BENEFITS

The main advantage of color Doppler EC following is a possibility of quick visualization and interpretations of normal and abnormal flows . Overlay color Doppler study onanatomical image does him more understandable for novice researchers . Spectral infor m tion is more challenging for interpretation .

Color Doppler study allows bo more accurately set the control volume of the pulse and line scan permanent – wave Doppler Skog study at according with real direction leniem flow . It allows you to improve the identification of under- sufficiency valves and intracardiac discharge of blood .

Distortion of the Doppler spectrum , observed with a pulse study , with a color Doppler study allows you to easily identify high -speed flows by the appearance of mosaic blood flow .

LIMITATIONS

how and everything echocardiographic techniques , color Doppler study can be maloinfor tive when no good visualization .

The quality of color Doppler studies , as the and pulse , it depends on the frequency of repetition of the pulse sensor and depth of study . With color Doppler skom study possible miss low velocity flow , especially if the signal is weak . Situation are exacerbated etsya at a high value of filter speed and low color gain . Color Doppler scan can mistakenly detect myocardial movement and stem pans , especially at low values of the filter velocity and high color gain values .

With a number of pathologies possible education multiple blood streams at limited space , like at si table , so and at diastole . Total overlay colors more can confuse , than to put an accurate diagnosis .

PERFORMANCE TECHNIQUE

Equipment fulfillment colored doppler is following is close to standard echocardiography and pulse hydrochloric doppler – echocardiography . how and at normal echocardiographic study , for receiving standard position use parasternal or apical accesses .

With obtaining a quality image including The chaetsya mode color Doppler study .

Color Doppler image automatically superimposes and displayed simultaneously with mill dard gray-scale.

For optimize color doppler image of it may be necessary to reject the sensor at that or other side . The resulting image is often a compromise. by quality two-dimensional and color Doppler image .

Settings Gain gray-scale image should be minimal for adequately visualized tion structures of the heart . Gain values too low not allow you to get a clear anatomical information

mation , and very high gain leads to WHO penetration artifacts and noisy images , it affects on quality and color Doppler study .

Follows blowing optimally adjust the parameters of the filter tion rate and color gain . Setting the filter value too high and low amplification reducible dit to possible underestimation of low-speed flows . Filter value too low and high gain on color doppler image result to the occurrence of artifacts from the structures of the heart , making it difficult to assess the real blood flow .

PULSE DOPPLEROVSKOE STUDY

Impulse Doppler study transmits ultrasound impulses in series . With this new pulse is sent after receiving reflected signal .

Required temporary delay for registration reflected signal limits maximum cha stota transmission pulses . therefore the mode not fits for registration high speed flows .

With speeds more than 2 m / s arises change by lariness blood flow, known as Effect distortions spectrum .

Impulse Doppler study provide begs the best quality spectrum at comparing with constantly wave that It has important value at calculations .

Impulse Doppler study used are calling for accurate localization abnormal speed streams identified at constantly – wave extra Plerovo research and colored doppler mapping .Indicators transmitral blood flow use for ratings diastolic functions left ventricle ( LV ). Indicators transaortic kro water flow use for calculations shock volume and cordial ejection .

PHYSICAL PRINCIPLES

Color Doppler study is an automat tizirovannymi option pulsed doppler research . Also this mode called doppler skim by research at real of time .

Color Doppler study allows in and zualize intracardiac blood flow at the form color cards blood flow . Color mapping blood flow sometimes called ” Non-invasive angiography, “so asat the same time men with information about functions rate and anatomy . After Togo as series pulses transmitted along one the lines scan by analogies with pulsed dopple rovskyresearch is reflected from red blood cells, is performed her analysis autocorrelator echocardiograph .

Autocorrelator compares frequency reflected signal with original frequency. After of this difference frequencies assigned to certain Colour by to a certain to the algorithm .

Analysis sets control volumes along each of sets lines scan allows to create coded different flowers card about land interest .

