Anterior cerebral bladder. Development of the nervous system
The nervous system begins to develop in the 3rd week of intrauterine development from the ectoderm (outer germ layer).
On the dorsal (dorsal) side of the embryo, the ectoderm thickens. This forms the neural plate. Then the neural plate bends deep into the embryo and a neural groove is formed. The edges of the neural groove close together to form the neural tube. A long, hollow neural tube, which lies first on the surface of the ectoderm, is separated from it and plunges inward, under the ectoderm. The neural tube expands at the anterior end, from which the brain later forms. The rest of the neural tube is converted to the brain.
Stages of embryogenesis of the nervous system in a transverse schematic section, a - medullary plate; b and c - medullary groove; d and e are the cerebral tube. 1 - horny leaf (epidermis); 2 - ganglion roller.
From cells migrating from the lateral walls of the neural tube, two neural crests - nerve cords - are laid. In the future, spinal and autonomous ganglia and Schwann cells are formed from the nerve cords, which form the myelin sheaths of nerve fibers. In addition, neural crest cells are involved in the formation of the pia mater and arachnoid. In the inner word of the neural tube, increased cell division occurs. These cells differentiate into 2 types: neuroblasts (precursors of neurons) and spongioblasts (precursors of glial cells). Simultaneously with cell division, the head end of the neural tube is subdivided into three sections - primary cerebral vesicles. Accordingly, they are called the anterior (I bladder), middle (II bladder) and posterior (III bladder) brain. In subsequent development, the brain is divided into the final (large hemispheres) and diencephalon. The midbrain is preserved as a whole, and the hindbrain is divided into two sections, including the cerebellum with the pons and the medulla oblongata. This is the 5-cystic stage of brain development.
Brain development (outline)
a - five cerebral pathways: 1 - the first bubble (terminal brain); 2 - the second bubble (diencephalon); 3 - the third bubble (midbrain); 4- fourth bladder (medulla oblongata); between the third and fourth bubble - isthmus; b - development of the brain (according to R. Sinelnikov).
A - the formation of primary blisters (up to the 4th week of embryonic development). B - E - formation of secondary bubbles. B, C - end of the 4th week; G - the sixth week; D - 8-9 weeks, ending with the formation of the main parts of the brain (E) - by 14 weeks.
3а - isthmus of the rhomboid brain; 7 end plate.
Stage A: 1, 2, 3 - primary cerebral vesicles
1 - forebrain,
2 - midbrain,
3 - hindbrain.
Stage B: the forebrain is divided into hemispheres and basal nuclei (5) and diencephalon (6)
Stage B: the rhomboid brain (3a) is subdivided into the hindbrain, which includes the cerebellum (8), pons (9) stage E, and medulla oblongata (10) stage E
Stage E: Spinal cord is formed (4)
The formation of neural bubbles is accompanied by the appearance of bends due to different rates of maturation of parts of the neural tube. By the 4th week of intrauterine development, the parietal and occipital bends are formed, and during the 5th week - the bridge bend. By the time of birth, only the bend of the brain stem is preserved almost at a right angle in the region of the junction of the midbrain and diencephalon.
Developing brain (3rd to 7th week of development)
Side view illustrating the bends in the midbrain (A), cervical (B) regions of the brain, as well as in the pons (C).
1 - eye bladder, 2 - forebrain, 3 - midbrain; 4 - hindbrain; 5 - auditory vesicle; 6 - spinal cord; 7 - diencephalon; 8 - terminal brain; 9 - rhombic lip. Roman numerals indicate the places of origin of the cranial nerves.
At the beginning, the surface of the cerebral hemispheres is smooth. First, at 11-12 weeks of intrauterine development, the lateral groove (Silvieva) is laid, then the central (Rolland) groove. The formation of furrows occurs quite quickly within the lobes of the hemispheres, due to the formation of furrows and convolutions, the area of \u200b\u200bthe cortex increases.
A- 11th week. B- 16_ 17 weeks. B- 24-26 weeks. G- 32-34 weeks. D - newborn. The formation of a lateral fissure (5), a central groove (7) and other grooves and convolutions is shown.
I - terminal brain; 2 - midbrain; 3 - cerebellum; 4 - medulla oblongata; 7 - central groove; 8 - bridge; 9 - furrows of the parietal region; 10 - grooves of the occipital region;
II - grooves of the frontal region.
Neuroblasts by migration form clusters - nuclei that form the gray matter of the spinal cord, and in the brain stem - some nuclei of the cranial nerves.
Somas of neuroblasts have a rounded shape. The development of a neuron is manifested in the appearance, growth and branching of processes. A small short protrusion forms on the neuron membrane at the site of the future axon - a growth cone. The axon is pulled out and delivered along it nutrients to the growth cone. At the beginning of development, a neuron forms more processes in comparison with the final number of processes of a mature neuron. Some of the processes are drawn into the soma of the neuron, and the rest grow towards other neurons, with which they form synapses.
The last two sketches show the difference in the structure of these cells in a two-year-old child and an adult.
In the spinal cord, axons are short and form intersegmental connections. Longer projection fibers are formed later. Somewhat later than the axon, the growth of dendrites begins. All branches of each dendrite are formed from one trunk. The number of branches and the length of the dendrites are not completed in the prenatal period.
The increase in brain mass in the prenatal period occurs mainly due to an increase in the number of neurons and the number of glial cells.
The development of the cortex is associated with the formation of cell layers (in the cerebellar cortex - three layers, and in the cerebral cortex - six layers).
In the formation of cortical layers big role the so-called glial cells play. These cells assume a radial position and form two vertically oriented long processes. Migration of neurons occurs along the processes of these radial glial cells. Initially, more superficial layers of the cortex are formed. Glial cells also take part in the formation of the myelin sheath. Sometimes one glial cell is involved in the formation of the myelin sheaths of several axons.
The main stages of development nervous system in the prenatal period.
| Fetal age (weeks) | Development of the nervous system |
| 2,5 | A neural groove is outlined |
| 3.5 | A neural tube and nerve cords are formed |
| 4 | 3 brain bladders are formed; nerves and ganglia are formed |
| 5 | 5 brain bladders are forming |
| 6 | The meninges are outlined |
| 7 | The cerebral hemispheres become large |
| 8 | Typical neurons appear in the cortex |
| 10 | The internal structure of the spinal cord is formed |
| 12 | General structural features of the brain are formed; differentiation of neuroglia cells begins |
| 16 | The lobes of the brain are distinguishable |
| 20-40 | Myelination of the spinal cord begins (20 weeks), layers of the cortex appear (25 weeks), grooves and convolutions are formed (28-30 weeks), myelination of the brain begins (36-40 weeks) |
Thus, the development of the brain in the prenatal period occurs continuously and in parallel, but is characterized by heterochrony: the rate of growth and development of phylogenetically older formations is higher than that of phylogenetically younger formations.
Genetic factors play a leading role in the growth and development of the nervous system during the prenatal period. The average brain weight of a newborn is about 350 g.
Morpho-functional maturation of the nervous system continues in the postnatal period. By the end of the first year of life, the weight of the brain reaches 1000 g, while in an adult the weight of the brain is on average 1400 g. Consequently, the main increase in brain weight occurs in the first year of a child's life.
The increase in brain mass in the postnatal period occurs mainly due to an increase in the number of glial cells. The number of neurons does not increase, since they lose the ability to divide already in the prenatal period. The total density of neurons (the number of cells per unit volume) decreases due to the growth of the soma and processes. Dendrites have an increased number of branches.
In the postnatal period, myelination of nerve fibers also continues both in the central nervous system and nerve fibers that make up the peripheral nerves (cranial and spinal.).
The growth of spinal nerves is associated with the development of the musculoskeletal system and the formation of neuromuscular synapses, and the growth of cranial nerves with the maturation of the sense organs.
Thus, if in the prenatal period, the development of the nervous system occurs under the control of the genotype and practically does not depend on the influence of the external environment, then in the postanatal period external stimuli become increasingly important. Stimulation of the receptors causes afferent impulse streams that stimulate the morpho-functional maturation of the brain.
Under the influence of afferent impulses, spines are formed on the dendrites of cortical neurons - outgrowths, which are special postsynaptic membranes. The more spines, the more synapses and the more the neuron takes part in information processing.
Throughout postnatal ontogenesis up to puberty, as well as in the prenatal period, the development of the brain occurs heterochronously. Thus, the final maturation of the spinal cord occurs earlier than the brain. The development of stem and subcortical structures, earlier than cortical, the growth and development of excitatory neurons outstrips the growth and development of inhibitory neurons. These are general biological laws of the growth and development of the nervous system.
