[PHY LEC - LE 2] 01 - RBC (V2).pdf

PHYSIOLOGY LECTURE | TRANS 1 LE RBC DR JCCHUA | Lecture Date (09/18/2023)...

PHYSIOLOGY LECTURE | TRANS 1 LE RBC DR JCCHUA | Lecture Date (09/18/2023) 02 8 OUTLINE HEMATOCRIT I. Blood III. Laboratory Values The fraction of the whole column occupied by the RBC A. Definition IV. Clinical Correlation → Formula: B. Composition A. Anemia II. Red Blood Cell B. Polycythemia A. Function V. Blood Types B. Structure A. ABO System → ~40% Female - lower due to menstruation 💬 C. Synthesis B. Rh System → ~45% Male - higher due to testosterone D. Hemoglobin VI. Review Questions Males generally have a higher amount of RBCs than females; E. Oxygen-Hemoglobin VII. References (higher hematocrit = increased viscosity) Dissociation Curve VIII. Appendix → ~55% Newborns F. Destruction of RBC G.Iron A. BLOOD COMPOSITION Cellular Components or Formed Elements (~45%) 📋 [2025A] ❗️ Must know 💬 Lecturer 📖 Book 📋 Previous Trans → Red Blood Cells (RBC) - Erythrocytes → White Blood Cells (WBC) - Leukocytes → Platelets - Thrombocytes SUMMARY OF ABBREVIATIONS ODC Oxygen Dissociation Curve RBC Red Blood Cell WBC White Blood Cell Hgb Hemoglobin PHSC Pluripotent Hematopoietic Stem Cell 2,3-DPG 2,3-diphosphoglycerate GM-CSF Granulocyte-macrophage colony-stimulating factor G-CSF Granulocyte colony-stimulating factor M-CSF Macrophage colony-stimulating factor IL-3 Interleukin 3 IL-5 Interleukin 5 TPO Thrombopoietin EPO Erythropoietin MCV Mean Cell Volume MCH Mean Cell Hemoglobin MCHC Mean Cell Hemoglobin Concentration RDW RBC Distribution Width CFU-E Colony-forming unit erythroid NV Normal Value Figure 1. Blood Components[PPT] LEARNING OBJECTIVES Plasma: Pale-white, watery (~55%) ✔ Discuss the components of blood. → Water (91%) ✔ Correlate the structure and characteristics of the erythrocyte → Proteins (7%) with its function. ▪ Albumin (60%) ✔ Identify the sites of hematopoiesis & the hematopoietic growth ▪ Globulin (35%) factors in fetal and adult life. ▪ Fibrinogen (4%) ✔ Discuss the differentiation and maturation of erythrocytes. ▪ Regulatory proteins (~1%) ✔ Explain the formation, composition, & function of hemoglobin in → Others (1%) fetal & adult life. ▪ Electrolytes, nutrients, & waste ✔ Explain the normal oxygen dissociation curve (ODC) and the factors affecting it. Serum vs Plasma 📋 [2025A] Serum is the fluid portion taken from the blood after it was ✔ Explain iron metabolism in relation to the red blood cells. Discuss the process of RBC destruction and recycling. allowed to clot. ✔ Define anemia and polycythemia. It is the plasma without the clotting factors: Factors I, II, V, ✔ Identify the major blood group systems and interpret a blood VIII typing result. IMPORTANCE OF PROTEINS IN THE BLOOD ✔ Given a blood type, predict the blood types that can be donated Albumin: major contributor to oncotic pressure; transports to the subject and the subject can donate to. lipids, hormones I. BLOOD → Oncotic pressure: pressure due to large proteins and/or other “Blood is a complex fluid consisting of plasma—extracellular large molecules; how well the solution is able to retain its water fluid rich in proteins—and of formed elements—red blood cells, (High oncotic pressure = water will tend to stay inside the white blood cells, and platelets.” (Boron) A specialized connective tissue 💬 solution); The purpose of oncotic pressure is to keep the fluids where they should be. Albumin in blood tends to keep fluids → ~7% body weight in females (70 ml/kg) 💬 → ~8% body weight in males (80 ml/kg) The difference in RBC count between males and in the veins and avoid edema. Globulin: transports ions, hormones, lipids; immune function 💬 females is usually attributed