AT color map blood flow encoded information tion as about speed, so and about direction blood flow . With overlay color cards blood flow on grayish two-dimensional pictureappears opportunity is full valuable interpretations received information .

Flow directed to sensor, coded shade mi red as well directed from sensor  shades blue colors .

With increasing speeds blood flow shade blue or red colors becomes more light . So way low speeds seem dark as well high cue  bright and light .

Turbulent high speed blood flow mapping is at colored doppler mode at the form mosaic flow with shades blue, green, and yellow flowers .

Like Effect changes colors underlines high speed blood flow and arises at connections with is by sight doppler spectrum at mode pulsed Doppler – echocardiography .

M-mode echocardiography

For create Images at M – mode ultrasound before is and is accepted only by one the lines scan . This line choose with using cursor by two-dimensional image so that she is wasperpendicular is

followable structure . Sensor reject so way to cursor was strictly perpendicular image . Insofar as at M – mode spend scanning along

one line, it provides much more high forge temporary permitting ability at comparing with two-dimensional Echocardiography . it special important at research nii movable structures.

M – mode presents by myself graphic image niya strength and depths reflected signal at dependencies from of time . Visualized motion and thickness walls ventricles change sizescameras hearts as well also opening and closing valves .

Synchronous a record ECG allows exactly define temporary specifications different of events relationship respectfully cordial cycle . Similarly define temporary specifications blood flow at colored mapping .

CONSTANT WAVE DOPPLER RESEARCH

AT mode constantly – wave doppler research knowledge happens constant broadcast and reception ultra sound signal . Behind score of this is possible check in high speedswithout restrictions at the form effect distortions spectrum .

Technique constantly – wave doppler is following not allows exactly define a source reflected signal at the limits lengths or widths ultrasound ray .

The mode doppler research used are calling for fast search high speed streams at heart. Insofar as Doppler shift frequencies locat ditsya at heard range, for deductions the bestspectrum at deviation and rotation sensor use , in Tom among other things, audio. By the results constantly wave doppler research define optimal a place for installations controlvolume at pulsed research . Constantly – wave Doppler study use for ratings manifestations stenosis and definitions degrees untill fatigue . Also is possible quantitative assessmentintracardiac reset left to the right . By trance tricuspid constantly – wave spectrum can calculate pressure at pulmonary arteries .

PHYSICAL PRINCIPLES OF DOPPLER RESEARCH

WITH effect Doppler we we meet on a daily basis, not realizing of this . Imagine to myself passing through by you car with siren . Tone sirens more tall at approaching car ( morehigh frequency ) than at him removal ( more than low frequency ). Change niya frequencies ( Doppler shift frequency ) depends from speeds the car and original frequencies sirens .Analysis ultrasound waves reflected from boundaries tissue, gives information about the depth and reflective abilities tissues . Classic Doppler is following uses ultrasound waves ,reflected ny from moving red blood cells . Effect Doppler is used for receiving information about speeds blood flow . Speed blood flow determined by by change to frequencies sentand accepted ultrasound momentum . Shift frequencies ( Doppler shift ) about portional respect speeds blood flow to speeds sound and original frequency.

is he computed by the next formula :

where F d – Doppler shift ; F0 – initial frequency ; V – speed blood flow ; WITH  with scab sound .

Therefore , the speed blood flow equals :

F xC V = – ——-.

F0 V more strict the form formula It has following

Fd x With V = ——————- •

2 F0 x Cos0

Original frequency multiplied by 2 so as dopple rovsky shift arises twice : when transfer momentum and at reflection .

Cosine theta (Cose) is introduced at formula for accounting corner between ultrasound by beam and bloodstream .

Cose = 1 if ultrasonic Ray parallel blood current . With this registered maximum speed. Cose = 0 when direction ultrasound ray perpen dicularly bloodstream . With this registeredzero speed. For correct measurements angle between ultra sound by beam and blood flow should be less than 20 ° .