Morphological maturation of the nervous system correlates with the characteristics of its functioning at each stage of ontogenesis. Thus, the earlier differentiation of excitatory neurons in comparison with inhibitory neurons ensures the predominance of the muscle tone of the flexors over the tone of the extensors. The arms and legs of the fetus are in a flexed position - this creates a posture that provides minimal volume, so that the fetus takes up less space in the uterus.
Improvement of the coordination of movements associated with the formation of nerve fibers occurs throughout the preschool and school periods, which is manifested in the sequential mastering of the posture of sitting, standing, walking, writing, etc.
An increase in the speed of movements is mainly due to the processes of myelination of peripheral nerve fibers and an increase in the speed of conduction of excitation of nerve impulses.
Earlier maturation of subcortical structures in comparison with cortical structures, many of which are part of the limbic structure, determine the peculiarities of the emotional development of children (high intensity of emotions, inability to restrain them is associated with the immaturity of the cortex and its weak inhibitory effect).
In old and senile age, anatomical and histological changes in the brain occur. Atrophy of the frontal and superior parietal lobes often occurs. The furrows become wider, the ventricles of the brain increase, the volume of the white matter decreases. Thickening of the meninges occurs.
With age, neurons decrease in size, and the number of nuclei in cells can increase. In neurons, the content of RNA, which is necessary for the synthesis of proteins and enzymes, also decreases. This impairs the trophic functions of neurons. It has been suggested that such neurons fatigue faster.
In old age, the blood supply to the brain is also disrupted, the walls of the blood vessels thicken and cholesterol plaques are deposited on them (atherosclerosis). It also impairs the functioning of the nervous system.
The head section of the neural tube is the rudiment from which the brain develops. In 4-week-old embryos, the brain consists of three cerebral vesicles, separated from each other by small narrowing of the walls of the neural tube. These are prosencephalon - forebrain, mesencephalon - midbrain and rhombencephalon - rhomboid (hind) brain. By the end of the 4th week, signs of differentiation of the anterior cerebral bladder into the future telencephalon - telen-cephalon and intermediate - diencephalon appear. Soon thereafter, the rhombencephalon is subdivided into the hindbrain, metencephalon, and the medulla oblongdta, s. bulbus.
The common cavity of the rhomboid brain is transformed into the IV ventricle, which in its posterior parts communicates with the central canal of the spinal cord and with the intershell space.
The walls of the neural tube in the midbrain bladder thicken more evenly. From the ventral sections of the neural tube, the legs of the brain, pedunculi cerebri, develop here, and from the dorsal sections - the plate of the midbrain roof, lamina tecti mesencephali. The most complex transformations in the development process undergoes the anterior cerebral bladder (prosencephalon). In the diencephalon (its posterior part), the lateral walls reach the greatest development, which form the visual hillocks (thalamuses). From the lateral walls of the diencephalon, eye vesicles are formed, each of which subsequently turns into the retina (retina) of the eyeball and optic nerve... The thin dorsal wall of the diencephalon grows together with the choroid, forming the roof of the third ventricle containing the choroid plexus, plexus choroideus ventriculi tertii. A blind unpaired outgrowth also appears in the dorsal wall, which subsequently turns into the pineal gland, or pineal gland, corpus pineale. In the area of \u200b\u200bthe thin lower wall, another unpaired protrusion forms, turning into a gray tubercle, tuber cinereum, funnel, infundibulum, and the posterior lobe of the pituitary gland, neurohypophysis.
The cavity of the diencephalon forms the third ventricle of the brain, which communicates with the fourth ventricle through the aqueduct of the midbrain.
The terminal brain, telencephalon, subsequently turns into two bubbles - the future cerebral hemispheres.
3. Shin arteries: topography, branches and areas supplied by them. Blood supply to the ankle.
Posterior tibial artery, a. tibialis posterior, serves as a continuation of the popliteal artery, passes in the ankle-knee canal.
Branches of the posterior tibial artery: 1. Muscular branches, rr. musculares, - to the muscles of the lower leg; 2. The branch around the fibula, circumflexus fibularis, supplies blood to the adjacent muscles. 3. Peroneal artery, a. regopea, supplies the triceps muscle of the leg, long and short peroneal muscles, is divided into its terminal branches: lateral ankle branches, rr. malleolares laterales, and calcaneal branches, rr. calcanei involved in the formation of the calcaneal network, rete calcaneum. A perforating branch, g. Perforans, and a connecting branch, g. Communicans, also depart from the peroneal artery.
4. Medial plantar artery, a. plantaris medialis, is divided into superficial and deep branches, rr. superficidlis et profundus. The superficial branch feeds the muscle that abducts the big toe, and the deep branch feeds the same muscle and the flexor flexor of the toes.
5. Lateral plantar artery, a. plantaris lateralis ,. forms a plantar arch at the level of the base of the metatarsal bones, arcus plantaris, gives branches to the muscles, bones and ligaments of the foot.
The plantar metatarsal arteries branch off from the plantar arch, aa. metatarsales plantares I-IV. The plantar metatarsal arteries in turn give off perforating branches, rr. perforantes, to the dorsal metatarsal arteries.
Each plantar metatarsal artery passes into the common plantar digital artery, a. digitalis plantaris communis. At the level of the main phalanges of the fingers, each common plantar digital artery (except the first) is divided into two own plantar digital arteries, aa. digitales plantares propriae. The first common plantar digital artery branches into three own plantar digital arteries: to the two sides of the thumb and to the medial side of the second toe, and the second, third and fourth arteries supply blood to the sides of the II, III, IV and V fingers facing each other. At the level of the metatarsal heads, the perforating branches are separated from the common plantar digital arteries to the dorsal digital arteries.
Anterior tibial artery, a. tibidlis anterior, departs from the popliteal artery in the popliteal.
Branches of the anterior tibial artery:
1. Muscular branches, rr. musculares, to the muscles of the lower leg.
2. Posterior tibial recurrent artery, a. hesyr-rens tibialis posterior, departs within the popliteal fossa, participates in the formation of the knee articular network, supplies the knee joint and the popliteal muscle with blood.
3. Anterior tibial recurrent artery, a. recurrens tibialis anterior, takes part in the blood supply to the knee and tibiofibular joints, as well as the anterior tibial muscle and the long extensor of the fingers.
4. Lateral anterior ankle artery, a. malleold-ris anterior laterdlis, begins above the lateral ankle, supplies blood to the lateral ankle, ankle and tarsal bones, takes part in the formation of the lateral ankle network, rete malleoldre laterale.
5. Medial anterior ankle artery, a. malleold-ris anterior medialis, sends branches to the capsule of the ankle joint, participates in the formation of the medial ankle network.
6. Dorsal artery of the foot, a. dorsdlis pedis, is divided into terminal branches: 1) the first dorsal metatarsal artery, a. metatarsdlis dorsdlis I, from which three dorsal digital arteries branch off, aa. digitdles dorsdles, to both sides of the dorsum of the thumb and the medial side of the second finger; 2) deep plantar branch, a. plantdris profunda, which runs through the first metatarsal space to the sole.
The dorsal artery of the foot also gives off the tarsal arteries - lateral and medial, aa. tarsales lateralis et medialis, to the lateral and medial edges of the foot and arcuate artery, and. ag-cuata, located at the level of the metatarsophalangeal joints. From the arcuate artery in the direction of the fingers, I-IV dorsal metatarsal arteries, aa. metatarsales dorsales I-IV, each of which at the beginning of the interdigital space is divided into two dorsal digital arteries, aa. digitales dorsales, heading to the back of the adjacent toes. From each of the dorsal digital arteries through the intermetatarsal spaces, the piercing branches extend to the plantar metatarsal arteries.
4. The vagus nerve, its branches, their anatomy, topography, areas of innervation.
The vagus nerve, n. Vagus, is a mixed nerve. Its sensory fibers end in the nucleus of a solitary pathway, motor fibers start from the double nucleus, and vegetative ones - from the posterior nucleus of the vagus nerve. The fibers provide parasympathetic innervation to the organs of the neck, chest and abdominal cavities. There are impulses along the fibers of the vagus nerve that slow down the heart rate, dilate blood vessels, narrow the bronchi, increase peristalsis and relax the sphincters of the intestine, cause increased secretion of the glands of the gastrointestinal tract.
Topographically, the vagus nerve can be divided into 4 sections: head, cervical, thoracic and abdominal.
The head section of the vagus nerve is located between the beginning of the nerve and the superior node. The following branches branch off in this department:
1. Meningeal branch, Mr. meningeus, departs from the superior node and goes to the dura mater of the brain in the region of the posterior cranial fossa, including the walls of the transverse and occipital sinuses.
