The development of the facial skull and the brain skull should be considered separately, as they have independent embryonic primitives, the characteristics of the structure and the function, although topographic analytomically are in close relationships. In constructing a brain skull, a more ancient formation of a skull takes place to take part, which is held by the cartilaginous stage of development, with which the capsules of the senses and phylogenetically, more young bones of the skull and face cruise, are affected by the connecting tissue. The base and arch of the skull take part in the formation of bone capacity for the central nervous system and protect the brain from damage.
Development of the brain part of the skull. The bones of the base of the skull take place three stages of development: the interfachant, cartilage and bone.
Primary segmentation in the head of the embryos is observed only in the occipital part, where at the level of the back of the brain there is a cluster of mesenchyma around the chord (Fig. 69). With the growth of the brain develops and the surrounding mesenchym; Its deep leaflete serves as a derivative of brain shells, and is external, turns into a membrane skull. The membrane skull in some aquatic animals is maintained throughout life, and in humans only occurs in the embryonic period and after birth in the form of spring and interfluents of the webbed fabric between the bones. During this period, the developing hemispheres of the brain do not meet obstacles from the connecting skull.
69. Scheduled pattern of pre-mining clusters of mesenchyma in a human embryo of 9 mm (bardin).
1 - chord;
2 - the occipital complex;
3 - III cervical vertebra;
4 - blade;
5 - Hand bones;
6 - palm plate;
7 - VII edge;
8 - I Lumbar vertebra;
9 - pelvis;
10 - leg bones;
11 - sacral vertebrae.
70. Booking of prejudo and oolehropod plates of developing skull.
1 - Prejudo plates (crossbars);
2 - Okolokhordovy plates;
3 - chord;
4 - olfactory capsule;
5 - visual fossa;
6 - hearing capsule;
7 - Basic Channel.
At the 7th week of intrauterine development, the conversion of the rumbled tissue of the skull in the cartilage is observed, and the roof and the front part of it remains smoky. The cartilage tissue base fabric is divided into cranial crossbars, lying ahead of the chord - more than the edges of the chord-paraphorodal plates and the capsules of the senses (Fig. 70). During this period of the development of the skull, blood vessels and nerves will germinate its cartilaginous base and take part in the formation of future holes, cracks and channels of the bones of the base of the skull (Fig. 71. A, b). Card crossbars and paraphorodal plates grow together into a common plate, which has a hole at the place of the future Turkish saddle, located near the front end of chord. Through this hole, the cells of the rear wall of the pharynx, forming the front part of the pituitary gland, the total cartilaginous plate also grows with olfactory, eye and hearing capsules and with a webbed roof of the skull. The front end of the cartilaginous base of the skull is converted to a vertical plate between the olfactory capsules in the form of a future nasal partition.
Later, on the 8-10th week of intrauterine development, in the cartilage base and the roof of the connecting skull, bone points arise (see the development of individual bones of the skull).
71. Cleaning base of the skull (by Hertwig).
A - embryo 7 weeks; B - fruit 3 months; 1 - olfactory capsule; 2 - lattice bone; 3 - upper basic slit; 4 - a big wing of a wedge-shaped bone; 5 - Turkish saddle; 6 - torn hole; 7 - hearing capsule; 8 - jugular hole; 9 - inner hearing aid; 10 - a large occipital hole.
Development of the face of the skull. The development of the bone of the face must be considered and compared with the development and structure of the bones of aquatic animals. Throughout their lives, there is a gill for life, and the human embryo has a relatively short time at the human embryo. A man and mammals in the stage of development of the web-based foundation and the skull vessel are laid seven gill arcs. During this period, the facial skull has a lot of common features with a shark skull (Fig. 72).
72. Skull of sharks (according to E. Gundrich).
1 - cerebral skull; 2 - opening for the exit II, III, IV and V pairs of cranial brain nerves; 3 - Square cartilage; 4 - Mekkelev cartilage; 5 - Harvesting; 6 - subwage cartilage; 7 - actually subwage cartilage; I - VII - gill arcs.
