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1 How does the micro and nanostrure of blood influence its rheology Anna Kucaba-Piętal (Rzeszów)

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Presentation on theme: "1 How does the micro and nanostrure of blood influence its rheology Anna Kucaba-Piętal (Rzeszów)"— Presentation transcript:

1 1 How does the micro and nanostrure of blood influence its rheology Anna Kucaba-Piętal (Rzeszów)

2 2 Blood as suspension Plasma Red Blood Cells White Blood Cells Platelets Contents I. II. Rheological parameters of blood Problems with theoretical modelling Blood viscosity Hematocrits’ effect on blood rheology Blood viscoelasticity Fahraeus–Lindquist Effect Perspectives

3 3 Blood Blood is a liquid tissue. Suspended in the plasma are seven types of cells and cell fragments Microscopic view of blood

4 4 Blood performs two major functions: 1) transports through the body: - oxygen and carbon dioxide - food molecules (glucose, lipids, amino acids) - ions (e.g., Na +, Ca 2+, HCO 3 − ) - wastes (e.g., urea) - hormones - heat 2) defends the body against infections and other foreign materials. All the WBCs participate in these defenses. Blood - functions

5 5 Adult ♂ contains 5-6L Adult ♀ contains 4-5L T  is about  F 5 times as viscous as water –pH ranges from 7.35 – 7.45 (slightly alkaline) Color ranges from scarlet (oxygenated blood) to Blood - characteristics deep red (deoxygenated blood).

6 6 Blood - components Blood is made of four components: Plasma (55%) Platelets (0,17%) White BC (0,1%) Red BC (45%)

7 7 Whole Blood Plasma (46-63%) Formed Elements (37-54%) 1. Water (92%) 2. Plasma Proteins (7%) 3. Other Solutes (1%) 1. Red Blood Cells (99.9%) 2. Platelets 3. White BC (0,1%) Blood as suspension

8 8 Plasma is the straw-colored liquid in which the blood cells are suspended. Composition of blood plasma: ComponentPercent Water~92 Proteins6–8 Salts0.8 Lipids0.6 Glucose (blood sugar)0.1 Plasma

9 9 Plasma transports materials needed by cells and materials that must be removed from cells: various ions (Na +, Ca 2+, HCO 3 −, etc. ) glucose and traces of other sugars amino acids other organic acids cholesterol and other lipids hormones urea and other wastes Plasma - functions

10 10 Serum Proteins Proteins make up 6–8% of the blood. They are about equally divided between serum albumin and a great variety of serum globulins. After blood is withdrawn from a vein and allowed to clot, the clot slowly shrinks. As it does so, a clear fluid called serum is squeezed out. Thus: Serum is blood plasma without fibrinogen and other clotting factors. The serum proteins can be separated by electrophoresis. Plasma - components

11 11 Red Blood Cells (Erythrocytes)

12 12 Most abundant blood cells In ♂, 1µL of blood contains million RBCs In ♀, 1µL of blood contains million RBCs Contains the red pigment hemoglobin which binds and transports O 2 and CO 2 Each RBC is a biconcave disc however while moving it deforms itself adapting like a liquid- filled baloon to the shape of capilaries. Red Blood Cells - characteristics

13 13 Red blood cells is a membrane filled with a solution of hemoglobin and various salts. They manufacture hemoglobin until it accounts for some 90% of the dry weight of the cell. The viscosity of the RBC interior fluid is five to ten times greater than of exterior fluid. RBC in quiescent plasma tend to form aggregates known as rouleax Red Blood Cells

14 14 Gas transporting protein molecule that makes up 95% of a red cell Each chain contains a single molecule of heme, an iron- containing pigment Each red cell has about 270,000,000 iron-rich hemoglobin molecules Note the 2  chains and 2 β chains. Notice how each has an associated heme molecule with an iron atom. Hemoglobine

15 15 RBCs transport oxygen from the lungs to all of living tissues of the body and carry away carbon dioxide. The RBC values can vary depending on such factors as health and altitude. Peruvians living at 18,000 feet may have as many as 8.3 x 10 6 RBCs per µl. People who are anemic have deficency in red cells. RBC precursors mature in the bone marrow closely attached to a macrophage. The nucleus is squeezed out of the cell and is ingested by the macrophage. Red Blood Cells - functions

16 16 Percentage of whole blood occupied by packed red blood cells Average in a ♂ is 46 (range of 40-54) Average in a ♀ is 42 (range of 37-47) Determined by centrifuging a blood sample so that all formed elements come out of suspension Low Hct values may indicate anemia whereas high values may indicate polycythemia Hematocrit

17 17 Are produced continously in our bone marrow from stem cells They can never divide After ≈120d, the RBC cell membrane ruptures, or the damage is detected by phagocytic cells in the liver and spleen Most of the iron in their hemoglobin is reclaimed for reuse macrophage phagocytizing multiple RBCs Lifecycle of an RBC RBC flow through capilaries

18 18 White blood cells are clear round cells that are bigger than red blood cells. White blood cells produce proteins called antibodies that help our bodies fight infections caused by bacteria, viruses, and foreign proteins. White Blood Cells

19 19 Help defend the body against invasion by pathogens, and they remove toxins, wastes, and abnormal/damaged cells A typical µL of blood contains WBCs (1% volume) Most of the WBCs in the body at a given moment are in the connective tissue proper or in organs of the lymphatic system Remain viable only last hours before they also are removed Leukocytes (leuko=white, cyte=cell) All contain nuclei and organelles White Blood Cells

20 20 Can be classified based on the appearance of granules when viewed under the light microscope. 1.Granulocytes_protect body from infection: Basophils Eosinophils Neutrophils 2.Agranulocytes are a part of immune system Lymphocytes Monocytes 1 2 Types of WBC