to testosterone. Fibrinogen: clotting If we assume that a typical Filipino weighs around 50kg, then the typical blood volume would be around 4 liters. Plasma proteins are made mostly in the liver. ❗️ Regulatory Proteins: enzymes, clotting factors, hormones → 55% plasma, 45% formed elements PHYSIOLOGY | LE 2 RBC | Julia, Lanuza, Laulita, Lazatin, Lim, Lego, Leveriza, D. Li, PAGE 1 of 13 PHYSIOLOGY | LE2 RBC | DR JCCHUA 💬 Electrolytes also contribute to osmotic pressure, but the majority is contributed by large molecules. C. SYNTHESIS LOCATION OF RBC SYNTHESIS 💬 CLINICAL APPLICATION If a patient has a liver problem, this might affect the levels of proteins in the blood. The patient may not be producing enough Embryonic Development → Yolk sac (Mesoblastic Phase) Middle Trimester: 4-6 months albumin that can lead to edema; or might not be producing → Mainly in the liver (Hepatic Phase) enough clotting factors that could lead to clotting problems → Spleen and lymph nodes play a minor role (e.g. low albumin = edema; low fibrinogen = clotting problems) Last month of gestation onwards (birth and as the person ages) → Bone marrow (Medullary Phase) Figure 2. Edema Foot looks puffy because the interstitial space has a lot of fluid. One reason for edema is if there is a low amount of proteins, especially albumin, in the blood B. FUNCTIONS OF BLOOD Transports gases, nutrients, hormones, wastes, cellular products Restricts fluid loss Regulates body temperature Figure 3. Bone Marrow Cellularity vs Age[PPT] → As blood flows throughout the body, it distributes warmth to the The graph represents the different bones involved in RBC more distal portions of the body. synthesis and percentage of marrow cellularity as we age → If a part of your body is pale or does not receive enough blood, Cellularity that part starts to feel cold. → amount of stem cells in the bone marrow that are needed for Regulates pH and electrolytes of interstitial fluid RBC synthesis Bone marrow involved in RBC synthesis becomes more 📋 II. RED BLOOD CELL concentrated to axial bones as age increases A. FUNCTION → Changes over the years: Major function: Transport Hgb (Hgb is an O2 carrier) ▪ Infancy: most of the RBC synthesis occurs in the long → Diffusion of gasses for O2 & CO2 balance bones, tibia and femur, and eventually declines in Other functions: adulthood (basically none, at approx. 18-25 y/o) → CO2 transport ▪ Adulthood: RBC synthesis is mainly concentrated to the → Acid-base buffer (also due to Hgb) vertebra, sternum, and rib. Average number: → ~5 million/mL Males → ~4.7 million/mL Females 💬 ▪ Cellularity steadily drops as we age In the elderly, bone marrow is less cellular, containing less stem cells, but their bone marrow can still produce an appropriate amount of RBCs as long as they are healthy. B. STRUCTURE Biconcave discs STEPS IN RBC SYNTHESIS No nucleus and other organelles → Cannot synthesize protein and cannot perform oxidative metabolism, ATP is generated exclusively by glycolysis (since no mitochondria) → Limited ability to repair self; limited lifespan Diameter: 7.8 µm → just enough to squeeze through smallest capillaries in a single file; narrowest capillaries diameter a little smaller than 7.8 µm Thickness: 2.5 µm thickest (periphery); 1µm center Very flexible, easily deformed → due to their biconcave shape, which allows them to bend/deform without damaging their cell membrane Large surface-to-volume ratio = ↑ diffusion area → Depression of disc increases surface area Contain 2,3-diphosphoglycerate (2,3-DPG) → Acts on Hgb; reduces O2 affinity of Hgb → Important for O2 release into the tissue (affinity to O2 must be low) Contain more glutathione than most cells → Protects against oxidant damage Contain carbonic anhydrase and Cl--HCO3- exchanger → Important in CO2 transport & maintaining the acid-base balance → Carbonic anhydrase rapidly interconverts CO2 and HCO3- Figure 4. Growth and Differentiation Factors [PPT] ▪ HCO3- is the main form of CO2 as it travels in the blood and in the RBCs All blood cells are derived from the Pluripotent Hematopoietic Stem Cell (PHSC) found in the bone marrow. CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3− 📖 ▪ Due to carbonic anhydrase catalyzing the equation: → Cl--HCO3- exchanger helps exchange chloride & bicarbonate 📋 → After division, some will remain as PHSC in the bone marrow (produced by RBC) → Some will become committed stem cells and form the ▪ Ensures that more CO2 & HCO3− produced inside RBC specific blood cells PHYSIOLOGY RBC | Julia, Kang, Laguardia, Laguitan, Laulita, TE | Juvagar, Laceda, AVPAA | J. Enriquez, T. Guzman PAGE 2 LEC | LE2 Lazatin, Lim, Lego, Leveriza, D. Li Lacson, Lanuza of 13 PHYSIOLOGY | LE2 RBC | DR JCCHUA ▪ caused by the large number of free ribosomes responsible Divided into two lineages for Hgb synthesis → Myeloid Lineage Third: Polychromatophil erythroblast − Erythrocytes (RBCs) 💬 ▪ Matures in the myeloid (bone marrow) Erythro = red, cyte = cells → Cells become filled with Hgb, causing cell to turn pink/red ▪ Where Hgb first appears − Platelets − WBCs, excluding lymphocytes absorbed or extruded from the cell 📖 📖 → Nucleus condenses to a small size and final remnant is [Guyton and Hall, 2020] 📋 [Guyton and Hall, 2020] → Lymphoid lineage → Endoplasmic reticulum is being reabsorbed ▪ Matures in the lymphoid organs Fourth: Orthochromatic erythroblast − T Lymphocytes → The ejected nucleus undergoes phagocytosis by macrophages − B Lymphocytes → Fried egg appearance HEMATOPOIETIC CYTOKINES Fifth: Reticulocyte → “Young adult” 📋 blood cells Examples: 📋 Signals or influences PHSC to differentiate into several different → Contains remnants of organelles → Exits the bone marrow and enters capillaries through diapedesis → GM-CSF: Granulocyte-macrophage colony-stimulating factor → G-CSF: Granulocyte colony-stimulating factor → M-CSF: Macrophage colony-stimulating factor enter circulation 📖 ▪ Squeezing through the pores of the capillary membrane to [Guyton and Hall, 2020] → IL-3, IL-5: Interleukin 3 and 5 → TPO: Thrombopoietin → Matures into erythrocytes in 1-2 days ▪ Remaining basophilic material disappears → ~1% of circulating RBCs 📖 [Guyton and Hall, 2020] → EPO: Erythropoietin Tips on memorization: 📋 IL-3, “3” = affects all THREE lineages (RBC, WBC, platelets) → Clinical indicator of bone marrow activity 📋 ▪ Increase: Bone marrow is very active as more production of RBCs are needed IL-5, 5th letter of the alphabet = E (Eosinophil) ▪ Decrease: Bone marrow is not very active due to deficiency All types of blood cells are produced via the myeloid lineage, except the lymphocytes 📋 in nutrients that prevents the bone marrow to produce RBCs Sixth: Erythrocytes cytokines (See Figure 23 in Appendix) 📋 Stem cell differentiation with influence of different hematopoietic → aka Red Blood Cells (RBCs) → Mature erythrocyte → Final product of erythropoiesis TREND OF RBC MATURATION → Released into the circulation from the bone marrow Increase in Hemoglobin (Hgb) as the cell matures into REGULATION → 💬 erythrocyte Cytoplasm initially appears blue and later on appears more Remember! Major function of RBC = transport hemoglobin = red due to inc. concentration of Hgb Decrease in size of the cell production is tissue oxygenation. ❗️ transport oxygen. Therefore, the most essential regulator of RBC Decrease in basophilic materials (nucleus and organelles) STIMULATION