The differences are that the shark has an open message between the outer and internal gill pockets. At the human embryo, gill cracks are closed with a connective tissue. In the future, various organs are formed from the gill arches (Table 2).
| The formation of skulls existing in the embryonic period in aquatic animals | The formation of skulls existing in adult water animals and in the embryonic period of humans | Hummer derivative in humans |
| I Glaba Arc | Dorsal cartilage Ventral cartilage |
Anvil (hearing stone) lower jaw hammer (hearing bone) |
| II Glaba Arc | Podium-jaw cartilage (upper part) Podium cartilage (bottom) | Stirrupp (hearing a hearing bone) Love-shaped process of temporal bone, small horn of podium bone, Shieldy-speaking bunch |
| The cavity between I and II gill arcs | Splashing | Drum cavity Hearing Pipe |
| III Zhebalny Arc | Gill arc Unpacking for the connection of gill arcs |
Large Horn of Podium Bones, Body of Podium Bone |
| IV Glaba Doug. | Gill arc | Thyroid cartilage larynges |
| V Zhaba Doug. | » » | |
| Vi Zhebalny Arc | Gill arcs in aquatic animals | |
| VII GORABLE DUGA | » » | Reducing |
Thus, only a part of the bones of the facial skull (lower jaw, the sublard bone, hearing bones) develops from the gill apparatus.
The process of forming a facial skull is traced at the human embryo and lower animal species. On the example of the development of the skull, you can make sure that the person passed the difficult path of evolutionary development from the water ancestor to the ground animal. Balfour and Dorn showed that the head represents the transformed end end of the body, which, as the entire body, was also segmented before the development of the central nervous system, was segmented. With the formation of the senses and brain organs at the front end of the body and the corresponding conversion of gill arcs in the jaw and submandibular arc, the vertebrae, the vertebral parts of the head merged with each other and gave the basis for the skull. Consequently, the precrowdal and paraphorodal plates are transformed parts of the axial skeleton.
Characteristic signs of chordovy:
- three-layer structure;
- secondary body cavity;
- the appearance of chord;
- conquest of all habitats (water, ground-air).
During the evolution, organs were improved:
- movements;
- reproduction;
- breathing;
- blood circulation;
- digestion;
- feelings;
- nervous (regulating and controlling all organs);
- changed bodies of the body.
Biological meaning of all living things:
general characteristics
Dwell - freshwater reservoirs; in sea water.
Life expectancy - from several months to 100 years.
Dimensions - From 10 mm to 9 meters. (Fish grows all life!).
Weight - From several grams to 2 tons.
Fish - the most ancient primary vertebrates. They are able to live only in the water, most species are good swimmers. The class of fish in the process of evolution was formed in the aquatic environment, the characteristic features of the structure of these animals are associated with it. The main type of translational movement is the lateral wave-like movements due to the contractions of the muscles of the tail department or the entire body. Breast and abdominal filth fins perform the function of stabilizers, serve for lifting and lowering the body, turns of stops, slow smooth movement, preservation of equilibrium. Unpaired spine and milking fins act like a keel, giving the body of fish stability. The mucous layer, on the surface of the skin, reduces friction and contributes to the rapid movement, and also protects the body from pathogens of bacterial and fungal diseases.
External structure of fish
Side Line
Well-developed side line organs. The side line perceives the direction and strength of water.
Due to this, even blinded it does not stumble upon obstacles and is able to catch moving prey.
Internal structure
Skeleton
The skeleton is a support for a well-developed cross-striped musculature. Some muscle segments were partially rebuilt, forming muscle groups in the head, jaws, gill covers, chest fins, etc. (Eye, superior and fasable muscles, muscles of paired fins).
Swimming bubble
Over the intestine is a thin-walled bag - a swimming bubble filled with a mixture of oxygen, nitrogen and carbon dioxide. The bubble was formed from the intestinal rose. The main function of the swimming bubble is hydrostatic. By changing the pressure of gases in the swimming bubble, the fish can change the depth of the dive.
If the volume of the swimming bubble does not change, the fish is located on the same depth, as if hung in the water temperature. When the volume of the bubble increases, the fish rises up. When lowering the reverse process takes place. The swimming bubble in part of the fish can participate in gas exchange (as an additional respiratory body), perform the functions of the resonator when reproducing various sounds, etc.
Body cavity
System of organs
Digestive
The digestive system begins the mouth of the hole. The perch and other predatory bone fish on the jaws and many bones of the oral cavity are numerous small sharp teeth that help to capture and retain production. There is no muscular language. Through the sip in the food esophagus, it gets in a large stomach, where it begins to digest under the action of hydrochloric acid and pepsin. Partially digested food enters the small intestine, where pancreatic and liver ducts are flowing. The latter highlights bile that clocks in the bustling bubble.
