. The fibers of the optic nerve end in them. In fish, this part of the brain is of primary importance; it is the center that has the main influence on the activity of the body. The gray matter covering the optic lobes has a complex layered structure, reminiscent of the structure of the cerebellar cortex or hemispheres

Thick optic nerves arise from the ventral surface of the optic lobes and cross beneath the surface of the diencephalon.

If you open the optic lobes of the midbrain, you can see that in their cavity a fold is separated from the cerebellum, called cerebellar valve (valvule cerebellis). On either side of it, in the bottom of the midbrain cavity, there are two bean-shaped elevations called semilunar bodies (tori semicircularis) and being additional centers of the statoacoustic organ.

Forebrain(prosencephalon) less developed than the middle one, it consists of the telencephalon and diencephalon.

Parts diencephalon lie around a vertical slit Lateral walls of the ventricle - visual cusps or thalamus ( thalamus) in fish and amphibians are of secondary importance (as coordinating sensory and motor centers). The roof of the third cerebral ventricle - the epithalamus or epithalamus - does not contain neurons. It contains the anterior choroid plexus (choroid cover of the third ventricle) and the superior medullary gland - pineal gland (epiphisis). The bottom of the third cerebral ventricle - the hypothalamus or hypothalamus in fish forms paired swellings - lower lobes (lobus inferior). In front of them lies the inferior medullary gland - pituitary gland (hypophisis). In many fish, this gland fits tightly into a special recess in the bottom of the skull and usually breaks off during preparation; then clearly visible funnel (infundibulum). optic chiasm (chiasma nervorum opticorum).

in bony fishes it is very small compared to other parts of the brain. Most fish (except lungfishes and lobe-finned fish) are distinguished by the everted (inverted) structure of the telencephalon hemispheres. They seem to be “turned” ventro-laterally. The roof of the forebrain does not contain nerve cells and consists of a thin epithelial membrane (pallium), which during dissection is usually removed along with the membrane of the brain. In this case, the preparation shows the bottom of the first ventricle, divided into two by a deep longitudinal groove striatum. Striatum (corpora striatum1) consist of two sections, which can be seen when viewing the brain from the side. In fact, these massive structures contain striatal and cortical material of a rather complex structure.

Olfactory bulbs (bulbus olfactorius) adjacent to the anterior margin of the telencephalon. They go ahead olfactory nerves. In some fish (for example, cod), the olfactory bulbs are placed far forward, in which case they connect to the brain olfactory tracts.

Cranial nerves of fish.

In total, 10 pairs of nerves extend from the fish’s brain. Basically (both in name and in function) they correspond to the nerves of mammals.

Structure of the frog brain

Brain frogs, like other amphibians, are characterized by the following features compared to fish:

b) weak development of the cerebellum;

c) weak expression of the bends of the brain, due to which the intermediate and middle sections are clearly visible from above.

Diamond brain(rhombencephalon)

Medulla oblongata (myelencephalon, medulla oblongata) , into which the spinal cord passes cranially, it differs from the latter in its greater width and the departure from its lateral surfaces of the large roots of the posterior cranial nerves. On the dorsal surface of the medulla oblongata there is diamond-shaped fossa (fossa rhomboidea), accommodating fourth cerebral ventricle (ventriculus quartus). On top it is covered with a thin vascular cap, which is removed along with the meninges. The ventral fissure, a continuation of the ventral fissure of the spinal cord, runs along the ventral surface of the medulla oblongata. The medulla oblongata contains two pairs of cords (bundles of fibers): the lower pair, separated by the ventral fissure, are motor, the upper pair are sensory. The medulla oblongata contains the centers of the maxillary and sublingual apparatus, the organ of hearing, as well as the digestive and respiratory systems.

Midbrain(mesencephalon) when viewed from the dorsal side, it is represented by two typical optic lobes(lobus opticus s. tectum opticus) , having the appearance of paired ovoid elevations forming the upper and lateral parts of the midbrain. The roof of the optic lobes is formed by gray matter - several layers of nerve cells. The tectum in amphibians is the most significant part of the brain. The optic lobes contain cavities that are lateral branches cerebral (Sylvii) aqueduct (aquaeductus cerebri (Sylvii), connecting the fourth cerebral ventricle with the third.

The bottom of the midbrain is formed by thick bundles of nerve fibers - cerebral peduncles (cruri cerebri), connecting the forebrain with the medulla oblongata and spinal cord.

Forebrain(prosencephalon) consists of the diencephalon and telencephalon, lying sequentially.

visible from above as a rhombus, with sharp angles directed to the sides.

10 pairs extend from the frog's brain cranial nerves. Their formation, branching and zone of innervation are not fundamentally different from those in mammals

Bird brain.

Diamond brain(rhombencephalon) includes the medulla oblongata and cerebellum.

