Introduction to Blood Physiology PDF

Introduction to Blood Physiology December 2023 Learning outcome 1. Explain the process of hematopoiesis. 2. Explain four major roles of blood: transport, hemostasis, homeostasis and immunity. 3. List whole blood components with their properties as plasma and formed elements. 4. Explain how plasma...

Introduction to Blood Physiology December 2023 Learning outcome 1. Explain the process of hematopoiesis. 2. Explain four major roles of blood: transport, hemostasis, homeostasis and immunity. 3. List whole blood components with their properties as plasma and formed elements. 4. Explain how plasma and serum are obtained 5. Explain plasma proteins and their roles. Blood • What type of information we can collect by taking blood sample and analyzing that sample? • Internal environment @ extracellular fluid • We can monitor internal environment by taking blood sample Characteristics and Volume of Blood • Blood accounts for approximately 7% of body weight. Its average volume in healthy adult males is 5–6 L (adult females 4–5 L). • Blood is 3-4 times more viscous than water • pH between 7.35 and 7.45 Blood 5 minutes at 10,000 g, the bottom fraction contains formed elements — RBCs (or erythrocytes), WBCs (leukocytes, which include granulocytes, lymphocytes, and monocytes), and platelets (thrombocytes); the top fraction is blood plasma. The RBCs having the highest density are at the bottom of the tube, whereas most of the WBCs and platelets form a whitish gray layer—the buffy coat — between the RBCs and plasma. The hematocrit (Ht or HCT) is the volume percentage (vol%) of red blood cells (RBCs) in blood. The hematocrit is a measure of concentration of RBCs, not of total body red cell mass. Normal range of Hct is 42-52% for men and 37-47% for women • Expansion of plasma volume in a pregnant woman reduces the hematocrit, whereas her total red cell volume also increases but less than plasma volume • Immediately after hemorrhage, the hematocrit may be normal despite the loss of blood volume • A lower-than-normal Hct indicates anemia – e.g., inadequate numbers of RBCs, iron deficiency, abnormalities related with hemoglobin • A higher-than-normal Hct indicates polycythemia – e.g., increase in RBCs because of living at high altitudes, strenuous athletic training, and tumors in the bone marrow • At hematocrits >60%, the cells are so tightly packed that further increases lead to cell-cell interactions that increasingly deform the RBCs • The combination of a high hematocrit and a high fibrinogen level can be expected to lead to extremely high viscosities BLOOD COMPOSITION Plasma • A pale-white watery solution of electrolytes, plasma proteins, carbohydrates, and lipids. • Pink-colored plasma suggests the presence of hemoglobin caused by hemolysis (lysis of RBCs) and release of hemoglobin into the plasma. • A brown-green color may reflect elevated bilirubin levels. • The electrolyte composition of plasma differs only slightly from that of interstitial fluid on account of the volume occupied by proteins Plasma Proteins • Comprise the following in decreasing order of electrophoretic mobility : albumin, α -globulins, β-globulins, fibrinogen, and γglobulins. • The three most abundant peaks are albumin, fibrinogen, and γ-globulins. • The γ-globulins include the immunoglobulins or antibodies, which can be separated into IgA, IgD, IgE, IgG, and IgM. Immunoglobulins are synthesized by B lymphocytes and plasma cells. Plasma Proteins Major plasma proteins 60% 4% 35% 1% Human Physiology: An Integrated Approach 6e , Pearson - Albumins transport some drugs, hormones, bile salts, bilirubin, fatty acids … - Alpha and beta globulins transport lipids and fat-soluble vitamins - Only gamma globulins (immunglobulins) are synthesized and secreted by specialized blood cells à antibodies - plasma proteins make the osmotic pressure of the blood higher than that of interstitial fluid Serum = plasma - clotting factors • • Many plasma proteins are involved in blood coagulation through coagulation cascades, the end point of which is the cleavage of fibrinogen into fibrin monomers that further assemble into a fibrin polymer. Serum, differs from plasma by the absence of fibrinogen and other coagulation factor. However, serum still contains albumin, antibodies, and other proteins. Note that plasma can also form a clot, but a plasma clot does not retract because it lacks platelets. The electrophoretic mobility of a protein depends on its molecular weight (size and shape) as well as its electrical charge. Blood smear preparation To prepare a thin smear of peripheral blood on a slide, we need approximately 10-15 μl of blood . Blood should be placed on a slide with pipette, near one of the ends of the slides. With another glass slide, spread the blood with continuous, rapid movement, while firming the slide in place with the other hand BLOOD COMPOSITION Hematopoiesis • Hematopoiesis is the process of generation of all the cell types present in blood. • Because of the diversity of cell types generated, hematopoiesis serves multiple roles ranging from the carriage of gases to immune responses and hemostasis. Genesis of Blood Cells (Hematopoiesis) In the adult, most of the blood cells are originated from hematopoietic stem cells (are capable of producing all types of blood cells) in the red bone marrow. Growth and reproduction of the different stem cells are controlled by multiple proteins growth factors and/or cytokines CYTOKINES • The chemical factors that control the production and development of blood cells. • Cytokines are peptides/proteins released from one cell that affect the growth or activity of other cells (both local and long-distance signals) • Colony stimulating factors (i.e. made by endothelial cells and white blood cells) • Interleukins (inter- between + leuko - white) Some of the cytokines that play role in hematopoiesis Human Physiology: An Integrated Approach 6e, Pearson IL, interleukin; CSF, colony-stimulating factor; G, granulocyte; M, macrophage; SCF, stem cell factor. Active cellular marrow is called red marrow; inactive marrow that is infiltrated with fat is called yellow marrow. OpenStax College - Anatomy & Physiology Active bone marrow is red, since it contains hemoglobin 75% of the cells in the marrow belong to the white blood cell-producing myeloid series and only 25% are maturing red cells. This difference in the marrow reflects the fact that the average life span of white cells is short, whereas that of red cells is long. Relative rates of red blood cell production in the bone marrow of different bones at different ages. Guyton & Hall: Textbook of Medical Physiology 12th Edition, by J.E.Hall In children, blood cells are actively produced in all the bones. In adults, the only areas producing blood cells are pelvis, spine, ribs, cranium and proximal ends of long bones. More than 100 billion cells are produced every day Bone marrow consist of blood cell in different stages of development Human Physiology: An Integrated Approach 6e, Pearson Leukocyte formula: Never (Neutrophils) Let (Lymphocytes) Monkeys (Monocytes) Eat (Eosinophils) Bananas (Basophils) *A mnemonic that is often used to remember the relative amount of each white blood cell Percentages: (60% neutrophils, 30% lymphocytes, 6% monocytes, 3% eosinophils, and 1% basophils) Importance of the formula • Granulocytes increase mostly in bacterial infections • Eosinophils increase mostly in parasitic infections & allergic reactions • Basophils increase mostly in allergic reactions • Lymphocytes increase mostly in viral infections • Monocytes increase mostly in chronic diseases 30