21 21 Types of WBC Eosinophil BasophilLymphocyte Monocyte 60% neutrophils 30% lymphocytes 6% monocytes 3% eosinophils 1% basophils Neutrophil

22 22 Platelets aren't really cells at all; they are just fragments of cells. When we are injured, platelets gather at the site of the injury and stick to the edges of the wound. They release chemicals that help start the process of blood clotting so that bleeding will stop. Platelets

23 23 Flattened disk-like cell fragments that are about 1µm by 4µm (1/3 size of RBC). Continuously being replaced. Each platelet circulates for days before being removed by splenic phagocytes. On average there are 350,000 platelets/µL of blood. Produced in the bone marrow. Large cells called megakaryocytes release fragments (platelets) into the circulation. Platelets

24 24 When blood vessels are cut or damaged, the loss of blood from the system must be stopped before shock and possible death occur. This is accomplished by solidification of the blood, a process called coagulation or clotting. A blood clot consists of a plug of platelets enmeshed in a network of insoluble fibrin molecules. Act as a participant in the vascular clotting system. Platelets are sometimes referred to as thrombocytes (thrombus=clot) Platelets - functions

25 25 Part Two

26 26 Why is it important to predict rheological parameters of blood? To use it in diagnostics of clinical disorders To maintain nonbiological fluids that has rheological properties comparble to blood Due to formulation blood flow equations

27 27 The viscosity and elasticity determine the pressure required to produce blood flow. The heart pumps energy into the blood with each beat. Portions of this energy are either dissipated or stored as the blood cells rearrange, orient and deform. Viscosity is an assessment of the rate of energy dissipation due to cell deformation and sliding. Elasticity is an assessment of the elastic storage of energy primarily in the kinetic deformability of the red blood cells. Rheological parameters

28 28 The blood viscosity is a function of the protein concentration of the haematocrit (Ht), of the pH of plasma, and of the temperature (this dependence is negligible in physiological condition). Blood is considered as a Newtonian fluid for high values of the gradient dv/dn (for the arterial flow) and non-Newtonian for low values, because in these circumstances the development of groups of 7-10 erythrocytes (rouleaux) is common; in this last case the viscosity is no longer constant. Among the main factors from which the blood viscosity depends, the haematocrit is quite effective. The erythrocytes tend to reduce the speed gradient dv/dn. This is the reason why the viscous term rises. Such increase is reduced by the deformability of the erythrocytes (that reduces the effect between the speeds of adjacent fluid threads) Blood viscosity I

29 29 for Ht=45% the viscosity of blood is: at 20ºC µ=3,45 cP at 37ºC µ=2,72 cP and that is it decreases with the temperature, even if in the physiological field of variation of the temperature it can be considered constant: The viscosity of the plasma is µ=1,2 cP. cP = 4 * Pa * s Plasma is a Newtonian fluid. Blood viscosity II

30 30 Results

31 31 Blood – viscosity

32 32 Blood is a concentrated suspension of Red Blood Cells; outside the range of dilute suspension Problems Particles change their shape in response to the fluid forces The nature of RBC membrane and its deformation stress/strain is much less established RBC tends to form agregates known as rouleaux

33 33 NEWTONIAN FLUID NON-NEWTONIAN FLUID Models F yu(y)  f .

34 34 Blood – Casson model  app = . 

35 35 Results

36 36 H micro- microvessel hematocrit Hematocrit in blood circulation H sys - large blood vessels hematocrit

37 37 The influence of blood cell concentration (hematocrit H) on viscosity and viscoelasticity of blood Hematocrit’s effect on blood rheology

38 The tendency of materials to respond to stress as if they were a combination of elastic solids and viscous fluids This property, possessed by all plastics to some degree, dictates that while plastics have solid-like characteristics such as elasticity, strength and form stability they also have liquid-like characteristics such as flow depending on time, temperature, rate and amount of loading Viscoelasticity

39 39 When the red cells are at rest they tend to aggregate In order for blood to flow freely, the size of these aggregates must be reduced The forces that disaggregate the cells also produce elastic deformation and orientation of the cells, causing elastic energy to be stored in the cellular microstructure of the blood. Parameters of human blood measured at a frequency near that of the human pulse. Blood Viscoelasticity I

40 40 Modification of plasma such as changes in osmotic pressure, pH, concentration of fibrinogen and other plasma proteins, and clinically introduced blood volume expanders, can have major effects on blood viscoelasticity The viscoelasticity for normal 0.46 H blood diluted to 0.31 H by the addition of Dextran 40 (D), autogenous plasma (P), and lactated Ringer's solution (L). Measurements were made at 2 Hz and 22 °C. Blood Viscoelasticity II

41 41 Variation in blood viscoelasticity among normals is very small. So it can be treated as a useful clinical parameter. viscoelasticity of an individual's blood changes significantly as the result of disease or surgical intervention Blood Viscoelasticity III Cardiopulmonary bypass surgery

42 42 In blood vessels with diameters less than 500  m both the hematocrit and viscosity decrease with diameter. The hematocrit in the capillary is greatly reduced because the red cells speed up relative to the plasma as they squeeze through the capillary. Since they must travel faster than the plasma, there must be fewer of them present to maintain the same proportions of cells and plasma as blood exits the capillary. This is the so-called Fahraeus-Lindquist Effect. The Fahraeus Effect Viscosity (µ) of blood versus the diameter (d) of the vessel (µm) d µ

43 43 Develop an understanding of how the micro- and nano-structure of blood influences its rheology Explore to use of rheological parameters in diagnostics and menagement of clinical disorders and inoptimisation of blood processing Perspectives:


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