Bài giảng Biology 25: Human Biology - Chapter 6

Chapter 6 Biology 25: Human BiologyProf. GonsalvesLos Angeles City CollegeLoosely Based on Mader’s Human Biology,7th edition1. BloodAverage Blood Volume: 4 to 6 liters.Blood composition:55% Plasma (fluid matrix of water, salts, proteins, etc.)45% Cellular elements:Red Blood Cells (RBCs): 5-6 million RBCs/ml of blood. Contain hemoglobin which transport oxygen and CO2.White Blood Cells (WBCs): 5,000-10,000 WBCs/ml of blood. Play an essential role in immunity and defense. Include:Lymphocytes: T cells and B cellsMacrophages (phagocytes)Granulocytes: Neutrophils, basophils, and eosinophils.Platelets: Cellular fragments. 250,000- 400,000/ml of blood. Important in blood clotting.Composition of BloodFormed Elements.Erythrocytes.Leukocytes.Platelets.Plasma.Composition of Human BloodPlasmaStraw-colored liquid.Consists of H20 and dissolved solutes.Ions, metabolites, hormones, antibodies.Na+ is the major solute of the plasma.Plasma ProteinsConstitute 7-9% of plasma.Provide the colloid osmotic pressure needed to draw H20 from interstitial fluid to capillaries.Maintain blood pressure.Albumin: Accounts for 60-80% of plasma proteins.Plasma ProteinsGlobulins:a globulin:Transport lipids and fat soluble vitamins.b globulin: Transport lipids and fat soluble vitamins.g globulin: Antibodies that function in immunity.Plasma ProteinsFibrinogen:Constitutes 4% of plasma proteins.Important clotting factor.Converted into fibrin during the clotting process.Formed Elements of BloodInclude 2 types of blood cells:RBCs (red blood cells):Most numerous of the two.WBCs (white blood cells).ErythrocytesFlattened biconcave discs.Provides increased surface area through which gas can diffuse.Lack nuclei and mitochondria.Half-life ~ 120 days.Contain 280 million hemoglobin with 4 heme chains (contain iron).LeukocytesContain nuclei and mitochondria.Move in amoeboid fashion.Can squeeze through capillary walls (diapedesis).Almost invisible, so named after stains.Neutrophils are the most abundant WBC.Accounts for 50 – 70% of WBCs.Involved in immune function.PlateletsAlso called thrombocytes.Smallest of formed elements.Are fragments of megakaryocytes.Lack nuclei.Have amoeboid movement.Important in blood clotting:Constitute most of the mass of the clot.Release serotonin to reduce blood flow to area.Secrete growth factorsMaintain the integrity of blood vessel wall.HematopoiesisFormation of blood cells.2 types of hematopoiesis:Erythropoiesis:Formation of RBCs.Leukopoiesis:Formation of WBCs.Occurs in myeloid tissue (bone marrow of long bones) and lymphoid tissue.Stem cells differentiate into blood cells.ErythropoiesisActive process.2.5 million RBCs are produced every second.Regulated by erythropoietin.Erythropoietin binds to membrane receptors, stimulating cell division. Old cells are destroyed in spleen and liver.Iron recycled back to myeloid tissue to be reused in RBC synthesis.Need iron, vitamin B12 and folic acid for synthesis.LeukopoiesisCytokines stimulate different types and stages of WBCs production.Multipotent growth factor-1, interleukin-1, and interleukin-3:Stimulate development of different types of WBC cells.Granulocyte-colony stimulating factor:Stimulates development of neutrophils.Granulocyte-monocyte colony stimulating factor:Simulates development of monocytes and eosinophils.Blood ClottingHemostatic mechanisms:Cessation of bleeding.Breakage of endothelial lining exposes collagen proteins causing:Vasoconstriction.Platelet plug.Web of fibrin.Function of PlateletsPlatelets normally repelled away from endothelial lining by prostacyclin (prostaglandin).Do not want to clot normal vessels.Damage to Endothelian WallExposes subendothelial tissue to blood.Platelet release reaction:Endothelial cells secrete von Willebrand factor to cause platelets to adhere to collagen.Platelet secretory granules release ADP, serotonin and thromboxane A2.Platelet Release ReactionSerotonin and thromboxane A2 stimulate vasoconstriction.ADP and thromboxane A2 make other platelets “sticky”.Platelets adhere to collagen. Produce