2. The auricular branch, Mr. auricularis, starts from the lower part of the upper node, penetrates into the jugular fossa, where it enters the mastoid tubule temporal bone... It innervates the skin of the posterior wall of the external auditory canal and the skin of the outer surface of the auricle.
Cervical department:
1. Pharyngeal branches, rr. pharyngei, go to the pharyngeal wall, where they form the pharyngeal plexus, plexus pharyngeus. The pharyngeal branches innervate the mucous membrane of the pharynx, constrictor muscles, the muscles of the soft palate, with the exception of the muscle that strains the palatine curtain.
2. Superior cervical cordial branches, rr. cardldci cervicales superiores enter the heart plexus.
3. The superior laryngeal nerve, item laryngeus superior, departs from the lower node of the vagus nerve, goes forward along the lateral surface of the pharynx and at the level of the hyoid bone is divided into external and internal branches. The outer branch, g. Externus, innervates the cricothyroid muscle of the larynx. The internal branch, g. Internus, accompanies the superior laryngeal artery and, together with the latter, perforates the thyroid-hyoid membrane. Its terminal branches innervate the mucous membrane of the larynx above the glottis and part of the mucous membrane of the root of the tongue.
4. Recurrent laryngeal nerve, item laryngeus recurrens, The terminal branch of the recurrent laryngeal nerve - the lower laryngeal nerve, item laryngealis inferior, innervates the mucous membrane of the larynx below the glottis and all the muscles of the larynx, except cricothyroid. The tracheal branches, esophageal branches, and the lower cervical cardiac branches, which go to the cardiac plexuses, also depart.
The thoracic region is the area from the level of recurrent nerve discharge to the level of the esophageal opening of the diaphragm. Branches of the thoracic vagus nerve:
1. Thoracic cordial branches, rr. cardiaci thorаcici, go to the cardiac plexus.
2. Bronchial branches, rr. bronchidles, go to the root of the lung, where, together with sympathetic nerves, they form a pulmonary plexus, plexus pulmonalis, which surrounds the bronchi and enters the lung with them.
3. The esophageal plexus, plexus esophageus, is formed by the branches of the right and left vagus nerves (trunks), which are connected to each other on the surface of the esophagus. Branches extend from the plexus to the wall of the esophagus.
Abdominal represented by the anterior and posterior trunks that emerge from the esophageal plexus.
1. Anterior vagus trunk, truncus vagalis anterior. From this vagus trunk, the anterior gastric branches depart, d. gdstrici anteriores, as well as hepatic branches, g. hepаtici, going between the leaves of the lesser omentum to the liver.
2. The posterior vagus trunk, truncus vagalis posterior, passes from the esophagus to the posterior wall of the stomach, goes along its lesser curvature, gives off the posterior gastric branches, rr. gdstrici posteriores, as well as celiac branches, rr. coeliaci. The celiac branches go down and back and reach the celiac plexus along the left gastric artery. Fibers go to the liver, spleen, pancreas, kidney, small intestine and the colon.
Ticket number 45
1.Diaphragm: position, parts, function, blood supply, innervation.
Diaphragm, diaphragma , - a movable muscle-tendon septum between the chest and abdominal cavities. The diaphragm is the main respiratory muscle and the most important abdominal organ. The muscle bundles of the diaphragm are located along the periphery. Converging upward, from the periphery to the middle of the diaphragm, muscle bundles continue to the tendon center, centrum tendineum.A distinction should be made between the lumbar, costal and sternal parts of the diaphragm.
Muscle-tendon bundles lumbar, pars lumbalis,diaphragms start from the anterior surface of the lumbar vertebrae with the right and left legs, crus dextrum et crus sinistrum,and from the medial and lateral arcuate ligaments. The right and left legs of the diaphragm below are woven into the anterior longitudinal ligament, and at the top their muscle bundles intersect in front of the body of the I lumbar vertebra, limiting the aortic opening, hiatus aorticus.Above and to the left of the aortic opening, the muscle bundles of the right and left legs of the diaphragm intersect again, and then diverge again, forming the esophageal opening, hiatus esophageus.
On each side between the lumbar and costal parts the diaphragm has a triangular area devoid of muscle fibers - the so-called lumbar-costal triangle. Here the abdominal cavity is separated from the chest cavity only by thin plates of intra-abdominal and intrathoracic fascia and serous membranes (peritoneum and pleura). Diaphragmatic hernias may form within this triangle.
Costal part, pars costalis,the diaphragm starts from the inner surface of the six to seven lower ribs with separate muscle bundles that wedge between the teeth of the transverse abdominal muscle.
Sternum,pars sternalis,starts from the back of the sternum.
Function: during contraction, the diaphragm moves away from the walls of the chest cavity, its dome flattens, which leads to an increase in the chest cavity and a decrease in the abdominal cavity. While contracting with the abdominal muscles, the diaphragm increases intra-abdominal pressure.
Innervation: n. phrenicus.
Blood supply: a. pericardiacophrenica, a. phrenica superior, a. phrenica inferior, a. musculophrenica, aa. intercostales posteriores.
2.Spleen: development, topography, structure, function, blood supply, innervation.
Spleen, lien,performs the functions of immune control of blood. It is located on the path of blood flow from the main vessel large circle circulation - the aorta into the portal vein system, which branches into the liver. The spleen is located in the abdominal cavity, in the region of the left hypochondrium, at the level from IX to XI ribs.
The spleen has two surfaces: the diaphragmatic and the visceral. Smooth convex diaphragmatic surface,fades diaphragmatica,facing lateral and up to the diaphragm. Anteromedial visceral surface,faces visceralis,uneven. On the visceral surface, gate of the spleen,hilum splenicum,and areas to which adjacent organs are adjacent. Gastric surface, faces gdstrica,in contact with the fundus of the stomach. Renal surface, faces rendlis,adjacent to the upper end of the left kidney and to the left adrenal gland. Colonic surface, fades colica,located below the gate of the spleen, closer to its anterior end.
The spleen has two edges: the upper and lower and two ends (poles): the posterior and the anterior.
The spleen is covered on all sides by the peritoneum. Only in the area of \u200b\u200bthe gate, where the tail of the pancreas faces, is there a small area free of the peritoneum.
From fibrous membrane,tunica fibrosa,located under the serous integument, connective tissue beams depart inside the organ - spleen trabeculae,trabeculae splenicae... There is a parenchyma between the trabeculae, pulp(pulp) spleen,pulpa splenica.Isolate red pulp, pulpa rubra,located between venous sinuses, sinus venularis,and white pulp, pulpa alba.
Development and age characteristics of the spleen.The anlage of the spleen appears at 5-6 weeks of intrauterine development in the form of a small accumulation of mesenchymal cells in the thickness of the dorsal mesentery. At 2-4 months of development, venous sinuses and other blood vessels form. In a newborn, the spleen is rounded, has a lobed structure.
Vessels and nerves of the spleen.The spleen is approached by the eponymous (splenic) artery, which is divided into several branches that enter the organ through its gate. The splenic branches form 4-5 segmental arteries, and the latter branch into trabecular arteries. Pulpal arteries with a diameter of 0.2 mm are directed to the spleen parenchyma, around which the periarterial lymphoid muffs and the periarterial zone of the splenic lymphoid nodules are located. Each pulpal artery eventually divides into tassels - arteries about 50 microns in diameter, surrounded by macrophage-lymphoid sleeves (ellipsoids). The capillaries formed during the branching of arteries flow into the wide splenic venular sinuses located in the red pulp.
Venous blood from the spleen parenchyma flows through the pulp, then trabecular veins. The splenic vein formed at the gate of the organ flows into the portal vein.
The innervation of the spleen is carried out along sympathetic fibers that are suitable for the spleen as part of the plexus of the same name. Afferent fibers are the processes of sensory neurons that lie in the spinal nodes.
3. Organs of the immune system: classification, general patterns of the anatomical organization of the immune system.
The immune systemunites organs and tissues that protect the body from genetically foreign cells or substances coming from outside or formed in the body.
The immune system is composed of all organs that participate in the formation of cells of the lymphoid series, carry out protective reactions of the body, create immunity - immunity to substances with foreign antigenic properties. The parenchyma of these organs is formed by lymphoid tissue, which is a morphofunctional complex of lymphocytes, plasmocytes, macrophages and other cells located in the loops of reticular tissue. The organs of the immune system include the bone marrow, in which the lymphoid tissue is closely connected with the hematopoietic, the thymus (thymus gland), the lymph nodes, spleen, accumulation of lymphoid tissue in the walls of the hollow organs of the digestive, respiratory systems and urinary tract (tonsils, lymphoid - Peyer's - plaques, single lymphoid nodules).