OF RBC PRODUCTION 📋 Decrease in nuclear size until finally extruded in Reticulocytes STAGES OF ERYTHROPOIESIS Figure 6. Effect of Kidney on Hematopoiesis [PPT] Tissue Oxygenation is an essential regulator of Red Blood Cell production. → Decrease in oxygen transported to the tissues brought about RBC production. Kidney hypoxia 📖 by medical conditions usually result in an increase in the rate of [Guyton and Hall, 2020] Figure 5. Stages of Erythropoiesis[PPT] → An increase in HIF-1 leads to an increase in EPO First: Proerythroblast production in the kidneys → Divides multiple times to produce multiple erythrocytes ▪ ↑ Hypoxia-inducible factor-1 = ↑ Erythropoietin (EPO) → Formed from the colony-forming-unit-erythroid (CFU-E) production in kidneys stem cell, which is one of the committed stem cells Other signals include: Norepinephrine, Epinephrine, and Second: Basophil erythroblast Prostaglandins → Start of Hgb synthesis EPO Production ▪ Nucleus has lost its nucleoli but still has light and dark → Maximum production of EPO is reached within 24 hours lace-like pattern → New RBC appears after 5 days → Stains with basic dyes → EPO increases both the quantity and speed of production PHYSIOLOGY RBC | Julia, Kang, Laguardia, Laguitan, Laulita, TE | Juvagar, Laceda, AVPAA | J. Enriquez, T. Guzman PAGE 3 LEC | LE2 Lazatin, Lim, Lego, Leveriza, D. Li Lacson, Lanuza of 13 PHYSIOLOGY | LE2 RBC | DR JCCHUA → (-) EPO = almost no RBC production → Hematopoietic cytokines - influencing factor that causes → (↑↑) EPO = >10x normal rate of production differentiation of PHSC into different lineages. ▪ Production continues until (-) hypoxia, or enough RBCs → Hypoxia-inducible factor-1 - activated when the kidney produced experiences hypoxia, which then stimulates production of → Formation of normal erythropoietin is: 90% from the kidneys, EPO that leads to more differentiation and RBC production. 10% from the liver → Megaloblastic anemia - deficiency in either Vit B12 or Folic the RBC formation needed by the body 📖 ▪ But the 10% is sufficient to cause only one-third to one-half [Guyton and Hall, 2020] ▪ When both kidneys are removed, or when the kidneys are acid, which are precursors in the production of RBCs. Upon examining a patient with chronic kidney disease, you notice that he looks pale. What would be the most likely very anemic 📖 destroyed by renal disease, the person invariably becomes [Guyton and Hall, 2020] explanation for this finding? → Decrease in EPO production CLINICAL APPLICATION 💬 → EPO production is 90% done by the kidneys and 10% by the liver. A decrease in EPO directly causes a patient to have Patient with severe kidney damage low erythrocyte production that can lead to anemia. → EPO is given to stimulate production of RBCs that will eventually prevent or correct anemia CLINICAL APPLICATION Blood Doping Checking for Pallor (paleness): → Some athletes inject themselves with EPO to increase → compare patient’s hands or check palpebral conjunctiva RBCs, thus increasing their performance in the sport. However, this is ILLEGAL. RBC MATURATION To ensure 📋 erythrocyte proper maturation Important nutrients for DNA synthesis: of proerythroblast to → Vitamin B12 ▪ Absorbed in GIT − Intrinsic factor (protein produced by the stomach which Figure 8. Pallor of Hand (left) and Palpebral Conjunctiva (right)[PPT] facilitates the absorption of Vitamin B12) → Folic acid D. HEMOGLOBIN ▪ Required Vit B12 for synthesis STRUCTURE CLINICAL APPLICATION Deficiency of either Vitamin B12 or Folic acid would lead to megaloblastic anemia → Impaired nuclear maturation thus the cell would retain the large nucleus and cell size characteristic of either cell stages, hence macrocytic. 