At the beginning of the small intestine, blind processes fall into it, due to which the ferrous and suction surface of the intestine increases. Unpained residues are displayed in the rear and through the posterior hole are removed outward.
Respiratory
Respiratory organs - Zhabra - located on four gill arcs in the form of a number of bright red gill petals covered outside the numerous finest folds that increase the relative surface of the gills.
Water falls into the mouth of the fish, flickering through the gill gaps, wash the gills, and throws out out from under the life lid. Gas exchange takes place in numerous gill capillaries, the blood in which flows to meet the washing gills of water. Fish is capable of assimilating 46-82% dissolved oxygen in water.
Opposite each row of gill petals there are whitish gill stamens, which are of great importance for nutrition of fish: some form a commodular apparatus with a corresponding structure, others contribute to holding mining in the oral cavity.
Blood
The circulatory system consists of a two-chamber heart and vessels. The heart has a atria and a ventricle.
Separation
The excretory system is represented by two dark-red tank-like kidneys lying below the spinal column almost along the entire body cavity.
The kidneys filters out of the blood of the decomposition of substances in the form of urine, which in two ureters enters the bladder, opening the outward behind the rear-ground opening. A significant part of the poisonous decay products (ammonia, urea, etc.) is derived from the body through the gill petals of fish.
Nervous
The nervous system has the form of a hollow tube thickened. Its ending its end forms a brain, in which there are five departments: front, intermediate, middle brain, cerebellum and an oblong brain.
Centers of different organs of feelings are placed in various brain departments. The cavity inside the spinal cord is called the cerebrospinal channel.
Sense organs
Taste receptors, or taste buds are in the mucous membrane of the oral cavity, on the head, the mustaches elongated the rays of the fins, are scattered over the entire surface of the body. In the surface layers of the skin, tactile calves and thermistors are scattered. Mainly on the head of fish concentrates the receptors of an electromagnetic feeling.
Two big eyes Located on the sides of the head. The crystal language is round, does not change the forms and almost concerns the flattened cornea (therefore the fish is minced and see no further than 10-15 meters). In most bone fish, the retina contains sticks and columns. This allows them to adapt to changing illumination. Most bone fish have color vision.
Head organs Presented only in the inner ear, or a webbed labyrinth, located on the right and left in the bones of the back of the skull. Sound orientation is very important for aquatic animals. The speed of propagation of sounds in water is almost 4 times more than in the air (and close to the sound permeability of the fishes body). Therefore, even a relatively simple arranged organ of hearing allows the fish to perceive sound waves. Hearing organs are anatomically associated with equilibrium authorities.
From the head to the tail fins along the body stretches a row of holes - side Line. The holes are associated with the channel immersed in the skin, which on the head strongly branches and forms a complex network. Side line is a characteristic sense body: thanks to her, fish perceive water fluctuations, direction and stream force, waves that are reflected from different items. With this body, the fish are focused in water flows, perceive the direction of movement of production or predator, are not encountered on solid items in barely transparent water.
Reproduction
Fish multiplied in water. Most species are laying off caviar, exterior fertilization, sometimes internal, in these cases there is a legability. The development of fertilized caviar lasts from several hours to several months. The larvae, which come out of the caviar, have the remainder of the yolk bag with the supply of nutrients. First, they are sedimed, and they feed only by these substances, and then begin to actively feed on various microscopic water organisms. A few weeks later, the scales are developing from the larvae and a male-similar to adult fish.
Spare fish is happening at different times of the year. Most freshwater fish puts the caviar among aquatic plants in shallow water. Fish fertility on average is much higher than the fecundity of ground vertebrates, it is associated with the big death of caviar and fry.
Gill dugsThe already mentioned in the previous article, in phylogenetic terms, are only a reminiscence on the development of gills, functioning as a breathing organs in lower animals (lancing, larvae of amphibians, fish). These arcs are formed in the field of the pharynganeal (head or pharyngeal) intestine, that is, approximately in the future cervical area. They arise as a result of the accumulation between the entoderm of the pharynganeal intestine and the surface ectoderm of the mesenchymal tissue in the form of semi-cup strips of thickening, clamping the pharynganeal intestine on both sides and are also included on the ventral wall.