With regard to the function of immunogenesis, the listed organs are divided into central and peripheral. To the central organs of the immune systeminclude bone marrow and thymus. In the bone marrow, B-lymphocytes (burs-dependent) are formed from its stem cells, which are independent in their differentiation from the thymus. The bone marrow in the human immunogenesis system is currently considered as an analogue of the bursa (bursa)Fabricius - a cell accumulation in the wall of the cloacal gut in birds.
TO peripheral organs of the immune system include the tonsils, lymphoid nodules located in the walls of the hollow organs of the digestive and respiratory systems, urinary tract, lymph nodes and spleen. The functions of the peripheral organs of the immune system are influenced by the central organs of immunogenesis.
4.The third branch of the trigeminal nerve and the area of \u200b\u200bits innervation.
Trigeminal nerve, item trigeminus,mixed nerve. The motor fibers of the trigeminal nerve start from its motor nucleus, which lies in the bridge. Sensory fibers of this nerve approach the pontine nucleus, as well as the nuclei of the midcerebral and spinal tract of the trigeminal nerve. This nerve innervates the skin of the face, frontal and temporal regions, the mucous membrane of the nasal cavity and paranasal sinuses, mouth, tongue, teeth, conjunctiva of the eye, chewing muscles, muscles of the floor of the oral cavity (maxillofacial muscle and anterior abdomen of the digastric muscle), as well as muscles straining the palatine curtain and eardrum. In the area of \u200b\u200ball three branches of the trigeminal nerve, there are autonomic (autonomous) nodes, which were formed from cells that were evicted during embryogenesis from the rhomboid brain. These nodes are identical in structure to the intraorgan nodes of the parasympathetic part of the autonomic nervous system.
The trigeminal nerve extends to the base of the brain with two roots (sensory and motor) at the point where the bridge joins the middle cerebellar peduncle. Sensitive root radix sensoria,much thicker than the motor root, radix motoria.Further, the nerve goes forward and somewhat laterally, enters into the splitting of the hard shell of the brain - trigeminal cavity, cavum trigeminale,lying in the area of \u200b\u200bthe trigeminal depression on the anterior surface of the temporal bone pyramid. In this cavity is a thickening of the trigeminal nerve - the trigeminal node, ganglion trigeminale(gasser knot). The trigeminal node has the shape of a crescent and is an accumulation of pseudo-unipolar sensitive nerve cells, the central processes of which form a sensitive root and go to its sensitive nuclei. The peripheral processes of these cells are directed as part of the branches of the trigeminal nerve and end with receptors in the skin, mucous membranes and other organs of the head. The motor root of the trigeminal nerve is adjacent to the trigeminal node from below, and its fibers are involved in the formation of the third branch of this nerve.
Three branches of the trigeminal nerve branch off from the trigeminal node: 1) the optic nerve (first branch); 2) the maxillary nerve (second branch); 3) the mandibular nerve (third branch). The optic and maxillary nerves are sensitive, and the mandibular nerves are mixed, it contains sensory and motor fibers. Each of the branches of the trigeminal nerve at its beginning gives off a sensitive branch to the hard shell of the brain.
Optic nerven. ophthalmicus,departs from the trigeminal nerve in the area of \u200b\u200bits node, is located in the thickness of the lateral wall of the cavernous sinus, penetrates into the orbit through the superior orbital fissure. Before entering the eye socket, the optic nerve gives tentorial (shell) branch, r. tentorii (meningeus).This branch is directed posteriorly and forks in the tentorium of the cerebellum. In the orbit, the optic nerve is divided into the lacrimal, frontal, and nasal ciliary nerves.
Maxillary nerven. maxillaris,departs from the trigeminal node, goes forward, leaves the cranial cavity through a round opening into the pterygo-palatine fossa.
Even in the cranial cavity from the maxillary nerve meningeal (middle) branch, r. meningeus (medius),which accompanies the anterior branch of the middle meningeal artery and innervates the dura mater of the brain in the region of the middle cranial fossa. In the pterygo-palatine fossa, the infraorbital and zygomatic nerves and nodal branches branch off from the maxillary nerve to the pterygopalatine node.
Mandibular nerven. mandibuldris,leaves the cranial cavity through the foramen ovale. It contains motor and sensory nerve fibers. When leaving the foramen ovale, motor branches extend from the mandibular nerve to the masticatory muscles of the same name.
Ticket number 51
1.Muscles and fascia of the lower leg, their topography, function, blood circulation, innervation. Anterior tibial, m. tibialis anterior. Start: lateral surface tibiae, interosseous membrane. Attachment: medial sphenoid and 1st metatarsal bones. Function: unbends the foot, raises its medial edge. Innervation: n. fibularis profundus. Blood supply: a. tibialis anterior.
Long finger extensor, m. extensor digitirum longus. Beginning: lateral condyle of the femur, fibula, interosseous membrane. Attachment: foot. Function: unbends toes and foot, raises the lateral edge of the foot. Innervation: n. fibularis profundus. Blood supply: a. tibialis anterior.
Long extensor of the big toe, m. extensor hallucis longus. Beginning: interosseous membrane, fibula. Attachment: nail phalanx of the 1st toe. Function: extends the foot and thumb. Innervation: n. fibularis profundus. Blood supply: a. tibialis anterior.
Triceps muscle of the leg, m. triceps surae: Calf muscle, m. gastrocnemius: lateral head (1), medial head (2), Flounder muscle, (3) m. soleus. Beginning: above the lateral condyle of the femur (1), above the medial condyle of the femur (2), the head and the upper third of the posterior surface of the fibula (3). Attachment: tendo calcaneus (calcaneal, Achilles tendon), calcaneal tubercle. Function: flexes the lower leg and foot and supines it - 1.2, flexes and supines the foot - 3. Innervation: n. tibialis. Blood supply: a. tibialis posterior.
Plantar, m. plantaris. Beginning: above the lateral condyle of the femur. Attachment: heel tendon. Function: tightens the capsule of the knee joint, flexes the lower leg and foot. Innervation: n. tibialis. Blood supply: a. poplitea.
Popliteal muscle, m. popliteus. Beginning: the outer surface of the lateral femoral condyle. Attachment: the posterior surface of the tibia. Function: bends the lower leg, turning it outward, tightens the capsule of the knee joint. Innervation: n. tibialis. Blood supply: a. poplitea.
Long finger flexor, m. flexor digitorum longus. Beginning: tibia. Attachment: distal phalanges of 2-5 fingers. Function: flexes and supines the foot, flexes the toes. Innervation: n. tibialis. Blood supply: a. tibialis posterior.
Long flexor of the big toe, m. flexor hallucis longus. Beginning: fibula. Attachment: distal phalanx of the thumb. Function: flexes and supines the foot, flexes the big toe. Innervation: n. tibialis. Blood supply: a. tibialis posterior, a. fibularis.
Posterior tibial muscle, m. tibialis posterior. Beginning: tibia, fibia, interosseous membrane. Attachment: foot. Function: flexes and supines the foot. Innervation: n. tibialis. Blood supply: a. tibialis posterior.
Peroneus longus muscle, m. fibularis longus. Beginning: fibula. Attachment: foot. Function: flexes and penetrates the foot. Innervation: n. fibularis superfacialis. Blood supply: a. inferior lateralis genus, a. fibularis.
Short peroneal muscle, m. fibularis brevis. Beginning: distal 2/3 fibulae. Attachment: tuberosity of the 5th metacarpal bone. Function: flexes and penetrates the foot. Innervation: n. peroneus superfacialis. Blood supply: a. peronea.
Shin fascia, fascia cruris, grows together with the periosteum of the anterior edge and medial surface of the tibia, covers the outside of the anterior, lateral and posterior muscle groups of the tibia in the form of a dense case from which the intermuscular septa extend.
2.Oral cavity, diaphragm of the mouth, palate, pharynx, vestibule and, accordingly, the oral cavity. Lips, cheeks, gums.
Oral cavity,cavitas oris,located at the bottom of the head, is the beginning of the digestive system. This space is limited from below by the muscles of the upper neck, which form the diaphragm (bottom) of the mouth, diaphragma oris;above is the sky; which separates the oral cavity from the nasal cavity. From the sides, the oral cavity is limited by the cheeks, the front - the lips, and from the back through the wide opening - throat,fauces,the oral cavity communicates with the pharynx. The teeth and tongue are located in the oral cavity, the ducts of the large and small salivary glands open into it.
