Chapter 17: Blood Flashcards
Functions of Blood:
o Transport
o Protection
o Regulation
Protective Functions of Blood:
o Defense against pathogens & toxins: o Leukocytes (white blood cells). o Antibodies. o Complement proteins. o Interferon & other chemicals. o Clotting: o Platelets. o Clotting factors & fibrinogen. o Blood shunting.
Regulatory Functions of Blood:
o Regulation of pH (7.35 to 7.45):
o Many blood proteins & solutes act as buffers.
o Regulation of body temperature:
o Cutaneous vasodilation/vasoconstriction.
o High specific heat of water.
o Regulation of fluid volume (osmotic pressure critical!)
o Regulation of ion composition of interstitial fluids.
General Characteristics of Blood:
o Unique colors:
o Scarlet color if oxygen rich (bright red).
o Dull red if oxygen poor (port wine color).
o High viscosity (5X more viscous than H20)(RBCs!).
o Osmolarity: 280 – 296 mOsm/Liter.
o Reflects # of particles & ability to attract H2O.
o Represents 7 to 8% of body weight.
o There are about 5 liters of blood in a human body.
Withdrawing Blood:
o Venipuncture: o Walls of veins are thinner. o Blood pressure (BP) is lower in veins than in arteries. o Arterial puncture: o Measure blood gases. o Capillary sticks: o Fingers, ear lobes, heel.
Composition of Blood:
o Plasma (55% of volume of blood): o Water. o Solutes. o Proteins. o Formed Elements (cells/cell (cells/cell fragments): o Erythrocytes (RBCs). o Leukocytes (WBCs). o Thrombocytes (platelets). o RBCs = 45 percent of volume of whole blood. o This percentage is called the PCV or the HEMATOCRIT. o 47 percent +/- 5 percent in males. o 42 percent +/- 5 percent in females.
Composition of Plasma:
o Plasma = straw-colored, liquid part of blood.
o 90 percent water (with over 100 substances dissolved in it).
o 8 percent plasma proteins.
o 1 – 2 percent other solutes.
Plasma Proteins:
o Hundreds of types of proteins in plasma all are chains of amino acids
o More than 90% are made by the LIVER !
o Typically, these plasma proteins STAY IN THE BLOOD VESSELS (too big to squeeze through most capillaries).
o ALBUMIN: 3.2 to 5.5 grams/dL.
o About 60 percent of all plasma proteins.
o Made by liver.
o Globulins (36 percent): alpha/beta/gamma.
o Alpha and beta globulins made by liver.
o Gamma globulins = immunoglobulins = antibodies are made by plasma cells (a differentiated form of a WBC).
o Fibrinogen (4 percent)
o Made by liver.
o Essential for blood clotting (hemostasis).
o Regulatory proteins (less than 1 percent)
o Enzymes, proenzymes, hormones, prohormones.
Plasma Proteins:
Albumin
o Major contributor to blood osmotic pressure!!!!! (attracts water to blood).
o Major contributor to blood viscosity.
o Transports:
o Fatty acids and bilirubin.
o Hormones (steroid hm, thyroid hormone).
o Ions and nutrients (Ca++, Zn++, Vit. B-6).
o Buffer for pH homeostasis.
o Crude indicator of protein nutritional status.
o Protein storage pool (half life = 14 to 20 days).
Plasma Proteins:
Globulins
o Alpha globulins (smallest in general): o e.g., HDL, VLDL, prothrombin. o e.g., haptoglobulin (transports hemoglobin released by dead RBCs). o Beta globulins (medium size): o e.g., LDL, transferrin, complement proteins. o Gamma globulins (largest): o Immunoglobulins = antibodies. o Made by plasma cells.
Hypoproteinemia:
o Low levels of protein in the blood.
o Causes (Etiology) of Hypoproteinemia:
o Liver disease interfering with protein synthesis.
o Kidney disease that permits proteins to leak out of the blood and into the urine.
o Severe burns—proteins escape in exudate.
o Severe trauma (necessitating REPAIR!).
o Extreme starvation.
o Diets severely deficient in protein.
o Consequences of Hypoproteinemia:
o Decreased osmolarity of blood (blood doesn’t attract water as much, water diffuses into the interstitial spaces between cells).
o Edema = excess fluid in interstitial spaces.
o Ascites = excess fluid in the peritoneal cavity.