Important consider that at doppler – echocardiography maximum speed succeeds to register at direction ultrasound ray parallel isle dummy bloodstream . AT otherwise casemaximum speed and , accordingly , the gradient Pressure (cm. below) will be undervalued . With this at standard Echocardiography the best quality Images is achieved at directionultrasound ray perpendicular investigated structure .

Insofar as value original frequency (2F0) is at denominator formula, the maximum values soon STI are recorded at using low frequency sensors (2.5 MHz ). Than above maximumspeed blood flow through stenotic valve , the above gradient pressure . It is obvious that at decreasing from version valve for ensure permanent shock

volume required increase speed . Increase speeds can be measured at using Doppler – echocardiography .

Gradient pressure through valve can be calculated with using simplified the equations Bernoulli :

D P = 4 V2,

Where R  gradient pressure ( in mm Hg. Art .); V – maxi little speed blood flow ( in m / s ).

This the equation often is used at doppler – echocardiographic research stenosis and untill fatigue valves as well also intracardiac discharges . High speed indicators blood flowcomplement anatomy chesky information by according to M – mode and two-dimensional Echocardiography . Analysis doppler signal provides information not only about speed, butand direction blood flow . Speed, direction to sensor , from are fighting above isolines ( positive values ), and speed, designed from sensor , – below isolines ( negative values ).

Reflected Doppler signal presents with the battle spectrum speeds by of time . Square under crooked spectrum denoted by as integral speeds blood flow . Value integral speedsblood flow depends on from maximum speeds and of time exile . The indicator can be calculated on most echo cardiographic devices .

Careful analysis spectrum speeds gives infor mation about density flow . Density depends on from numbers red blood cells, moving with certain by speed . With uniform or laminarcharacter blood current most red blood cells moving with the same speed, at the same time speeding up and slowing down . With this spectrum speeds It has narrow the borderand only a little number red blood cells moving with other sko rosty . This phenomenon is described as low variability speed . With turbulent character blood flow through stenoticvalve is observed wide scatter values speeds red blood cells . With this Doppler spectrum you looking ” Filled . “ This phenomenon is described as high variability speeds or “Expansion spectrum . “

Should have at mind that turbulent character blood flow and expansion spectrum often associate, but not are identical high speeds signal . Inten sivness doppler signal on grayishimage is presented different shades gray . Maximum number erythrocytes, driving camping with certain speed, forms dark part spectrum . Few red blood cells, moving with highspeed, form light part spectrum . The best way this it is seen at doppler research ste – nozirovannogo valve . The greatest density spectrum celebrated at contour lines, so as mostred blood cells moving with low by speed directly above or under valve . Small part erythrocy com , speeding up through stenotic the valve moves with high by speed .

AT clinical practice are used modes constantly – wave and pulsed Doppler research . With constantly – wave doppler research are used two piezoelectric crystal . One constantlytransmits as well other constantly takes signal without delays by of time . it allow ate measure high speeds without clear localization the source signal by throughout the lengthUltrasound kovogo ray .

With pulsed doppler research one piezoelectric crystal is used as for re cottages pulse, so and for reception reflected signal through preset time.

Impulse Doppler research allows exactly define a source speed signal . For localization the source ” Control volume ” , about meaningful small rectangle or circle, set at regioninterest , focusing by two-dimensional image . Control volume can shift up and way down by go ultrasound ray for receiving maximum speed .

AT connections with by the presence of delays by of time at at eat reflected ultrasound signal pulsed Doppler study correctly defines speeds only up to 2 m / s .

but pulsed Doppler study allows receive spectrum more high qualities by by comparison with constantly – wave .

With pulsed research frequency repetitions pulses must not less than at two times exceed measurable speed. Frequency repetitions pulses going down with an increase depthsresearch . Maxi little Doppler shift the frequency of which can correctly measure at given frequency repetitions momentum , called the limit Nyquist .