The alveolar processes of the jaws and teeth divide the oral cavity into vestibule of the mouth,vestibulum oris,and the oral cavity itself,cavitas oris rgbrpa.The vestibule of the mouth is limited from the outside by the lips and cheeks, and from the inside by the gums - by the mucous membrane covering the alveolar processes of the upper and alveolar part lower jaw, and teeth. Behind the vestibule of the mouth is the actual oral cavity. The vestibule and the oral cavity itself communicate with each other through the gap between the upper and lower teeth. The entrance to the oral cavity, or rather on its threshold, - mouth gaprima dris,limited by the lips.
Upper lip and lower lip,labium superius et labium inferius,represent musculocutaneous folds. The base of the lips is formed by the fibers of the circular muscle of the mouth. The outer surface of the lips is covered with skin, the inner surface is covered with a mucous membrane. At the edge of the lips, the skin passes into the mucous membrane (transition zone, intermediate part). The mucous membrane of the lips on the eve of the mouth passes to the alveolar processes and the alveolar part of the jaws and forms well-defined folds along the midline - the frenulum of the upper lip and the frenum of the lower lip, frenulum labli superioris et frenulum labii inferioris.The lips, upper and lower, limiting the mouth gap, on each side pass one into the other in the corners of the mouth by means of the labial commissure - lip adhesions,commissura labiorum.
Solid sky, palatum durum, occupies the front two-thirds of the palate; its basis is formed by the palatine processes of the maxillary bones and the horizontal plates of the palatine bones. The suture of the palate is located along the median line on the mucous membrane covering the hard palate, raphe palati,from which 1-6 transverse palatine folds depart to the sides.
Soft sky,palatum molle,makes up one third of the entire sky and is located behind the hard palate. Formed by the connective tissue plate (palatine aponeurosis), which attaches to the posterior edge of the horizontal plates of the palatine bones, muscles that are woven into this plate, and the mucous membrane that covers the soft palate from above and below. The anterior part of the soft palate is horizontal, and the posterior, freely hanging, forms a palatine curtain, velum palatinum.The posterior part of the soft palate ends with a free edge with a small rounded process in the middle - the palatine tongue, uvula palatina.
The composition of the soft palate includes the following striated muscles: muscle straining the palatine curtain, muscle lifting the palatine curtain, muscle of the uvula, palatopharyngeal muscle, and palatopharyngeal muscle.
3.Lymphatic bed and regional lymph nodes of the uterus and rectum.
Diverting drugs uterus go in 2 directions: 1) from the bottom of the uterus along the tubes to the ovaries and further to the lumbar nodes, 2) from the body and cervix in the thickness of the broad ligament to the internal and external lateral nodes. Also flows into lnn. Sacrales and into the inguinal nodes along the round uterine ligament.
Regional lymph nodes of the uterus are located from the iliac arteries (common, external and internal) to the point of origin of the superior mesenteric artery from the aorta. The nodes are located along the common and internal iliac vessels and below the site of division of the common iliac artery into the external and internal. Also, the dummy has common iliac lymph nodes and nodes in the region of the aortic bifurcation.
On both sides, the LUs lie in the form of chains from the level of the beginning of the uterine artery to the point of origin of the inferior mesenteric artery from the aorta.
Nodes rectumaccompanying in the form of a chain the superior rectal artery-nodi lymphoidei rectales superiores. The lymphatic vessels and lymph nodes of the rectum are located mainly in the direction of the rectal arteries. From the upper part of the intestine, lymph flows into the nodes located along the superior rectal artery, from the part of the intestine corresponding to the hemorrhoidal zone, into the hypogastric lymph nodes, from the anus, into the inguinal lymph nodes. The diverting lymphatic vessels of the rectum anastomose with the lymphatic vessels of other organs of the small pelvis.
4.Vegetative plexuses of the chest and abdominal cavities.
Vegetative plexuses of the abdominal cavity
Abdominal aortic plexuslocated in the abdominal cavity on the anterior and lateral surfaces of the abdominal aorta. It is formed by several prevertebral sympathetic nodes, branches of the large and small internal nerves, nerve trunks, as well as fibers of the posterior trunk of the vagus nerve and sensory branches of the right phrenic nerve. This plexus has only 3-5 large nodes. The main ones are:
1. Paired celiac nodes, ganglia coeliaca,lunar shape, located to the right and left of the celiac trunk.
2. Unpaired superior mesenteric node, gan mesentericum sup -at the place of discharge from the aorta of the artery of the same name.
3. Paired aortorenal nodes, gan aortorenalia -at the origin of the renal arteries from the aorta.
Numerous branches branch off from the nodes of the abdominal aortic plexus - "the solar plexus ».
Distinguish secondary vegetative plexuses of the abdominal organs:
1. Celiac plexus unpaired, represented by numerous nerve trunks, entwining the celiac trunk and continuing on its branches.
2. Phrenic plexus, plexus phrenici,paired along the way aa. phrenicae inferiores.
3. Gastric plexus along the way left gastric arterythe upper gastric plexus is formed, along the right- bottom.
4. Splenic plexus
5. Hepatic plexus along the course a. hepatica propria.
6. Adrenal plexus
7. Renal plexus,
8. Testicular plexus, in women - ovarian plexus .
9. Superior mesenteric plexus.
10. Intermesenteric plexus,
11. Inferior mesenteric plexus.
The brain is formed from the anterior section of the neural tube, which already in the earliest stages of development differs from the trunk section in its width. The uneven growth of various sections of the wall of this section leads to the formation of three protrusions located one after another - the primary cerebral vesicles: anterior, prosencephalon, middle, mesencephalon, and posterior, rhombencephalon. Further, the anterior and posterior cerebral vesicles are subdivided into two secondary cerebral vesicles, resulting in five intercommunicating cerebral vesicles, from which all parts of the brain develop: terminal, telencephalon, intermediate, diencephalon, middle, mesencephalon, posterior metencephalon, and accessory, myelencephalon. The process of formation of five cerebral vesicles occurs simultaneously with the appearance of bends of the head section of the cerebral tube in the sagittal direction. First, the dorsal parietal bend appears in the mesencephalon, then in the same direction - the occipital bend between the myelencephalon and the spinal cord and, finally, the third ventral bridge bend - in the metencephalon. This process is accompanied by increased growth of the lateral sections of the head end of the neural tube and a lag in the growth of the dorsal and ventral walls (integumentary and bottom plates). The thickened lateral sections are divided by a border groove into the basal and pterygoid plates, of which the neuroblasts of the basal plate form the motor, and the neuroblasts of the wing plate form the sensory centers. Important autonomous centers are located between both plates in the intermediate zone. The border groove is traced throughout the trunk and head sections of the neural tube to the diencephalon. Here the main plate ends, in connection with which, the nerve cells of the telencephalon are derived only from the wing plate. The most significant differentiation and changes in shape are observed during the development of the derivatives of the anterior cerebral bladder telencephalon and diencephalon.
Figure: Development of the brain (by R.D.Sinelnikov).
a - five cerebral vesicles; 1 - the first bubble - the terminal brain; 2 - second bubble - diencephalon; 3 - third bubble - midbrain; 4 - fourth bubble - the hindbrain proper; 5 - fifth bubble - medulla oblongata; between the third and fourth bubbles - isthmus; b - model developing brain at the stage of five bubbles.
The terminal brain, telencephalon, is formed from a paired protrusion forward and outward of the wall of the primary anterior cerebral bladder, from which the right and left hemispheres of the brain develop. The striae of these protrusions rapidly increase in volume, significantly outstripping other parts of the brain in growth, and cover the derivatives of other cerebral vesicles, first from the sides, and then from the front and from above. The uneven growth of the medulla determines the appearance of grooves and convolutions on the surface of the formed hemispheres, among which those that appear the earliest (sulcus cerebri lateralis, sulcus centralis, etc.) are very constant. Along with the growth of the hemispheres, the longitudinal gap between them deepens and the configuration of their cavities - the lateral ventricles - changes sharply. The interventricular opening, which communicates the lateral ventricles with the third, narrows. At the base of the hemispheres, accumulations of gray matter develop - basal or subcortical nuclei. The olfactory brain rudiment also belongs to the derivatives of telencephalon.
The diencephalon, diencephalon, forms from the back of the anterior cerebral bladder. In the process of development, there is a sharp thickening of the side walls of this section, where large accumulations of gray matter are formed - the visual hillocks. In addition, at a very early stage of development, when the division of the anterior cerebral bladder is just beginning, the lateral walls give off external protrusions - two eye vesicles, from which the retina and optic nerves develop later. The strong development of the optic hillocks sharply narrows the diencephalon cavity and turns it into a narrow longitudinal slit - the third ventricle. From the dorsal wall of the diencephalon, the pineal gland develops, and from the protrusion of the ventral wall, a gray tubercle, a funnel and the posterior lobe of the pituitary gland are formed. Behind the gray tubercle, the rudiments of the papillary bodies are determined.