Plasma Solutes (1-2 Percent of Plasma):
o Electrolytes. o Osmotic balance (especially sodium ion). o pH buffering (e.g., HCO3-). o Waste products of metabolism. o Protein metabolism produces NH3, urea. o Uric acid, creatinine, lactic acid. o Nutrients. o Glucose, but NOT glycogen! o Respiratory gases. o Miscellaneous (vitamins, growth factors, hm).
Formed Elements:
o Erythrocytes (RBCs) o 5 million RBCs/uL o Hematocrit = Percent of total blood volume occupied by RBCs = about 45 percent. o Leukocytes (WBCs) o 5,000 to 10,000 WBCs/uL. o 5 main types of WBCs. o Thrombocytes (platelets) o 150,000 to 400,000 platelets/uL. o Cell fragments.
Hemopoiesis (Hematopoiesis):
o Hemopoiesis = production of blood cells (all types).
o Location of hemopoiesis:
o Before birth: yolk sac, liver, spleen, thymus, lymph nodes.
o After birth: red bone marrow
• Sternum, ribs, clavicle, scapula, cranial bones
• Ilium of os coxae, vertebrae
• Proximal epiphyses of humerus/femur
Hemocytoblast:
o Type of stem cell that can differentiate into several cell LINES. o Lymphoid stem cell lines: o T lymphocytes. o B lymphocytes. o Myeloid stem cell line: o RBCs. o Platelets. o Neutrophils, eosinophils, basophils, monocytes (all of these are WBCs).
Regulation of Hemopoiesis:
o Erythropoiesis = formation of RBCs:
o Regulated by the hormone erythropoietin (EPO).
o EPO made primarily by kidney.
o Epoietin alfa = drug.
o Thrombopoiesis =formation of platelets:
o Regulated by hormone thrombopoietin (TPO).
o TPO (hormone made by liver) stimulates megakaryocyte production.
o Leukopoiesis = formation of WBCs:
o Regulation varies in response to pathogens.
o Production stimulated by cytokines, interleukins, and colony stimulating factors.
Characteristics of Erythrocytes:
o Biconcave disc about 7.5 um in diameter.
o Squeeze thru narrow capillaries.
o Live about 120 days.
o No nucleus in mature RBC.
o No mitochondria (no aerobic metabolism).
o Plasma membrane contains glycoproteins and glycolipids that we refer to as “antigens” which determine the different blood groups (A, B, AB, O).
o RBCs carry oxygen and other blood gases.
o Each RBC contains 250 to 280 million hemoglobin (Hb) molecules inside it!!!
o Each Hb molecule has the capacity to carry 4 oxygen molecules… so one RBC carries more than 1 billion O2 molecules!
o RBCs can also carry CO2, CO, and NO on their hemoglobin molecules.
Hemoglobin (Hb):
o PROTEIN CHAINS (part that can bind CO2):
o 2 alpha polypeptide chains.
o 2 beta polypeptide chains.
o HEME GROUPS (part that can bind O2):
o 4 non-protein porphyrin rings = heme.
o Each heme has an iron ion at its center.
o Each iron ion can carry one O2 molecule (reversibly).
o The shape of the polypeptide chains in hemoglobin are critical to the shape of the RBC!!!
o Fetal hemoglobin is different from adult Hb (binds O2 more readily).
o One way to treat sickle cell dz is to give meds that stimulate the production of FETAL Hb in adults!
o Normal Hb is approximately Hct/3 usually about 15 grams/dL.
o Males: 13 – 18 grams/dL.
o Females: 12 – 16 grams/dL.
Special Characteristic of Hemoglobins:
o Can monitor blood glucose control by a glycosylated hemoglobin test.
o HbA1-C test.
o Measures amount of glucose “sticking” to Hb over life of RBC.
o Should definitely be less than 7.0 percent.
o HbA1-C results less than 7.0 suggest that the diabetic is out of control.
o Normal FBS = 70 – 100 mg/dL.
Functions of RBCs:
o Contributes greatly to the viscosity of blood.
o Oxygen transport: 98.5% of all O2 is carried on the heme portion of Hb within the RBCs.
o Oxyhemoglobin.
o Deoxyhemoglobin.
o Carbon dioxide transport: ~20% of all CO2 is carried on the polypeptide chains of Hb within the RBCs (carbaminohemoglobin).
o Nitric oxide (NO) can also be carried by Hb… causes vasodilation of blood vessels.
o Carbon Monoxide binds to iron with a greater affinity than oxygen… dangerous!
