Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Physiological bases of hemodinamic hemodinamic – is a chapter of physiology of blood circulation system, which is study causes, conditions and mechanisms of blood moving in cardio-vascular system. Types of blood moving Fluid stream in the pipe is described by formula: Q= (P1-P2)/R, where Q - fluid volume, P1 - pressure in the beginning of the pipe, P2 - pressure in the end of the pipe, R - peripheral resistance of the pipe. Peripheral resistance of vessels Peripheral resistance in vessels according to Poiseuille's formula depends on length of vessels (l), viscosity of blood (η) and crosssection of vessel (r): R= 8lŋ/πr. Paradoxes of blood flow. In capillaries blood flow resistance is lower because of such mechanism. In capillaries blood cells move one after another, dividing only by plasma, which decreases friction between blood cells and capillary wall. On other side, capillaries are shorter, than arterioles, which caused lower blood flow resistance too. Viscosity of blood is also important for resistance of vessels. It depends on quantity of blood cells, protein rate in plasma, especially globulins and fibrinogen. Considerable increase of blood viscosity may cause lower blood returning to the heart and than disorders of blood circulation. In large arteries centralization of blood flow is observed. Blood cells moves in the central part of blood stream, and plasma is peripheral. Instead increase of blood viscosity in arterioles is caused by higher friction between cells and vessels wall. Functional types of vessels - Elastic (damping) vessels. Large arteries belong to this group. The main function of these vessels is to turn ejection of blood into continuous blood flow. It is possible due to elastic properties of its wall; - Resistive vessels are arterioles, precapillary sphincters and venuls. These vessels may regulate the blood flow in capillaries by changing their tonus; - Exchange vessels are capillaries. Their walls due to the special structure permit exchange of materials between blood and tissues; -Capacitive vessels are veins. To sure one-way direction of blood flow veins have valves if lying below the heart. Veins contain 75-80 % of circulating blood. Veins of skin and abdominal cavity may function as depot of blood. Functional types of vessels Functional peculiarities of vessels 1. Еlasticity 2. Соntractility 3. Тоne 4. Permability Blood pressure Transversal pressure - is difference between pressure inside the vessel and squeeze of it from the tissues. Hydrostatic pressure is corresponding to weight of all blood in vessel when it has vertical position. For vessels of head and neck this pressure decreases towards the heart. For vessels of limbs it has outward direction. That is why hydrodynamic pressure in vessels over heart is decreased due to hydrostatical pressure. Below heart hydrodynamic pressure is increased, because it is summarized with hydrodynamic pressure. Linear velocity of blood flow Blood flow also is characterized by linear velocity of blood circulation: V=Q/πr2, where V - linear velocity, Q - blood volume, r - radius of vessel. Аrterial pressure Аrterial pressure – pressure, which have the blood in the arterial vessels of human body. Factors: – cardiac – vessels – blood Kinds of arterial pressure 1. systolic (less than 139 мм Hg) 2. diastolic (less than 89 мм HG) 3. puls pressure (PP=SP-DP). 4. Middle dynamical pressure (PP/3+DP) Determine of arterial pressure Arterial pressure Notion Arterial pressure Systolic, мм Diastolic, мм Hg Hg Optimal < 120 < 80 Normal < 130 <85 130-139 85-89 >140 >90 140-149 90-94 Higher normal Hipertension Mesure hyprtension Arterial pulse 60-90 per minute Sphigmogram а-аnacrota; b-catacrota; і-іncisura; с-dicrota. Properties of arterial pulse 1. Pulse rate per minute – 75±15. 2. Pulse rhythmisity