With exceeding limit Nyquist is observed Effect distortions spectrum (aliasing effect ), which leads to artificial change polarity sko rosti and deformations reflected signal .

Effect distortions spectrum can to avoid behind account :

 high frequencies repetitions pulses ;

 multiple control volumes ;

 decrease depths doppler research ;

 offsets isolines spectral scales .

AT clinical practice are used various re presses Echocardiography .

Seroshkalnaya EchoCG : • two-dimensional Echocardiography ;  M – mode EchoCG ( M – motion, English , movement ).

Doppler – echocardiography : • constantly – wave Doppler research ;  imp ulsnoe Doppler research . Various modes Echocardiography not compete as well dopol

ny friend other. how Generally, they use at combining nii . Everything modes Echocardiography use ultrasound, however, differ by way reception and analysis reflected soundwaves .

FIZICH ESKA NATURE ULTRASOUND

Sound presents by myself mechanical fluctuations ha zoobrazny , liquid or dense environment . Each sound characterized by certain frequency, speed and in intensity . Frequencysound presents by myself number cycles dilution and compression at second. Unit measure of frequencies sound is an Hertz ( Hz ) and him derivatives . 1 Hz corresponds to 1cycle at second. Also are used concepts kHz (1 kHz = 103 Hz ) and MHz (1 MHz = 106 Hz ). Often that sound perceived human ear as height sound . Length the waves  thisdistance that passes sound behind one cycle dilution and compression that corresponds to distance between in two consecutive peaks . Frequency and length the wavesinterconnected . Insofar as sound overcomes certain distance behind second than more cycles sound hesitation at second ( more frequency), the in short length the waves . SpeedSound = Frequency Length the waves .

Speed sound is measured at meters at second ( m / s ) and determined by properties environment in which sound spreads . AT soft tissues speed sound with puts 1540 m / s .Intensity or volume sound is measured at decibels. Than above intensity sound , the more distance at which he heard . Sound with by frequency higher than perceived humanchesky ear ( over 20 kHz ), called ultrasound . A technique that uses ultrasound for heart research , got title echocardiography ( echocardiography ). Ultrasound formed thanks toproperty of some crystals perform mechanical fluctuations under WHO by action electricity . The Effect received on rank piezoelectric ( pressure – electricity ). If a to file electricvoltage on piezoelectric crystal, it starts vibrate .

Ultrasonic sensor contains some crystals, which pass on formed ultrasound the waves through body the patient .

Large part ultrasound waves dissipates or absorbed tissues, and only small their part reflected and caught sensor . Reflected the waves deform piezoelectric crystals with image by knowledge electric fields . Reflected signal carries information about the depth and character investigated tissue . AT the greatest degrees reflection ultrasound happened walks onthe border tissue with different density . Veli rank electric field formed reflected ultrasound waves determines intensity and brightness Images on the screen device .

Structures with high reflective capacity (e.g., bones) in grayish image boo are blowing white colors , structures with low reflective ability ( for example , muscle ) – gray color, notreflecting ultrasound structure (e.g., WHO spirit ) – black colors .

Location on the screen structure, which reflected ultrasound depends from delays between transmitted and accepted ultrasound momentum . More deep located structures are displayed at bottom parts picture, then as superficial structures  at top parts screen . So , the image on the screen It has view triangle with top vertex formed ultrasound sensor .

With spreading ultrasound at homogeneous environment happens gradual dissipation and damping signal at the original direction . With passing nii ultrasound through Wednesdaywith different density on the border mediums part ultrasound waves reflected at the reverse direction .

Exactly reflected ultrasound the waves perceived disappear sensor and analyzed ultrasound device . Length ultrasonic the waves connected with by speed and by frequency as follows ratio ( Length Waves = Speed / Frequency ). Insofar as length the waves back proportional to rate than above frequency ultrasound, the in short length the waves .

Than in short length wavelength, the more permitting and less penetrating ability to . So , you sokochastotnye sensors (5.0 to 7.5 MHz) provide the good resolution at researchsuperficial structures and at children ( table . 1.1).