The middle cerebral bladder, mesencephalon, is characterized by a fairly uniform thickening of the walls, which turns its cavity into a narrow canal - the cerebral aqueduct, connecting the third and fourth ventricles of the brain. From the dorsal wall of the bladder, a plate of a quadruple develops, first the lower and then the upper tubercles. The ventral wall of the bladder, due to the development of cells and fibers of other parts of the brain, turns into massive fibrous bundles - the legs of the brain.
The posterior cerebral bladder, rhombencephalon, is subdivided into the hindbrain, metencephalon, and the medulla oblongata, myelencephalon, as well as into a narrow constriction - the isthmus of the rhomboid brain, isthmus rhombencephali, which separates the hindbrain from the middle. From the isthmus, the upper legs of the cerebellum and the anterior cerebral sail develop. On the ventral side, a bridge is formed, and on the dorsal side, first the worm, and then the cerebellar hemispheres. The development of the myelencephalon leads to the formation of the medulla oblongata.
The metencephalon and myelencephalon cavities merge and form the IV ventricle of the brain, which communicates with the central canal of the spinal cord and cerebral aqueduct. The ventral and lateral walls of the ventricle sharply thicken during development, while the dorsal wall remains thin and in the medulla oblongata it consists only of the epithelial layer, which grows together with the choroid, forming the tela chorioidea inferior.
As a result of the interaction of the middle part of the chordomesoderm with the dorsal plate of the ectoderm in the embryo from the 11th day of the prenatal period, the development of the nervous system begins (Fig. 491, A). The multiplication of nerve cells in the area of \u200b\u200bthe nerve sulcus leads to its closure in the cerebral tube, which up to 4-5 weeks has holes at the ends - blastopores (Fig. 491, B). The brain tube is detached from the ectodermal layer, plunging into the thickness of the middle germ layer. Simultaneously with the formation of the cerebral tube, paired nerve strips are laid under the epidermis layer, from which the ganglionic plates are formed. Ganglionic plates are the ancestors of the paravertebral head and spinal nerve nodes, which are a homologue of the paired nerve chain of invertebrates. Based on phylogenetic prerequisites, the ganglionic plates should have developed in embryogenesis earlier than the brain tube, but in reality they arise after the brain tube. This circumstance indicates that the progressive development of the central nervous system and its dominant functional significance in humans are preserved in the prenatal and postnatal periods.
491. Formation of the neural groove and neural tube at the 3rd week of embryonic development (according to Bartelmetz).
A: 1 - nerve groove; 2 - ectoderm; 3 - mesenchyme; 4 - endoderm; 5 - celoma; B: - the appearance of the embryo at the 3rd week of embryonic development. The neural tube at the head and tail ends of the body is open (according to Corner).
Following the laying of the ganglionic plates and the cerebral tube, intensive growth of the anterior end of the embryo is observed, mainly due to the development of the cerebral tube and sensory organs. From the cerebral tube, five cerebral vesicles and the spinal cord are isolated.
The developmental stage of one cerebral bladder corresponds to 16-20 days of intrauterine development, when the anterior end of the open cerebral tube overtakes the anterior end of the notochord in growth. During this period, at the level of the posterior part of the cerebral bladder, the auditory placodes are laid, representing the protrusion of the ectoderm (). The stage of development of two cerebral vesicles is observed after the 21st day of intrauterine development. The head end of the notochord lags behind the anterior part of the cerebral tube, which is separated by some narrowing into the prechordal and suprachordal cerebral vesicles. The prechordal brain bladder is not closed and covers the mouth bay, hanging over the anlage of the heart (Fig. 492). The brain tube is bent at the anterior end.
492. Sagittal section of the embryo at 10-11 weeks of development (according to Yu. G. Shevchenko).
1 - isthmus of the brain; 2 - the cavity of the hindbrain; 3 - longitudinal posterior bundle; 4 - bridge; 5 - transverse paths to the cores of the bridge (from the cortex to the cores of the bridge); 6 - pyramidal paths; 7 - spinal cord; 8 - spinal cord; 9 - spinal column; 10 - trachea; 11 - esophagus; 12 - epiglottis; 13 - language; 14 - pituitary gland; 15 - hypothalamus; 16 - diencephalon cavity; 17 - the cavity of the telencephalon; 18 - terminal brain; 19 - midbrain.
The stage of development of three cerebral vesicles is noted at 4-5 weeks of the prenatal period. The bubbles are called: front (prosencephalon), middle (mesencephalon), rhomboid (rhombencephalon) (Fig. 492). They differ from one another in bends and narrowings that deform the cerebral tube not only outside, but also its cavity. The wall of the cerebral vesicles is formed by three layers: 1) the matrix layer, or the embryonic layer, consisting of poorly differentiated cells; 2) the intermediate layer; 3) the marginal layer with few cellular elements. In the ventral wall of the cerebral vesicles, the interstitial layer is well developed, from which numerous nuclei are subsequently formed, and the dorsal wall is almost devoid of them. The anterior neuropore is closed by a structureless endplate. In the area of \u200b\u200bthe lateral wall of the anterior cerebral bladder, in which the eye cups are laid, the matrix layer of cells doubles and expands, forming the retina. The eye vesicles are formed at the site of the division of the anterior cerebral bladder into two parts. In the same period of development, the posterior part of the cerebral tube, corresponding to the spinal cord, has an inner ependymal and outer nuclear layers, which are more compact on the ventral wall. On the ventral wall of the cerebral vesicles, a ventral cerebral fold is formed, which contributes to the narrowing of the cavity of the cerebral vesicles. In the same way, the laying of the funnel and the pituitary gland occurs on the ventral wall of the anterior cerebral bladder (Fig. 492).
At 6-7 weeks of embryonic development, the period of formation of five cerebral vesicles begins. The forebrain is divided into the telencephalon and the diencephalon. The midbrain (mesencephalon) is not divided into secondary bubbles. The rhomboid brain is divided into the hindbrain (metencephalon) and the medulla oblongata (myelencephalon). During this period, the brain tube is strongly curved and the forebrain hangs over the horny bay and the heart. In the neural tube bends are distinguished: 1) the parietal bend, which has a bulge in the dorsal direction at the level of the midbrain (Fig. 492); 2) a ventral bridge protrusion at the level of the bridge; 3) the occipital bend, in location corresponding to the level of the spinal cord and medulla oblongata.
Endbrain (telencephalon) (I brain bladder)... In a 7-8-week-old embryo in the endbrain, in the lateral and medial regions, the development of the medial and lateral tubercles is observed, which represent the nucl anlage. caudatus et putamen. From the protrusion of the ventral wall of the telencephalon, the olfactory bulb and tract are also formed. At the end of the 8th week of embryonic development, a qualitative restructuring of the endbrain is carried out: a longitudinal groove appears along the midline, dividing the brain into two thin-walled cerebral hemispheres. These bean-shaped hemispheres lie outside the massive nuclei of the diencephalon, midbrain, and hindbrain. From the 6-week period, the primary stratification of the cortex begins due to the migration of neuroblasts in the pre- and post-mitotic phase. Only from the 9-10th week of embryonic development there is a rapid growth of the cerebral hemispheres and conducting systems that establish a connection between all the nuclei of the central nervous system. After 3 months of fetal development, thickening of the cerebral cortex, isolation of cell layers and growth of individual brain lobes occur. By the 7th month, a six-layered crust is formed. The lobes of the cerebral hemispheres develop unevenly. The temporal lobes grow faster, then the frontal, occipital and parietal lobes.
Outside the hemispheres, at the junction of the frontal and temporal lobes, there is an area in the area of \u200b\u200bthe lateral fossae that is lagging behind in growth. In this place, that is, in the walls of the lateral fossae, the basal nodes of the cerebral hemispheres and the cortex of the insula are laid. The developing cerebral hemispheres cover the third cerebral bladder by the sixth month of intrauterine development, and the fourth and fifth cerebral vesicles - by the ninth month. After the 5th month of development, a more rapid increase in the mass of the white matter is noted than in the cerebral cortex. The mismatch between the growth of white matter and bark contributes to the formation of many convolutions, grooves and crevices. At the third month on the medial surface of the hemispheres, the gyri of the hippocampus are laid, on the IV - the groove of the corpus callosum, on the V-cingulate gyrus, the spur, occipito-parietal and lateral grooves. On the 6th-7th months, grooves appear on the dorsolateral surface: central, pre- and postcentral grooves, grooves of the temporal lobes, the superior and inferior grooves of the frontal lobe, inter-parietal groove. During the period of development of the nodes and thickening of the cortex, the wide cavity of the endbrain turns into a narrow slit-lateral ventricle, entering the frontal, temporal and occipital lobes. The thin wall of the brain, together with the choroid, protrudes into the cavity of the ventricles, forming the choroid plexus.