Statistics About RBCs:
o 25 trillion RBCs in adult circulation! o 2.5 million RBCs destroyed each second! o Normal RBC count = 5 million RBCs/uL. o 5.1 – 5.8 million/uL in males. o 4.3 – 5.2 million/uL in females. o Represents about 45% of total blood volume (hematocrit)(know for exam). o 40 to 54 percent in males. o 38 to 46 percent in females.
Erythropoiesis:
o Under the regulation of Erythropoietin (EPO).
o 2.5 million RBCs destroyed each second!
o EPO is made by kidney cells in response to hypoxia: Anemias, High altitude, Increased O2 demand, Lung dz, Circulatory problems.
o Many nutrients are essential to erythropoiesis: iron, Vitamin B-12 and folate, Vitamn B-6, protein, Vitamin C.
Maturation of RBCs:
o Pluripotent Stem Cell-Myeloid stem cell- Colony forming unit E- proerythroblast- erythroblast- reticulocyte- mature RBC.
Reticulocytes:
o 0.5 to 1.5 percent of RBCs in peripheral blood.
o Have very few organelles (some RER and ribosomes for Hb production).
Lifespan/Death of RBCs:
o Lots of wear and tear going through narrow capillaries, RBC loses elasticity with age.
o No ability to repair itself.
o Lifespan is about 120 days (about 4 months).
o HbA1C test = diagnosis for diabetes.
o Removed from blood and destroyed by FIXED MACROPHAGES (phagocytes).
o Liver.
o Spleen.
o Red bone marrow.
Recycling of RBC:
o Globin (protein) portions separated from heme portions…globin just broken down into a.a. that are recycled.
o Heme pigment harder to recycle:
o IRON removed & attached to transferrin (a plasma protein that transports iron in blood).
o Free iron is toxic to cells! But necessary!!
o Transferrin delivers iron to wherever it is needed…stored as ferritin or hemosiderin.
Recycling of Heme Ring:
o Heme pigment converted to biliverdin, then unconjugated bilirubin, then (liver ) conjugated bilirubin, then secreted into bile, then (intestine) urobilinogen, then stercobilin (feces) or urobilin (urine).
Erythrocyte Disorders:
o Anemias: o Low numbers of RBCs. o Low amount of Hb inside an RBC. o Abnormal/defective Hb inside the RBC. o Polycythemias: o Extremely high numbers of RBCs. o Polycythemia vera. o Secondary polycythemias.
Anemia:
o Condition where the oxygen carrying capacity of the blood is reduced lots of disorders/diseases can cause this!!!
o Symptoms of anemia: Fatigue or lethargy, SOB on exertion, Pale skin, Cold intolerance, Picasm Serious cardiovascular consequences if severe.
3 Categories of Anemia:
o Low numbers of RBCs:
o Hemorrhagic anemia (excess blood loss)
• Sudden hemorrhage (e.g., aneurysms, trauma).
• Chronic blood loss (menses, ulcers, parasites, hemorrhoids, hemophilia).
o Hemolytic anemia (abn./premature rupture):
• Toxins, blood transfusions, drug reactions.
• Vitamin E deficiency, malaria, marathon running.
o Inadequate erythropoiesis:
• Chronic kidney dz.
• Inadequate nutrients for cell division (e.g., pernicious anemia from inadequate Vitamin B-12 absorption).
o Aplastic anemia (bone marrow failure):
• Cancer of bone marrow/radiation Rx.
• Some meds/poisons/bacterial toxins/viruses.
o Low amount of Hb inside RBCs:
o Lack of nutritional building blocks for Hb.
• Protein deficiency.
• Vitamin C, B-6, & copper deficiency.
• IRON DEFICIENCY (microcytic anemia).
o Defective Hb inside RBCs:
o The RBCs that are produced are fragile & rupture prematurely.
o Thalassemia:
• Mediterranean Sea countries.
• RBC count may be less than 2 million cells/uL.
o Sickle Cell Trait: one defective gene (heterozygous).
o Sickle Cell Anemia: 2 defective genes (homozygous).
Parietal Cells: Secrete Intrinsic Factor:
o B-12 bound to dietary protein in food.
o Pepsin and acid free it from this dietary pro.
o B-12 combines with cobalophilin (a protein from saliva).
o Pancreatic proteases cleave this bond.
o B-12 binds with intrinsic factor.
o Receptor mediated endocytosis in ileum.