Than below frequency ultrasound, the more length the waves . Than more length wavelength, the less permit walking and more penetrating ability to . So , the low-frequencysensors (2.5 to 3.5 MHz) provide a good penetrating ability at research more deep structures and at adults patients .

X-ray examination of blood vessels

At present, almost all blood vessels (angio- or angiography) are available on live x-rays. The clinic uses various methods of X-ray examination of vessels filled with a radiopaque substance: examination of vessels (angiography), arteries (arteriography), heart and main arteries (angiocardiography), veins (phlebography) and lymphatic vessels (lymphography). In various types of aortography (injection of radiopaque substances, etc.), the aorta can be traced along its entire length and in all its parts: ascending, arc, thoracic and abdominal – with large arteries of the abdominal cavity: splenic, renal, etc. leaving it.

In the left (nipple) oblique position, all parts of the aorta are visible: ascending, arch and descending – to the diaphragm. Bright oval space, limited in front by the shadow of the heart, and above and behind – by the aorta (retrocardial pulmonary field) is called the aortic window. This “window” is narrow or wide, depending on the shape of the chest, the height of the standing of the diaphragm and the position of the heart. In people with a wide and short rib cage, with a high standing of the diaphragm with a horizontal position of the heart, there is a high standing and “unfolded” type of aorta. In this case, both knees of the aorta (ascending and descending) are more distant from each other: the “aortic window” is extended, the aortic arch is relatively straight. In people with a narrow and long rib cage and low standing of the diaphragm with the vertical position of the heart, inverse ratios are observed.

Using an injection of a contrast agent in the abdominal aorta, an image of the abdominal aorta, pars abdominalis aortae, is obtained. Also visible is its bifurcation and the course of both common iliac arteries and their large branches. In the living, due to the intravital tone and mobility of neighboring organs, the abdominal part of the aorta may shift slightly to the right and slightly arcuately bulge to the right, which can be mistaken for pathology, such as pushing the aorta with a tumor.

An x-ray examination of the remaining blood vessels of a living person by injecting (injecting) directly into the vessels of contrasting substances with simultaneous x-rays at the time of injection is called angiography.

When injected into the carotid artery, the common carotid artery is examined, dividing it into the external and internal carotid arteries and branching them in the head and brain (arterial encephalography, or brain angiography).

Introducing contrast agents into the brachial or femoral artery receive the image of large arterial trunks of limbs and their branches.

Selective (selective) arteriography of the arteries of the abdominal cavity allows studying the celiac trunk, mesenteric, renal arteries and their branches. At the same time, the entry of arteries into the gates of organs, in particular the spleen, liver and kidneys, is clearly noticeable. During radiography of the arteries of the parenchymatous organs, not only extraorgan vessels, but also intraorgan vessels are visible.

Features of blood circulation of the fetus. Placental circulation

Oxygen and nutrients are delivered to the fetus from the mother’s blood with the help of the placenta – placental circulation. It occurs as follows. The arterial blood enriched with oxygen and nutrients flows from the mother’s placenta into the umbilical vein, which enters the fetal body in the navel and goes up to the liver, lying down in its left longitudinal sulcus. At the level of the gate of the liver v. The umbilicalis is divided into two branches, one of which immediately flows into the portal vein, and the other, called ductus venosus, rambles along the lower surface of the liver to its posterior margin, where it flows into the trunk of the inferior vena cava.

The fact that one of the branches of the umbilical vein delivers pure arterial blood through the portal vein of the liver gives rise to a relatively large liver; The latter circumstance is associated with the necessary for the developing organism the function of the blood formation of the liver, which prevails in the fetus and decreases after birth. After passing through the liver, blood through the hepatic veins flows into the inferior vena cava.

Thus, all the blood from v. Umbilicalis, either directly (through ductus venosus), or indirectly (through the liver) enters the inferior vena cava, where it is mixed with venous blood flowing through the inferior vena cava inferior from the lower half of the fetus.