Medulla oblongata (myelencephalon, medulla oblongata) behind it directly passes into the spinal cord (medulla spinalis). Anteriorly, it wedges between the optic lobes of the midbrain. The medulla oblongata has a thick bottom, in which lie the nuclei of gray matter - the centers of many vital functions of the body (including equilibrium-auditory, somatic motor and autonomic). The gray matter in birds is covered with a thick layer of white, formed by nerve fibers connecting the brain to the spinal cord. In the dorsal part of the medulla oblongata there is diamond-shaped fossa (fossa rhomboidea), which is a cavity fourth cerebral ventricle (ventriculus quartus). The roof of the fourth cerebral ventricle is formed by a membranous vascular tegmentum; in birds it is completely covered by the posterior part of the cerebellum.

Cerebellum in birds it is large and is represented practically only worm (vermis), located above the medulla oblongata. The cortex (gray matter located superficially) has deep grooves that significantly increase its area. The cerebellar hemispheres are poorly developed. In birds, the sections of the cerebellum associated with muscle sense are well developed, while the sections responsible for the functional connection of the cerebellum with the cerebral cortex are practically absent (they develop only in mammals). The cavity is clearly visible in the longitudinal section cerebellar ventricle (ventriculus cerebelli), as well as alternation of white and gray matter, forming a characteristic pattern tree of life (arbor vitae).

Midbrain(mesencephalon) represented by two very large ones, shifted to the side visual lobes (lobus opticus s. tectum opticus). In all vertebrates, the size and development of the optic lobes is related to the size of the eyes. They are clearly visible from the side and from the ventral side, while from the dorsal side they are almost completely covered by the posterior sections of the hemispheres. In birds, almost all the fibers of the optic nerve come to the optic lobes, and the optic lobes remain extremely important parts of the brain (however, in birds, the cerebral cortex begins to compete with the optic lobes in importance). The sagittal section shows that in the forward direction the cavity of the fourth ventricle, narrowing, passes into the cavity of the midbrain - cerebral or Sylvian aqueduct (aquaeductus cerebri). Orally, the aqueduct passes, expanding, into the cavity of the third cerebral ventricle of the diencephalon. The conventional anterior border of the midbrain is formed posterior commissure (comissura posterior), clearly visible on a sagittal section in the form of a white spot.

Included forebrain(prosencephalon) there are the diencephalon and the telencephalon.

Diencephalon in birds it is externally visible only from the ventral side. The middle part of the longitudinal section of the diencephalon is occupied by a narrow vertical fissure third ventricle (ventriculus tertius). In the upper part of the ventricular cavity there is a hole (paired) leading into the cavity of the lateral ventricle - Monroe (interventricular) foramen (foramen interventriculare).

The lateral walls of the third cerebral ventricle are formed by a fairly well developed thalamus (thalamus), the degree of development of the thalamus is related to the degree of development of the hemispheres. Although it does not have the significance of a higher visual center in birds, it nevertheless performs important functions as a motor correlative center.

In the anterior wall of the third ventricle lies anterior commissure (comissura anterior), consisting of white fibers connecting the two hemispheres

The floor of the diencephalon is called hypothalamus (hypothalamus). When viewed from below, lateral thickenings of the bottom are visible - visual tracts (tractus opticus). Between them the anterior end of the diencephalon includes optic nerves (nervus opticus), forming optic chiasm (chiasma opticum). The posterior lower corner of the third cerebral ventricle corresponds to the cavity funnels (infunbulum). From below, the funnel is usually covered by the subcerebral gland, which is well developed in birds - pituitary gland (hypophysis).

From the roof of the diencephalon (epithalamus) extending upward having a cavity pedicle of the pineal organ. Above is himself pineal organ- pineal gland (epiphysis), it is visible from above, between the posterior edge of the cerebral hemispheres and the cerebellum. The anterior part of the roof of the diencephalon is formed by the choroid plexus extending into the cavity of the third ventricle.

Telencephalon in birds it consists of cerebral hemispheres (hemispherium cerebri), separated from each other by deep longitudinal fissure (fissura interhemispherica). The hemispheres in birds are the largest formations of the brain, but their structure is fundamentally different from that of mammals. Unlike the brain of many mammals, the greatly enlarged hemispheres of the bird's brain do not bear grooves and convolutions; their surface is smooth on both the ventral and dorsal sides. The cortex as a whole is poorly developed, primarily due to the reduction of the olfactory organ. The thin medial wall of the forebrain hemisphere in the upper part is represented by nerve substance old bark (archipallium). Material neocortex(poorly developed) (neopallium) along with a significant mass striatum (corpus striatum) forms a thick lateral wall of the hemisphere or a lateral outgrowth, protruding into the cavity of the lateral ventricle. Therefore the cavity lateral ventricle (ventriculus lateralis) hemisphere is a narrow gap located dorsomedially. In birds, unlike mammals, significant development in the hemispheres is achieved not by the cerebral cortex, but by the striatum. It has been revealed that the striatum is responsible for innate stereotypical behavioral reactions, while the neocortex provides the ability for individual learning. Some bird species have been found to have better-than-average development of a portion of the neocortex, such as crows, known for their learning abilities.

Olfactory bulbs (bulbis olfactorius) located on the ventral side of the forebrain. They are small in size and approximately triangular in shape. They enter from the front olfactory nerve.