Diencephalon (II brain bladder)... Has an uneven wall thickness. The lateral walls are thickened and are the tab of the thalamus, the inner part of the nucl. lentiformis, internal and external geniculate bodies.
In the lower wall of the diencephalon, protrusions are formed: the bookmarks of the retina and optic nerve, the optic pocket, the pocket of the pituitary funnel, the intersavoid and mastoid pockets. With the funnel of the pituitary gland, epithelial cells secreted from the head intestine grow together, forming the pituitary gland. Bottom wall, in addition to such pockets, it has several protrusions for the formation of a gray tubercle and mastoid bodies, which grow together with the pillars of the vault (derivatives of the cerebral bladder I). The upper wall is thin and devoid of the matrix cell layer. At the junction of the II and III cerebral vesicles, a pineal gland (corpus pineale) grows from the upper wall. A posterior cerebral commissure, leashes, leash triangles are formed under it. The rest of the upper wall is transformed into the choroid plexus, which is drawn into the cavity of the third ventricle.
The anterior wall of the diencephalon is formed by a derivative of the telencephalon in the form of lamina terminalis.
Midbrain (mesencephalon) (III brain bladder)... It has a thicker ventral wall. Its cavity turns into a cerebral aqueduct, which communicates the III and IV cerebral ventricles. From the ventral wall, after the third month, the legs of the brain develop, containing ascending (dorsally) and descending (ventrally) pathways, between which the black matter, red nuclei, nuclei of the III and IV pairs of cranial nerves are laid. The anterior perforated substance is located between the legs. Initially, the lower colliculus develops from the dorsal wall, and then the upper colliculus of the midbrain. From these tubercles, bundles of fibers emerge - brachia colliculorum superius et inferius to connect with the nuclei of the III cerebral bladder and the upper legs of the cerebellum to connect with the nuclei of the cerebellum.
Hindbrain (metencephalon) (IV brain bladder) and medulla oblongata (myelencephalon) (V brain bladder) elongated along one line and do not have clear intervesical boundaries.
The brain develops from the anterior, enlarged section of the brain tube. Development goes through several stages. In a 3-week-old embryo, there is a stage of two cerebral vesicles - anterior and posterior. The anterior bubble in terms of growth rates overtakes the notochord and is ahead of it. The posterior is located above the notochord. At the age of 4-5 weeks, the third brain bladder forms. Further, the first and third cerebral vesicles are divided into two, each resulting in 5 bubbles. From the first cerebral bladder, the paired terminal brain (telen-cephalon) develops, from the second - the diencephalon (diencephalon), from the third - the midbrain (mesencephalon), from the fourth - the hindbrain (meten-cephalon), from the fifth - the medulla oblongata (myelencephalon ). Simultaneously with the formation of 5 bubbles, the brain tube bends in the sagittal direction. In the midbrain region, a bend in the dorsal direction is formed - the parietal bend. On the border with the anlage of the spinal cord - another bend also goes in the dorsal direction - the occipital, in the hindbrain region, a cerebral bend is formed, going in the ventral direction.
In the fourth week of embryogenesis, protrusions in the form of bags are formed from the wall of the diencephalon, which later takes the form of glasses - these are the eye glasses. They come into contact with the ectoderm and induce lens placodes in it. The optic cups maintain a connection with the diencephalon in the form of eye stalks.
Subsequently, the stems turn into optic nerves. The retina of the eye with receptor cells develops from the inner layer of the glass. From the outside - the choroid and sclera. Thus, the visual receptor apparatus is, as it were, a part of the brain brought out to the periphery.
This protrusion of the wall of the anterior cerebral bladder gives rise to the olfactory tract and the olfactory bulb.
Heterochronous maturation of neural systems in the brain
The sequence of maturation of the neural systems of the brain in embryogenesis is determined not only by the regularities of phylogenesis, but, to a large extent, is determined by the stages in the formation of functional systems (Fig. V. 1). First of all, those structures ripen that should prepare the fetus for birth, that is, for life in new conditions, outside the mother's body.
Several stages can be distinguished in the maturation of the neural systems of the brain.
First step. Single neurons of the anterior midbrain and cells of the mesencephalic nucleus of the trigeminal (V) nerve mature most early. The fibers of these cells germinate earlier than others in
the direction of the ancient cortex and further to the neocortex. Due to their influence, the neocortex is involved in the implementation of adaptive processes. Mesencephalic neurons are involved in maintaining the relative constancy of the internal environment, primarily, the blood gas composition and are involved in the mechanisms of general regulation metabolic processes... The cells of the mesencephalic nucleus of the trigeminal nerve (V) are also associated with the muscles involved in the sucking act and are part of the functional system associated with the formation of the sucking reflex.
Second phase. Under the influence of cells maturing at the first stage, the underlying structures of the brain stem of cells maturing at the first stage develop. These are separate groups of neurons of the reticular formation of the medulla oblongata, the posterior part of the pons and neurons of the motor nuclei of the cranial nerves. (V, VII, IX, X, XI, XII), ensuring the coordination of the three most important functional systems: sucking, swallowing and breathing. This entire system of neurons is characterized by an accelerated rate of maturation. They quickly outrun neurons maturing at the first stage in terms of maturity.
At the second stage, early maturing neurons of the vestibular nuclei localized at the bottom of the rhomboid fossa are active. The vestibular system develops at an accelerated rate in humans. Already by 6-7 months of embryonic life, it reaches the degree of development characteristic of an adult.
Stage three. The maturation of neural ensembles of the hypothalamic and thalamic nuclei also occurs heterochronously and is determined by their inclusion in various functional systems. For example, the nuclei of the thalamus, involved in the thermoregulation system, develop rapidly.
In the thalamus, neurons of the anterior nuclei mature later than others, but the rate of their maturation sharply jumps up to birth. This is due to their participation in the integration of olfactory impulses and impulses of other modalities that determine survival in new environmental conditions.
Fourth stage. Maturation of reticular neurons first, then - of the remaining cells of the paleocortex, archicortex, and basal forebrain. They are involved in the regulation of olfactory reactions, maintaining homeostasis, etc. The ancient and old cortex, which occupy a very small area of \u200b\u200bthe hemisphere in humans, are already fully formed by birth.
Fifth stage. Maturation of neural assemblies of the hippocampus and limbic cortex. This occurs at the end of embryogenesis, and the development of the limbic cortex continues into early childhood. The limbic system is involved in organizing and regulating emotions and motivations. For a child, this is primarily food and drink motivation, etc.
In the same sequence in which the parts of the brain mature, myelination of the corresponding fiber systems occurs. The neurons of early maturing systems and structures of the brain send their processes to other areas, usually in the oral direction, and, as it were, induce the subsequent stage of development.
The development of the neocortex has its own characteristics, but it also proceeds according to the principle of heterochrony. So, according to the phylogenetic principle, the ancient crust appears the earliest in evolution, then the old one, and only after that the new crust appears. In human embryogenesis, a new cortex is laid earlier than the old and ancient crust, but the latter develop at a rapid pace and reach the maximum area and differentiation by the middle of embryogenesis. Then they begin to shift to the medial and basal surfaces and are partially reduced. The insular region, which is only partially occupied by the neocortex, quickly begins its development and matures by the end of the prenatal period.
Those areas of the neocortex that are associated with phylogenetically older vegetative functions, for example, the limbic region, mature most rapidly. Then the areas that form the so-called projection fields of various sensory systems mature, where sensory signals from the senses come. So, the occipital region is laid in the embryo at 6 lunar months, but its full maturation is completed by the age of 7 years.
Associative fields ripen somewhat later. The last to mature are the most phylogenetically young and functionally the most complex fields, which are associated with the implementation of specifically human functions of a higher order - abstract thinking, articulate speech, gnosis, praxis, etc. These are, for example, speech-motor fields 44 and 45. Cortex the frontal region is laid in a 5-month-old fetus, full maturation is delayed up to 12 years of life. Fields 44 and 45 require a longer time to develop, even at high ripening rates. They continue to grow and develop during the first years of life, during adolescence and even in adults. At the same time, the number of nerve cells does not increase, but the number of processes and the degree of their branching, the number of spines on the dendrites, the number of synapses increase, myelination of nerve fibers and plexuses occurs. The development of new areas of the cortex is facilitated by educational and educational programs that take into account the peculiarities of the functional organization of the child's brain.