Mixed (arterial and venous) blood through the inferior vena cava flows into the right atrium. From the right atrium, it is guided by a valve of the inferior vena cava, valvula venae cavae inferioris, through the foramen ovale (located in the atrial septum) into the left atrium. From the left atrium, the mixed blood enters the left ventricle, then into the aorta, bypassing the pulmonary circulation that is not yet functioning.

In addition to the inferior vena cava, the superior vena cava and the venous (coronary) sinus of the heart flow into the right atrium. Venous blood entering the superior vena cava from the upper half of the body, then enters the right ventricle, and from the latter into the pulmonary trunk. However, due to the fact that the lungs do not function as a respiratory organ, only a small part of the blood enters the lung parenchyma and from there through the pulmonary veins into the left atrium. Most of the blood from the pulmonary trunk along the ductus arteriosus passes into the descending aorta and from there to the viscera and lower extremities. Thus, despite the fact that in general the mixed blood flows through the vessels of the fetus (with the exception of v. Umbilicalis and ductus venosus before its inflow into the inferior vena cava), its quality below the confluence of the ductus arteriosus deteriorates significantly. Consequently, the upper body (head) receives blood richer in oxygen and nutrients. The lower half of the body eats worse than the upper, and lags behind in its development. This explains the relatively small size of the pelvis and lower limbs of the newborn.

The act of birth represents a leap in the development of an organism, during which fundamental qualitative changes of vital processes take place. The developing fetus moves from one environment (uterine cavity with its relatively constant conditions: temperature, humidity, etc.) to another (outside world with its changing conditions), as a result of which the metabolism, as well as the ways of nutrition and respiration, change radically. Instead of nutrients previously obtained through blood, food enters the digestive tract, where it undergoes digestion and absorption, and oxygen begins to flow not from the mother’s blood, but from the outside air due to the inclusion of respiratory organs. All this is reflected in the blood circulation.

At birth, there is a sharp transition from placental circulation to the pulmonary. At the first inhalation and stretching of the lungs with air, the pulmonary vessels greatly expand and fill with blood. Then ductus arteriosus collapses and obliterates during the first 8–10 days, turning into ligamentum arteriosum.

The umbilical artery overgrown during the first 2 – 3 days of life, the umbilical vein – a little later (6 – 7 days). The flow of blood from the right atrium to the left through the oval hole stops immediately after birth, as the left atrium is filled with blood coming from the lungs, and the difference in blood pressure between the right and left atria is equalized. The closure of the oval hole occurs much later than the obliteration of ductus arteriosus, and often the hole persists during the first year of life, and in 1/3 of cases it lasts a lifetime. The described changes are confirmed by X-ray live research.

Veins of the lower limbs (legs).

Deep and superficial veins of the legs. As in the upper limb, the veins of the lower limb are divided into deep and superficial, or subcutaneous, which pass independently of the arteries.

Deep veins of the foot, and the legs are double and accompany the same arteries. V. poplitea, composed of all deep veins of the leg, is a single trunk located in the popliteal fossa posterior and somewhat laterally from the artery of the same name. V. femoralis is solitary, initially located laterally from the artery of the same name, then gradually passes to the back surface of the artery, and even higher – to its medial surface and passes in this position under the inguinal ligament in the lacuna vasorum. Tributaries v. femoralis all double.