platelet plug.Strengthened by activation of plasma clotting factors. Platelet plug strengthened by fibrin.Clot reaction:Contraction of the platelet mass forms a more compact plug. Conversion of fibrinogen to fibrin occurs.Fluid squeezed from the clot is called serum (plasma without fibrin).Clotting FactorsIntrinsic Pathway:Initiated by exposure of blood to a negatively charged surface (collagen).This activates Factor XII (protease), which activates other clotting factors.Ca++ and phospholipids convert prothrombin to thrombin.Thrombin converts fibrinogen to fibrin.Produces meshwork of insoluble fibrin polymers.Conversion of Fibrinogen to FibrinExtrinsic PathwayThromboplastin is not a part of the blood, so called extrinsic pathway.Damaged tissue release a thromboplastin.Thromboplastin initiates a short cut to formation of fibrin.Dissolution of ClotsActivated factor XII converts an inactive molecule into the active form (kallikrein). Kallikrein converts plasminogen to plasmin.Plasmin is an enzyme that digests the fibrin.Clot dissolution occurs. Types of Blood VesselsA. Arteries and Arterioles: Carry blood away from heart to body. Have high pressure.Have thick muscular walls, which make them elastic and contractile.Vasoconstriction: Arteries contract:Reducing flow of blood into capillaries.Increasing blood pressure.Vasodilation: Arteries relax:Increasing blood flow into capillaries.Decreasing blood pressure. Types of Blood VesselsCapillaries: Only blood vessels whose walls are thin enough to permit gas exchange.Blood flows through capillaries relatively slowly, allowing sufficient time for diffusion or active transport of substances across walls.Only about 5 to 10% of capillaries have blood flowing through them. Only a few organs (brain and heart) always carry full load of blood. Blood flow to different organs is controlled by precapillary sphincters of smooth muscle.Types of Blood VesselsVeins and Venules:Collect blood from all tissues and organs and carry it back towards heart.Have low pressure and thin walls.Veins have small valves that prevent backflow of blood towards capillaries, especially when standing. If the valves cease to work properly, may result in:Varicose veins: Distended veins in thighs and legs.Hemorroids: Distended veins and inflammation of the rectal and anal areas.Lymphatic and Immune SystemComponents: Lymph, lymphatic vessels, bone marrow, thymus, spleen, and lymph nodes.Functions: Defends against infection: bacteria, fungi, viruses, etc.Destruction of cancer and foreign cells.Synthesis of antibodies and other immune molecules.Synthesis of white blood cells.Homeostatic Role:Returns fluid and proteins that have leaked from blood capillaries into tissues. Up to 4 liters of fluid every day.Fluid returned near heart/venae cavae.Red Blood Cell AntigensABO system:Major group of antigens of RBCs.Type A:Only A antigens present.Type B:Only B antigens present.Type AB:Both A and B antigens present.Type O:Neither A or B antigens present.RBC AntigensEach person inherits 2 genes that control the production of ABO groups.Type A:May have inherited A gene from each parent.May have inherited A gene from 1 parent and O gene from the other.RBC AntigensType B:May have inherited B gene from each parent.May have inherited B gene from 1 parent and O gene from the other parent.Type AB:Inherited the A gene from one parent and the B gene from the other parent.Type O:Inherited O gene from each parent.Transfusion ReactionsIf blood types do not match, the recipient’s antibodies attach to donor’s RBCs and agglutinate.Type O:Universal donor.Recipient’s antibodies cannot agglutinate the donor’s RBCs.Type AB universal recipient:Lack the anti-A and anti-B antibodies.Cannot agglutinate donor’s RBCs.Rh FactorAnother group of antigens found on RBCs.Rh positive:Have these antigens.Rh negative:Do not have these antigens.Significant when Rh negative mother give birth to Rh positive baby.At birth, mother may become exposed to Rh positive blood of fetus.Mother at subsequent pregnancies may produce antibodies against the Rh factor.