Between these arcs The entoderm of the pharynganeal intestine is made towards the indentation of the outer ectoderma, due to which the grooves (grooves, pockets) occur in the external (surface) side and on the inner (intestinal) side, in which Etoderma directly, without the mediation of mesenchym, is in contact with the intestinal entoderm. Thus, individual arcs are separated by a membrane formed by ectoderma and entoderm, which are called Membranae Obturantes.
In animals, breathable gillsMEMBRANA OBTURANS is perforated between arcs, due to which gummy slots arise in these places, through which water from the intestine enters the external environment. From the water to the blood circulating in the capillary networks of vessels in the tissue of gill arcs (modified in these animals into the breathing organs - gills), oxygen comes. The person's perforation of Membranae Obturantes is observed only in rare cases, therefore the formation of true gill cracks does not occur.
Gill dugs, external and inner gill grooves are only transient formations in humans. In the process of further development, they are transformed into a number of important organs arising from both gill arcs, so from the entodermal liner of the inner gill grooves, and to a lesser extent - from the ectoderma of the outer gill grooves. The development of these formations, called in accordance with the Latin name of the Zhaba Arc (Arcus Branchialis) Branhiogenic, will be described in more detail below.
If you look at the ventral surface The head end of the embryo achieves approximately 3.5 mm, then it can be noted that a significant part of this surface is occupied by a large protrusion of the frontal area - Processus Frontalis. Under this protrusion there is a wide cavity that arose as a result of the inhibitory of the outer ectoderma between the two parts of the separated one of the first grease arc (jaw arc), that is, between the bookmarks of the future upper and lower jaws.
Etoderma, lining the bottom of this cavity, heads to the blind end of the head bowel and adjoins it, forming together with it already mentioned partition between the bookmarks of the primary oral cavity and the head end of the intestine, called the pharynganeal membrane. Over time, this membrane is perforated, due to which the message appears with the external environment. The induction of the outer ectoderma towards the head intestinal and its cavity serve as a bookmark of the robust cavity of the mouth.
Primary mouth cavity It is limited from the sides of two steam of processes, not yet connected ventral and medial, which penetrate here, coming out of the side walls of the head end of the embryo. We are talking about the topless (Processus Maxillaris) and the Lumandless Processs (Processus MandiBulares) lying above and under it. Both pairs of these processes are formed as a result of the dismemberment of the first (maxillary) gill arc. The third and fourth gill arcs at this stage of development do not reach the ventral wall of the embryo head.
Opening of the primary oral cavity In this stage of development (at the end of the first month), there are five tubercles, so-called processes, namely: from above the unpacking abnormal process (Processus Frontalis), with sides hole limited by paired maxillary process (Processus Maxillares), and the lower edge of the holes are limited Farm Mandibulares (Processus Mandibulares), which, fightering in the midline into a single arcamine mandibular process, form a laying for the lower jaw.
The main part of the respiratory system of fish is the gills. It is due to them that the bulk of oxygen comes into the blood, and carbon dioxide is distinguished from the blood. However, gas exchange from fish is not only through the gills. All kinds of breathing takes part. But at the same time, in species living in water bodies with a large oxygen content, breathing through the skin is insignificant. And in fish that live in the conditions of the deficiency of oxygen (soma, carps, acne), skin gas exchange can occupy a substantial part of breathing. Also in bone fish, a small gas exchange occurs in the swimming bubble. At bubble bubble, the swimming bubble even looked into a cellular light, so they can breathe not only in water, but also in the air.
Describing the respiratory system of fish, usually consider the structure of their gill apparatus, which is in the field of pharynx. The gills are out gill slotssupporting them gwee Doug., lady petals and gill stamens. In bone fish, the mandatory structure of the respiratory system is also a couple gill covers. They protect the gills from the fall of foreign particles. The protective function is performed by gummy stamens. They are addressed towards the pharynx and protect thin and gentle gill petals from the particles from the side of the pharynx. Gas exchange is carried out in gill petals. Therefore, they can be considered the most important part of the respiratory system of fish. In many highly developed in the evolutionary plan of fish, gill petals seemed to be branched (on primary gill petals perpendicular to the secondary gill plates). This increases the overall surface of the petals, which means the body area of \u200b\u200bthe fish on which gas exchange occurs.