Of the subcutaneous veins of the lower extremity, two trunks are the largest: v. saphena magna and v. saphena parva. Vena saphena magna, the large saphenous vein, originates on the dorsal surface of the foot from rete venosum dorsale pedis and arcus venosus dorsalis pedis. Having received several tributaries from the foot, it goes upwards along the medial side of the shin and thigh. In the upper third of the thigh, it is bent on the anteromedialal surface and, lying on the wide fascia, goes to hiatus saphenus. In this place v. saphena magna joins the femoral vein, spreading over the lower horn of the crescent edge. Quite often v. saphena magna is double, and both of its trunk can flow separately into the femoral vein. Of the other subcutaneous inflows of the femoral vein, v. epigastrica superficialis, v. circumflexa ilium superficialis, vv. pudendae externae, accompanying the same arteries. They flow in part directly into the femoral vein, part in v. saphena magna at its confluence with hiatus saphenus. V. saphena parva, small saphenous vein, starts on the lateral side of the dorsal surface of the foot, bends around the bottom and back of the lateral ankle and rises further along the back of the tibia; first, it goes along the lateral edge of the Achilles tendon, and further upwards in the middle of the posterior part of the lower leg, respectively, the groove between the heads m. gastrocnemii. Reaching the lower corner of the popliteal fossa, v. saphena parva flows into the popliteal vein. V. saphena parva is connected by branches with v. saphena magna.

Patterns of vein distribution.

1. In the veins, blood flows in most parts of the body (trunk and limbs) against the direction of gravity and therefore slower than in the arteries. Its balance in the heart is achieved by the fact that the venous bed in its mass is much wider than the arterial one. The greater width of the venous bed compared with the arterial is provided by the following anatomical devices: a large caliber of veins, a large number of them, paired accompaniment of arteries, the presence of veins not accompanying the arteries, a large number of anastomoses and greater density of the venous network, the formation of venous plexuses and sinuses, the presence of portal system in the liver. Because of this, venous blood flows to the heart through three large vessels (two hollow veins and the coronary sinus, not to mention the small veins of the heart), while the about one pulmonary trunk.

2. The deep veins accompanying the arteries, i.e., the vein satellites (venae commitantes), in their distribution obey the same laws as the arteries they accompany (see “Regularities in the distribution of arteries”), while most of them accompany the arteries in double number. Paired veins are found mainly where the venous outflow is most difficult, that is, in the extremities, since such a structure has developed even in four-legged animals, in which both pairs of extremities occupy a sheer position and the torso is horizontal.

3. Accordingly, the grouping of the whole body around the nervous system deep veins are located along the nerve tube and nerves. Thus, parallel to the spinal cord is the inferior vena cava, and each segment of the spinal cord corresponds to segmental veins, for example, vv. lumbales and rr. spinales.

4. According to the division of the body into the organs of plant and animal life, the veins are divided into parietal – from the walls of the body cavities and visceral – from their contents, i.e. from the inside.

5. Most of the veins are located on the principle of bilateral symmetry.

6. The veins of the trunk walls retain a segmental structure.

7. Deep veins go along with other parts of the vascular system – arteries and lymphatic vessels, as well as nerves, participating in the formation of neurovascular bundles.

8. Veins also go according to the skeleton. So, along the spine is the inferior vena cava, along the ribs – intercostal veins, along the bones of the limbs – the veins of the same name: shoulder, radial, ulnar, femoral, etc.

9. The veins travel along the shortest distance, that is, approximately in a straight line connecting the place of origin of this vein to its confluence.

10. Superficial veins lying under the skin accompany the skin nerves. A significant part of the superficial veins form subcutaneous venous networks that have no relation to either the nerves or the arteries.

11. Venous plexuses are found mainly on the internal organs, which change their volume, but are located in cavities with unyielding walls, and facilitate the outflow of venous blood with an increase in organs and compression of their walls. This explains the abundance of venous plexuses around the pelvic organs (bladder, uterus, rectum), in the spinal canal, where the pressure of the cerebrospinal fluid constantly fluctuates, and in other similar places.

12. In the cranial cavity, where the slightest obstruction of the venous outflow affects the brain function, there are, in addition to the veins, special devices – the venous sinuses with unyielding walls formed by a hard shell. Therefore, they lie mainly at the site of attachment of durae matris processes to the bones of the skull (sutures of the integumentary bones and sinous bones of the sinuses).

13. Special devices include veins located in the channels diploe – venae diploicae.