📋 RBC morphology would be Figure 9. Structure of Hgb[PPT] Figure 7. Macrocytic RBCs [PPT] Each Hgb consists of 4 subunits → Each subunit contains Heme + Polypeptide Chain CONCEPT CHECKPOINT ▪ Heme: Iron-containing part, site where Oxygen binds, Describe the following terms: porphyrin derivative (Blue discs in Figure 9) 💬 → Hematocrit - the fraction of the column occupied by RBC 📖 The proportion of blood that is red blood cells [Guyton and Hall, 2020] connected to the polypeptide chain 📋 − Iron is in the center of the structure and the heme is → Plasma - extracellular fluid rich in proteins, the pale white watery part in a centrifuged blood atoms embedded into the heme 💬 − Each complete hemoglobin molecule contains 4 iron − Each heme can only bind 1 molecule of O2 → Serum - Plasma without the clotting factors ▪ Polypeptides (globin portion) What is the importance of the proteins in plasma? − Synthesized by ribosomes → Keeps the oncotic pressure in the blood to prevent 4 kinds of globin chains extravasation of the water component, thus preventing → α, β, γ, δ edema, facilitates transport of nutrients, lipids, hormones, → Type of Hgb is dictated by the combination of chains (See facilitation of blood clotting. 💬 and other protein bound molecules (ex. Medications), and Tables 1-3) Define the following: PHSC; Myeloid lineage; Lymphoid lineage; Hematopoietic cytokines; Hypoxia-inducible Hemoglobin A → Found in adults 💬 → ~95-98% of adult Hgb factor-1; Megaloblastic anemia → Composed of: 2α and 2β chains → PHSC - Origin of all blood cells, influenced by Hematopoietic cytokines to determine its lineage ▪ 2α2β is the normal composition of hemoglobin → Myeloid lineage - where erythrocytes, granulocytes, monocyte, and platelets originate age 💬 The type of hemoglobin predominant changes depending on your → Lymphoid lineage - where T & B Lymphocytes originate → During fetal stage, Hemoglobin F (Hgb F) is predominant ▪ Composed of 2α + 2γ chains PHYSIOLOGY RBC | Julia, Kang, Laguardia, Laguitan, Laulita, TE | Juvagar, Laceda, AVPAA | J. Enriquez, T. Guzman PAGE 4 LEC | LE2 Lazatin, Lim, Lego, Leveriza, D. Li Lacson, Lanuza of 13 PHYSIOLOGY | LE2 RBC | DR JCCHUA → At ~3 months old, Hemoglobin A (Hgb A) is predominant ▪ Also known as Adult Hgb ▪ Composed of 2α + 2β chains SYNTHESIS No need to memorize the steps in the synthesis of heme 💬 1. Succinyl-Coa from Krebs cycle will bind to glycine, forming ▪ Some other forms of Hgb may be present such as γ and δ chains (See Figure 9) Porphobilinogen 2. Porphobilinogen will bind together, forming Protoporphyrin IX 3. Protoporphyrin IX binds with Fe2+, forming heme 4. Heme binds with globin, forming hemoglobin chain Hgb synthesis starts at the level of the Polychromatophil 💬 erythroblast and proceeds until mature Erythrocytes are formed (See Figure 5) Figure 10. Globin synthesis vs Age[PPT] 📋 Table 1. Fetal/embryonic quaternary structures of hemoglobin Form Chain component Hemoglobin F α2γ2 Gower 1 Hgb ζ2ε2 Gower 2 Hgb α2ε2 Portland Hgb ζ2γ2 Table 2. Newborn quaternary structures of hemoglobin Form Chain component % Figure 12. Process of Synthesis of Hgb[PPT] Hemoglobin F (Fetal Hgb) α2γ2 75% 💬 Size decreases because as the RBC matures the unnecessary contents are removed. Hemoglobin A α2β2 25% FUNCTION Table 3. Adult quaternary structures of hemoglobin Form Hemoglobin A Chain component α2β2 % 95-98% polypeptide chain 💬 Recall: Each Hgb has 4 heme groups, each with their associated Each heme group can bind one molecule of O2 (Normal; → Can only bind O2 if it is in the Fe2+ (ferrous) state Predominant) Type of Hgb chain determines the affinity for O2 Hemoglobin A2 α2δ2 2.5% Hemoglobin F (Fetal Hgb) α2γ2