A network of blood vessels that bring venous blood to the gills can be attributed to the respiratory system of fish, which brought arterial blood from the gills. In the gill petals, the blood vessels disintegrate into a network of small capillaries that are close to the surface. It is here that gas exchange occurs (oxygen comes from the water from the water, and carbon dioxide is released from the blood).
The respiratory mechanism in bone fish is such. When inhaling (at the same time, the fish lifts the gill covers) water enters the mouth, then it reaches the pharynx and when exhaling, which is carried out by reducing the muscles of the pharynx and pressing the gill covers to the body, pushes through the gill slots, washing the gill petals. With a quick movement, bone fish breathe passively (as well as cartilaginous) without the movement of gill lids and muscle tension: the water simply cries in the mouth and flows out of the gill slots.
In bone fish there are no gill partitions that are in cartilage fish. Therefore, in bone fish, gill petals are located right on the gill arcs and are washed with water from all sides.
The respiratory system of bone fish is very effective in the sense that they absorb most of the oxygen from the water that has passed through their gills. This is important because the water contains less oxygen than in the air.
Gills Located in gill cavityCover gill lid..
Structure gill apparatus different groups of fish may vary: head Fish Basching gills, cartilage - lamellar, y kostysy - Greats.
Interesting that water for breathing enters the gills kostyish fish Through the oral hole, not outside.
In the process of evolution, gIRMATIC apparatus of fish It was constantly improved, and the area of \u200b\u200bthe breathing surface of the gills increased. Most fish breathing dissolved in water oxygen, but some are partially and oxygen from the air.
Gill apparatus bony fish has five gwee Doug.(1 - in fig.) Located in the gill cavity and covered solid gill lid.. Four arcs on the external convex side have two rows lady petals(4 - in Fig.) Supported by reference cartilage. On the other side of the gill arc deposit gill stamens (2 - in fig.), Playing a filter role: protecting gill apparatus from food particles (predators Stychkin also additionally fix production).
In turn, gill petalsand covered thin petals: in them and happens Gas exchange. Number lepoles May be different from different species of fish.
Glaba arterysuitable Lepalsy, it takes over the oxidized (arterial) blood and is enriched with oxygen (3 - heart in Fig.).
Fish breath It happens as follows: when inhaling the mouth opening opens, the gill arches are departed to the sides, the gill covers with outer pressure are tightly pressed against the head and closed the gill slots.
Due to the difference in pressure, water is absorbed into gill cavity, washing gill petals. When you exhale the oral opening of the fish closes, gill arcs and gill covers move towards each other: the pressure in the gill cavity increases, the gill cracks open, and the water squeezes out through them. When swimming, fish can create a water current, moving with an open mouth.
In the capillaries of the gill petals occurs gas exchange and water-salt exchange: Oxygen falls out of the water to blood, and stand out Carbon dioxide (CO 2), ammonia, urea. Due to the active gills have bright pink color. Blood in the gills capillaries flows in the direction opposite to the current water, which ensures maximum extraction of oxygen from the water (up to 80% dissolved in water oxygen).
In addition to gills Fish has I. additional respiratory organshelping them to carry adverse oxygen conditions:
— leather; In some species of fish, especially living in muddy and poor oxygen, skin breathing is very intense: up to 85% of the oxygen absorbed from water;
— : especially in two-way fish; Out of water, the fish may begin to absorb oxygen from the swimming bubble;
— intestines;
— supervisory organs;
— special additional organs: W. labyrinth fish there is Labyrinth - Advanced pocket-shaped guery cavity department, the walls of which are permeated with a dense network of capillaries, in which gas exchange occurs. Labyrinth fish Breathe atmosphere oxygen, swallowing it from the water surface, and can do without water for several days. TO Additional respiratory authorities You can also attribute: blind gastric grown, pair grows in a throat and other fishe organs. 
In Fig.: 1 - protrusion in the oral cavity, 2 - the superior organ, 3, 4, 5 - the division of the swimming bubble, 6 - the protrusion in the stomach, 7 is the oxygen absorption site in the intestine, 8 - the gills.
Fish males need more oxygen than females. Rhythm Rhythm Fish primarily determined by the oxygen content in water, as well as concentration carbon dioxide and other factors. In this case, the sensitivity of fish to a lack of oxygen in water and blood is much larger than to excess carbon dioxide (CO 2).
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