As a result of the uneven growth of sections of the cortex during ontogeny (both pre- and postnatal), in some areas there is, as it were, the pushing back of certain sections deep into the furrows due to the influx of adjacent, functionally more important ones above them. An example of this is the gradual immersion of the islet deep into the Sylvian fissure due to the powerful growth of adjacent parts of the cortex, which develop with the appearance and improvement of the child's articulate speech - the frontal and temporal operculum - the speech-motor and speech-auditory centers, respectively. The ascending and horizontal anterior branches of the Sylvian cleft are formed from the influx of the triangular gyrus and develop in humans at the very late stages of the prenatal period, but this can also occur postnatally, rather in adulthood.
In other areas, the uneven growth of the cortex is manifested in the reverse order: a deep groove, as it were, unfolds, and new sections of the cortex, previously hidden in the depth, emerge on the surface. This is how the transverse occipital groove disappears at the later stages of prenatal ontogenesis, and the parieto-occipital gyri - cortical sections associated with the implementation of more complex visual-gnostic functions; the projection visual fields move to the medial surface of the hemisphere.
The rapid increase in the area of \u200b\u200bthe neocortex leads to the appearance of furrows dividing the hemispheres into convolutions. (There is another explanation for the formation of furrows - this is the germination of blood vessels). The deepest grooves (cracks) are formed first. For example, from 2 months of embryogenesis, a sylvian fossa appears and a groove is laid. Shallower primary and secondary grooves appear later, create a general plan for the structure of the hemisphere. After birth, tertiary grooves appear - small, varying in shape, they individualize the pattern of grooves on the surface of the hemisphere. In general, the order of furrow formation is as follows. By the 5th month of embryogenesis, the central and transverse occipital grooves appear, by the 6th month - the upper and lower frontal, marginal and temporal grooves, by the 7th month - the upper and lower pre- and postcentral, as well as the interparietal grooves, by the 8th month the middle frontal month.
By the time a child is born, different parts of his brain are not developed equally. The structures of the spinal cord, the reticular formation and some nuclei of the medulla oblongata (nuclei of the trigeminal, vagus, hypoglossal nerves, vestibular nuclei), midbrain (red nucleus, substantia nigra), individual nuclei of the hypothalamus and limbic system are more differentiated. The neural complexes of the phylogenetically younger regions of the cortex - the temporal, inferior parietal, frontal, and striopal-lidar system, optic hillocks, many nuclei of the hypothalamus and cerebellum - are relatively far from final maturation.
The sequence of maturation of brain structures is determined by the timing of the onset of activity of the functional systems that these structures are part of. So, the vestibular and auditory apparatus begin to form relatively early. Already at the stage of 3 weeks, thickening of the ectoderm is outlined in the embryo, which turns into auditory placodes. By the 4th week, the auditory vesicle is formed, consisting of the vestibular and cochlear sections. By the 6th week, the semicircular canals are differentiated. At 6.5 weeks, afferent fibers ripen, coming from the vestibular ganglion into the rhomboid fossa. At 7-8 weeks, the cochlea and spiral ganglion develop.
In the auditory system, at birth, a hearing aid is formed that is able to perceive stimuli.
Along with the olfactory one, the hearing aid is leading from the first months of life. The central auditory tract and cortical auditory zones mature later.
By the time of birth, the apparatus that provides the sucking reflex is fully matured. It is formed by the branches of the trigeminal (V pair), facial (VII pair), lingo-pharyngeal (IX pair) and vagus (X pair) nerves. All fibers are myelinated at birth.
The visual apparatus develops partially by the time of birth. The visual central pathways to birth are myelinated, while the peripheral (optic nerve) is myelinated after birth. The ability to see the world around us is the result of learning. It is determined by the conditioned reflex interaction of sight and touch. Hands are the first object of their own body that comes into the child's field of vision. Interestingly, the position of the hand, which allows the eye to see it, is formed long before birth, in an embryo of 6-7 weeks (see Fig. VIII. 1).
As a result of myelination of the optic, vestibular and auditory nerves, a 3-month-old child has an accurate positioning of the head and eyes to the source of light and sound. A 6 month old baby begins to manipulate objects under visual control.
The structures of the brain, which ensure the improvement of motor reactions, are also consistently maturing. At 6-7 weeks, the red nucleus of the midbrain matures in the embryo, which plays an important role in the organization of muscle tone and in the implementation of set reflexes when coordinating the posture in accordance with the rotation of the trunk, arms, and head. By 6-7 months of prenatal life, the higher subcortical motor nuclei - striated bodies - mature. The role of the tone regulator in different positions and involuntary movements passes to them.
The movements of the newborn are inaccurate, undifferentiated. They are provided by influences coming from the striatum. In the first years of a child's life, fibers grow from the bark to the striatum, and the activity of the striatum begins to be regulated by the bark. The movements become more precise and differentiated.
Thus, the extrapyramidal system becomes under the control of the pyramidal system. The process of myelination of the central and peripheral pathways of the functional movement system occurs most intensively up to 2 years. During this period, the child begins to walk.
The age from birth to 2 years is a special period during which the child also acquires the unique ability to articulate speech. The development of a child's speech occurs only through direct communication with people around him, about the learning process. The apparatus that regulates speech includes the complex innervation of various organs of the head, larynx, lips, tongue, myelinating pathways in the central nervous system, as well as the formed specifically human complex of speech fields of the cortex of 3 centers - speech-motor, speech-auditory, speech-visual, united by a system of bundles of associative fibers into a single morphological and functional speech system. Human speech is a specifically human form of higher nervous activity.
Brain mass: age, individual and sex variability
Brain mass during embryogenesis changes unevenly. In a 2-month-old fetus, it is ~ 3 g. For a period of up to 3 months, the brain mass increases ~ 6 times and is 17 g, by 6 lunar months - another 8 times: -130 g. In a newborn, the brain mass reaches: 370 g - in boys and 360 g - in girls. By the age of 9 months, it doubles: 400 g. By the age of 3, the mass of the brain triples. By the age of 7, it reaches 1260 g - in boys and 1190 g - in girls. The maximum brain mass is reached in the 3rd decade of life. At older ages, it decreases.
The brain mass of an adult male is 1150-1700 g. Throughout life, the brain mass of men is higher than that of women. Brain mass has a noticeable individual variability, but cannot serve as an indicator of the level of development of a person's mental abilities. It is known, for example, that I.S. Turgenev's brain mass was 2012, Cuvier - 1829, Byron - 1807, Schiller - 1785, Bekhterev - 1720, I.P. Pavlova - 1653, D.I. Mendeleev - 1571, A. France - 1017
To assess the degree of brain development, a "cerebralization index" (the degree of brain development with the excluded influence of body weight) was introduced. According to this index, a person is sharply different from animals. It is very important that during ontogenesis in humans it is possible to distinguish a special period in development, which is distinguished by the maximum "index of cerebralization". This period corresponds to the period of early childhood, from 1 to 4 years. After this period, the index declines. Changes in the cerebralization index are confirmed by neurohistological data. So, for example, the number of synapses per unit area of \u200b\u200bthe parietal cortex after birth increases sharply only up to 1 year, then decreases slightly until 4 years of age and drops sharply after 10 years of a child's life. This indicates that it is the period of early childhood that is the time of a huge number of possibilities inherent in the nervous tissue of the brain. The further development of human mental abilities largely depends on their implementation.
In conclusion of the chapters on the development of the human brain, it should be emphasized once again that the most important specifically human feature is the unique heterochrony of the neocortex anlage, in which the development and final maturation of the brain structures associated with the implementation of higher-order functions occur for a fairly long time after birth. Perhaps this was the greatest aromorphosis that determined the separation of the human branch in the process of anthropogenesis, since it "introduced" the process of learning and education into the formation of the human personality.
On this day:
- Birthdays
- 1904 Born Nikolay Nikolaevich Voronin - Soviet archaeologist, one of the largest specialists in ancient Russian architecture.
- Death days
- 1947 Died - Russian artist, mystic philosopher, writer, traveler, archaeologist, public figure. The author of the idea and initiator of the Roerich Pact, the first international treaty in history on the protection of cultural heritage, which established the priority of protecting cultural property over military necessity. He carried out excavations in the Petersburg, Pskov, Novgorod, Tver, Yaroslavl, Smolensk provinces.